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  Subjects -> BIOLOGY (Total: 3134 journals)
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BIOTECHNOLOGY (236 journals)                  1 2 | Last

Showing 1 - 200 of 237 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
Advanced Biomedical Research     Open Access  
Advances in Bioscience and Biotechnology     Open Access   (Followers: 14)
Advances in Genetic Engineering & Biotechnology     Hybrid Journal   (Followers: 8)
African Journal of Biotechnology     Open Access   (Followers: 6)
Algal Research     Partially Free   (Followers: 10)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 64)
American Journal of Bioinformatics Research     Open Access   (Followers: 7)
American Journal of Polymer Science     Open Access   (Followers: 31)
Anadolu University Journal of Science and Technology : C Life Sciences and Biotechnology     Open Access  
Animal Biotechnology     Hybrid Journal   (Followers: 8)
Annales des Sciences Agronomiques     Full-text available via subscription  
Applied Biochemistry and Biotechnology     Hybrid Journal   (Followers: 43)
Applied Bioenergy     Open Access  
Applied Biosafety     Hybrid Journal  
Applied Food Biotechnology     Open Access   (Followers: 3)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 63)
Applied Mycology and Biotechnology     Full-text available via subscription   (Followers: 4)
Arthroplasty Today     Open Access   (Followers: 1)
Artificial Cells, Nanomedicine and Biotechnology     Hybrid Journal   (Followers: 1)
Asia Pacific Biotech News     Hybrid Journal   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 8)
Asian Pacific Journal of Tropical Biomedicine     Open Access   (Followers: 2)
Australasian Biotechnology     Full-text available via subscription   (Followers: 1)
Banat's Journal of Biotechnology     Open Access  
BBR : Biochemistry and Biotechnology Reports     Open Access   (Followers: 5)
Bio-Algorithms and Med-Systems     Hybrid Journal   (Followers: 2)
Bio-Research     Full-text available via subscription   (Followers: 2)
Bioactive Materials     Open Access   (Followers: 1)
Biocatalysis and Agricultural Biotechnology     Hybrid Journal   (Followers: 4)
Biocybernetics and Biological Engineering     Full-text available via subscription   (Followers: 5)
Bioethics UPdate     Hybrid Journal  
Biofuels     Hybrid Journal   (Followers: 11)
Biofuels Engineering     Open Access   (Followers: 1)
Biological & Pharmaceutical Bulletin     Full-text available via subscription   (Followers: 4)
Biological Cybernetics     Hybrid Journal   (Followers: 10)
Biomarkers and Genomic Medicine     Open Access   (Followers: 3)
Biomarkers in Drug Development     Partially Free   (Followers: 1)
Biomaterials Research     Open Access   (Followers: 4)
BioMed Research International     Open Access   (Followers: 4)
Biomédica     Open Access  
Biomedical and Biotechnology Research Journal     Open Access  
Biomedical Engineering Research     Open Access   (Followers: 6)
Biomedical glasses     Open Access  
Biomedical Reports     Full-text available via subscription  
BioMedicine     Open Access  
Biomedika     Open Access  
Bioprinting     Hybrid Journal   (Followers: 1)
Bioresource Technology Reports     Hybrid Journal   (Followers: 1)
Bioscience, Biotechnology, and Biochemistry     Hybrid Journal   (Followers: 21)
Biosimilars     Open Access   (Followers: 1)
Biosurface and Biotribology     Open Access  
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
BioTechniques : The International Journal of Life Science Methods     Full-text available via subscription   (Followers: 28)
Biotechnologia Acta     Open Access   (Followers: 1)
Biotechnologie, Agronomie, Société et Environnement     Open Access   (Followers: 2)
Biotechnology     Open Access   (Followers: 5)
Biotechnology & Biotechnological Equipment     Open Access   (Followers: 4)
Biotechnology Advances     Hybrid Journal   (Followers: 33)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 155)
Biotechnology and Bioprocess Engineering     Hybrid Journal   (Followers: 5)
Biotechnology and Genetic Engineering Reviews     Hybrid Journal   (Followers: 13)
Biotechnology and Health Sciences     Open Access   (Followers: 1)
Biotechnology and Molecular Biology Reviews     Open Access   (Followers: 1)
Biotechnology Annual Review     Full-text available via subscription   (Followers: 5)
Biotechnology for Biofuels     Open Access   (Followers: 10)
Biotechnology Frontier     Open Access   (Followers: 2)
Biotechnology Journal     Hybrid Journal   (Followers: 16)
Biotechnology Law Report     Hybrid Journal   (Followers: 4)
Biotechnology Letters     Hybrid Journal   (Followers: 34)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Biotechnology Reports     Open Access  
Biotechnology Research International     Open Access   (Followers: 1)
Biotechnology Techniques     Hybrid Journal   (Followers: 10)
Biotecnología Aplicada     Open Access  
Bioteknologi (Biotechnological Studies)     Open Access  
Biotribology     Hybrid Journal   (Followers: 1)
BMC Biotechnology     Open Access   (Followers: 16)
Cell Biology and Development     Open Access  
Chinese Journal of Agricultural Biotechnology     Full-text available via subscription   (Followers: 4)
Communications in Mathematical Biology and Neuroscience     Open Access  
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computer Methods and Programs in Biomedicine     Hybrid Journal   (Followers: 8)
Contributions to Tobacco Research     Open Access   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biotechnology     Hybrid Journal   (Followers: 20)
Crop Breeding and Applied Biotechnology     Open Access   (Followers: 3)
Current Bionanotechnology     Hybrid Journal  
Current Biotechnology     Hybrid Journal   (Followers: 4)
Current Opinion in Biomedical Engineering     Hybrid Journal   (Followers: 1)
Current Opinion in Biotechnology     Hybrid Journal   (Followers: 56)
Current Pharmaceutical Biotechnology     Hybrid Journal   (Followers: 9)
Current Research in Bioinformatics     Open Access   (Followers: 12)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Current trends in Biotechnology and Pharmacy     Open Access   (Followers: 8)
EBioMedicine     Open Access  
Electronic Journal of Biotechnology     Open Access  
Entomologia Generalis     Full-text available via subscription  
Environmental Science : Processes & Impacts     Full-text available via subscription   (Followers: 4)
Experimental Biology and Medicine     Hybrid Journal   (Followers: 3)
Folia Medica Indonesiana     Open Access  
Food Bioscience     Hybrid Journal  
Food Biotechnology     Hybrid Journal   (Followers: 9)
Food Science and Biotechnology     Hybrid Journal   (Followers: 8)
Frontiers in Bioengineering and Biotechnology     Open Access   (Followers: 6)
Frontiers in Systems Biology     Open Access   (Followers: 2)
Fungal Biology and Biotechnology     Open Access   (Followers: 2)
GM Crops and Food: Biotechnology in Agriculture and the Food Chain     Full-text available via subscription   (Followers: 1)
GSTF Journal of BioSciences     Open Access  
HAYATI Journal of Biosciences     Open Access  
Horticulture, Environment, and Biotechnology     Hybrid Journal   (Followers: 11)
IEEE Transactions on Molecular, Biological and Multi-Scale Communications     Hybrid Journal   (Followers: 1)
IET Nanobiotechnology     Hybrid Journal   (Followers: 2)
IIOAB Letters     Open Access  
IN VIVO     Full-text available via subscription   (Followers: 4)
Indian Journal of Biotechnology (IJBT)     Open Access   (Followers: 2)
Indonesia Journal of Biomedical Science     Open Access   (Followers: 2)
Indonesian Journal of Biotechnology     Open Access   (Followers: 1)
Industrial Biotechnology     Hybrid Journal   (Followers: 18)
International Biomechanics     Open Access  
International Journal of Bioinformatics Research and Applications     Hybrid Journal   (Followers: 13)
International Journal of Biomechatronics and Biomedical Robotics     Hybrid Journal   (Followers: 4)
International Journal of Biomedical Research     Open Access   (Followers: 2)
International Journal of Biotechnology     Hybrid Journal   (Followers: 5)
International Journal of Biotechnology and Molecular Biology Research     Open Access   (Followers: 2)
International Journal of Biotechnology for Wellness Industries     Partially Free   (Followers: 1)
International Journal of Environment, Agriculture and Biotechnology     Open Access   (Followers: 5)
International Journal of Functional Informatics and Personalised Medicine     Hybrid Journal   (Followers: 4)
International Journal of Medicine and Biomedical Research     Open Access   (Followers: 1)
International Journal of Nanotechnology and Molecular Computation     Full-text available via subscription   (Followers: 3)
International Journal of Radiation Biology     Hybrid Journal   (Followers: 4)
Iranian Journal of Biotechnology     Open Access  
ISABB Journal of Biotechnology and Bioinformatics     Open Access  
Italian Journal of Food Science     Open Access   (Followers: 1)
Journal of Biometrics & Biostatistics     Open Access   (Followers: 3)
Journal of Bioterrorism & Biodefense     Open Access   (Followers: 6)
Journal of Petroleum & Environmental Biotechnology     Open Access   (Followers: 1)
Journal of Advanced Therapies and Medical Innovation Sciences     Open Access  
Journal of Advances in Biotechnology     Open Access   (Followers: 5)
Journal Of Agrobiotechnology     Open Access  
Journal of Analytical & Bioanalytical Techniques     Open Access   (Followers: 7)
Journal of Animal Science and Biotechnology     Open Access   (Followers: 4)
Journal of Applied Biomedicine     Open Access   (Followers: 2)
Journal of Applied Biotechnology     Open Access   (Followers: 2)
Journal of Applied Biotechnology Reports     Open Access   (Followers: 2)
Journal of Applied Mathematics & Bioinformatics     Open Access   (Followers: 5)
Journal of Biologically Active Products from Nature     Hybrid Journal   (Followers: 1)
Journal of Biomaterials and Nanobiotechnology     Open Access   (Followers: 6)
Journal of Biomedical Photonics & Engineering     Open Access  
Journal of Biomedical Practitioners     Open Access  
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Bioprocessing & Biotechniques     Open Access  
Journal of Biosecurity, Biosafety and Biodefense Law     Hybrid Journal   (Followers: 3)
Journal of Biotechnology     Hybrid Journal   (Followers: 68)
Journal of Biotechnology and Strategic Health Research     Open Access  
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 9)
Journal of Chitin and Chitosan Science     Full-text available via subscription  
Journal of Colloid Science and Biotechnology     Full-text available via subscription  
Journal of Commercial Biotechnology     Full-text available via subscription   (Followers: 6)
Journal of Crop Science and Biotechnology     Hybrid Journal   (Followers: 3)
Journal of Essential Oil Research     Hybrid Journal   (Followers: 2)
Journal of Experimental Biology     Full-text available via subscription   (Followers: 24)
Journal of Genetic Engineering and Biotechnology     Open Access   (Followers: 5)
Journal of Ginseng Research     Open Access  
Journal of Industrial Microbiology and Biotechnology     Hybrid Journal   (Followers: 16)
Journal of Integrative Bioinformatics     Open Access  
Journal of International Biotechnology Law     Hybrid Journal   (Followers: 3)
Journal of Medical Imaging and Health Informatics     Full-text available via subscription  
Journal of Molecular Biology and Biotechnology     Open Access  
Journal of Molecular Microbiology and Biotechnology     Full-text available via subscription   (Followers: 11)
Journal of Nano Education     Full-text available via subscription  
Journal of Nanobiotechnology     Open Access   (Followers: 4)
Journal of Nanofluids     Full-text available via subscription   (Followers: 1)
Journal of Organic and Biomolecular Simulations     Open Access  
Journal of Plant Biochemistry and Biotechnology     Hybrid Journal   (Followers: 4)
Journal of Science and Applications : Biomedicine     Open Access  
Journal of the Mechanical Behavior of Biomedical Materials     Hybrid Journal   (Followers: 11)
Journal of Trace Elements in Medicine and Biology     Hybrid Journal   (Followers: 1)
Journal of Tropical Microbiology and Biotechnology     Full-text available via subscription  
Journal of Yeast and Fungal Research     Open Access   (Followers: 1)
Marine Biotechnology     Hybrid Journal   (Followers: 4)
Messenger     Full-text available via subscription  
Metabolic Engineering Communications     Open Access   (Followers: 4)
Metalloproteinases In Medicine     Open Access  
Microalgae Biotechnology     Open Access   (Followers: 2)
Microbial Biotechnology     Open Access   (Followers: 9)
MicroMedicine     Open Access   (Followers: 3)
Molecular and Cellular Biomedical Sciences     Open Access  
Molecular Biotechnology     Hybrid Journal   (Followers: 13)
Molecular Genetics and Metabolism Reports     Open Access   (Followers: 3)
Nanobiomedicine     Open Access  
Nanobiotechnology     Hybrid Journal   (Followers: 2)
Nanomaterials and Nanotechnology     Open Access  
Nanomaterials and Tissue Regeneration     Open Access  
Nanomedicine and Nanobiology     Full-text available via subscription  
Nanomedicine Research Journal     Open Access  
Nanotechnology Reviews     Hybrid Journal   (Followers: 5)
Nature Biotechnology     Full-text available via subscription   (Followers: 535)

        1 2 | Last

Journal Cover Journal of Experimental Biology
  [SJR: 1.815]   [H-I: 135]   [24 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0022-0949 - ISSN (Online) 1477-9145
   Published by Company of Biologists, The Homepage  [5 journals]
  • Sensitive high-frequency hearing in earless and partially eared harlequin
           frogs (Atelopus) [RESEARCH ARTICLE]
    • Authors: Womack, M. C; Christensen-Dalsgaard, J, Coloma, L. A, Hoke, K. L.
      Abstract: Molly C. Womack, Jakob Christensen-Dalsgaard, Luis A. Coloma, and Kim L. Hoke

      Harlequin frogs, genus Atelopus, communicate at high frequencies despite most species lacking a complete tympanic middle ear that facilitates high-frequency hearing in most anurans and other tetrapods. Here, we tested whether Atelopus are better at sensing high-frequency acoustic sound compared with other eared and earless species in the Bufonidae family, determined whether middle ear variation within Atelopus affects hearing sensitivity and tested potential hearing mechanisms in Atelopus. We determined that at high frequencies (2000–4000 Hz), Atelopus are 10–34 dB more sensitive than other earless bufonids but are relatively insensitive to mid-range frequencies (900–1500 Hz) compared with eared bufonids. Hearing among Atelopus species is fairly consistent, evidence that the partial middle ears present in a subset of Atelopus species do not convey a substantial hearing advantage. We further demonstrate that Atelopus hearing is probably not facilitated by vibration of the skin overlying the normal tympanic membrane region or the body lung wall, leaving the extratympanic hearing pathways in Atelopus enigmatic. Together, these results show Atelopus have sensitive high-frequency hearing without the aid of a tympanic middle ear and prompt further study of extratympanic hearing mechanisms in anurans.
      PubDate: 2018-05-29T03:34:49-07:00
      DOI: 10.1242/jeb.169664
      Issue No: Vol. 221, No. 10 (2018)
       
  • Correction: Sex reversal induces size and performance differences among
           females of the African pygmy mouse, Mus minutoides (doi:
           10.1242/jeb.157552) [CORRECTION]
    • Authors: Ginot, S; Claude, J, Perez, J, Veyrunes, F.
      Abstract: Samuel Ginot, Julien Claude, Julie Perez, and Frederic Veyrunes


      PubDate: 2018-05-25T04:31:48-07:00
      DOI: 10.1242/jeb.183392
      Issue No: Vol. 221, No. 10 (2018)
       
  • Acid-base regulation in the air-breathing swamp eel (Monopterus albus) at
           different temperatures [RESEARCH ARTICLE]
    • Authors: Thinh, P. V; Phuong, N. T, Brauner, C. J, Huong, D. T. T, Wood, A. T, Kwan, G. T, Conner, J. L, Bayley, M, Wang, T.
      Abstract: Phan Vinh Thinh, Nguyen Thanh Phuong, Colin J. Brauner, Do Thi Thanh Huong, Andrew T. Wood, Garfield T. Kwan, Justin L. Conner, Mark Bayley, and Tobias Wang

      Vertebrates reduce arterial blood pH (pHa) when body temperature increases. In water breathers, this response occurs primarily by reducing plasma HCO3– levels with small changes in the partial pressure of CO2 (PCO2). In contrast, air breathers mediate the decrease in pHa by increasing arterial PCO2 (PaCO2) at constant plasma HCO3– by reducing lung ventilation relative to metabolic CO2 production. Much less is known about bimodal breathers, which utilize both water and air. Here, we characterized the influence of temperature on arterial acid–base balance and intracellular pH (pHi) in the bimodal-breathing swamp eel, Monopterus albus. This teleost uses the buccopharyngeal cavity for gas exchange and has very reduced gills. When exposed to ecologically relevant temperatures (20, 25, 30 and 35°C) for 24 and 48 h, pHa decreased by –0.025 pH units (U) °C–1 in association with an increase in PaCO2, but without changes in plasma [HCO3–]. pHi was also reduced with increased temperature. The slope of pHi of liver and muscle was –0.014 and –0.019 U °C–1, while the heart muscle showed a smaller reduction (–0.008 U °C–1). When exposed to hypercapnia (7 or 14 mmHg) at either 25 or 35°C, M. albus elevated plasma [HCO3–] and therefore seemed to defend the new pHa set-point, demonstrating an adjusted control of acid–base balance with temperature. Overall, the effects of temperature on acid–base balance in M. albus resemble those in air-breathing amniotes, and we discuss the possibility that this pattern of acid–base balance results from a progressive transition in CO2 excretion from water to air as temperature rises.
      PubDate: 2018-05-25T01:36:42-07:00
      DOI: 10.1242/jeb.172551
      Issue No: Vol. 221, No. 10 (2018)
       
  • Polarized object detection in crabs: a two-channel system [RESEARCH
           ARTICLE]
    • Authors: Basnak, M. A; Perez-Schuster, V, Hermitte, G, Beron de Astrada, M.
      Abstract: Melanie Ailin Basnak, Veronica Perez-Schuster, Gabriela Hermitte, and Martin Beron de Astrada

      Many animal species take advantage of polarization vision for vital tasks such as orientation, communication and contrast enhancement. Previous studies have suggested that decapod crustaceans use a two-channel polarization system for contrast enhancement. Here, we characterize the polarization contrast sensitivity in a grapsid crab. We estimated the polarization contrast sensitivity of the animals by quantifying both their escape response and changes in heart rate when presented with polarized motion stimuli. The motion stimulus consisted of an expanding disk with an 82 deg polarization difference between the object and the background. More than 90% of animals responded by freezing or trying to avoid the polarized stimulus. In addition, we co-rotated the electric vector (e-vector) orientation of the light from the object and background by increments of 30 deg and found that the animals' escape response varied periodically with a 90 deg period. Maximum escape responses were obtained for object and background e-vectors near the vertical and horizontal orientations. Changes in cardiac response showed parallel results but also a minimum response when e-vectors of object and background were shifted by 45 deg with respect to the maxima. These results are consistent with an orthogonal receptor arrangement for the detection of polarized light, in which two channels are aligned with the vertical and horizontal orientations. It has been hypothesized that animals with object-based polarization vision rely on a two-channel detection system analogous to that of color processing in dichromats. Our results, obtained by systematically varying the e-vectors of object and background, provide strong empirical support for this theoretical model of polarized object detection.
      PubDate: 2018-05-25T01:36:42-07:00
      DOI: 10.1242/jeb.173369
      Issue No: Vol. 221, No. 10 (2018)
       
  • Combined use of two supervised learning algorithms to model sea turtle
           behaviours from tri-axial acceleration data [RESEARCH ARTICLE]
    • Authors: Jeantet, L; Dell'Amico, F, Forin-Wiart, M.- A, Coutant, M, Bonola, M, Etienne, D, Gresser, J, Regis, S, Lecerf, N, Lefebvre, F, de Thoisy, B, Le Maho, Y, Brucker, M, Chatelain, N, Laesser, R, Crenner, F, Handrich, Y, Wilson, R, Chevallier, D.
      Abstract: L. Jeantet, F. Dell'Amico, M.-A. Forin-Wiart, M. Coutant, M. Bonola, D. Etienne, J. Gresser, S. Regis, N. Lecerf, F. Lefebvre, B. de Thoisy, Y. Le Maho, M. Brucker, N. Chatelain, R. Laesser, F. Crenner, Y. Handrich, R. Wilson, and D. Chevallier

      Accelerometers are becoming ever more important sensors in animal-attached technology, providing data that allow determination of body posture and movement and thereby helping to elucidate behaviour in animals that are difficult to observe. We sought to validate the identification of sea turtle behaviours from accelerometer signals by deploying tags on the carapace of a juvenile loggerhead (Caretta caretta), an adult hawksbill (Eretmochelys imbricata) and an adult green turtle (Chelonia mydas) at Aquarium La Rochelle, France. We recorded tri-axial acceleration at 50 Hz for each species for a full day while two fixed cameras recorded their behaviours. We identified behaviours from the acceleration data using two different supervised learning algorithms, Random Forest and Classification And Regression Tree (CART), treating the data from the adult animals as separate from the juvenile data. We achieved a global accuracy of 81.30% for the adult hawksbill and green turtle CART model and 71.63% for the juvenile loggerhead, identifying 10 and 12 different behaviours, respectively. Equivalent figures were 86.96% for the adult hawksbill and green turtle Random Forest model and 79.49% for the juvenile loggerhead, for the same behaviours. The use of Random Forest combined with CART algorithms allowed us to understand the decision rules implicated in behaviour discrimination, and thus remove or group together some ‘confused’ or under­-represented behaviours in order to get the most accurate models. This study is the first to validate accelerometer data to identify turtle behaviours and the approach can now be tested on other captive sea turtle species.
      PubDate: 2018-05-23T06:52:30-07:00
      DOI: 10.1242/jeb.177378
      Issue No: Vol. 221, No. 10 (2018)
       
  • Multiple spectral channels in branchiopods. I. Vision in dim light and
           neural correlates [RESEARCH ARTICLE]
    • Authors: Lessios, N; Rutowski, R. L, Cohen, J. H, Sayre, M. E, Strausfeld, N. J.
      Abstract: Nicolas Lessios, Ronald L. Rutowski, Jonathan H. Cohen, Marcel E. Sayre, and Nicholas J. Strausfeld

      Animals that have true color vision possess several spectral classes of photoreceptors. Pancrustaceans (Hexapoda+Crustacea) that integrate spectral information about their reconstructed visual world do so from photoreceptor terminals supplying their second optic neuropils, with subsequent participation of the third (lobula) and deeper centers (optic foci). Here, we describe experiments and correlative neural arrangements underlying convergent visual pathways in two species of branchiopod crustaceans that have to cope with a broad range of spectral ambience and illuminance in ephemeral pools, yet possess just two optic neuropils, the lamina and the optic tectum. Electroretinographic recordings and multimodel inference based on modeled spectral absorptance were used to identify the most likely number of spectral photoreceptor classes in their compound eyes. Recordings from the retina provide support for four color channels. Neuroanatomical observations resolve arrangements in their laminas that suggest signal summation at low light intensities, incorporating chromatic channels. Neuroanatomical observations demonstrate that spatial summation in the lamina of the two species are mediated by quite different mechanisms, both of which allow signals from several ommatidia to be pooled at single lamina monopolar cells. We propose that such summation provides sufficient signal for vision at intensities equivalent to those experienced by insects in terrestrial habitats under dim starlight. Our findings suggest that despite the absence of optic lobe neuropils necessary for spectral discrimination utilized by true color vision, four spectral photoreceptor classes have been maintained in Branchiopoda for vision at very low light intensities at variable ambient wavelengths that typify conditions in ephemeral freshwater habitats.
      PubDate: 2018-05-22T07:10:21-07:00
      DOI: 10.1242/jeb.165860
      Issue No: Vol. 221, No. 10 (2018)
       
  • Multiple spectral channels in branchiopods. II. Role in light-dependent
           behavior and natural light environments [RESEARCH ARTICLE]
    • Authors: Lessios, N; Rutowski, R. L, Cohen, J. H.
      Abstract: Nicolas Lessios, Ronald L. Rutowski, and Jonathan H. Cohen

      Light is a primary environmental factor used by aquatic invertebrates for depth selection behavior. Many branchiopod crustaceans live in ephemeral aquatic habitats. All branchiopod crustaceans studied to date express four or more visual opsins in their compound eyes. We asked whether two branchiopods, Triops longicaudatus and Streptocephalus mackini, use multiple spectral channels to regulate their position in the water column. At the lowest intensities that elicited photonegative behavior, both species had broad spectral bandwidths, suggesting they use multiple spectral photoreceptor classes. Male S. mackini were more likely to maintain a vertical position 8.0–12.0 cm below the surface than females, independently of whether females were present. Male photopositive behavior at low intensity was restricted to a narrow bandwidth centered at 532 nm, suggesting a single photoreceptor class is used to maintain position above females. We compared ephemeral pools from two regions in Arizona and found that diffuse light attenuation coefficients were two orders of magnitude greater than the most heavily attenuating coastal waters. At less than 1 m of depth, pools were often dimmer than terrestrial habitats under starlight. Soil particle size distribution in each region affected spectral light environments, and behavioral responses of field-caught shrimp were adapted to the spectral properties of their region. The results suggest that branchiopods predominantly use luminance vision summed from multiple spectral photoreceptor classes for depth selection in dim, spectrally variable environments. The neuroanatomical basis for summation is described in a companion paper.
      PubDate: 2018-05-22T07:10:21-07:00
      DOI: 10.1242/jeb.165878
      Issue No: Vol. 221, No. 10 (2018)
       
  • Passive water collection with the integument: mechanisms and their
           biomimetic potential [REVIEW]
    • Authors: Comanns P.
      Abstract: Philipp Comanns

      Several mechanisms of water acquisition have evolved in animals living in arid habitats to cope with limited water supply. They enable access to water sources such as rain, dew, thermally facilitated condensation on the skin, fog, or moisture from a damp substrate. This Review describes how a significant number of animals – in excess of 39 species from 24 genera – have acquired the ability to passively collect water with their integument. This ability results from chemical and structural properties of the integument, which, in each species, facilitate one or more of six basic mechanisms: increased surface wettability, increased spreading area, transport of water over relatively large distances, accumulation and storage of collected water, condensation, and utilization of gravity. Details are described for each basic mechanism. The potential for bio-inspired improvement of technical applications has been demonstrated in many cases, in particular for several wetting phenomena, fog collection and passive, directional transport of liquids. Also considered here are potential applications in the fields of water supply, lubrication, heat exchangers, microfluidics and hygiene products. These present opportunities for innovations, not only in product functionality, but also for fabrication processes, where resources and environmental impact can be reduced.
      PubDate: 2018-05-22T07:07:48-07:00
      DOI: 10.1242/jeb.153130
      Issue No: Vol. 221, No. 10 (2018)
       
  • Choosy hoverflies make swift exit to evade predator wasps [INSIDE JEB]
    • Authors: Knight K.
      Abstract: Kathryn Knight


      PubDate: 2018-05-22T05:19:57-07:00
      DOI: 10.1242/jeb.183004
      Issue No: Vol. 221, No. 10 (2018)
       
  • Gestational low-protein intake enhances whole-kidney miR-192 and miR-200
           family expression and epithelial-to-mesenchymal transition in rat adult
           male offspring [RESEARCH ARTICLE]
    • Authors: Sene, L. B; Rizzi, V. H. G, Gontijo, J. A. R, Boer, P. A.
      Abstract: Leticia B. Sene, Victor Hugo Goncalves Rizzi, Jose A. R. Gontijo, and Patricia A. Boer

      Studies have shown that adult offspring of mothers fed a protein-restricted diet during pregnancy present a pronounced reduction of nephron number associated with decreased fractional urinary sodium excretion and arterial hypertension. Additionally, recent advances in our understanding of the molecular pathways that govern the association of gestational nutritional restriction, intrauterine growth retardation and inflammation with impaired nephrogenesis, nephron underdosing and kidney fibrosis point to the epithelial to mesenchymal transition (EMT) as a common factor. In the current study, protein and sodium urinary excretion rates were evaluated in rats, and immunohistochemistry and western blot techniques were used to characterize kidney structure changes in 16 week old male offspring of mothers fed a low-protein diet during pregnancy (LP group) compared with age-matched (NP) controls. We also verified the expression of miRNA, mRNA and protein markers of fibrosis and the EMT in whole kidney prepared from LP offspring. We found, surprisingly, that arterial hypertension and long-term hyperfiltration, manifest by proteinuria, were associated with increased renal miR-192 and miR-200 family expression in 16 week old LP relative to age-matched NP rats. Measurement of kidney fibrosis and EMT-related protein markers, by histochemistry and immunoblot techniques, showed a significant rise of TGF-β1 and type-I collagen content in glomeruli and tubulointerstitial areas, accompanied by enhanced fibronectin and ZEB1 and decreased E-cadherin immunoreactivity in 16 week old LP offspring. The results were partially confirmed by increased gene (mRNA) expression of collagen 1α1, collagen 1α2 and ZEB1 in LP whole kidneys compared with those of age-matched NP offspring. In view of the presumed functional overload in the remaining nephrons, we suggest that hypertension and proteinuria development following maternal protein restriction may be a preponderant factor for EMT and structural kidney changes in LP offspring. However, our study was not wholly able to establish the precise role of miRNAs in LP kidney disorders. Thus, further studies will be required to assess the contribution of the miR family to renal injury in a gestational protein-restricted model of fetal programming.
      PubDate: 2018-05-22T05:19:56-07:00
      DOI: 10.1242/jeb.171694
      Issue No: Vol. 221, No. 10 (2018)
       
  • Visual approach computation in feeding hoverflies [RESEARCH ARTICLE]
    • Authors: Thyselius, M; Gonzalez-Bellido, P. T, Wardill, T. J, Nordström, K.
      Abstract: Malin Thyselius, Paloma T. Gonzalez-Bellido, Trevor J. Wardill, and Karin Nordström

      On warm sunny days, female hoverflies are often observed feeding from a wide range of wild and cultivated flowers. In doing so, hoverflies serve a vital role as alternative pollinators, and are suggested to be the most important pollinators after bees and bumblebees. Unless the flower hoverflies are feeding from is large, they do not readily share the space with other insects, but instead opt to leave if another insect approaches. We used high-speed videography followed by 3D reconstruction of flight trajectories to quantify how female Eristalis hoverflies respond to approaching bees, wasps and two different hoverfly species. We found that, in 94% of the interactions, the occupant female left the flower when approached by another insect. We found that compared with spontaneous take-offs, the occupant hoverfly's escape response was performed at ~3 times higher speed (spontaneous take-off at 0.2±0.05 m s–1 compared with 0.55±0.08 m s–1 when approached by another Eristalis). The hoverflies tended to take off upward and forward, while taking the incomer's approach angle into account. Intriguingly, we found that, when approached by wasps, the occupant Eristalis took off at a higher speed and when the wasp was further away. This suggests that feeding hoverflies may be able to distinguish these predators, demanding impressive visual capabilities. Our results, including quantification of the visual information available before occupant take-off, provide important insight into how freely behaving hoverflies perform escape responses from competitors and predators (e.g. wasps) in the wild.
      PubDate: 2018-05-22T05:19:56-07:00
      DOI: 10.1242/jeb.177162
      Issue No: Vol. 221, No. 10 (2018)
       
  • Scaling of avian bipedal locomotion reveals independent effects of body
           mass and leg posture on gait [REVIEW]
    • Authors: Daley, M. A; Birn-Jeffery, A.
      Abstract: Monica A. Daley and Aleksandra Birn-Jeffery

      Birds provide an interesting opportunity to study the relationships between body size, limb morphology and bipedal locomotor function. Birds are ecologically diverse and span a large range of body size and limb proportions, yet all use their hindlimbs for bipedal terrestrial locomotion, for at least some part of their life history. Here, we review the scaling of avian striding bipedal gaits to explore how body mass and leg morphology influence walking and running. We collate literature data from 21 species, spanning a 2500x range in body mass from painted quail to ostriches. Using dynamic similarity theory to interpret scaling trends, we find evidence for independent effects of body mass, leg length and leg posture on gait. We find no evidence for scaling of duty factor with body size, suggesting that vertical forces scale with dynamic similarity. However, at dynamically similar speeds, large birds use relatively shorter stride lengths and higher stride frequencies compared with small birds. We also find that birds with long legs for their mass, such as the white stork and red-legged seriema, use longer strides and lower swing frequencies, consistent with the influence of high limb inertia on gait. We discuss the observed scaling of avian bipedal gait in relation to mechanical demands for force, work and power relative to muscle actuator capacity, muscle activation costs related to leg cycling frequency, and considerations of stability and agility. Many opportunities remain for future work to investigate how morphology influences gait dynamics among birds specialized for different habitats and locomotor behaviors.
      Keywords: Comparative biomechanics of movement
      PubDate: 2018-05-22T02:33:08-07:00
      DOI: 10.1242/jeb.152538
      Issue No: Vol. 221, No. 10 (2018)
       
  • Kinematics of burrowing by peristalsis in granular sands [RESEARCH
           ARTICLE]
    • Authors: Dorgan K. M.
      Abstract: Kelly M. Dorgan

      Peristaltic burrowing in muds applies normal forces to burrow walls, which extend by fracture, but the kinematics and mechanics of peristaltic burrowing in sands has not been explored. The opheliid polychaete Thoracophelia mucronata uses direct peristalsis to burrow in beach sands, with kinematics consistent with the ‘dual anchor system’ of burrowing described for diverse organisms. In addition to expansions associated with a constrictive direct peristaltic wave, worms alternately expand the head region, which is separated by septa from the open body cavity, and expansible lateral ridges that protrude from the 10th setiger. Tracking of chaetae with fluorescent dye showed that the body wall advances while segments are thin, then stationary segments expand, applying normal forces to burrow walls. These normal forces likely compact burrow walls and serve as anchors. Perhaps more importantly, peristaltic movements minimize friction with the burrow wall, which would expand dilatant sands. Considerable slipping of worms burrowing in a lower-density sand analog suggests that this dual-anchor peristaltic burrowing may be limited to a narrow range of mechanical properties of substrata, consistent with the limited habitat of T. mucronata in a narrow swash zone on dissipative beaches.
      Keywords: Comparative biomechanics of movement
      PubDate: 2018-05-22T02:33:08-07:00
      DOI: 10.1242/jeb.167759
      Issue No: Vol. 221, No. 10 (2018)
       
  • Reduced non-bicarbonate skeletal muscle buffering capacity in mice with
           the mini-muscle phenotype [SHORT COMMUNICATION]
    • Authors: Kay, J. C; Ramirez, J, Contreras, E, Garland, T.
      Abstract: Jarren C. Kay, Jocelyn Ramirez, Erick Contreras, and Theodore Garland Jr

      Muscle pH decreases during exercise, which may impair function. Endurance training typically reduces muscle buffering capacity as a result of changes in fiber-type composition, but existing comparisons of species that vary in activity level are ambiguous. We hypothesized that high-runner (HR) lines of mice from an experiment that breeds mice for voluntary wheel running would have altered muscle buffering capacity as compared with their non-selected control counterparts. We also expected that 6 days of wheel access, as used in the selection protocol, would reduce buffering capacity, especially for HR mice. Finally, we expected a subset of HR mice with the ‘mini-muscle’ phenotype to have relatively low buffering capacity as a result of fewer type IIb fibers. We tested non-bicarbonate buffering capacity of thigh muscles. Only HR mice expressing the mini-muscle phenotype had significantly reduced buffering capacity, females had lower buffering capacity than males, and wheel access had no significant effect.
      PubDate: 2018-05-22T02:33:08-07:00
      DOI: 10.1242/jeb.172478
      Issue No: Vol. 221, No. 10 (2018)
       
  • Thermosensory perception regulates speed of movement in response to
           temperature changes in Drosophila melanogaster [RESEARCH ARTICLE]
    • Authors: Soto-Padilla, A; Ruijsink, R, Sibon, O. C. M, van Rijn, H, Billeter, J.-C.
      Abstract: Andrea Soto-Padilla, Rick Ruijsink, Ody C. M. Sibon, Hedderik van Rijn, and Jean-Christophe Billeter

      Temperature influences the physiology and behavior of all organisms. For ectotherms, which lack central temperature regulation, temperature adaptation requires sheltering from or moving to a heat source. As temperature constrains the rate of metabolic reactions, it can directly affect ectotherm physiology and thus behavioral performance. This direct effect is particularly relevant for insects, as their small bodies readily equilibrate with ambient temperature. In fact, models of enzyme kinetics applied to insect behavior predict performance at different temperatures suggesting that thermal physiology governs behavior. However, insects also possess thermosensory neurons critical for locating preferred temperatures, showing cognitive control. This suggests that temperature-related behavior can emerge directly from a physiological effect, indirectly as a consequence of thermosensory processing, or through a combination of both. To separate the roles of thermal physiology and cognitive control, we developed an arena that allows fast temperature changes in time and space, and in which animals' movements are automatically quantified. We exposed wild-type Drosophila melanogaster and thermosensory receptor mutants to a dynamic temperature environment and tracked their movements. The locomotor speed of wild-type flies closely matched models of enzyme kinetics, but the behavior of thermosensory mutants did not. Mutations in thermosensory receptor gene dTrpA1 (Transient Receptor Potential A1) expressed in the brain resulted in a complete lack of response to temperature changes, while mutations in peripheral thermosensory receptor gene Gr28b(D) resulted in a diminished response. We conclude that flies react to temperature through cognitive control, informed by interactions between various thermosensory neurons, the behavioral output of which resembles models of enzyme kinetics.
      PubDate: 2018-05-22T02:33:08-07:00
      DOI: 10.1242/jeb.174151
      Issue No: Vol. 221, No. 10 (2018)
       
  • Cues for cavity nesters: investigating relevant zeitgebers for emerging
           leafcutting bees, Megachile rotundata [RESEARCH ARTICLE]
    • Authors: Bennett, M. M; Rinehart, J. P, Yocum, G. D, Doetkott, C, Greenlee, K. J.
      Abstract: Meghan M. Bennett, Joseph P. Rinehart, George D. Yocum, Curt Doetkott, and Kendra J. Greenlee

      Photoperiod is considered the universal zeitgeber, regulating physiological processes in numerous animals. However, for animals in light-restricted habitats (e.g. burrows or cavities), thermoperiod may be a more important cue. Our study tested this hypothesis in the alfalfa leafcutting bee, Megachile rotundata, which nests in cavities and undergoes development within a brood cell. We assessed the role of environmental cues (thermoperiod and photoperiod) on the process of adult emergence by examining: (1) whether those cues direct circadian rhythms, (2) which cue is more dominant and (3) how sensitive developing bees and emergence-ready adults are to cues. Although we found that 20% of light penetrates the brood cell, and bees respond to photoperiod by synchronizing emergence, thermoperiod is the dominant cue. When presented with a conflicting zeitgeber, bees entrained to the thermophase instead of the photophase. When temperature cues were removed, we observed free-running of emergence, indicating that underlying circadian mechanisms can be synchronized by daily fluctuations in temperature. We also found that emerging bees were highly sensitive to even small increases in temperature, entraining to a ramp speed of 0.33°C h–1. The response and sensitivity to temperature cues suggest that M. rotundata evolved a temperature-mediated clock to time emergence from light-restricted cavities.
      PubDate: 2018-05-22T02:33:08-07:00
      DOI: 10.1242/jeb.175406
      Issue No: Vol. 221, No. 10 (2018)
       
  • The effect of rearing environment on memory formation [RESEARCH ARTICLE]
    • Authors: Rothwell, C. M; Spencer, G. E, Lukowiak, K.
      Abstract: Cailin M. Rothwell, Gaynor E. Spencer, and Ken Lukowiak

      Lymnaea stagnalis is a well-studied model system for determining how changes in the environment influence associative learning and memory formation. For example, some wild strains of L. stagnalis, collected from separate geographic locations, show superior memory-forming abilities compared with others. Here, we studied memory formation in two laboratory-bred L. stagnalis strains, derived from the same original population in The Netherlands. The two strains were reared in two different laboratories at the University of Calgary (C-strain) and at Brock University (B-strain) for many years and we found that they differed in their memory-forming ability. Specifically, the C-strain required only two training sessions to form long-term memory (LTM) whereas the B-strain required four sessions to form LTM. Additionally, the LTM formed by the B-strain persisted for a shorter amount of time than the memory formed by the C-strain. Thus, despite being derived from the same original population, the C- and B-strains have developed different memory-forming abilities. Next, we raised the two strains from embryos away from home (i.e. in the other laboratory) over two generations and assessed their memory-forming abilities. The B-strain reared and maintained at the University of Calgary demonstrated improved memory-forming ability within a single generation, while the C-strain reared at Brock University retained their normal LTM-forming ability across two subsequent generations. This suggests that local environmental factors may contribute to the behavioural divergence observed between these two laboratory-bred strains.
      PubDate: 2018-05-22T02:33:08-07:00
      DOI: 10.1242/jeb.180521
      Issue No: Vol. 221, No. 10 (2018)
       
  • Brains, not biochemistry, speed up hot flies [INSIDE JEB]
    • Authors: Knight K.
      Abstract: Kathryn Knight


      PubDate: 2018-05-22T02:33:08-07:00
      DOI: 10.1242/jeb.183020
      Issue No: Vol. 221, No. 10 (2018)
       
  • Of what use is connectomics' A personal perspective on the Drosophila
           connectome [COMMENTARY]
    • Authors: Meinertzhagen I. A.
      Abstract: Ian A. Meinertzhagen

      The brain is a network of neurons and its biological output is behaviour. This is an exciting age, with a growing acknowledgement that the comprehensive compilation of synaptic circuits densely reconstructed in the brains of model species is now both technologically feasible and a scientifically enabling possibility in neurobiology, much as 30 years ago genomics was in molecular biology and genetics. Implemented by huge advances in electron microscope technology, especially focused ion beam-scanning electron microscope (FIB-SEM) milling (see Glossary), image capture and alignment, and computer-aided reconstruction of neuron morphologies, enormous progress has been made in the last decade in the detailed knowledge of the actual synaptic circuits formed by real neurons, in various brain regions of the fly Drosophila. It is useful to distinguish synaptic pathways that are major, with 100 or more presynaptic contacts, from those that are minor, with fewer than about 10; most neurites are both presynaptic and postsynaptic, and all synaptic sites have multiple postsynaptic dendrites. Work on Drosophila has spearheaded these advances because cell numbers are manageable, and neuron classes are morphologically discrete and genetically identifiable, many confirmed by reporters. Recent advances are destined within the next few years to reveal the complete connectome in an adult fly, paralleling advances in the larval brain that offer the same prospect possibly within an even shorter time frame. The final amendment and validation of segmented bodies by human proof-readers remains the most time-consuming step, however. The value of a complete connectome in Drosophila is that, by targeting to specific neurons transgenes that either silence or activate morphologically identified circuits, and then identifying the resulting behavioural outcome, we can determine the causal mechanism for behaviour from its loss or gain. More importantly, the connectome reveals hitherto unsuspected pathways, leading us to seek novel behaviours for these. Circuit information will eventually be required to understand how differences between brains underlie differences in behaviour, and especially to herald yet more advanced connectomic strategies for the vertebrate brain, with an eventual prospect of understanding cognitive disorders having a connectomic basis. Connectomes also help us to identify common synaptic circuits in different species and thus to reveal an evolutionary progression in candidate pathways.
      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.164954
      Issue No: Vol. 221, No. 10 (2018)
       
  • Nest predation risk modifies nestlings immune function depending on the
           level of threat [RESEARCH ARTICLE]
    • Authors: Roncalli, G; Colombo, E, Soler, M, Tieleman, B. I, Versteegh, M. A, Ruiz-Raya, F, Gomez Samblas, M, Ibanez-Alamo, J. D.
      Abstract: Gianluca Roncalli, Elisa Colombo, Manuel Soler, B. Irene Tieleman, Maaike A. Versteegh, Fran Ruiz-Raya, Mercedes Gomez Samblas, and Juan Diego Ibanez-Alamo

      Predation risk is thought to modify the physiology of prey mainly through the stress response. However, little is known about its potential effects on the immunity of animals, particularly in young individuals, despite the importance of overcoming wounding and pathogen aggression following a predator attack. We investigated the effect of four progressive levels of nest predation risk on several components of the immune system in common blackbird (Turdus merula) nestlings by presenting them with four different calls during 1 h: non-predator calls, predator calls, parental alarm calls and conspecific distress calls to induce a null, moderate, high and extreme level of risk, respectively. Nest predation risk induced an increase in ovotransferrin, immunoglobulin and the number of lymphocytes and eosinophils. Thus, the perception of a potential predator per se could stimulate the mobilization of a nestling's immune function and enable the organism to rapidly respond to the immune stimuli imposed by a predator attack. Interestingly, only high and extreme levels of risk caused immunological changes, suggesting that different immunological parameters are modulated according to the perceived level of threat. We also found a mediator role of parasites (i.e. Leucocytozoon) and the current health status of the individual, as only nestlings not parasitized or in good body condition were able to modify their immune system. This study highlights a previously unknown link between predation risk and immunity, emphasizing the complex relationship among different selective pressures (predation, parasitism) in developing organisms and accentuating the importance of studying predation from a physiological point of view.
      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.170662
      Issue No: Vol. 221, No. 10 (2018)
       
  • Biochemical bases of growth variation during development: a study of
           protein turnover in pedigreed families of bivalve larvae (Crassostrea
           gigas) [RESEARCH ARTICLE]
    • Authors: Pan, T.- C. F; Applebaum, S. L, Frieder, C. A, Manahan, D. T.
      Abstract: T.-C. Francis Pan, Scott L. Applebaum, Christina A. Frieder, and Donal T. Manahan

      Animal size is a highly variable trait regulated by complex interactions between biological and environmental processes. Despite the importance of understanding the mechanistic bases of growth, predicting size variation in early stages of development remains challenging. Pedigreed lines of the Pacific oyster (Crassostrea gigas) were crossed to produce contrasting growth phenotypes to analyze the metabolic bases of growth variation in larval stages. Under controlled environmental conditions, substantial growth variation of up to 430% in shell length occurred among 12 larval families. Protein was the major biochemical constituent in larvae, with an average protein-to-lipid content ratio of 2.8. On average, 86% of protein synthesized was turned over (i.e. only 14% retained as protein accreted), with a regulatory shift in depositional efficiency resulting in increased protein accretion during later larval growth. Variation in protein depositional efficiency among families did not explain the range in larval growth rates. Instead, changes in protein synthesis rates predicted 72% of growth variation. High rates of protein synthesis to support faster growth, in turn, necessitated greater allocation of the total ATP pool to protein synthesis. An ATP allocation model is presented for larvae of C. gigas that includes the major components (82%) of energy demand: protein synthesis (45%), ion pump activity (20%), shell formation (14%) and protein degradation (3%). The metabolic trade-offs between faster growth and the need for higher ATP allocation to protein synthesis could be a major determinant of fitness for larvae of different genotypes responding to the stress of environmental change.
      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.171967
      Issue No: Vol. 221, No. 10 (2018)
       
  • Expression of calcium channel transcripts in the zebrafish heart:
           dominance of T-type channels [RESEARCH ARTICLE]
    • Authors: Haverinen, J; Hassinen, M, Dash, S. N, Vornanen, M.
      Abstract: Jaakko Haverinen, Minna Hassinen, Surjya Narayan Dash, and Matti Vornanen

      Calcium channels are necessary for cardiac excitation–contraction (E–C) coupling, but Ca2+ channel composition of fish hearts is still largely unknown. To this end, we determined transcript expression of Ca2+ channels in the heart of zebrafish (Danio rerio), a popular model species. Altogether, 18 Ca2+ channel α-subunit genes were expressed in both atrium and ventricle. Transcripts for 7 L-type (Cav1.1a, Cav1.1b, Cav1.2, Cav1.3a, Cav1.3b, Cav1.4a, Cav1.4b), 5 T-type (Cav3.1, Cav3.2a, Cav3.2b, Cav3.3a, Cav3.3b) and 6 P/Q-, N- and R-type (Cav2.1a, Cav2.1b, Cav2.2a, Cav2.2b, Cav2.3a, Cav2.3b) Ca2+ channels were expressed. In the ventricle, T-type channels formed 54.9%, L-type channels 41.1% and P/Q-, N- and R-type channels 4.0% of the Ca2+ channel transcripts. In the atrium, the relative expression of T-type and L-type Ca2+ channel transcripts was 64.1% and 33.8%, respectively (others accounted for 2.1%). Thus, at the transcript level, T-type Ca2+ channels are prevalent in zebrafish atrium and ventricle. At the functional level, peak densities of ventricular T-type (ICaT) and L-type (ICaL) Ca2+ current were 6.3±0.8 and 7.7±0.8 pA pF–1, respectively. ICaT mediated a sizeable sarcolemmal Ca2+ influx into ventricular myocytes: the increment in total cellular Ca2+ content via ICaT was 41.2±7.3 µmol l–1, which was 31.7% of the combined Ca2+ influx (129 µmol l–1) via ICaT and ICaL (88.5±20.5 µmol l–1). The diversity of expressed Ca2+ channel genes in zebrafish heart is high, but dominated by the members of the T-type subfamily. The large ventricular ICaT is likely to play a significant role in E–C coupling.
      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.179226
      Issue No: Vol. 221, No. 10 (2018)
       
  • IGF-1 induces SOCS-2 but not SOCS-1 and SOCS-3 transcription in juvenile
           Nile tilapia (Oreochromis niloticus) [SHORT COMMUNICATION]
    • Authors: Liu, C.-Z; Luo, Y, Limbu, S. M, Chen, L.-Q, Du, Z.-Y.
      Abstract: Cai-Zhi Liu, Yuan Luo, Samwel Mchele Limbu, Li-Qiao Chen, and Zhen-Yu Du

      Insulin-like growth factor-1 (IGF-1) plays a crucial role in regulating growth in vertebrates whereas suppressors of cytokine signaling (SOCS) act as feedback inhibitors of the GH/IGF-1 axis. Although SOCS-2 binds the IGF-1 receptor and inhibits IGF-1-induced STAT3 activation, presently there is no clear evidence as to whether IGF-1 could induce SOCS gene expression. The current study aimed to determine whether IGF-1 could induce the transcription of SOCS in juvenile Nile tilapia (Oreochromis niloticus). We show that there is a common positive relationship between the mRNA expression of IGF-I and SOCS-2 under different nutritional statuses and stimulants, but not the mRNA expression of SOCS-1 and SOCS-3. Furthermore, rhIGF-1 treatment and transcriptional activity assay confirmed the hypothesis that IGF-1 could induce SOCS-2 expression, whereas it had no effect or even decreased the expression of SOCS-1 and SOCS-3. Overall, we obtained evidence that the transcription of SOCS-2, but not SOCS-1 or SOCS-3, could be induced by IGF signaling, suggesting that SOCS-2 serves as a feedback suppressor of the IGF-1 axis in juvenile Nile tilapia.
      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.179291
      Issue No: Vol. 221, No. 10 (2018)
       
  • Protein synthesis marks out fastest growing oyster larvae [INSIDE JEB]
    • Authors: Knight K.
      Abstract: Kathryn Knight


      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.181867
      Issue No: Vol. 221, No. 10 (2018)
       
  • Harassed nestlings boost immune system when danger is at hand [INSIDE JEB]
    • Authors: Knight K.
      Abstract: Kathryn Knight


      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.183012
      Issue No: Vol. 221, No. 10 (2018)
       
  • Correction: Take-off mechanisms in parasitoid wasps (doi:
           10.1242/jeb.161463) [CORRECTION]
    • Authors: Burrows, M; Dorosenko, M.
      Abstract: M. Burrows and M. Dorosenko


      PubDate: 2018-05-20T23:53:51-07:00
      DOI: 10.1242/jeb.184697
      Issue No: Vol. 221, No. 10 (2018)
       
  • Behavioral and physiological adaptations to high-flow velocities in chubs
           (Gila spp.) native to Southwestern USA [RESEARCH ARTICLE]
    • Authors: Moran, C. J; Gerry, S. P, O'Neill, M. W, Rzucidlo, C. L, Gibb, A. C.
      Abstract: Clinton J. Moran, Shannon P. Gerry, Matthew W. O'Neill, Caroline L. Rzucidlo, and Alice C. Gibb

      Morphological streamlining is often associated with physiological advantages for steady swimming in fishes. Though most commonly studied in pelagic fishes, streamlining also occurs in fishes that occupy high-flow environments. Before the installation of dams and water diversions, bonytail (Cyprinidae, Gila elegans), a fish endemic to the Colorado River (USA), regularly experienced massive, seasonal flooding events. Individuals of G. elegans display morphological characteristics that may facilitate swimming in high-flow conditions, including a narrow caudal peduncle and a high aspect ratio caudal fin. We tested the hypothesis that these features improve sustained swimming performance in bonytail by comparing locomotor performance in G. elegans with that of the closely related roundtail chub (Gila robusta) and two non-native species, rainbow trout (Oncorhynchus mykiss) and smallmouth bass (Micropterus dolomieu), using a Brett-style respirometer and locomotor step-tests. Gila elegans had the lowest estimated drag coefficient and the highest sustained swimming speeds relative to the other three species. There were no detectible differences in locomotor energetics during steady swimming among the four species. When challenged by high-velocity water flows, the second native species examined in this study, G. robusta, exploited the boundary effects in the flow tank by pitching forward and bracing the pelvic and pectoral fins against the acrylic tank bottom to ‘hold station’. Because G. robusta can station hold to prevent being swept downstream during high flows and G. elegans can maintain swimming speeds greater than those of smallmouth bass and rainbow trout with comparable metabolic costs, we suggest that management agencies could use artificial flooding events to wash non-native competitors downstream and out of the Colorado River habitat.
      PubDate: 2018-05-18T07:30:56-07:00
      DOI: 10.1242/jeb.158972
      Issue No: Vol. 221, No. 10 (2018)
       
  • Update and extension of the 'Equivalent Slope of speed changing level
           locomotion in humans: a computational model for shuttle running [RESEARCH
           ARTICLE]
    • Authors: Minetti, A. E; Pavei, G.
      Abstract: Alberto E. Minetti and Gaspare Pavei

      Controlled experimental protocols for metabolic cost assessment of speed changing locomotion are quite complex to be designed and managed. The use of the ‘equivalent slope’, i.e. the gradient locomotion at constant speed metabolically equivalent to a level progression in acceleration, proved to be useful to estimate the metabolic cost of speed changing gaits. However, its use with steep slopes forces to extrapolate the experimental cost vs. gradient function for constant running speed, resulting in less reliable estimates. The present study extended the model to work also with deceleration, and revised that predictive equation to be applied to much higher levels of speed change. The case of shuttle running at different distances (from 5+5 to 20+20m) was then investigated throughout the novel approach and software, and the predictions in terms of metabolic cost and efficiency well compare to the experimental data.
      PubDate: 2018-06-12T03:17:56-07:00
      DOI: 10.1242/jeb.182303
       
  • Comparative feeding strategies and kinematics in phocid seals: suction
           without specialized skull morphology [RESEARCH ARTICLE]
    • Authors: Kienle, S. S; Hermann-Sorensen, H, Costa, D. P, Reichmuth, C, Mehta, R. S.
      Abstract: Sarah S. Kienle, Holly Hermann-Sorensen, Daniel P. Costa, Colleen Reichmuth, and Rita S. Mehta

      Feeding kinematic studies inform our understanding of behavioral diversity and provide a framework for studying the flexibility and constraints of different prey acquisition strategies. However, little is known about the feeding behaviors used by many marine mammals. We characterized the feeding behaviors and associated kinematics of captive bearded (Erignathus barbatus), harbor (Phoca vitulina), ringed (Pusa hispida), and spotted (Phoca largha) seals through controlled feeding trials. All species primarily used a suction feeding strategy but were also observed using a biting strategy, specifically pierce feeding. Suction feeding was distinct from pierce feeding and was characterized by significantly faster feeding times, smaller gape and gape angles, smaller gular depressions, and fewer jaw motions. Most species showed higher variability in suction feeding performance than pierce feeding, indicating that suction feeding is a behaviorally flexible strategy. Bearded seals were the only species for which there was strong correspondence between skull and dental morphology and feeding strategy, providing further support for their classification as suction feeding specialists. Harbor, ringed, and spotted seals have been classified as pierce feeders based on skull and dental morphologies. Our behavioral and kinematic analyses show that suction feeding is also an important feeding strategy for these species, indicating that skull morphology alone does not capture the true diversity of feeding behaviors used by pinnipeds. The ability of all four species to use more than one feeding strategy is likely advantageous for foraging in spatially and temporally dynamic marine ecosystems that favor opportunistic predators.
      PubDate: 2018-06-12T03:17:56-07:00
      DOI: 10.1242/jeb.179424
       
  • Cardiac plasticity influences aerobic performance and thermal tolerance in
           a tropical, freshwater fish at elevated temperatures [RESEARCH ARTICLE]
    • Authors: Nyboer, E. A; Chapman, L. J.
      Abstract: Elizabeth A. Nyboer and Lauren J. Chapman

      Fishes faced with novel thermal conditions often modify physiological functioning to compensate for elevated temperatures. This physiological plasticity (thermal acclimation) has been shown to improve metabolic performance and extend thermal limits in many species. Adjustments in cardiorespiratory function are often invoked as mechanisms underlying thermal plasticity because limitations in oxygen supply have been predicted to define thermal optima in fishes, however few studies have explicitly linked cardiorespiratory plasticity to metabolic compensation. Here we quantify thermal acclimation capacity in the commercially harvested Nile perch (Lates niloticus) of East Africa, and investigate mechanisms underlying observed changes. We reared juvenile Nile perch for 3 months under two temperature regimes, and then measured a series of metabolic traits (e.g., aerobic scope, AS) and critical thermal maximum (CTmax) upon acute exposure to a range of experimental temperatures. We also measured morphological traits of heart ventricles, gills, and brains to identify potential mechanisms for compensation. We found that long-term (3-months) exposure to elevated temperature induced compensation in upper thermal tolerance (CTmax) and metabolic performance (SMR, MMR and AS), and induced cardiac remodeling in Nile perch. Furthermore, variation in heart morphology influenced variations in metabolic function and thermal tolerance. These results indicate that plastic changes enacted over longer exposures lead to differences in metabolic flexibility when acutely exposed to temperature variation. Furthermore, we established functional links between cardiac plasticity, metabolic performance, and thermal tolerance, providing evidence that plasticity in cardiac capacity may be one mechanism for coping with climate change.
      PubDate: 2018-06-12T03:17:56-07:00
      DOI: 10.1242/jeb.178087
       
  • Repeated freezing induces a trade-off between cryoprotection and egg
           production in the goldenrod gall fly, Eurosta solidaginis [RESEARCH
           ARTICLE]
    • Authors: Marshall, K. E; Sinclair, B. J.
      Abstract: Katie E. Marshall and Brent J. Sinclair

      Internal ice formation leads to wholesale changes in ionic, osmotic and pH homeostasis, energy metabolism, and mechanical damage, across a small range of temperatures, and is thus an abiotic stressor that acts at a distinct, physiologically-relevant, threshold. Insects that experience repeated freeze-thaw cycles over winter will cross this stressor threshold many times over their lifespan. Here we examine the effect of repeatedly crossing the freezing threshold on short-term physiological parameters (metabolic reserves and cryoprotectant concentration) as well as long-term fitness-related performance (survival and egg production) in the freeze-tolerant goldenrod gall fly Eurosta solidaginis. We exposed overwintering prepupae to a series of low temperatures (-10, -15, or -20 °C) with increasing numbers of freezing events (3, 6, or 10) with differing recovery periods between events (1, 5, or 10 days). Repeated freezing increased sorbitol concentration by about 50% relative to a single freezing episode, and prompted prepupae to modify long chain triacylglycerols to acetylated triacylglycerols. Long-term, repeated freezing did not significantly reduce survival, but did reduce egg production by 9.8% relative to a single freezing event. Exposure temperature did not affect any of these measures, suggesting that threshold crossing events may be more important to fitness than the intensity of stress in E. solidaginis overwintering.
      PubDate: 2018-06-12T03:17:56-07:00
      DOI: 10.1242/jeb.177956
       
  • Cardiac mitochondrial metabolism may contribute to differences in thermal
           tolerance of red- and white-blooded Antarctic notothenioid fishes
           [RESEARCH ARTICLE]
    • Authors: O'Brien, K. M; Rix, A. S, Egginton, S, Farrell, A. P, Crockett, E. L, Schlauch, K, Woolsey, R, Hoffman, M, Merriman, S.
      Abstract: Kristin M. O'Brien, Anna S. Rix, Stuart Egginton, Anthony P. Farrell, Elizabeth L. Crockett, Karen Schlauch, Rebekah Woolsey, Megan Hoffman, and Sean Merriman

      Studies in temperate fishes provide evidence that cardiac mitochondrial function and the capacity to fuel cardiac work contributes to thermal tolerance. Here we tested the hypothesis that decreased cardiac aerobic metabolic capacity contributes to the lower thermal tolerance of the haemoglobinless Antarctic icefish, Chaenocephalus aceratus, compared to the red-blooded Antarctic species, Notothenia coriiceps. Maximal activities of citrate synthase (CS) and lactate dehydrogenase (LDH), respiration rates of isolated mitochondria, adenylate levels, and changes in mitochondrial protein expression were quantified from hearts of animals held at ambient temperature or exposed to their critical thermal maximum (CTMAX). Compared to C. aceratus, activity of CS, ATP concentration, and energy charge were higher in hearts of N. coriiceps at ambient temperature and CTMAX. While state 3 mitochondrial respiration rates were not impaired by exposure to CTMAX in either species, state 4 rates, indicative of proton leakage, increased following exposure to CTMAX in C. aceratus but not N. coriiceps. The interactive effect of temperature and species resulted in an increase in antioxidants and aerobic metabolic enzymes in N. coriiceps, but not C. aceratus. Together, our results support the hypothesis that the lower aerobic metabolic capacity of C. aceratus hearts contributes to its low thermal tolerance.
      PubDate: 2018-06-12T03:17:56-07:00
      DOI: 10.1242/jeb.177816
       
  • Short- and long-term effects of altered point of ground reaction force
           application on human running energetics [RESEARCH ARTICLE]
    • Authors: Ekizos, A; Santuz, A, Arampatzis, A.
      Abstract: Antonis Ekizos, Alessandro Santuz, and Adamantios Arampatzis

      The current study investigates an acute and a gradual transition of the point of force application (PFA) from the rearfoot towards the fore of the foot during running, on the rate of metabolic energy consumption. The participants were randomly assigned in two experimental and one control groups: a short-term intervention group (STI, N=17; two training sessions), a long-term intervention group (LTI, N=10; 14-week gradual transition) and a control group (CG, N=11). Data were collected at two running velocities (2.5 and 3.0 m/s). The cost coefficient (i.e. energy required for a unit of vertical ground reaction force, J/N) decreased (p
      PubDate: 2018-06-12T03:17:56-07:00
      DOI: 10.1242/jeb.176719
       
  • Skin glands of an aquatic salamander vary in size and distribution and
           release antimicrobial secretions effective against chytrid fungal
           pathogens [RESEARCH ARTICLE]
    • Authors: Pereira, K. E; Crother, B. I, Sever, D. M, Fontenot, C. L, Pojman, J. A, Wilburn, D. B, Woodley, S. K.
      Abstract: Kenzie E. Pereira, Brian I. Crother, David M. Sever, Clifford L. Fontenot Jr., John A. Pojman Sr., Damien B. Wilburn, and Sarah K. Woodley

      Amphibian skin is unique among vertebrate classes, containing a large number of multicellular exocrine glands that vary among species and have diverse functions. The secretions of skin glands contain a rich array of bioactive compounds including antimicrobial peptides (AMPs). Such compounds are important for amphibian innate immune responses and may protect some species from chytridiomycosis, a lethal skin disease caused by the fungal pathogens, Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal). While the bioactivity of skin secretions against Bd has been assessed for many amphibian taxa, similar studies are lacking for Bsal, a chytrid fungus that is especially pathogenic for salamanders. We studied the skin glands and their potential functions in the aquatic salamander, Three-toed Amphiuma (Amphiuma tridactylum). Skin secretions of captive adult salamanders were analyzed by RP-HPLC and tested against the growth of Bd and Bsal using in-vitro assays. We found that compounds within collected skin secretions were similar between male and female salamanders and inhibited the growth of Bd and Bsal. Thus, skin secretions that protect against Bd may also provide protection against Bsal. Histological examination of the skin glands of preserved salamanders revealed the presence of enlarged granular glands concentrated within caudal body regions. A site of potential gland specialization was identified at the tail base and may indicate specialized granular glands related to courtship and communication.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.183707
       
  • Volitional control of social vocalisations and vocal usage learning in
           bats [RESEARCH ARTICLE]
    • Authors: Lattenkamp, E. Z; Vernes, S. C, Wiegrebe, L.
      Abstract: Ella Z. Lattenkamp, Sonja C. Vernes, and Lutz Wiegrebe

      Bats are gregarious, highly vocal animals that possess a broad repertoire of social vocalisations. For in-depth studies of their vocal behaviours, including vocal flexibility and vocal learning, it is necessary to gather repeatable evidence from controlled laboratory experiments on isolated individuals. However, such studies are rare for one simple reason: eliciting social calls in isolation and under operant control is challenging and has rarely been achieved. To overcome this limitation, we designed an automated setup that allows conditioning of social vocalisations in a new context, and tracks spectro-temporal changes in the recorded calls over time. Using this setup, we were able to reliably evoke social calls from temporarily isolated lesser spear-nosed bats (Phyllostomus discolor). When we adjusted the call criteria that could result in food reward, bats responded by adjusting temporal and spectral call parameters. This was achieved without the help of an auditory template or social context to direct the bats. Our results demonstrate vocal flexibility and vocal usage learning in bats. Our setup provides a new paradigm that allows the controlled study of the production and learning of social vocalisations in isolated bats, overcoming limitations that have, until now, prevented in-depth studies of these behaviours.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.180729
       
  • Innate turning preference of leaf-cutting ants in the absence of external
           orientation cues [RESEARCH ARTICLE]
    • Authors: Endlein, T; Sitti, M.
      Abstract: Thomas Endlein and Metin Sitti

      Many ants use a combination of cues for orientation but how do ants find their way when all external cues are suppressed' Do they walk in a random way or are their movements spatially oriented' Here we show for the first time that leaf-cutting ants (Acromyrmex lundii) have an innate preference of turning counter-clockwise (left) when external cues are precluded. We demonstrated this by allowing individual ants to run freely on the water surface of a newly-developed treadmill. The surface tension supported medium-sized workers but effectively prevented ants from reaching the wall of the vessel, important to avoid wall-following behaviour (thigmotaxis). Most ants ran for minutes on the spot but also slowly turned counter-clockwise in the absence of visual cues. Reconstructing the effectively walked path revealed a looping pattern which could be interpreted as a search strategy. A similar turning bias was shown for groups of ants in a symmetrical Y-maze where twice as many ants chose the left branch in the absence of optical cues. Wall-following behaviour was tested by inserting a coiled tube before the Y-fork. When ants traversed a left-coiled tube, more ants chose the left box and vice versa. Adding visual cues in form of vertical black strips either outside the treadmill or on one branch of the Y-maze led to oriented walks towards the strips. It is suggested that both, the turning bias and the wall-following are employed as search strategies for an unknown environment which can be overridden by visual cues.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.177006
       
  • The essential oil of Lippia alba and its components affect Drosophila
           behavior and synaptic physiology [RESEARCH ARTICLE]
    • Authors: da Silva, L. V. F; Veras Mourao, R. H, Manimala, J, Lnenicka, G. A.
      Abstract: Lenise Vargas Flores da Silva, Rosa Helena Veras Mourao, Jibin Manimala, and Gregory A. Lnenicka

      Lippia alba is a flowering shrub in the verbena family and its essential oil (EO) is known for its sedative, antidepressant and analgesic properties. In the Amazon region of Brazil, it is used in aquaculture to anesthetize fish during transport. Many of the specialized metabolites found in EOs presumably evolved to protect plants from herbivores, especially insects. We used Drosophila to test the behavioral and physiological actions of this EO and its components. We found that 150 min exposure to the EO vapors resulted in immobilization of adult flies. Gas chromatography-mass spectrometry identified the major components of the EO as the monoterpenes: citral (59%), carvone (7%) and limonene (7%). Fly immobilization by the EO was due to citral and carvone with citral producing more rapid effects than carvone. We tested whether the EO affected synaptic physiology by applying it to the larval neuromuscular junction. The EO delivered at 0.012% (v/v) produced over a 50% reduction in EPSP amplitude within 3-4 min. When the EO components were applied at 0.4 mM, citral and carvone produced a significant reduction in EPSP amplitude with citral producing the largest effect. Measurement of miniature EPSP amplitudes demonstrated that citral produced over a 50% reduction in transmitter release. Ca-imaging experiments showed that citral produced about 30% reduction in presynaptic Ca influx, which likely resulted in the decrease in transmitter release. Thus, the EO blocks synaptic transmission, largely due to citral, and this likely contributes to its behavioral effects.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.176909
       
  • Short-duration respirometry underestimates metabolic rate for
           discontinuous breathers [METHODS [amp ] TECHNIQUES]
    • Authors: Winwood-Smith, H. S; White, C. R.
      Abstract: Hugh S. Winwood-Smith and Craig R. White

      Metabolic rate is commonly estimated from rates of gas exchange. An underappreciated factor that can influence estimates is patterns of pulmonary respiration. Amphibians display discontinuous respiratory patterns, often including long apnoeas, in addition to cutaneous gas exchange. The contribution of cutaneous exchange increases at low temperatures when metabolic rate is low. Due to the relatively low permeability of skin, measurements that disproportionately capture cutaneous exchange can produce underestimates of metabolic rate. The permeability of amphibian skin to CO2 is greater than O2, therefore calculating the ratio of whole-animal CO2 emission to O2 uptake (the respiratory exchange ratio, RER) can be used to avoid underestimates of metabolic rate by ensuring that observed values of RER fall within the normal physiological range (~0.7 to 1). Using data for cane toads Rhinella marina we show that short-duration measurements lead to underestimates of metabolic rate and overestimates of RER. At low temperatures this problem is exacerbated, requiring over 12 hours for RER to fall within the normal physiological range. Many published values of metabolic rate in animals that utilise cutaneous exchange may be underestimates.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.175752
       
  • Shifts in space and time: ecological transitions affect the evolution of
           resting metabolic rates in microteiid lizards [RESEARCH ARTICLE]
    • Authors: Bars-Closel, M; Camacho, A, Kohlsdorf, T.
      Abstract: Melissa Bars-Closel, Agustin Camacho, and Tiana Kohlsdorf

      Ecological diversification often encompasses exposure to new thermal regimes given by the use of specific spatial (microhabitat) and temporal (activity periods) niches. Empirical evidence provides links between temperature and physiology (e.g. rates of oxygen consumption), fostering predictions of evolutionary changes in metabolic rates coupled with ecological shifts. One example of such correspondence is the evolution of fossoriality and nocturnality in vertebrate ectotherms, where changes in metabolic rates coupled with niche transitions are expected. Because most studies address single transitions (fossoriality or nocturnality), metabolic changes associated with concomitant shifts in spatial and temporal components of habitat usage are underestimated, and it remains unclear which transition plays a major role for metabolic evolution. Integrating multiple ecological aspects that affect the evolution of thermosensitive traits is essential for a proper understanding of physiological correlates in niche transitions. Here we provide the first phylogenetic multidimensional description of effects from ecological niche transitions both in space (origin of fossorial lineages) and time (origin of nocturnal lineages) on the evolution of lizard metabolic rates (Gymnophthalmidae). We found that evolution of resting metabolic rates was affected by both niche transitions, but with opposite trends. Evolution of fossoriality in endemic diurnal microteiids is coupled with a less thermally-sensitive metabolism and higher metabolic rates. In contrast, a reduction in metabolic rates was detected in the endemic fossorial-nocturnal lineage, although metabolic thermal sensitivity remained as high as that observed in epigeal species, a pattern that likely reduces locomotion costs at lower temperatures and also favors thermoregulation in subsuperficial sand layers.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.175661
       
  • Digestive and locomotor capacity show opposing responses to changing food
           availability in an ambush predatory fish [RESEARCH ARTICLE]
    • Authors: Fu, S.-J; Peng, J, Killen, S. S.
      Abstract: Shi-Jian Fu, Jing Peng, and Shaun S. Killen

      Metabolic rates vary widely within species, but little is known about how variation in the "floor" (i.e. standard metabolic rate in ectotherms; SMR) and "ceiling" (maximum metabolic rate; MMR) for an individual's aerobic scope (AS) are linked with the digestive and locomotor function. Any links among metabolic traits and aspects of physiological performance may also be modulated by fluctuations in food availability. This study followed changes in SMR, MMR, and digestive and locomotor capacity in Southern catfish (Silurus meridionalis) throughout 15 days of food deprivation and 15 days of refeeding. Individuals down-regulated SMR during food deprivation and showed only a 10% body mass decrease during this time. While critical swim speed (Ucrit), was robust to food-deprivation, digestive function decreased after fasting with a reduced peak oxygen uptake during specific dynamic action (SDA) and prolonged SDA duration. During refeeding, individuals displayed rapid growth and digestive function recovered to pre-fasting levels. However, refed fish showed a lower Ucrit than would be expected for their increased body length and in comparison to measures at the start of the study. Reduced swimming ability may be a consequence of compensatory growth: growth rate was negatively correlated with changes in Ucrit during refeeding. Southern catfish down-regulate digestive function to reduce energy expenditure during food deprivation, but regain digestive capacity during refeeding, potentially at the cost of decreased swimming performance. The plasticity of maintenance requirements suggests that SMR is a key fitness trait for in this ambush predator. Shifts in trait correlations with food availability suggest that the potential for correlated selection may depend on context.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.173187
       
  • Quantifying syringeal dynamics in vitro using electroglottography
           [RESEARCH ARTICLE]
    • Authors: Rasmussen, J. H; Herbst, C. T, Elemans, C. P. H.
      Abstract: Jeppe H. Rasmussen, Christian T. Herbst, and Coen P. H. Elemans

      The complex and elaborate vocalizations uttered by many of the 10,000 extant bird species are considered a major driver in their evolutionary success, warranting study of the underlying mechanisms of vocal production. Additionally, birdsong has developed into a highly productive model system for vocal imitation learning and motor control, where, in contrast to humans, we have experimental access to the entire neuromechanical control loop. In human voice production, complex laryngeal geometry, vocal fold tissue properties, airflow and laryngeal musculature all interact to ultimately control vocal fold kinematics. Quantifying vocal fold kinematics is thus critical to understanding neuromechanical control of voiced sound production, but in vivo imaging of vocal fold kinematics in birds is experimentally challenging. Here we adapted and tested electroglottography (EGG) as a novel tool for examining vocal fold kinematics in the avian vocal organ, the syrinx. We furthermore imaged and quantified syringeal kinematics in the pigeon (Columba livia) syrinx with unprecedented detail. Our results show that EGG signals predict 1) the relative amount of contact between the avian equivalent of vocal folds and 2) essential parameters describing vibratory kinematics, such as fundamental frequency, and timing of syringeal opening and closing events. As such EGG provides novel opportunities for measuring syringeal vibratory kinematic parameters in vivo. Furthermore, the opportunity for imaging syringeal vibratory kinematics from multiple planar views (horizontal and coronal) simultaneously promotes birds as an excellent model system for studying kinematics and control of voiced sound production in general, including humans and other mammals.
      PubDate: 2018-06-07T05:38:28-07:00
      DOI: 10.1242/jeb.172247
       
  • Rapid embryonic accretion of docosahexaenoic acid (DHA) in the brain of an
           altricial bird with an aquatic-based maternal diet [SHORT COMMUNICATION]
    • Authors: Price, E. R; Sirsat, S. K. G, Sirsat, T. S, Venables, B. J, Dzialowski, E. M.
      Abstract: Edwin R. Price, Sarah K. G. Sirsat, Tushar S. Sirsat, Barney J. Venables, and Edward M. Dzialowski

      Docosahexaenoic acid (DHA) is an important and abundant fatty acid moiety in vertebrate brains. We measured brain phospholipid composition during development in red-winged blackbirds (Agelaius phoeniceus), an altricial species that breeds in aquatic habitats. We also manipulated diet by feeding nestlings fish oil or sunflower oil. Finally, we assessed selective uptake of yolk by comparing the yolk fatty acid composition of freshly laid eggs and day-old hatchlings. Relative to other altricial species, blackbirds achieved high DHA in brain phospholipids (20% of phospholipid fatty acids in day-old hatchlings). This was not a result of selective uptake from the yolk, but rather a consequence of a high proportion of DHA in the yolk (2.5% of total lipids) at laying. Our dietary study confirmed that nestling brains are sensitive to fatty acid supply. Red-winged blackbirds may be able to advance cognitive development relative to other altricial species due to their aquatic maternal diet.
      PubDate: 2018-05-31T08:21:14-07:00
      DOI: 10.1242/jeb.183533
       
  • Haltere removal alters responses to gravity in standing flies [SHORT
           COMMUNICATION]
    • Authors: Daltorio, K; Fox, J.
      Abstract: Kathryn Daltorio and Jessica Fox

      Animals detect the force of gravity with multiple sensory organs, from subcutaneous receptors at body joints to specialized sensors like the vertebrate inner ear. The halteres of flies, specialized mechanoreceptive organs derived from hindwings, are known to detect body rotations during flight, and some groups of flies also oscillate their halteres while walking. The dynamics of halteres are such that they could act as gravity detectors for flies standing on substrates, but their utility during non-flight behaviors is not known. We observed the behaviors of intact and haltere-ablated flies during walking and during perturbations in which the acceleration due to gravity suddenly changed. We found that intact halteres are necessary for flies to maintain normal walking speeds on vertical surfaces and to respond to sudden changes in gravity. Our results suggest that halteres can serve multiple sensory purposes during different behaviors, expanding their role beyond their canonical use in flight.
      PubDate: 2018-05-31T08:21:14-07:00
      DOI: 10.1242/jeb.181719
       
  • Woodpecker drumming behavior is linked to the elevated expression of genes
           that encode calcium handling proteins in the neck musculature [SHORT
           COMMUNICATION]
    • Authors: Schuppe, E. R; Petersen, J. O, Fuxjager, M. J.
      Abstract: Eric R. Schuppe, John O. Petersen, and Matthew J. Fuxjager

      Many animals perform elaborate physical displays for social communication. Identifying molecular mechanisms that co-evolve with these complex behavioral signals can therefore help reveal how forces of selection shape animal design. To study this issue, we examine gene expression profiles in select skeletal muscles that actuate woodpecker drum displays. This remarkable whole-body signal is produced when individuals rapidly hammer their bill against trees. We find that, compared to muscles that play no part in producing this behavior, the main muscle used to drum abundantly expresses two genes that encode proteins that support myocytic calcium (Ca2+) handling dynamics—namely parvalbumin (PV) and sarcoplasmic reticulum Ca2+ ATPase (SERCA1). Meanwhile, we find no such difference in the expression of another gene similarly vital to Ca2+ handling, the ryanodine receptor (RYR1). These differences are not present in a non-woodpecker species, which readily produce much slower drum-like movements for foraging (but not social signaling). Our data therefore point to an association between the fast drum displays of woodpeckers and muscle-specific expression of genes whose protein products enhance select aspects of myocytic Ca2+ handling.
      PubDate: 2018-05-31T08:21:14-07:00
      DOI: 10.1242/jeb.180190
       
  • Almost like a whale - First evidence of suction-feeding in a seabird
           [SHORT COMMUNICATION]
    • Authors: Enstipp, M. R; Descamps, S, Fort, J, Gremillet, D.
      Abstract: Manfred R. Enstipp, Sebastien Descamps, Jerome Fort, and David Gremillet

      Little auks (Alle alle) are one of the most numerous seabird species in the world that feed primarily on copepods in arctic waters. Their high daily energy requirements leave them vulnerable to current changes in the arctic plankton community, where a smaller, less profitable copepod species (Calanus finmarchicus) becomes increasingly abundant. Little auks have been estimated to require ~60,000 copepods per day, necessitating prey capture rates of ~6 copepods per second underwater. To achieve such performance, it has been suggested that little auks capture their prey by (non-visual) filter-feeding. We tested this hypothesis by exposing little auks to varying copepod densities within a shallow experimental pool and filming their prey capture behaviour. At none of the copepod densities tested did birds filter-feed. Instead, all birds captured copepods by what we identified as visually guided suction-feeding, achieved through an extension of their sub-lingual pouch. Suction-feeding is very common in fish and marine mammals, but to the best of our knowledge, this is the first time that it has been specifically identified in a seabird species. While presumably less efficient than filter-feeding, this behaviour may allow little auks to foster higher resilience when facing the consequences of arctic climate change.
      PubDate: 2018-05-29T02:15:05-07:00
      DOI: 10.1242/jeb.182170
       
  • Low thermal dependence of the contractile properties of a wing muscle in
           the bat Carollia perspicillata [RESEARCH ARTICLE]
    • Authors: Rummel, A. D; Swartz, S. M, Marsh, R. L.
      Abstract: Andrea D. Rummel, Sharon M. Swartz, and Richard L. Marsh

      Temperature affects contractile rate properties in muscle, which may affect locomotor performance. Endotherms are known to maintain high core body temperatures, but temperatures in the periphery of the body can fluctuate. Such a phenomenon occurs in bats, whose wing musculature is relatively poorly insulated, resulting in substantially depressed temperatures in the distal wing. We examined a wing muscle in the small-bodied tropical bat Carollia perspicillata and a hindlimb muscle in the laboratory mouse at 5°C intervals from 22 to 42°C to determine the thermal dependence of the contractile properties of both muscles. We found that the bat ECRL had low thermal dependence from near body temperature to 10°C lower, with Q10 values of less than 1.5 for relaxation from contraction and shortening velocities in that interval, and with no significant difference in some rate properties in the interval between 32 and 37°C. In contrast, for all temperature intervals below 37°C, Q10 values for the mouse EDL were 1.5 or higher, and rate properties differed significantly across successive temperature intervals from 37 to 22°C. An ANCOVA analysis found that the thermal dependencies of all measured isometric and isotonic rate processes were significantly different between the bat and mouse muscles. The relatively low thermal dependence of the bat muscle likely represents a downward shift of its optimal temperature and may be functionally significant in light of the variable operating temperatures of bat wing muscles.
      PubDate: 2018-05-29T02:15:05-07:00
      DOI: 10.1242/jeb.180166
       
  • Seminal fluid enhances competitiveness of territorial males sperm in a
           fish with alternative male reproductive tactics [RESEARCH ARTICLE]
    • Authors: Poli, F; Locatello, L, Rasotto, M. B.
      Abstract: Federica Poli, Lisa Locatello, and Maria B. Rasotto

      The most common adaptation to sperm competition in males is represented by an increase in the sperm number and/or quality released at mating, to raise their probability of egg fertilization. However, rapidly mounting evidence highlights that seminal fluid may directly influence the competitive fertilization success of a male by affecting either own and/or rival sperm performances. In the black goby, Gobius niger, an external fertilizer with guard-sneaker mating tactics and high sperm competition level, sneaker males’ ejaculates contain less seminal fluid and more sperm, that are also of better quality, than those of territorial males. However, territorial males, gain a higher paternity success inside natural nests. Here, we ask whether the seminal fluid can contribute to territorial males’ reproductive success by enhancing their sperm performances and/or by decreasing those of sneaker males. Using sperm and seminal fluid manipulation and in vitro fertilization tests, we found that own seminal fluid influences the velocity and fertilization ability of sperm only in territorial males, making them as faster as those of sneakers and with similar fertilization rate. Moreover, both sneaker and territorial males’ sperm remain unaffected by the seminal fluid of rival males. Thus, black goby males respond to the different level of sperm competition faced by differently allocating in sperm and non-sperm components of the ejaculate, with sneakers primarily investing in sperm of intrinsic high quality and territorial males relying on the effect of seminal fluid to increase the lower intrinsic quality of their sperm.
      PubDate: 2018-05-29T02:15:05-07:00
      DOI: 10.1242/jeb.175976
       
  • Transverse anisotropy in the deformation of the muscle during dynamic
           contractions [RESEARCH ARTICLE]
    • Authors: Randhawa, A; Wakeling, J. M.
      Abstract: Avleen Randhawa and James M. Wakeling

      When pennate muscle fibres shorten, the transverse deformation of fibres results in an increase in pennation angle of fascicles (bundles of fibres) and transverse deformation of muscle belly. Transverse shape changes of a muscle can influence force generation. Recent modelling studies predicted asymmetrical transverse deformations in the muscle fascicles in the gastrocnemii. However, these predictions have not been tested experimentally. Since muscle is a 3D entity it is important to explore the structural changes in a 3D perspective to enhance our understanding of the underlying structural mechanisms that have functional implications.The medial and lateral gastrocnemius muscles from 12 subjects were imaged during plantarflexion movements on a dynamometer. The muscle belly was simultaneously scanned from two orthogonal directions using two ultrasound probes. Fascicle deformations were measured from the two orthogonal ultrasound scans to provide 3D information of muscle geometry.Whilst transverse deformations in the medial gastrocnemius were similar from the two directions, the data for the lateral gastrocnemius confirm that transverse anisotropy can occur in the muscle fascicles. As the lateral gastrocnemius fascicle length shortened, the pennation angle increased and the fascicles bulged transversally in one direction (closest to the typical 2D scanning plane) while thinning in other orthogonal direction. It is suggested that the transverse deformation of the muscle fascicles depends on the stiffness of the aponeuroses, properties of connective tissue structures surrounding muscle, and compressive forces both internal and external to the muscle. These results highlight that muscle fascicles do not bulge uniformly and the implications for this behavior on muscle function remain largely unexplored.
      PubDate: 2018-05-29T02:15:05-07:00
      DOI: 10.1242/jeb.175794
       
  • Can physiological engineering/programming increase multi-generational
           thermal tolerance to extreme temperature events' [RESEARCH ARTICLE]
    • Authors: Sorby, K. L; Green, M. P, Dempster, T. D, Jessop, T. S.
      Abstract: Kris L. Sorby, Mark P. Green, Tim D. Dempster, and Tim S. Jessop

      Organisms increasingly encounter higher frequencies of extreme weather events as a consequence of global climate change. Currently, few strategies are available to mitigate climate change effects on animals arising from acute extreme high temperature events. We tested the capacity of physiological engineering to influence the intra- and multi-generational upper thermal tolerance capacity of a model organism Artemia, subjected to extreme high temperatures. Enhancement of specific physiological regulators during development could affect thermal tolerances or life-history attributes affecting subsequent fitness. Using experimental Artemia populations we exposed F0 individuals to one of four treatments; heat hardening (28°C to 36°C, 1°C per 10 minutes), heat hardening plus serotonin (0.056 µg ml–1), heat hardening plus methionine (0.79 mg ml–1), and a control treatment. Regulator concentrations were based on previous literature. Serotonin may promote thermotolerance, acting upon metabolism and life-history. Methionine acts as a methylation agent across generations. For all groups, measurements were collected for three performance traits of individual thermal tolerance (upper sublethal thermal limit, lethal limit, and dysregulation range) over two generations. Results showed no treatment increased upper thermal limit during acute thermal stress, although serotonin-treated and methionine-treated individuals outperformed controls across multiple thermal performance traits. Additionally, some effects were evident across generations. Together these results suggest phenotypic engineering provides complex outcomes; and if implemented with heat hardening can further influence performance in multiple thermal tolerance traits, within and across generations. Potentially, such techniques could be up-scaled to provide resilience and stability in populations susceptible to extreme temperature events.
      PubDate: 2018-05-29T02:15:05-07:00
      DOI: 10.1242/jeb.174672
       
  • Foraging strategy of wasps - optimisation of intake rate or
           efficiency' [RESEARCH ARTICLE]
    • Authors: Kovac, H; Stabentheiner, A, Brodschneider, R.
      Abstract: Helmut Kovac, Anton Stabentheiner, and Robert Brodschneider

      In endothermic wasps, foraging is an expensive activity. To maximise the benefit for the colony, wasps can optimise either the intake rate or energetic efficiency of a foraging trip. We investigated the foraging behaviour of Vespine wasps under variable environmental and reward conditions. We trained them to forage for 0.5 molar sucrose solution from an artificial flower in a flow-through respiratory measurement chamber, and simultaneously measured their body temperature using infrared thermography to investigate interactions between thermoregulation and energetics. Measurement of carbon dioxide release (for energetic calculations) and load weight enabled the direct determination of foraging efficiency. An unlimited reward increased the wasps’ energetic effort to increase the suction speed through high body temperatures. With reduced reward (limited flow), when an increased body temperature could not increase suction speed, the wasps decreased their body temperature to reduce the metabolic effort. Solar heat gain was used differently, either to increase body temperature without additional metabolic effort or to save energy. The foraging efficiency was mainly determined by the flow rate, ambient temperature and solar heat gain. In shade, an unlimited sucrose flow and a high ambient temperature yielded the highest energetic benefit. A limited flow reduced foraging efficiency in the shade, but only partly in sunshine. Solar radiation boosted the efficiency at all reward rates. Wasps responded flexibly to varying reward conditions by maximising intake rate at unlimited flow and switching to the optimisation of foraging efficiency when the intake rate could not be enhanced due to a limited flow rate.
      PubDate: 2018-05-29T02:15:05-07:00
      DOI: 10.1242/jeb.174169
       
  • Biomechanical factors influencing successful self-righting in the
           pleurodire turtle, Emydura subglobosa [SHORT COMMUNICATION]
    • Authors: Rubin, A. M; Blob, R. W, Mayerl, C. J.
      Abstract: Alex M. Rubin, Richard W. Blob, and Christopher J. Mayerl

      Self-righting performance is a key ability for most terrestrial animals, and has been used as a metric of fitness, exhaustion, and thermal limits in a variety of taxa. However, there is little understanding of the underlying mechanisms that drive variation in self-righting performance. To evaluate the mechanical factors that contribute to success versus failure when animals attempt to self-right, we compared force production and kinematic behavior in the rigid-bodied, pleurodire turtle Emydura subglobosa between successful and unsuccessful self-righting efforts. We found that the moment exerted during efforts to roll the body and the velocity of that roll are the primary drivers behind self-righting success. Specifically, turtles that self-righted successfully produced both larger moments and faster rolls than turtles that failed. In contrast, the angle at which the head was directed to lever the body and the extent of yaw that was incorporated in addition to roll had little impact on the likelihood of success. These results show that specific performance metrics can predict the ability of animals to self-right, providing a framework for biomimetic applications as well future comparisons to test for differences in self-righting performance across animals from different environments, sexes, populations, and species.
      PubDate: 2018-05-24T04:24:14-07:00
      DOI: 10.1242/jeb.182642
       
  • Rapid depth perception in hunting archerfish II. An analysis of potential
           cues [RESEARCH ARTICLE]
    • Authors: Reinel, C. P; Schuster, S.
      Abstract: Caroline P. Reinel and Stefan Schuster

      Based on the initial movement of falling prey hunting archerfish select a C-start that turns them right to where their prey is going to land and lends the speed to arrive simultaneously with prey. Our preceding study suggested that the information sampled in less than 100 ms also includes the initial height of falling prey. Here we examine which cues the fish might be using to gauge height so quickly. First, we show that binocular cues are not required: C-starts that either could or could not have used binocular information were equally fast and precise. Next, we explored whether the fish were using simplifying assumptions about the absolute size of their prey or its distance from a structured background. However, experiments with unexpected changes from the standard conditions failed to cause any errors. We then tested the hypothesis that the fish might infer depth from accommodation or from cues related to blurring in the image of their falling prey. However, the fish determined also the height of 'fake-flies' correctly, whose image could never be focused and whose combined size and degree of blurring should have mislead the fish. Our findings are not compatible with the view that the fish uses a flexible combination of cues. They also do not support the view that height is gauged relative to structures in the vicinity of starting prey. We suggest that the fish use an elaborate analysis of looming to rapidly gauge initial height.
      PubDate: 2018-05-24T04:24:14-07:00
      DOI: 10.1242/jeb.177352
       
  • Can honey bees discriminate between floral-fragrance isomers'
           [RESEARCH ARTICLE]
    • Authors: Aguiar, J. M. R. B. V; Roselino, A. C, Sazima, M, Giurfa, M.
      Abstract: Joao Marcelo Robazzi Bignelli Valente Aguiar, Ana Carolina Roselino, Marlies Sazima, and Martin Giurfa

      Many flowering plants present variable complex fragrances, which usually include different isomers of the same molecule. As fragrance is an essential cue for flower recognition by pollinators, we ask if honey bees discriminate between floral-fragrance isomers in an appetitive context. We used the olfactory conditioning of the proboscis extension response (PER), which allows training a restrained bee to an odor paired with sucrose solution. Bees were trained under an absolute (a single odorant rewarded) or a differential conditioning regime (a rewarded vs. a non-rewarded odorant) using four different pairs of isomers. One hour after training, discrimination and generalization between pairs of isomers were tested. Bees trained under absolute conditioning exhibited high generalization between isomers and discriminated only one out of four isomer pairs; after differential conditioning, they learned to differentiate between two out of four pairs of isomers but in all cases generalization responses to the non-rewarding isomer remained high. Adding an aversive taste to the non-rewarded isomer facilitated discrimination of isomers that otherwise seemed non-discriminable, but generalization remained high. Although honey bees discriminated isomers under certain conditions, they achieved the task with difficulty and tended to generalize between them, thus showing that these molecules were perceptually similar to them. We conclude that the presence of isomers within floral fragrances might not necessarily contribute to a dramatic extent to floral odor diversity.
      PubDate: 2018-05-24T04:24:13-07:00
      DOI: 10.1242/jeb.180844
       
  • In vivo aerobic metabolism of the rainbow trout gut and the effects of an
           acute temperature increase and stress event [SHORT COMMUNICATION]
    • Authors: Brijs, J; Gräns, A, Hjelmstedt, P, Sandblom, E, van Nuland, N, Berg, C, Axelsson, M.
      Abstract: Jeroen Brijs, Albin Gräns, Per Hjelmstedt, Erik Sandblom, Nicole van Nuland, Charlotte Berg, and Michael Axelsson

      The fish gut is responsible for numerous potentially energetically costly processes, yet, little is known about its metabolism. Here, we provide the first in vivo measurements for aerobic metabolism of the gut in a teleost fish by measuring gut blood flow, as well as arterial and portal venous oxygen content. At 10°C, gut oxygen uptake rates were 4.3±0.5 ml O2 h–1 kg–1 (~11% of whole animal oxygen uptake). Following acute warming to 15°C, gut blood flow increased ~3.4-fold and gut oxygen uptake rate increased ~3.7-fold (16.0±3.3 ml O2 h–1 kg–1), now representing ~25% of whole animal oxygen uptake. Although gut blood flow decreased following an acute stress event at 15°C, gut oxygen uptake remained unchanged due to a ~2-fold increase in oxygen extraction. The high metabolic thermal sensitivity of the gut discovered here could have important implications on the overall aerobic capacity and performance of fish and warrants further investigations.
      PubDate: 2018-05-24T04:24:13-07:00
      DOI: 10.1242/jeb.180703
       
  • Contribution of a natural polymorphism, protein kinase G, modulates
           electroconvulsive seizure recovery in D. melanogaster [RESEARCH ARTICLE]
    • Authors: Kelly, S. P; Risley, M. G, Miranda, L. E, Dawson-Scully, K.
      Abstract: Stephanie P. Kelly, Monica G. Risley, Leonor E. Miranda, and Ken Dawson-Scully

      Drosophila melanogaster is a well-characterized model for neurological disorders and is widely used for investigating causes of altered neuronal excitability leading to seizure-like behavior. One method used to analyze behavioral output of neuronal perturbance is recording the time to locomotor recovery from an electroconvulsive shock. Based on this behavior, we sought to quantify seizure susceptibility in larval D. melanogaster with differences in the enzymatic activity levels of a major protein, cGMP-dependent protein kinase (PKG). PKG, encoded by foraging, has two natural allelic variants and has previously been implicated in several important physiological characteristics including: foraging patterns, learning and memory, and environmental stress tolerance. The well-established NO/cGMP/PKG signaling pathway found in the fly, which potentially targets downstream K+ channel(s), which ultimately impacts membrane excitability; leading to our hypothesis: altering PKG enzymatic activity modulates time to recovery from an electroconvulsive seizure. Our results show that by both genetically and pharmacologically increasing PKG enzymatic activity, we can decrease the locomotor recovery time from an electroconvulsive seizure in larval D. melanogaster.
      PubDate: 2018-05-24T04:24:13-07:00
      DOI: 10.1242/jeb.179747
       
  • Rapid depth perception in hunting archerfish I. The predictive C-starts
           use an independent estimate of target height [RESEARCH ARTICLE]
    • Authors: Reinel, C. P; Schuster, S.
      Abstract: Caroline P. Reinel and Stefan Schuster

      Archerfish dislodge aerial prey with water jets and use their predictive C-starts to secure it. Their C-starts turn the fish to the later point of impact and set the speed so that the fish would arrive just in time. The starts are adjusted on the basis of information on speed, direction, timing and horizontal start position of prey movement – sampled during less than 100 ms after prey starts falling. Presently it is unclear, if one essential parameter, the initial height of prey can also be determined during this brief sampling time. Shooters and probably also observing bystanders already know target height ­– to hit and to shape their jets and would simply have to feed this information into their C-start circuitry. We challenged archerfish by launching initially invisible prey objects either from the expected height level, at which the fish were looking and at which they fired shots, or from more lateral positions and a lower or a higher initial height. The arrangement was so that an analysis of the direction and the linear speed chosen by the starting fish could decide whether the C-start information is based on the expected height or on the actual height, that can be detected only after hidden prey has begun falling. Our findings demonstrate that the fish quickly estimate initial height during the initial falling phase of prey and do not simply use the expected height level to which they were cued.
      PubDate: 2018-05-24T04:24:13-07:00
      DOI: 10.1242/jeb.177345
       
  • New approaches for assessing squid fin motions: Coupling proper orthogonal
           decomposition with volumetric particle tracking velocimetry [RESEARCH
           ARTICLE]
    • Authors: Bartol, I. K; Krueger, P. S, York, C. A, Thompson, J. T.
      Abstract: Ian K. Bartol, Paul S. Krueger, Carly A. York, and Joseph T. Thompson

      Squids, which swim using a coupled fin/jet system powered by muscular hydrostats, pose unique challenges for the study of locomotion. The high flexibility of the fins and complex flow fields generated by distinct propulsion systems require innovative techniques for locomotive assessment. For this study, we used proper orthogonal decomposition (POD) to decouple components of the fin motions and defocusing digital particle tracking velocimetry (DDPTV) to quantify the resultant 3D flow fields. Kinematic footage and DDPTV data were collected from brief squid Lolliguncula brevis [3.1 to 6.5 cm dorsal mantle length (DML)] swimming freely in a water tunnel at speeds of 0.39 – 7.20 DML s–1. Both flap and wave components were present in all fin motions, but the relative importance of the wave components was higher for arms-first swimming than tail-first swimming and for slower versus higher speed swimming. When prominent wave components were present, more complex interconnected vortex ring wakes were observed, while fin movements dominated by flapping resulted in more spatially separated vortex ring patterns. Although the jet often produced the majority of the thrust for steady rectilinear swimming, our results demonstrated that the fins can contribute more thrust than the jet at times, consistently produce comparable levels of lift to the jet during arms-first swimming, and can boost overall propulsive efficiency. By producing significant drag signatures, the fins can also aid in stabilization and maneuvering. Clearly fins play multiple roles in squid locomotion, and when coupled with the jet, allow squid to perform a range of swimming behaviors integral to their ecological success.
      PubDate: 2018-05-22T08:28:57-07:00
      DOI: 10.1242/jeb.176750
       
  • The Mauthner cell in a fish with top-performance and yet flexibly-tuned
           C-starts II. Physiology [RESEARCH ARTICLE]
    • Authors: Machnik, P; Leupolz, K, Feyl, S, Schulze, W, Schuster, S.
      Abstract: Peter Machnik, Kathrin Leupolz, Sabine Feyl, Wolfram Schulze, and Stefan Schuster

      The parallel occurrence in archerfish of fine-tuned and yet powerful predictive C-starts as well as of kinematically identical escape C-starts makes archerfish an interesting system to test hypotheses on the roles played by the Mauthner cells, a pair of giant reticulospinal neurons. In this study we show that the archerfish Mauthner cell shares all hallmark physiological properties with that of goldfish. Visual and acoustic inputs are received by the ventral and lateral dendrite, respectively, and cause complex postsynaptic potentials (PSPs) even in surgically anaesthetised fish. PSP shape did not indicate major differences between the species, but simple light flashes caused larger PSPs in archerfish, often driving the cell to fire an action potential. Probing archerfish in the classical tests for feedback inhibition, established in the Mauthner-associated networks in goldfish, revealed no differences between the two species, including the indications for electrical and chemical synaptic components. Also the established hallmark experiments on feed-forward inhibition showed no differences between the goldfish and archerfish Mauthner system. Extending these experiments to visual stimuli also failed to detect any differences between the two species and suggests that acoustical and visual input cause feed-forward inhibition, whose magnitude, time course and duration matches that of the respective PSPs both in archerfish and goldfish. Our findings question simple views on the role of the Mauthner cell and suggest that the archerfish Mauthner cell should be a good system to explore the function of these giant neurons in more sophisticated C-start behaviours.
      PubDate: 2018-05-22T08:28:57-07:00
      DOI: 10.1242/jeb.175588
       
  • The Mauthner cell in a fish with top-performance and yet flexibly-tuned
           C-starts I. Identification and comparative morphology [RESEARCH ARTICLE]
    • Authors: Machnik, P; Leupolz, K, Feyl, S, Schulze, W, Schuster, S.
      Abstract: Peter Machnik, Kathrin Leupolz, Sabine Feyl, Wolfram Schulze, and Stefan Schuster

      Archerfish use two powerful C-starts: One to escape threats, the other to secure prey that they have downed with a shot of water. The two C-starts are kinematically equivalent, are variable in both phases, and the predictive C-starts – used in hunting – are adjusted in the angle of turning and in the final linear speed to where and when their prey will hit the water surface. Presently nothing is known about the circuits that drive the archerfish C-starts. As the starting point for a neuroethological analysis, we first explored the presence and morphology of any paired Mauthner cell, a key cell in the teleost fast-start system. We show that archerfish have a typical Mauthner cell in each medullary hemisphere and that these send by far the largest axons down the spinal cord. Stimulation of the spinal cord caused short-latency all-or-none field potentials that could be detected even at the surface of the medulla and that had the archerfish Mauthner cell as its only source. The archerfish's Mauthner cell is remarkably similar morphologically to that of equally sized goldfish, except that the archerfish's ventral dendrite is slightly longer and its lateral dendrite thinner. Our data provide the necessary starting point for the dissection of the archerfish fast-start system and of any role potentially played by its Mauthner cell in the two C-start manoeuvres. Moreover, they do not support the recently expressed view that Mauthner cells should be reduced in animals with highly variable fast-start manoeuvres.
      PubDate: 2018-05-22T08:28:56-07:00
      DOI: 10.1242/jeb.182535
       
  • Effects of chronic exposure to 12{per thousand} saltwater on the endocrine
           physiology of juvenile American alligator (Alligator mississippiensis)
           [RESEARCH ARTICLE]
    • Authors: Faulkner, P. C; Burleson, M. L, Simonitis, L, Marshall, C, Hala, D, Petersen, L. H.
      Abstract: P. C. Faulkner, M. L. Burleson, L. Simonitis, C. Marshall, D. Hala, and L. H. Petersen

      American alligator (Alligator mississippiensis, Linnaeus) habitats are prone to saltwater intrusion following major storms, hurricanes or droughts. Anthropogenic impacts affecting hydrology of freshwater systems may exacerbate saltwater intrusion into freshwater habitats. The endocrine system of alligators is susceptible to changes in the environment but it is currently not known how the crocodilian physiological system responds to environmental stressors such as salinity. Juvenile alligators were exposed to 12 saltwater for 5 weeks to determine effects of chronic exposure to saline environments. Following 5 weeks, plasma levels of hormones (e.g., progesterone, testosterone, estradiol, corticosterone, aldosterone, angiotensin II) were quantified using LC-MS/MS. Compared to freshwater kept subjects, saltwater exposed alligators had significantly elevated plasma levels of corticosterone, 11-deoxycortisol, 17α-hydroxyprogesterone, testosterone, 17β-estradiol, estrone and estriol while pregnenolone and angiotensin II (ANG II) were significantly depressed and aldosterone (ALDO) levels were unchanged (slightly depressed). However, saltwater exposure did not affect gene expression of renal mineralo- and glucorticoid (MR, GR) and angiotensin type 1 (AT-1) receptors or morphology of lingual glands. On the other hand, saltwater exposure significantly reduced plasma glucose concentrations whereas parameters diagnostic of perturbed liver function (enzymes AST, ALT) and kidney function (creatinine, creatine kinase) were significantly elevated. Except for plasma potassium levels (K+), plasma ions Na+ and Cl– were significantly elevated in saltwater alligators. Overall, this study demonstrated significant endocrine and physiological effects in juvenile alligators chronically exposed to a saline environment. Results provide novel insights into the effects of a natural environmental stressor (salinity) on renin-angiotensin-aldosterone system and steroidogenesis of alligators.
      PubDate: 2018-05-18T03:30:44-07:00
      DOI: 10.1242/jeb.181172
       
  • Stumbling corrective reaction elicited by mechanical and electrical
           stimulation of the saphenous nerve in walking mice [RESEARCH ARTICLE]
    • Authors: Mayer, W. P; Akay, T.
      Abstract: William Paganini Mayer and Turgay Akay

      The ability to walk around in a natural environment requires the capacity to cope with unexpected obstacles that may disrupt locomotion. One such mechanism is called the stumbling corrective reaction (SCR) that enables animals to step over obstacles that would otherwise disturb the progression of swing movement. Here we use in vivo motion analysis and physiological recording techniques to describe the SCR in mice. We show that SCR can be elicited consistently in mice during locomotion by inserting an obstacle along the path of leg movement during swing phase. Furthermore, we show that the same behavior can be elicited if the saphenous nerve, a cutaneous nerve that would detect contact of the leg with an object, is stimulated electrically. This suggests that cutaneous afferent feedback is sufficient to elicit SCR. We further show that the SCR is phase dependent occurring only with stimulation during swing phase, but not during early stance. During SCR elicited by either method, the foot is lifted higher to clear the object by flexing the knee, via the semitendinosus muscle, and ankle joint, by tibialis anterior contraction. The latter also exhibits a brief extension before flexion onset. Our data provide a detailed description of SCR in mice and will be crucial for future research that aims to identify the interneurons of the premotor network controlling SCR and its neuronal mechanisms by combining motion analysis, electrophysiology, and mouse genetics.
      PubDate: 2018-05-18T03:30:44-07:00
      DOI: 10.1242/jeb.178095
       
  • First demonstration of olfactory learning and long term memory in honey
           bee queens [RESEARCH ARTICLE]
    • Authors: Gong, Z; Tan, K, Nieh, J. C.
      Abstract: Zhiwen Gong, Ken Tan, and James C. Nieh

      As the primary source of colony reproduction, social insect queens play a vital role. However, the cognitive abilities of queens are not well understood, although queen learning and memory are essential in multiple species such as honey bees, in which virgin queens must leave the nest and then successful learn to navigate back over repeated nuptial flights. Honey bee queen learning has never been previously demonstrated. We therefore tested olfactory learning in queens and workers and examined the role of DNA methylation, which plays a key role in long term memory formation. We provide the first evidence that honey bee queens have excellent learning and memory. The proportion of honey bee queens that exhibited learning was 5-fold higher than workers at every tested age and, for memory, 4-fold higher than workers at a very young age. DNA methylation may play a key role in this queen memory because queens exhibiting remote memory had a more consistent elevation in Dnmt3 gene expression as compared to workers. Both castes also showed excellent remote memory (7 day memory), which was reduced by 14-20% by the DNA methylation inhibitor, zebularine. Given that queens live about 10-fold longer than workers, these results suggest that queens can serve as an excellently long-term reservoir of colony memory.
      PubDate: 2018-05-18T03:30:44-07:00
      DOI: 10.1242/jeb.177303
       
  • Visual field shape and foraging ecology in diurnal raptors [RESEARCH
           ARTICLE]
    • Authors: Potier, S; Duriez, O, Cunningham, G. B, Bonhomme, V, O'Rourke, C, Fernandez-Juricic, E, Bonadonna, F.
      Abstract: Simon Potier, Olivier Duriez, Gregory B. Cunningham, Vincent Bonhomme, Colleen O'Rourke, Esteban Fernandez-Juricic, and Francesco Bonadonna

      Birds, particularly raptors, are believed to forage primarily using visual cues. However, raptor foraging tactics are highly diverse — from chasing mobile prey to scavenging — which may reflect adaptations of their visual systems. To investigate this, we studied the visual field configuration of 15 species of diurnal Accipitriformes that differ in such tactics, first focusing on the binocular field and blind area by using a single traits approach, and then exploring the shape of the binocular field with morphometric approaches. While the maximum binocular field width did not differ in species of different foraging tactics, the overall shape of their binocular fields did. In particular, raptors chasing terrestrial prey (ground predators) had a more protruding binocular field and a wider blind area above the head than did raptors chasing aerial or aquatic prey and obligate scavengers. Ground predators that forage on mammals from above have a wide but short bill — which increases ingestion rate — and large suborbital ridge to avoid sun glare. This may explain the protruding binocular field and the wide blind area above the head. By contrast, species from the two other groups have long but narrow bills used to pluck, flake or tear food and may need large visual coverage (and reduced suborbital ridges) to increase their foraging efficiency (e.g. using large visual coverage to follow the escaping prey in three dimensions or detect conspecifics). We propose that binocular field shape is associated with bill and suborbital ridge shape and, ultimately, foraging strategies.
      PubDate: 2018-05-18T03:30:44-07:00
      DOI: 10.1242/jeb.177295
       
  • Turning workers into false queens- the role of exogenous pheromones in
           regulating reproduction in worker honey bees [RESEARCH ARTICLE]
    • Authors: Yusuf, A. A; Crewe, R. M, Pirk, C. W. W.
      Abstract: Abdullahi A. Yusuf, Robin M. Crewe, and Christian W. W. Pirk

      One of the responses that honey bee workers can make in the event of queen loss is to develop into false queens. False queens are workers that exhibit both behavioural and physiological traits similar to those of a true queen. However, the presence of more than one false queen in a colony distorts the established hierarchies. As transformation into a false queen occurs after emergence as an adult, we tested the effect of worker mobile pheromone carriers (PCs) treated with exogenously supplied pheromones on their nestmates. The PCs carried either synthetic mandibular gland pheromones or pheromones extracted from capensis parasitic workers. Only PCs attracted retinues of workers, increased pheromone production, and activated their ovaries becoming false queens. Pheromones from capensis workers were more effective than extracts of commercially available synthetic queen pheromones in eliciting these effects. Using this simple mobile pheromone delivery system, we have shown that, carrying amounts of exogenous pheromone can induce pheromone production in the carrier resulting in the production of false queens within experimental groups. Possible implications of using this technique to modify and regulate worker reproduction in colonies are discussed.
      PubDate: 2018-05-18T03:30:44-07:00
      DOI: 10.1242/jeb.175505
       
  • Kinematic control of male Allen's Hummingbird wing trill over a range of
           flight speeds [RESEARCH ARTICLE]
    • Authors: Clark, C. J; Mistick, E. A.
      Abstract: Christopher J. Clark and Emily A. Mistick

      Wing trills are pulsed sounds produced by modified wing feathers at one or more specific points in time during a wingbeat. Male Allen's Hummingbird (Selasphorus sasin) produce a sexually dimorphic 9 kHz wing trill in flight. Here we investigate the kinematic basis for trill production. The wingtip velocity hypothesis posits that trill production is modulated by the airspeed of the wingtip at some point during the wingbeat, whereas the wing rotation hypothesis posits that trill production is instead modulated by wing rotation kinematics. To test these hypotheses, we flew six male Allen's Hummingbirds in an open jet wind tunnel at flight speeds of 0, 3, 6, 9, 12 and 14 m s–1, and recorded their flight with two 'acoustic cameras' placed below and behind, or below and lateral to the flying bird. The acoustic cameras are phased arrays of 40 microphones that used beamforming to spatially locate sound sources within a camera image. Trill Sound Pressure Level (SPL) exhibited a U-shaped relationship with flight speed in all three camera positions. SPL was greatest perpendicular to the stroke plane. Acoustic camera videos suggest that the trill is produced during supination. The trill was up to 20 dB louder during maneuvers than it was during steady state flight in the wind tunnel, across all airspeeds tested. These data provide partial support for the wing rotation hypothesis. Altered wing rotation kinematics could allow male Allen's Hummingbird to modulate trill production in social contexts such as courtship displays.
      PubDate: 2018-05-18T03:30:44-07:00
      DOI: 10.1242/jeb.173625
       
  • Simulated work-loops predict maximal human cycling power [RESEARCH
           ARTICLE]
    • Authors: Martin, J. C; Nichols, J. A.
      Abstract: James C. Martin and Jennifer A. Nichols

      Fish, birds, and lizards sometimes perform locomotor activities with maximized muscle power. Whether humans maximize muscular power is unknown because current experimental techniques cannot be applied non-invasively. This study uses simulated muscle work loops to examine whether voluntary maximal cycling is characterized by maximized muscle power. The simulated work loops leverage experimentally measured joint angles, anatomically realistic muscle parameters (muscle-tendon lengths, velocities, and moment arms), and a published muscle model to calculate powers and forces for thirty-eight muscles. For each muscle, stimulation onset and offset were optimized to maximize muscle work and power for the complete shortening/lengthening cycle. Simulated joint powers and total leg power (i.e., summed muscle powers) were compared to previously reported experimental joint and leg powers. Experimental power values were closely approximated by simulated maximal power for the leg (intraclass correlation coefficient (ICC)=0.91), the hip (ICC=0.92), and knee (ICC=0.95), but less closely for the ankle (ICC=0.74). Thus, during maximal cycling, humans maximize muscle power at the hip and knee, but the ankle acts to transfer (instead of maximize) power. Given that only the timing of muscle stimulation onsets and offsets were altered, these results suggest that human motor control strategies may optimize muscle activations to maximize power. The simulations also provide insights into biarticular muscles by demonstrating that the powers at each joint spanned by a biarticular muscle can be substantially greater than the net power produced by the muscle. Our work loop simulation technique may be useful for examining clinical deficits in muscle power production.
      PubDate: 2018-05-17T08:01:17-07:00
      DOI: 10.1242/jeb.180109
       
  • Drivers of the dive response in pinnipeds; apnea, submergence or
           temperature' [RESEARCH ARTICLE]
    • Authors: Kaczmarek, J; Reichmuth, C, McDonald, B. I, Kristensen, J. H, Larson, J, Johansson, F, Sullivan, J. L, Madsen, P. T.
      Abstract: Jeppe Kaczmarek, Colleen Reichmuth, Birgitte I. McDonald, Jakob H. Kristensen, Josefin Larson, Fredrik Johansson, Jenna L. Sullivan, and Peter T. Madsen

      Long and deep dives in marine mammals are enabled by high mass-specific oxygen stores and the dive response (DR), which reduces oxygen consumption in concert with increased peripheral vasoconstriction and a lowered heart rate during dives. Diving heart rates of pinnipeds are highly variable and modulated by many factors, such as breath holding (apnea), pressure, swimming activity, temperature, and even cognitive control. However, the individual effects of these factors on diving heart rate are poorly understood due to the difficulty of parsing their relative contributions in diving pinnipeds. Here, we examined the effects of apnea and external sensory inputs as autonomic drivers of bradycardia. Specifically, we hypothesized that 1) water stimulation of facial receptors would—as is the case for terrestrial mammals—enhance the dive response, 2) increasing the facial area stimulated would lead to a more intense bradycardia, and 3) cold water would elicit a more pronounced bradycardia than warm water. Three harbor seals (Phoca vitulina) and a California sea lion (Zalophus californianus) were trained to breath-hold in air and with their heads submerged in a basin with variable water level and temperature. We show that bradycardia occurs during apnea without immersion. We also demonstrate that bradycardia is strengthened with both increasing area of facial submersion and colder water. Thus, we conclude that initiation of the DR in pinnipeds is more strongly related to breath holding than in terrestrial mammals, but the degree of the DR is potentiated autonomically via stimulation of facial mechano- and thermoreceptors upon submergence.
      PubDate: 2018-05-17T08:01:17-07:00
      DOI: 10.1242/jeb.176545
       
  • Adaptive control of dynamic balance in human gait on a split-belt
           treadmill [RESEARCH ARTICLE]
    • Authors: Buurke, T. J. W; Lamoth, C. J. C, Vervoort, D, van der Woude, L. H. V, den Otter, R.
      Abstract: Tom J. W. Buurke, Claudine J. C. Lamoth, Danique Vervoort, Lucas H. V. van der Woude, and Rob den Otter

      Human bipedal gait is inherently unstable and staying upright requires adaptive control of dynamic balance. Little is known about adaptive control of dynamic balance in reaction to long-term, continuous perturbations. We examined how dynamic balance control adapts to a continuous perturbation in gait, by letting people walk faster with one leg than the other on a treadmill with two belts (i.e. split-belt walking). In addition, we assessed whether changes in mediolateral dynamic balance control coincide with changes in energy use during split-belt adaptation. In nine minutes of split-belt gait, mediolateral margins of stability and mediolateral foot roll-off changed during adaptation to the imposed gait asymmetry, especially on the fast side, and returned to baseline during washout. Interestingly, no changes in mediolateral foot placement (i.e. step width) were found during split-belt adaptation. Furthermore, the initial margin of stability and subsequent mediolateral foot roll-off were strongly coupled to maintain mediolateral dynamic balance throughout the gait cycle. Consistent with previous results net metabolic power was reduced during split-belt adaptation, but changes in mediolateral dynamic balance control were not correlated with the reduction of net metabolic power during split-belt adaptation. Overall, this study has shown that a complementary mechanism of relative foot positioning and mediolateral foot roll-off adapts to continuously imposed gait asymmetry to maintain dynamic balance in human bipedal gait.
      PubDate: 2018-05-17T08:01:17-07:00
      DOI: 10.1242/jeb.174896
       
  • When fed foods with similar palatability, healthy adult dogs and cats
           choose different macronutrient compositions [RESEARCH ARTICLE]
    • Authors: Hall, J. A; Vondran, J. C, Vanchina, M. A, Jewell, D. E.
      Abstract: Jean A. Hall, Jodi C. Vondran, Melissa A. Vanchina, and Dennis E. Jewell

      Dogs and cats make short-term food choices based on palatability. We hypothesized that if palatability were masked, long-term food choices would be based on physiologic requirements, and circulating metabolite concentrations would reflect those choices. Four experimental foods with similar palatability, but varying in macronutrient composition, were prepared for healthy adult dogs (n=17) and cats (n=27). Food 1 was high protein; Food 2 was high fat; Food 3 was high carbohydrates; and Food 4 was balanced for macronutrients. By choosing any combination of foods, dogs and cats could individually set their macronutrient intake. Plasma metabolomic profiles were determined at baseline and after animals had consumed their food intake of choice for 28 days. Based on food intake calculations over 28 days, dogs on average chose to consume most of their calories from fat (41.1±4.3%) and then carbohydrate (35.8±3.7%), whereas cats on average chose to consume most of their calories from carbohydrate (43.1±4.0%) and then protein (30.3±3.9%; all P
      PubDate: 2018-05-17T08:01:17-07:00
      DOI: 10.1242/jeb.173450
       
  • Maternally derived yolk antioxidants buffer the developing avian embryo
           against oxidative stress induced by hyperoxia [RESEARCH ARTICLE]
    • Authors: Watson, H; Salmon, P, Isaksson, C.
      Abstract: Hannah Watson, Pablo Salmon, and Caroline Isaksson

      In oviparous animals, maternally transferred antioxidants protect the embryo from oxidative damage from high rates of reactive oxygen species (ROS) production incurred by rapid growth. Elevated ROS exposure – beyond that incurred by normal growth - can occur as a result of exposure to exogenous factors (e.g. pollutants, toxins, radiation), increasing the risk of oxidative damage, with potentially adverse consequences for embryonic development and long-term fitness. The capacity of the avian embryo's antioxidant protection system to counter an increased exogenous oxidative threat is poorly understood. We induced an external oxidative challenge via experimental increase in ambient oxygen concentration throughout incubation of wild great tit Parus major eggs in the laboratory. At day 11 of incubation, brain tissue revealed no consistent differences in oxidative stress status – as measured by antioxidant levels (superoxide dismutase and total glutathione), lipid peroxidation and telomere length - between control (21% oxygen) and hyperoxic (40% oxygen) embryos. However, the level of vitamin E was significantly lower and lipid peroxidation was significantly higher in yolks of eggs reared under elevated oxygen concentrations. The results suggest that maternally derived yolk antioxidants successfully buffer developing embryonic tissues against an increased exogenous oxidative threat. Furthermore, vitamin E plays a more important role in protecting the embryo than carotenoids. However, the depletion of antioxidants and increased peroxidation of lipids in the yolk could have negative consequences for embryonic development – in particular for the brain and heart that require highly unsaturated fatty acids - and protection against the oxidative burst following hatching.
      PubDate: 2018-05-10T04:41:36-07:00
      DOI: 10.1242/jeb.179465
       
  • Intrinsic anti-inflammatory properties in the serum of two species of
           deep-diving seal [RESEARCH ARTICLE]
    • Authors: Bagchi, A; Batten, A. J, Levin, M, Allen, K. N, Fitzgerald, M. L, Hückstädt, L. A, Costa, D. P, Buys, E. S, Hindle, A. G.
      Abstract: Aranya Bagchi, Annabelle J. Batten, Milton Levin, Kaitlin N. Allen, Michael L. Fitzgerald, Luis A. Hückstädt, Daniel P. Costa, Emmanuel S. Buys, and Allyson G. Hindle

      Weddell and elephant seals are deep diving mammals, which rely on lung collapse to limit nitrogen absorption and prevent decompression injury. Repeated collapse and re-expansion exposes the lungs to multiple stressors, including ischemia/reperfusion, alveolar shear stress, and inflammation. There is no evidence, however, that diving damages pulmonary function in these species. To investigate potential protective strategies in deep-diving seals, we examined the inflammatory response of seal whole blood exposed to lipopolysaccharide (LPS), a potent endotoxin. IL6 cytokine production elicited by LPS exposure was 50-500x lower in blood of healthy northern elephant seals and Weddell seals compared to that of healthy human blood. In contrast to the ~6x increased production of IL6 protein from LPS-exposed Weddell seal whole blood, isolated Weddell seal peripheral blood mononuclear cells, under standard cell culture conditions using media supplemented with fetal bovine serum (FBS), produced a robust LPS response (~300x). Induction of Il6 mRNA expression as well as production of IL6, IL8, IL10, KC-like and TNFα were reduced by substituting FBS with an equivalent amount of autologous seal serum. Weddell seal serum (WSS) also attenuated the inflammatory response of RAW 267.4 mouse macrophage cells exposed to LPS. Cortisol level and the addition of serum lipids did not impact the cytokine response in cultured cells. These data suggest that seal serum possesses anti-inflammatory properties, which may protect deep divers from naturally occurring inflammatory challenges such as dive-induced hypoxia-reoxygenation and lung collapse.
      PubDate: 2018-05-10T04:41:36-07:00
      DOI: 10.1242/jeb.178491
       
  • High resting metabolic rates with low thermal dependence induce active
           dives in overwintering Pacific juvenile loggerhead turtles [RESEARCH
           ARTICLE]
    • Authors: Kinoshita, C; Fukuoka, T, Niizuma, Y, Narazaki, T, Sato, K.
      Abstract: Chihiro Kinoshita, Takuya Fukuoka, Yasuaki Niizuma, Tomoko Narazaki, and Katsufumi Sato

      The metabolic rate and activity of sea turtles generally decreases with decreasing seasonal ambient temperature. Juvenile loggerhead turtles in the Mediterranean Sea made prolonged inactive dives (>400 min), indicating a state of dormancy during the cold winter period. However, seasonal differences in dive duration were not detected in juvenile loggerheads in the western North Pacific, even though the ambient water temperature changed by more than 10°C. Thus, metabolic states might differ among populations, explaining differences in the diving behaviour of juveniles during winter. Here, we test the hypothesis that the active overwintering behaviour of juvenile loggerheads in the western North Pacific is driven by a high resting metabolic rate (RMR) with low thermal dependence. The RMR of juveniles in the western North Pacific (N=13) was 1.4 to 5.7 times higher (Q10=1.8) than that of juveniles in the Mediterranean Sea (Q10=5.4). To validate the high RMR values in the western North Pacific, the difference between core body temperature and ambient water temperature (Tb) was estimated from measured RMR and was compared with measured Tb. The measured and estimated Tb matched each other. In addition, most of the dives conducted by the turtles in the western North Pacific were within the calculated aerobic dive limit (cADL) expected from the measured metabolic rate. Our results indicate that high RMR with low thermal dependence induces active diving during the overwintering periods of juvenile loggerheads in the western North Pacific, supporting the suggestion that metabolic states differ among populations.
      PubDate: 2018-05-10T04:41:36-07:00
      DOI: 10.1242/jeb.175836
       
  • Time optimized path-choice in the termite hunting ant Megaponera analis
           [RESEARCH ARTICLE]
    • Authors: Frank, E. T; Hönle, P. O, Linsenmair, K. E.
      Abstract: Erik T. Frank, Philipp O. Hönle, and K. Eduard Linsenmair

      Trail network systems among ants have received a lot of scientific attention due to their various applications in problem solving of networks. Recent studies have shown that ants select the fastest available path when facing different velocities on different substrates, rather than the shortest distance. The progress of decision-making by these ants is determined by pheromone-based maintenance of paths, which is a collective decision. However, path optimization through individual decision-making remains mostly unexplored. Here we present the first study of time-optimized path selection via individual decision-making by scout ants. Megaponera analis scouts search for termite foraging sites and lead highly organized raid columns to them. The path of the scout determines the path of the column. Through installation of artificial roads around M. analis nests we were able to influence the pathway choice of the raids. After road installation 59% of all recorded raids took place completely or partly on the road, instead of the direct, i.e. distance-optimized, path through grass from the nest to the termites. The raid velocity on the road was more than double the grass velocity, the detour thus saved 34.77±23.01% of the travel time compared to a hypothetical direct path. The pathway choice of the ants was similar to a mathematical model of least time allowing us to hypothesize the underlying mechanisms regulating the behavior. Our results highlight the importance of individual decision-making in the foraging behavior of ants and show a new procedure of pathway optimization.
      PubDate: 2018-05-10T04:41:36-07:00
      DOI: 10.1242/jeb.174854
       
  • Environmental history impacts gene expression during diapause development
           in the alfalfa leafcutting bee, Megachile rotundata [RESEARCH ARTICLE]
    • Authors: Yocum, G. D; Childers, A. K, Rinehart, J. P, Rajamohan, A, Pitts-Singer, T. L, Greenlee, K. J, Bowsher, J. H.
      Abstract: George D. Yocum, Anna K. Childers, Joseph P. Rinehart, Arun Rajamohan, Theresa L. Pitts-Singer, Kendra J. Greenlee, and Julia H. Bowsher

      Our understanding of the mechanisms controlling insect diapause has increased dramatically with the introduction of global gene expression techniques, such as RNA-seq. However, little attention has been given to how ecologically relevant field conditions may affect gene expression during diapause development because previous studies have focused on laboratory reared and maintained insects. To determine whether gene expression differs between laboratory and field conditions, prepupae of the alfalfa leafcutting bee, Megachile rotundata, entering diapause early or late in the growing season were collected. These two groups were further subdivided in early autumn into laboratory and field maintained groups, resulting in four experimental treatments of diapausing prepupae: early and late field, and early and late laboratory. RNA-seq and differential expression analyses were performed on bees from the four treatment groups in November, January, March and May. The number of treatment-specific differentially expressed genes (97 to 1249) outnumbered the number of differentially regulated genes common to all four treatments (14 to 229), indicating that exposure to laboratory or field conditions had a major impact on gene expression during diapause development. Principle component analysis and hierarchical cluster analysis yielded similar grouping of treatments, confirming that the treatments form distinct clusters. Our results support the conclusion that gene expression during the course of diapause development is not a simple ordered sequence, but rather a highly plastic response determined primarily by the environmental history of the individual insect.
      PubDate: 2018-05-10T04:41:36-07:00
      DOI: 10.1242/jeb.173443
       
  • Central nervous shutdown underlies acute cold tolerance in tropical and
           temperate Drosophila species [RESEARCH ARTICLE]
    • Authors: Andersen, M. K; Jensen, N. J. S, Robertson, R. M, Overgaard, J.
      Abstract: Mads Kuhlmann Andersen, Nikolaj Johannes Skole Jensen, R. Meldrum Robertson, and Johannes Overgaard

      When cooled, insects first lose their ability to perform coordinated movements (CTmin) after which they enter chill coma (chill coma onset, CCO). Both these behaviours are popular measures of cold tolerance that correlate remarkably well with species distribution. To identify and understand the neuromuscular impairment that causes CTmin and CCO we used inter- and intraspecific model systems of Drosophila species that have varying cold tolerance as a consequence of adaptation or cold acclimation. Our results demonstrate that CTmin and CCO correlate strongly with a spreading depolarization (SD) within the central nervous system (CNS). We show that this SD is associated with a rapid increase in extracellular [K+] within the CNS causing neuronal depolarization that silences the CNS. The CNS shutdown is likely caused by a mismatch between passive and active ion transport within the CNS and in a different set of experiments we examine inter- and intraspecific differences in sensitivity to SD events during anoxic exposure. These experiments show that cold adapted or acclimated flies are better able to maintain ionoregulatory balance when active transport is compromised within the CNS. Combined, we demonstrate that a key mechanism underlying chill coma entry of Drosophila is CNS shutdown, and the ability to prevent this CNS shutdown is therefore an important component of acute cold tolerance, thermal adaptation and cold acclimation in insects.
      PubDate: 2018-05-08T03:07:02-07:00
      DOI: 10.1242/jeb.179598
       
  • The sea urchin Diadema africanum uses low resolution vision to find
           shelter and deter enemies [RESEARCH ARTICLE]
    • Authors: Kirwan, J. D; Bok, M. J, Smolka, J, Foster, J. J, Hernandez, J. C, Nilsson, D.-E.
      Abstract: John D. Kirwan, Michael J. Bok, Jochen Smolka, James J. Foster, Jose Carlos Hernandez, and Dan-Eric Nilsson

      Many sea urchins can detect light on their body surface and some species are reported to possess image-resolving vision. Here we measure the spatial resolution of vision in the long-spined sea urchin Diadema africanum, using two different visual responses: a taxis towards dark objects and an alarm response of spine-pointing towards looming stimuli. For the taxis response we used visual stimuli, which were isoluminant to the background, to discriminate spatial vision from phototaxis. Individual animals were placed in the centre of a cylindrical arena under bright down-welling light, with stimuli of varying angular width placed on the arena wall at pseudorandom directions from the centre. We tracked the direction of movement of individual animals in relation to the stimuli to determine whether the animals oriented towards the stimulus. We found that D. africanum responds by taxis towards isoluminant stimuli with a spatial resolution in the range 29°–69°. This corresponds to a theoretical acceptance angle of 38°–89°, assuming a contrast threshold of 10%. The visual acuity of the alarm response of D. africanum was tested by exposing animals to different sized dark looming and appearing stimuli on a monitor. We found that D. africanum displays a spine-pointing response to appearing black circles of 13°-25° angular width, corresponding to an acceptance angle of 60°–116°, assuming the same contrast threshold as above.
      PubDate: 2018-05-08T03:07:02-07:00
      DOI: 10.1242/jeb.176271
       
  • Selection for relative brain size affects context-dependent male
           preferences, but not discrimination, of female body size in guppies
           [RESEARCH ARTICLE]
    • Authors: Corral-Lopez, A; Kotrschal, A, Kolm, N.
      Abstract: Alberto Corral-Lopez, Alexander Kotrschal, and Niclas Kolm

      Understanding what drives animal decisions is fundamental in evolutionary biology, and mate choice decisions are arguably some of the most important decisions in any individual's life. As cognitive ability can impact decision-making, elucidating the link between mate choice and cognitive ability is necessary to fully understand mate choice. To experimentally study this link, we used guppies (Poecilia reticulata) artificially selected for divergence in relative brain size and with previously demonstrated differences in cognitive ability. A previous test in our female guppy selection lines demonstrated the impact of brain size and cognitive ability on information processing during female mate choice decisions. Here we evaluated the effect of brain size and cognitive ability on male mate choice decisions. Specifically, we investigated the preferences of large-brained, small-brained, and non-selected guppy males for female body size, a key indicator of female fecundity in this species. For this, male preferences were quantified in dichotomous choice tests when presented to dyads of females with small, medium and large body size differences. All types of males showed preference for larger females but no effect of brain size was found in the ability to discriminate between differently sized females. However, we found that non-selected and large-brained males, but not small-brained males, showed context-dependent preferences for larger females depending on the difference in female size. Our results have two important implications. First, they provide further evidence that male mate choice occurs also in a species in which secondary sexual ornamentation occurs only in males. Second, they show that brain size and cognitive ability have important effects on individual variation in mating preferences and sexually selected traits.
      PubDate: 2018-05-08T03:07:02-07:00
      DOI: 10.1242/jeb.175240
       
  • Effects of flight activity and age on oxidative damage in the honey bee,
           Apis mellifera [RESEARCH ARTICLE]
    • Authors: Margotta, J. W; Roberts, S. P, Elekonich, M. M.
      Abstract: Joseph W. Margotta, Stephen P. Roberts, and Michelle M. Elekonich

      Frequent and highly aerobic behaviors likely contribute to naturally occurring stress, accelerate senescence, and limit lifespan. To understand how the physiological and cellular mechanisms that determine the onset and duration of senescence are shaped by behavioral development and behavioral duration, we exploited the tractability of the honey bee (Apis mellifera) model system. First, we determined if a cause-effect relationship exists between honey bee flight and oxidative stress by comparing oxidative damage accrued from intense flight bouts to damage accrued from D-galactose ingestion, which induces oxidative stress and limit lifespan in other insects. Second, we experimentally manipulated the duration of honey bee flight across a range of ages to determine their effects on reactive oxygen species (ROS) accumulation and associated enzymatic antioxidant protective mechanisms. In bees fed D-galactose, lipid peroxidation (MDA) was higher than in bees fed sucrose and age-matched bees with high and low flight experience collected from a colony. Bees with high amounts of flight experience exhibited elevated 8-OHdG, a marker of oxidative DNA damage, relative to bees with less flight experience. Bees with high amounts of flight experience also showed increased levels of pro-oxidants (superoxide and H2O2) and decreased or unchanged levels of antioxidants (SOD and catalase). These data implicate an imbalance of pro- to antioxidants in flight-associated oxidative stress and reveal how behavior can damage a cell and consequently limit lifespan.
      PubDate: 2018-05-03T01:33:51-07:00
      DOI: 10.1242/jeb.183228
       
  • Structural and functional characterization of the contractile aorta and
           
    • Authors: Sigle, L. T; Hillyer, J. F.
      Abstract: Leah T. Sigle and Julian F. Hillyer

      The primary pump of the circulatory system of insects is a dorsal vessel that traverses the length of the insect. The anterior portion, located in the head, neck and thorax, is the aorta, and the posterior portion, located in the abdomen, is the heart. Here, we characterize the structure and function of the aorta and conical chamber of the mosquito, Anopheles gambiae. The aorta begins in the head with an excurrent opening located above the dorsal pharyngeal plate and ends at the thoraco-abdominal junction where it joins the conical chamber of the heart. The aorta lacks ostia, and based on the diameter of the vessel as well as the density and helical orientation of muscle, is comprised of three regions: the anterior aorta, the bulbous chamber, and the posterior aorta. The aorta contracts in the anterograde direction, but these contractions are independent of heart contractions and do not play a major role in hemolymph propulsion. Intravital imaging of the venous channels, the first abdominal segment and the neck revealed that hemolymph only travels through the aorta in the anterograde direction, and does so only during periods of anterograde heart flow. Furthermore, hemolymph only enters the thoraco-abdominal ostia of the conical chamber when the heart contracts in the retrograde direction, propelling this hemolymph to the posterior of the body. Finally, very few hemocytes associate with the aorta, and unlike what is seen in the periostial regions of the heart, infection does not induce the aggregation of hemocytes on the aorta.
      PubDate: 2018-05-03T01:33:51-07:00
      DOI: 10.1242/jeb.181107
       
  • The neuromechanics of proleg grip release [RESEARCH ARTICLE]
    • Authors: Mukherjee, R; Vaughn, S, Trimmer, B. A.
      Abstract: Ritwika Mukherjee, Samuel Vaughn, and Barry A. Trimmer

      Because soft animals are deformable their locomotion is particularly affected by external forces and they are expected to face challenges controlling movements in different environments and orientations. We have used the caterpillar Manduca sexta to study neuromechanical strategies of soft-bodied scansorial locomotion. Manduca locomotion critically depends on the timing of proleg grip release which is mediated by the principle planta retractor muscle and its single motoneuron, PPR. During upright crawling, PPR firing frequency increases approximately 0.6 seconds before grip release but during upside-down crawling, this activity begins significantly earlier, possibly pre-tensioning the muscle. Under different loading conditions the timing of PPR activity changes relative to the stance/swing cycle. PPR motor activity is greater during upside-down crawling but these frequency changes are too small to produce significant differences in muscle force. Detailed observation of the proleg tip show that it swells before the retractor muscle is activated. This small movement is correlated with the activation of more posterior body segments suggesting that it results from indirect mechanical effects. The timing and direction of this proleg displacement implies that proleg grip release is a dynamic interplay of mechanics and active neural control.
      PubDate: 2018-05-03T01:33:51-07:00
      DOI: 10.1242/jeb.173856
       
  • The analysis and interpretation of critical temperatures [RESEARCH
           ARTICLE]
    • Authors: Kingsolver, J. G; Umbanhowar, J.
      Abstract: Joel G. Kingsolver and James Umbanhowar

      Critical temperatures are widely used to quantify the upper and lower thermal limits of organisms. But measured critical temperatures often vary with methodological details, leading to spirited discussions about the potential consequences of stress and acclimation during the experiments. We review a model based on the simple assumption that failure rate increases with increasing temperature, independent of previous temperature exposure, water loss or metabolism during the experiment. The model predicts that mean critical thermal maximal temperatures (CTmax) increases nonlinearly with starting temperature and ramping rate, a pattern frequently observed in empirical studies. We then develop a statistical model that estimates a failure rate function (the relationship between failure rate and current temperature) using maximum likelihood; the best model accounts for 58% of the variation in CTmax in an exemplary dataset for tsetse flies. We then extend the model to incorporate potential effects of stress and acclimation on the failure rate function; the results show how stress accumulation at low ramping rate may increase the failure rate and reduce observed values of CTmax. We also applied the model to an acclimation experiment with hornworm larvae that used a single starting temperature and ramping rate; the analyses show that increasing acclimation temperature significantly reduced the slope of the failure rate function, increasing the temperature at which failure occurred. The model directly applies to critical thermal minima, and can utilize data from both ramping and constant temperature assays. Our model provides a new approach to analyzing and interpreting critical temperatures.
      PubDate: 2018-05-03T01:33:51-07:00
      DOI: 10.1242/jeb.167858
       
  • Kleptoplasts photoacclimation state modulates the photobehaviour of the
           solar-powered sea slug Elysia viridis [SHORT COMMUNICATION]
    • Authors: Cartaxana, P; Morelli, L, Quintaneiro, C, Calado, G, Calado, R, Cruz, S.
      Abstract: Paulo Cartaxana, Luca Morelli, Carla Quintaneiro, Goncalo Calado, Ricardo Calado, and Sonia Cruz

      Some sacoglossan sea slugs incorporate intracellular functional algal chloroplasts (kleptoplasty) for periods ranging from a few days to several months. Whether this association modulates the photobehaviour of solar-powered sea slugs is unknown. In this study, the long-term retention species Elysia viridis showed avoidance of dark independently of light acclimation state. On the contrary, Placida dendritica, which shows non-functional retention of kleptoplasts, showed no preference over dark, low or high light. High light acclimated (HLac) E. viridis showed a higher preference for high light than low light acclimated (LLac) conspecifics. The position of the lateral folds (parapodia) was modulated by irradiance, with increasing light levels leading to a closure of parapodia and protection of kleptoplasts from high light exposure. Furthermore, closure of parapodia occurred at higher irradiances in HLac E. viridis. Our results strongly indicate that kleptoplasts photoacclimation state modulates the photobehaviour of the solar-powered sea slug E. viridis.
      PubDate: 2018-04-30T04:59:51-07:00
      DOI: 10.1242/jeb.180463
       
  • Holding tight on feathers - structural specializations and attachment
           properties of the avian ectoparasite Crataerina pallida (Diptera,
           Hippoboscidae) [RESEARCH ARTICLE]
    • Authors: Petersen, D. S; Kreuter, N, Heepe, L, Büsse, S, Wellbrock, A. H. J, Witte, K, Gorb, S. N.
      Abstract: Dennis S. Petersen, Nils Kreuter, Lars Heepe, Sebastian Büsse, Arndt H. J. Wellbrock, Klaudia Witte, and Stanislav N. Gorb

      The louse fly Crataerina pallida is an obligate blood-sucking ecto-parasite of the common swift Apus apus. Due to reduction of the wings, C. pallida is unable to fly, thus an effective and reliable attachment to their host's plumage is of outmost importance. Its attachment system shows several modifications in comparison to other calyptrate flies. The most prominent ones are the large tridentate claws and the dichotomously shaped setae located on the pulvilli. Based on data from morphological analysis, confocal laser scanning microscopy, cryo-scanning electron microscopy and traction force experiments, performed on native (feathers) as well as artificial substrates (glass, epoxy-resin and silicone rubber), we showed that the entire attachment system is highly adapted to the fly's lifestyle as an ectoparasite. The claws in particular are the main contributor to strong attachment to the host. Resulting attachment forces on feathers make it impossible to detach C. pallida without damage of feathers or legs of the fly itself. Well-developed pulvilli are responsible for the attachment to smooth surfaces. Both dichotomously shaped setae and high setal density explain high safety factors observed on smooth substrates. For the first time, we demonstrated a material gradient within the setae with soft, resilin dominated apical tips and stiff, more sclerotized bases in Diptera. The empodium seems not to be directly involved in the attachment process, but it might operate as a cleaning device and may be essential to maintain the functionality of the entire attachment system.
      PubDate: 2018-04-30T04:59:51-07:00
      DOI: 10.1242/jeb.179242
       
  • Non-linear amplification of graded voltage signals in the first-order
           visual interneurons of the butterfly Papilio xuthus [RESEARCH ARTICLE]
    • Authors: Rusanen, J; Frolov, R, Weckström, M, Kinoshita, M, Arikawa, K.
      Abstract: Juha Rusanen, Roman Frolov, Matti Weckström, Michiyo Kinoshita, and Kentaro Arikawa

      Lamina monopolar cells (LMCs) are the first-order visual interneurons of insects and crustacea, primarily involved in achromatic vision. Here we investigated morphological and electrophysiological properties of LMCs in the butterfly Papilio xuthus. Using intracellular recording coupled with dye injection, we found two types of LMCs. Cells with roundish terminals near the distal surface of the medulla demonstrating no or small depolarizing spikes were classified as L1/2. LMCs with elongated terminals deep in the medulla that showed prominent spiking were classified as L3/4. The majority of LMCs of both types had broad spectral sensitivities, peaking between 480 and 570 nm. Depending on the experimental conditions, spikes varied from small to action potential-like events, with their amplitudes and rates decreasing as stimulus brightness increased. When the eye was stimulated with naturalistic contrast-modulated time series, spikes were reliably triggered by high-contrast components of the stimulus. Spike-triggered average functions showed that spikes emphasize rapid membrane depolarizations. Our results suggest that spikes are mediated by voltage-activated Na+ channels, which are mainly inactivated at rest. Strong local minima in the coherence functions of spiking LMCs indicate that the depolarizing conductance contributes to the amplification of graded responses even when detectable spikes are not evoked. We propose that the information transfer strategies of spiking LMCs change with light intensity. In dim light, both graded voltage signals and large spikes are used together without mutual interference, due to separate transmission bandwidths. In bright light, signals are non-linearly amplified by the depolarizing conductance in the absence of detectable spikes.
      PubDate: 2018-04-30T04:59:51-07:00
      DOI: 10.1242/jeb.179085
       
  • X-ray computed tomography study of the flight-adapted tracheal system in
           the blowfly Calliphora vicina analysing the ventilation mechanism and
           flow-directing valves [RESEARCH ARTICLE]
    • Authors: Wasserthal, L. T; Cloetens, P, Fink, R. H, Wasserthal, L. K.
      Abstract: Lutz Thilo Wasserthal, Peter Cloetens, Rainer H. Fink, and Lennard Knut Wasserthal

      After the discovery of the flight-motor driven unidirectional gas exchange with rising PO2 in the blowfly, X-ray computer tomography (CT) was used to visualize the organization of the tracheal system in the anterior body with emphasis on the arrangement of the pathways for the airflows. The fly's head is preferentially supplied by cephalic tracheae originating from the ventral orifice of the mesothoracic spiracle (Sp1). The respiratory airflow during flight is a by-product of cyclic deformations of the thoracic box by the flight muscles. The air sacs below the tergal integument (scutum and scutellum) facilitate the respiratory airflow: The shortening of the thorax turns the scutellum and the wings downward and the scutum upward with a volume increase in the scutal air sacs. The resulting negative pressure sucks air from Sp1 through special tracheae towards the scutal air sacs. The airflow is directed by two valves that open alternately: (1) The hinged filter flaps of the metathoracic spiracles (Sp2) are passively pushed open during the upstroke by the increased tracheal pressure, thereby enabling expiration. (2) A newly described tracheal valve-like septum behind the regular spiracular valve lids of Sp1 opens passively and air is sucked in through Sp1 during the downstroke and prevents expiration by closing during the upstroke. This stabilizes the unidirectional airflow. The tracheal volume of the head, thorax and abdomen and their mass were determined. Despite the different anatomy in birds and flies the unidirectional airflow reveals a comparable efficiency of the temporal throughput in flies and hummingbirds.
      PubDate: 2018-04-30T04:59:51-07:00
      DOI: 10.1242/jeb.176024
       
  • Serotonin has opposite effects on the aggressiveness of crayfish, facing
           either a smaller or a larger rival: alteration of size perception [SHORT
           COMMUNICATION]
    • Authors: Bacque-Cazenave, J; Cattaert, D, Delbecque, J. P, Fossat, P.
      Abstract: Julien Bacque-Cazenave, Daniel Cattaert, Jean Paul Delbecque, and Pascal Fossat

      We injected serotonin (5-HT) in adult male crayfish before pairing them with size-matched non-injected competitors, and we observed dyadic agonistic interactions. Paradoxically, 5-HT elicited opposite behavioral responses if the injected animal was opposed by a smaller or larger rival: the level of aggressiveness of the injected crayfish was higher in front of a larger rival but lower in front of a smaller rival. Our results indicate that the effects of 5-HT on aggressiveness are dependent on the perception of the relative size difference of the opponent. In both cases, however, 5-HT significantly delayed the decision to retreat. We conclude that 5-HT does not primarily act on aggressiveness but rather on the brain centers that integrate risk assessment and/or decision-making, which then modulate the aggressive response. Our study supports a reinterpretation of the role of 5-HT in crustacean agonistic behavior that may be of interest for other animals.
      PubDate: 2018-04-26T02:20:25-07:00
      DOI: 10.1242/jeb.177840
       
  • Growth hormone transgenesis in coho salmon disrupts muscle immune function
           impacting cross-talk with growth systems [RESEARCH ARTICLE]
    • Authors: Alzaid, A; Kim, J.-H, Devlin, R. H, Martin, S. A. M, Macqueen, D. J.
      Abstract: Abdullah Alzaid, Jin-Hyoung Kim, Robert H. Devlin, Samuel A. M. Martin, and Daniel J. Macqueen

      Suppression of growth during infection may aid resource allocation towards effective immune function. Past work supporting this hypothesis in salmonid fish revealed an immune-responsive regulation of the insulin-like growth factor (IGF) system, an endocrine pathway downstream of growth hormone (GH). Skeletal muscle is the main target for growth and energetic storage in fish, yet little is known about how its growth is regulated during an immune response. We addressed this knowledge gap by characterizing muscle immune responses in size-matched coho salmon (Oncorhynchus kisutch) achieving different growth rates. We compared a wild-type strain with two GH transgenic groups from the same genetic background achieving either maximal or suppressed growth, a design separating GH's direct effects from its influence on growth rate and nutritional state. Fish were sampled 30h post-injection with PBS (control) or mimics of bacterial or viral infection. We quantified mRNA expression levels for genes from the GH, GH receptor, IGF hormone, IGF1 receptor and IGF-binding protein families, along with immune genes involved in inflammatory or antiviral responses and muscle growth status marker genes. We demonstrate dampened immune function in GH transgenics compared to wild-type. The muscle of GH transgenics achieving rapid growth showed no detectable antiviral response, coupled with evidence of a constitutive inflammatory state. GH and IGF system gene expression was strongly altered by GH transgenesis and fast growth, both for baseline expression and responses to immune stimulation. Thus, GH transgenesis strongly disrupts muscle immune status and normal GH and IGF system expression responses to immune stimulation.
      PubDate: 2018-04-26T02:20:25-07:00
      DOI: 10.1242/jeb.173146
       
  • Locomotor muscle fiber heterogeneity and metabolism in the fastest
           large-bodied rorqual: the fin whale (Balaenoptera physalus) [RESEARCH
           ARTICLE]
    • Authors: Rivero; J.-L. L.
      Abstract: Jose-Luis L. Rivero

      From a terrestrial ancestry, fin whale (Balaenoptera physalus) is one of the largest animal on Earth with a sprinter antipredator strategy, and a characteristic feeding mode, lunge feeding, which involve bouts of high-intensity muscle activity demanding high metabolic output. We investigated the locomotor muscle morphology and metabolism of this cetacean to determine whether its muscle profile (1) explains this unique swimming performance and feeding behaviour, (2) is or is not homogeneous within the muscle, and (3) predicts allometric variations inherent to an extreme body size. A predominantly fast-glycolytic phenotype characterized the fin whale locomotor muscle, composed of abundant fast-twitch (type IIA) fibers with high glycolytic potential, low oxidative capacity, relatively small size, and reduced number of capillaries. Compared to superficial areas, deep regions of this muscle exhibited a slower and more oxidative profile, suggesting a division of labour between muscle strata. As expected, the fin whale locomotor muscle only expressed the two slowest myosin heavy chain isoforms (I and IIA). However, it displayed anaerobic (glycolytic) and aerobic (lipid-based metabolism) capabilities higher than would be predicted from the allometric perspective of its extreme body size. Relationships between muscle metabolism and body mass were fiber-type specific. The ‘sprinter’ profile of the fin whale swimming muscle, particularly of its superficial compartment, supports physiological demands during both high-speed swimming and the lunge, when energy expenditure reaches maximal or supramaximal levels. Comparatively, the slower and more oxidative profile of the deep compartment of this muscle seems to be well designed for sustained, low-intensity muscle activity during routine swimming.
      PubDate: 2018-04-24T02:52:01-07:00
      DOI: 10.1242/jeb.177758
       
  • Individual differences in torpor expression in adult mice are related to
           relative birth weight [RESEARCH ARTICLE]
    • Authors: Kato, G. A; Sakamoto, S. H, Eto, T, Okubo, Y, Shinohara, A, Morita, T, Koshimoto, C.
      Abstract: Goro A. Kato, Shinsuke H. Sakamoto, Takeshi Eto, Yoshinobu Okubo, Akio Shinohara, Tetsuo Morita, and Chihiro Koshimoto

      Daily torpor is a physiological adaptation in small mammals and birds, characterised by drastic reductions in metabolism and body temperature. Energy-constraining conditions, such as cold and starvation, are known to cause the expression of daily torpor. However, the reason for high degrees of inter- and intra- individual variation in torpor expression (TE) in similar situations is not clear. As littermates of altricial animals are exposed to an uneven allocation of maternal resources from conception to weaning, we tested whether early nutritional experiences have long-term effects on TE in adults. We used full-sibling littermates of laboratory mice that as adults were starved overnight to induce torpor. We measured body weight from birth until adulthood as an indicator of nutritional status, and calculated the relative body weight (RBW) as an indicator of the difference in nutritional status within a litter. After maturation, we subjected mice to five repeated torpor induction trials involving 24 hours of fasting and 5 days of recovery. Half of the female mice displayed great individual variation in TE, whereas male mice rarely exhibited daily torpor. In females, RBW at birth influenced TE, irrespective of body weight in adulthood; thus, female mice born with low RBWs displayed high TE in adulthood. In conclusion, we provide evidence that TE in mice differs among littermates, and that this variation is linked closely to heterogeneous nutritional experiences during the foetal period.
      PubDate: 2018-04-20T01:48:39-07:00
      DOI: 10.1242/jeb.171983
       
  • Cherchez la femme - impact of ocean acidification on the egg jelly coat
           and attractants for sperm [RESEARCH ARTICLE]
    • Authors: Foo, S. A; Deaker, D, Byrne, M.
      Abstract: Shawna A. Foo, Dione Deaker, and Maria Byrne

      The impact of ocean acidification on marine invertebrate eggs and consequences for sperm chemotaxis are unknown. In the sea urchins Heliocidaris tuberculata and H. erythrogramma, with small (93µm) and large (393µm) eggs, respectively, we documented the effect of decreased pH on the egg jelly coat, an extracellular matrix that increases target size for sperm and contains sperm attracting molecules. In near future conditions (pH 7.8, 7.6) the jelly coat of H. tuberculata decreased by 11 and 21%, reducing egg target size by 9 and 17%, respectively. In contrast, the egg jelly coat of H. erythrogramma was not affected. The reduction in the jelly coat has implications for sperm chemotaxis in H. tuberculata. In the presence of decreased pH and egg chemicals, the sperm of this species increased their velocity, motility and linearity, behaviour that was opposite to that seen for sperm exposed to egg chemicals in ambient conditions. Egg chemistry appears to cause a reduction in sperm velocity where attractants guide them in the direction of the egg. Investigation of the effects of decreased pH on sperm isolated from egg chemistry does not provide an integrative assessment of the effects of ocean acidification on sperm function. Differences in the sensitivity of the jelly coat of the two species is likely associated with egg evolution in H. erythrogramma. We highlight important unappreciated impacts of ocean acidification on marine gamete functionality, and insights into potential winners and losers in a changing ocean, pointing to the advantage conveyed by evolution of large eggs.
      PubDate: 2018-04-19T01:50:17-07:00
      DOI: 10.1242/jeb.177188
       
  • Odor discrimination learning in the Indian greater short-nosed fruit bat
           (Cynopterus sphinx): differential expression of Egr-1, C-fos and PP-1 in
           the olfactory bulb, amygdala and hippocampus [RESEARCH ARTICLE]
    • Authors: Mukilan, M; Bogdanowicz, W, Marimuthu, G, Rajan, K. E.
      Abstract: Murugan Mukilan, Wieslaw Bogdanowicz, Ganapathy Marimuthu, and Koilmani Emmanuvel Rajan

      Activity-dependent expression of immediate-early genes (IEGs) is induced by exposure to odor. The present study was designed to investigate whether there is differential expression of IEGs (Egr-1, C-fos) in the brain region mediating olfactory memory in the Indian greater short-nosed fruit bat Cynopterus sphinx. We assumed that differential expression of IEGs in different brain regions may orchestrate a preference odor (PO) and aversive odor (AO) memory in C. sphinx. We used preferred (0.8% wt/wt of cinnamon powder) and aversive (0.4% wt/vol of citral) odor substances, with freshly-prepared chopped apple, to assess the behavioural response and induction of IEGs in the olfactory bulb, hippocampus and amygdala. After experiencing PO and AO, the bats initially responded to both, later only engaging in feeding bouts in response to the PO food. The expression pattern of Egr-1 and C-fos in the olfactory bulb, hippocampus and amygdala was similar at different time points (15, 30 and 60 min) following the response to PO, but different for AO. The response to AO elevated the level of C-fos expression within 30 min and reduced it at 60 min in both the olfactory bulb and the hippocampus, as opposed to the continuous increase noted in the amygdala. In addition, we tested whether an epigenetic mechanism entailing protein phosphatase-1 (PP-1) acts on IEG expression. The observed PP-1 expression and the level of unmethylated/methylated promoter revealed that the C-fos expression is possibly controlled by an odor-mediated regulation of PP-1. These results in turn imply that the differential expression of C-fos in the hippocampus and amygdala may contribute to olfactory learning and memory in C. sphinx.
      PubDate: 2018-04-19T01:50:17-07:00
      DOI: 10.1242/jeb.175364
       
  • Paralytic hypo-energetic state facilitates anoxia tolerance despite ionic
           imbalance in adult Drosophila melanogaster [RESEARCH ARTICLE]
    • Authors: Campbell, J. B; Andersen, M. K, Overgaard, J, Harrison, J. F.
      Abstract: Jacob B. Campbell, Mads Kuhlmann Andersen, Johannes Overgaard, and Jon F. Harrison

      Oxygen limitation plays a key role in many pathologies; yet, we still lack a fundamental understanding of the mechanisms responsible for variation in anoxia tolerance. Most vertebrate studies suggest that anoxia tolerance involves the ability to maintain cellular ATP despite the loss of aerobic metabolism. However, insects such as adult D. melanogaster are able to survive long periods of anoxia (LT50: ~8 h) in a hypo-energetic state characterized by low [ATP]. In this study, we tested for possible mechanisms that allow D. melanogaster adults to survive long periods of anoxia. Adults are paralyzed within 30 sec, and after two hours of anoxia ATP was 3% of normal, [K+]o increased threefold, pH dropped 1 unit, yet survival was 100%. With 0.5-6 h of anoxia, adults maintained low but constant ATP levels while [K+]o and pHo continued to change. When returned to normoxia, adults restore [K+]o and activity. With longer durations of anoxia, ATP levels decreased and [K+]o rose further, and both correlated tightly with decreased survival. This response contrasts with the anoxia-sensitive larval stage (LT50: ~1 h). During anoxia, larvae attempt escape for up to 30 min and after two hours of anoxia, ATP was
      PubDate: 2018-04-03T06:35:20-07:00
      DOI: 10.1242/jeb.177147
       
  • Japanese macaque phonatory physiology [RESEARCH ARTICLE]
    • Authors: Herbst, C. T; Koda, H, Kunieda, T, Suzuki, J, Garcia, M, Fitch, W. T, Nishimura, T.
      Abstract: Christian T. Herbst, Hiroki Koda, Takumi Kunieda, Juri Suzuki, Maxime Garcia, W. Tecumseh Fitch, and Takeshi Nishimura

      While the call repertoire and its communicative function is relatively well explored in Japanese macaques (Macaca fuscata), little empirical data is available on the physics and the physiology of this species' vocal production mechanism. Here, a 6 year old female Japanese macaque was trained to phonate under an operant conditioning paradigm. The resulting "coo" calls, and spontaneously uttered "growl" and "chirp" calls, were recorded with sound pressure level (SPL) calibrated microphones and electroglottography (EGG), a non-invasive method for assessing the dynamics of phonation. A total of 448 calls were recorded, complemented by ex vivo recordings on an excised Japanese macaque larynx. In this novel multidimensional investigative paradigm, in vivo and ex vivo data were matched via comparable EGG waveforms. Subsequent analysis suggests that the vocal range (range of fundamental frequency and SPL) was comparable to that of a 7-10 year old human, with the exception of low-intensity chirps, whose production may be facilitated by the species' vocal membranes. In coo calls, redundant control of fundamental frequency in relation to SPL was also comparable to humans. EGG data revealed that growls, coos, and chirps were produced by distinct laryngeal vibratory mechanisms. EGG further suggested changes in the degree of vocal fold adduction in vivo, resulting in spectral variation within the emitted coo calls, ranging from "breathy" (including aerodynamic noise components) to "non-breathy". This is again analogous to humans, corroborating the notion that phonation in humans and non-human primates is based on universal physical and physiological principles.
      PubDate: 2018-04-03T06:35:20-07:00
      DOI: 10.1242/jeb.171801
       
 
 
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