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BIOTECHNOLOGY (236 journals)                  1 2 | Last

Showing 1 - 200 of 239 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
Advanced Biomedical Research     Open Access  
Advances in Bioscience and Biotechnology     Open Access   (Followers: 16)
Advances in Genetic Engineering & Biotechnology     Hybrid Journal   (Followers: 7)
Advances in Regenerative Medicine     Open Access   (Followers: 2)
African Journal of Biotechnology     Open Access   (Followers: 6)
Algal Research     Partially Free   (Followers: 11)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Bioinformatics Research     Open Access   (Followers: 7)
American Journal of Polymer Science     Open Access   (Followers: 32)
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 Biosafety     Hybrid Journal  
Applied Food Biotechnology     Open Access   (Followers: 3)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 64)
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: 9)
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)
Beitr?ge zur Tabakforschung International/Contributions to Tobacco Research     Open Access   (Followers: 2)
Bio-Algorithms and Med-Systems     Hybrid Journal   (Followers: 2)
Bio-Research     Full-text available via subscription   (Followers: 3)
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   (Followers: 1)
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)
Biosensors Journal     Open Access  
Biosimilars     Open Access   (Followers: 1)
Biosurface and Biotribology     Open Access  
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
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: 6)
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: 153)
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: 2)
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: 40)
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  
BIOTIK : Jurnal Ilmiah Biologi Teknologi dan Kependidikan     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)
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)
Indonesian Journal of Medicine     Open Access  
Industrial Biotechnology     Hybrid Journal   (Followers: 17)
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: 3)
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)
JMIR Biomedical Engineering     Open Access  
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: 64)
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   (Followers: 1)
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: 25)
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: 17)
Journal of Integrative Bioinformatics     Open Access  
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: 12)
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)
Meat Technology     Open Access  
Messenger     Full-text available via subscription  
Metabolic Engineering Communications     Open Access   (Followers: 4)
Metalloproteinases In Medicine     Open Access  
Microbial Biotechnology     Open Access   (Followers: 9)
MicroMedicine     Open Access   (Followers: 3)
Molecular and Cellular Biomedical Sciences     Open Access   (Followers: 1)
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  
Nanomedicine and Nanobiology     Full-text available via subscription  
Nanomedicine Research Journal     Open Access  

        1 2 | Last

Journal Cover
Journal of Experimental Biology
Journal Prestige (SJR): 1.611
Citation Impact (citeScore): 3
Number of Followers: 25  
  Full-text available via subscription Subscription journal
ISSN (Print) 0022-0949 - ISSN (Online) 1477-9145
Published by Company of Biologists, The Homepage  [5 journals]
  • Automated measurement of upper thermal limits in small aquatic animals
    • Authors: Burton, T; Zeis, B, Einum, S.
      Abstract: Tim Burton, Bettina Zeis, and Sigurd Einum

      We present a method for automating the measurement of upper thermal limits in small aquatic organisms. Upper thermal limits are frequently defined by the cessation of movement at high temperature, with measurement being performed by manual observation. Consequently, estimates of upper thermal limits may be subject to error and bias, both within and among observers. Our method utilises video-based tracking software to record the movement of individuals when exposed to high, lethal temperatures. We develop an algorithm in the R computing language that can objectively identify the loss of locomotory function from tracking data. Using independent experimental data, we validate our approach by demonstrating the expected response in upper thermal limits to acclimation temperature.
      PubDate: 2018-09-13T00:45:58-07:00
      DOI: 10.1242/jeb.182386
      Issue No: Vol. 221, No. 17 (2018)
  • Cardiorespiratory interactions in the Pacific spiny dogfish, Squalus
           suckleyi [RESEARCH ARTICLE]
    • Authors: Acharya-Patel, N; Deck, C. A, Milsom, W. K.
      Abstract: Neha Acharya-Patel, Courtney A. Deck, and William K. Milsom

      Elasmobranchs are a group of cartilaginous fish with no direct sympathetic innervation of the heart or gills. Fast cardiorespiratory regulation is controlled solely by the parasympathetic branch of the autonomic nervous system. Cardiovascular changes associated with ventilation are commonly present in the form of respiratory sinus arrhythmia (RSA) and as cardiorespiratory synchrony (CRS, in which there is a 1:1 beat to breath ratio). The latter has been hypothesized to maximize oxygen uptake, coupling the pulsatile flows of blood and water in the gills. Given this, we hypothesized that CRS should be more prevalent in situations of low oxygen supply and RSA should be abolished by vagotomy. To test this, we investigated the role of the vagus nerve in mediating cardiorespiratory responses to changing environmental oxygen conditions in the elasmobranch Squalus suckleyi. Hypoxia and hyperoxia had little effect on heart rate but did alter breathing frequency and amplitude. Atropine yielded an overall tachycardia in all oxygen conditions and abolished all heart rate variability (HRV), suggesting that HRV solely reflects fluctuating vagal tonus on the heart. Regardless of the presence of atropine, hypoxia still induced an increase in ventilation rate and depth. CRS was only found during progressive hyperoxia post-atropine, when heart rate was uninhibited and ventilation was slowed owing to the increase in oxygen supply, suggesting that in S. suckleyi, CRS is an epiphenomenon and not actively regulated to maximize gas exchange efficiency.
      PubDate: 2018-09-13T00:45:58-07:00
      DOI: 10.1242/jeb.183830
      Issue No: Vol. 221, No. 17 (2018)
  • Synaptic convergence of afferent inputs in primary infrared-sensitive
           nucleus (LTTD) neurons of rattlesnakes (Crotalinae) as the origin for
           sensory contrast enhancement [RESEARCH ARTICLE]
    • Authors: Bothe, M. S; Luksch, H, Straka, H, Kohl, T.
      Abstract: Maximilian S. Bothe, Harald Luksch, Hans Straka, and Tobias Kohl

      Pitvipers have a specialized sensory system in the upper jaw to detect infrared (IR) radiation. The bilateral pit organs resemble simple pinhole cameras that map IR objects onto the sensory epithelium as blurred representations of the environment. Trigeminal afferents transmit information about changing temperature patterns as neuronal spike discharge in a topographic manner to the hindbrain nucleus of the lateral descending trigeminal tract (LTTD). A presumed, yet so far unknown neuronal connectivity within this central nucleus exerts a synaptic computation that constrains the relatively large receptive field of primary afferent fibers. Here, we used intracellular recordings of LTTD neurons in isolated rattlesnake brains to decipher the spatio-temporal pattern of excitatory and inhibitory responses following electrical stimulation of single and multiple peripheral pit organ-innervating nerve branches. The responses of individual neurons consisted of complex spike sequences that derived from spatially and temporally specific interactions between excitatory and inhibitory synaptic inputs from the same as well as from adjacent peripheral nerve terminal areas. This pattern complies with a central excitation that is flanked by a delayed lateral inhibition, thereby enhancing the contrast of IR sensory input, functionally reminiscent of the computations for contrast enhancement in the peripheral visual system.
      PubDate: 2018-09-13T00:45:58-07:00
      DOI: 10.1242/jeb.185611
      Issue No: Vol. 221, No. 17 (2018)
  • How pit vipers see (infra)red [INSIDE JEB]
    • Authors: Knight; K.
      Abstract: Kathryn Knight

      PubDate: 2018-09-13T00:45:58-07:00
      DOI: 10.1242/jeb.188870
      Issue No: Vol. 221, No. 17 (2018)
  • Vocal tract modelling in fallow deer: are male groans nasalized'
    • Authors: Reby, D; Wyman, M. T, Frey, R, Charlton, B. D, Dalmont, J. P, Gilbert, J.
      Abstract: D. Reby, M. T. Wyman, R. Frey, B. D. Charlton, J. P. Dalmont, and J. Gilbert

      Males of several species of deer have a descended and mobile larynx, resulting in an unusually long vocal tract, which can be further extended by lowering the larynx during call production. Formant frequencies are lowered as the vocal tract is extended, as predicted when approximating the vocal tract as a uniform quarter wavelength resonator. However, formant frequencies in polygynous deer follow uneven distribution patterns, indicating that the vocal tract configuration may in fact be rather complex. We CT-scanned the head and neck region of two adult male fallow deer specimens with artificially extended vocal tracts and measured the cross-sectional areas of the supra-laryngeal vocal tract along the oral and nasal tracts. The CT data were then used to predict the resonances produced by three possible configurations, including the oral vocal tract only, the nasal vocal tract only, or combining the two. We found that the area functions from the combined oral and nasal vocal tracts produced resonances more closely matching the formant pattern and scaling observed in fallow deer groans than those predicted by the area functions of the oral vocal tract only or of the nasal vocal tract only. This indicates that the nasal and oral vocal tracts are both simultaneously involved in the production of a non-human mammal vocalization, and suggests that the potential for nasalization in putative oral loud calls should be carefully considered.
      PubDate: 2018-09-11T07:05:56-07:00
      DOI: 10.1242/jeb.179416
      Issue No: Vol. 221, No. 17 (2018)
  • Fallow deer bucks croon through their noses to sound bigger [INSIDE JEB]
    • Authors: Knight; K.
      Abstract: Kathryn Knight

      PubDate: 2018-09-11T07:05:56-07:00
      DOI: 10.1242/jeb.188052
      Issue No: Vol. 221, No. 17 (2018)
  • Physiology, activity and costs of parental care in birds [COMMENTARY]
    • Authors: Williams; T. D.
      Abstract: Tony D. Williams

      Parental care is assumed to be costly in that it requires sustained, high-intensity activity sufficient to cause costs of reproduction (decreased survival and future fecundity of parents). Costs of reproduction are, in turn, thought to have a physiological basis where intense activity causes a decrease in parental condition. However, attempts to identify the physiological basis of costs of reproduction have produced mixed results. Here, I argue that in birds, the central idea that parental care represents sustained, high-intensity work might be incorrect. Specifically: (a) the duration of intense activity associated with chick-rearing might be quite limited; (b) flight, the most obvious sustained, high-intensity activity, might only represent a small component of an individual's overall activity budget; (c) some (high-quality) individuals might be able to tolerate costs of intense activity, either owing to their physiological state or because they have access to more resources, without perturbation of physiological homeostasis; and (d) individuals might utilise other mechanisms to modulate costs of activity, for example, mass loss, again avoiding more substantial physiological costs. Furthermore, I highlight the important fact that life-history theory predicts that reproductive trade-offs should only be expected under food stress. Most birds breed in spring and early summer precisely because of seasonal increases in food abundance, and so it is unclear how often parents are food stressed. Consequently, I argue that there are many reasons why costs of reproduction, and any physiological signature of these costs, might be quite rare, both temporally (in different years) and among individuals.
      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.169433
      Issue No: Vol. 221, No. 17 (2018)
  • To stroll or to sprint' Humans consider time and effort [OUTSIDE JEB]
    • Authors: Stenum; J.
      Abstract: Jan Stenum

      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.170118
      Issue No: Vol. 221, No. 17 (2018)
  • Don't want grumpy spiders' Keep it cool [OUTSIDE JEB]
    • Authors: Stawski; C.
      Abstract: Clare Stawski

      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.170159
      Issue No: Vol. 221, No. 17 (2018)
  • Pythons sacrifice muscle to provide water for their eggs [OUTSIDE JEB]
    • Authors: Joyce; W.
      Abstract: William Joyce

      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.170175
      Issue No: Vol. 221, No. 17 (2018)
  • Hypoxia-induced changes in hemoglobins of Lake Victoria cichlids [RESEARCH
    • Authors: van den Thillart, G; Wilms, I, Nieveen, M, Weber, R. E, Witte, F.
      Abstract: Guido van den Thillart, Inger Wilms, Maaike Nieveen, Roy E. Weber, and Frans Witte

      In a previous study, broods of the Lake Victoria cichlid Haplochromis ishmaeli raised under hypoxic or normoxic conditions showed striking differences in isohemoglobin (isoHb) pattern that were not observed in two other cichlids that do not belong to the Lake Victoria species flock. We therefore hypothesized that the adaptive mechanism seen in H. ishmaeli in response to hypoxia constitutes a trait that the Lake Victoria species flock inherited from ancestors that lived in hypoxic environments. We tested this hypothesis by designing split-brood experiments with three other representative species from the same species flock: the insectivorous Haplochromis thereuterion, the mollusk-shelling Platytaeniodus degeni and the zooplanktivorous Haplochromis piceatus, while keeping H. ishmaeli as a reference. Split broods were raised, under either normoxia or hypoxia. All hypoxia-raised (HR) individuals of each of the four species exhibited a distinctly different isoHb pattern compared with their normoxia-raised (NR) siblings. The hemoglobin of HR H. thereuterion showed higher O2 affinity compared with NR siblings particularly in the presence of ATP and GTP, indicating that blood of HR juveniles has significantly improved O2-binding affinity under hypoxic conditions. We also tested the capacity to acclimate at greater age in two species by reversing the O2 condition after 7 (H. thereuterion) and 4 (H. ishmaeli) months. After reacclimation for 1 and 2 months, respectively, we found incomplete reversal with intermediate isoHb patterns. As three of the four species do not encounter hypoxic conditions in their environment, this unique trait seems to be a relic inherited from predecessors that lived in hypoxic environments.
      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.177832
      Issue No: Vol. 221, No. 17 (2018)
  • Chirping and asymmetric jamming avoidance responses in the electric fish
           Distocyclus conirostris [SHORT COMMUNICATION]
    • Authors: Petzold, J. M; Alves-Gomes, J. A, Smith, G. T.
      Abstract: Jacquelyn M. Petzold, Jose A. Alves-Gomes, and G. Troy Smith

      Electrosensory systems of weakly electric fish must accommodate competing demands of sensing the environment (electrolocation) and receiving social information (electrocommunication). The jamming avoidance response (JAR) is a behavioral strategy thought to reduce electrosensory interference from conspecific signals close in frequency. We used playback experiments to characterize electric organ discharge frequency (EODf), chirping behavior and the JAR of Distocyclus conirostris, a gregarious electric fish species. EODs of D. conirostris had low frequencies (~80–200 Hz) that shifted in response to playback stimuli. Fish consistently lowered EODf in response to higher-frequency stimuli but inconsistently raised or lowered EODf in response to lower-frequency stimuli. This led to jamming avoidance or anti-jamming avoidance, respectively. We compare these behaviors with those of closely related electric fish (Eigenmannia and Sternopygus) and suggest that the JAR may have additional social functions and may not solely minimize the deleterious effects of jamming, as its name suggests.
      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.178913
      Issue No: Vol. 221, No. 17 (2018)
  • The effect of chronic and acute stressors, and their interaction, on
           testes function: an experimental test during testicular recrudescence
    • Authors: Abolins-Abols, M; Hanauer, R. E, Rosvall, K. A, Peterson, M. P, Ketterson, E. D.
      Abstract: Mikus Abolins-Abols, Rachel E. Hanauer, Kimberly A. Rosvall, Mark P. Peterson, and Ellen D. Ketterson

      Organisms are expected to invest less in reproduction in response to a stressor, but theory predicts that this effect should depend on the frequency and duration of stressors in the environment. Here, we investigated how an acute stressor affected testes function in a songbird, and how chronic stressors influenced the acute stress response. We exposed male dark-eyed juncos (Junco hyemalis) either to chronic or minimal (control) disturbance during testicular recrudescence, after which we measured baseline testosterone, testosterone after an acute handling stressor, and capacity to produce testosterone after hormonal stimulation. In a 2x2 design, we then killed males from the two chronic treatment groups either immediately or after an acute stressor to investigate the effect of long- and short-term stressors on the testicular transcriptome. We found that chronically disturbed birds had marginally lower baseline testosterone. The acute stressor suppressed testosterone in control birds, but not in the chronic disturbance group. The ability to elevate testosterone did not differ between the chronic treatments. Surprisingly, chronic disturbance had a weak effect on the testicular transcriptome, and did not affect the transcriptomic response to the acute stressor. The acute stressor, on the other hand, upregulated the cellular stress response and affected expression of genes associated with hormonal stress response. Overall, we show that testicular function is sensitive to acute stressors but surprisingly robust to long-term stressors, and that chronic disturbance attenuates the decrease in testosterone in response to an acute stressor.
      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.180869
      Issue No: Vol. 221, No. 17 (2018)
  • Correction: Reducing gravity takes the bounce out of running
           (doi:10.1242/jeb.162024) [CORRECTION]
    • Authors: Polet, D. T; Schroeder, R. T, Bertram, J. E. A.
      Abstract: Delyle T. Polet, Ryan T. Schroeder, and John E. A. Bertram

      PubDate: 2018-09-10T01:51:26-07:00
      DOI: 10.1242/jeb.191445
      Issue No: Vol. 221, No. 17 (2018)
  • Head-mounted sensors reveal visual attention of free-flying homing pigeons
    • Authors: Kano, F; Walker, J, Sasaki, T, Biro, D.
      Abstract: Fumihiro Kano, James Walker, Takao Sasaki, and Dora Biro

      Gaze behavior offers valuable insights into attention and cognition. However, technological limitations have prevented the examination of animals' gaze behavior in natural, information-rich contexts; for example, during navigation through complex environments. Therefore, we developed a lightweight custom-made logger equipped with an inertial measurement unit (IMU) and GPS to simultaneously track the head movements and flight trajectories of free-flying homing pigeons. Pigeons have a limited range of eye movement, and their eye moves in coordination with their head in a saccadic manner (similar to primate eye saccades). This allows head movement to act as a proxy for visual scanning behavior. Our IMU sensor recorded the 3D movement of the birds' heads in high resolution, allowing us to reliably detect distinct saccade signals. The birds moved their head far more than necessary for maneuvering flight, suggesting that they actively scanned the environment. This movement was predominantly horizontal (yaw) and sideways (roll), allowing them to scan the environment with their lateral visual field. They decreased their head movement when they flew solo over prominent landmarks (major roads and a railway line) and also when they flew in pairs (especially when flying side by side, with the partner maintained in their lateral visual field). Thus, a decrease in head movement indicates a change in birds' focus of attention. We conclude that pigeons use their head gaze in a task-related manner and that tracking flying birds' head movement is a promising method for examining their visual attention during natural tasks.
      PubDate: 2018-09-06T14:50:14-07:00
      DOI: 10.1242/jeb.183475
      Issue No: Vol. 221, No. 17 (2018)
  • Getting inside the mind of a pigeon [INSIDE JEB]
    • Authors: Knight; K.
      Abstract: Kathryn Knight

      PubDate: 2018-09-06T14:50:14-07:00
      DOI: 10.1242/jeb.188045
      Issue No: Vol. 221, No. 17 (2018)
  • Rethinking the evolution of the human foot: insights from experimental
           research [REVIEW]
    • Authors: Holowka, N. B; Lieberman, D. E.
      Abstract: Nicholas B. Holowka and Daniel E. Lieberman

      Adaptive explanations for modern human foot anatomy have long fascinated evolutionary biologists because of the dramatic differences between our feet and those of our closest living relatives, the great apes. Morphological features, including hallucal opposability, toe length and the longitudinal arch, have traditionally been used to dichotomize human and great ape feet as being adapted for bipedal walking and arboreal locomotion, respectively. However, recent biomechanical models of human foot function and experimental investigations of great ape locomotion have undermined this simple dichotomy. Here, we review this research, focusing on the biomechanics of foot strike, push-off and elastic energy storage in the foot, and show that humans and great apes share some underappreciated, surprising similarities in foot function, such as use of plantigrady and ability to stiffen the midfoot. We also show that several unique features of the human foot, including a spring-like longitudinal arch and short toes, are likely adaptations to long distance running. We use this framework to interpret the fossil record and argue that the human foot passed through three evolutionary stages: first, a great ape-like foot adapted for arboreal locomotion but with some adaptations for bipedal walking; second, a foot adapted for effective bipedal walking but retaining some arboreal grasping adaptations; and third, a human-like foot adapted for enhanced economy during long-distance walking and running that had lost its prehensility. Based on this scenario, we suggest that selection for bipedal running played a major role in the loss of arboreal adaptations.
      Keywords: Comparative biomechanics of movement
      PubDate: 2018-09-06T07:26:29-07:00
      DOI: 10.1242/jeb.174425
      Issue No: Vol. 221, No. 17 (2018)
  • Fluid shift versus body size: changes of hematological parameters and body
           fluid volume in hindlimb-unloaded mice, rats and rabbits [RESEARCH
    • Authors: Andreev-Andrievskiy, A. A; Popova, A. S, Lagereva, E. A, Vinogradova, O. L.
      Abstract: Alexander A. Andreev-Andrievskiy, Anfisa S. Popova, Evgeniia A. Lagereva, and Olga L. Vinogradova

      The cardiovascular system is adapted to gravity, and reactions to the loss of gravity in space are presumably dependent on body size. The dependence of hematological parameters and body fluid volume on simulated microgravity have never been studied as an allometric function before. Thus, we estimated red blood cell (RBC), blood and extracellular fluid volume in hindlimb-unloaded (HLU) or control (attached) mice, rats and rabbits. RBC decrease was found to be size independent, and the allometric dependency for RBC loss in HLU and control animals shared a common power (–0.054±0.008) but a different Y0 coefficient (8.66±0.40 and 10.73±0.49, respectively, P
      PubDate: 2018-09-06T07:26:29-07:00
      DOI: 10.1242/jeb.182832
      Issue No: Vol. 221, No. 17 (2018)
  • A machine vision system for zooplankton behavioural studies: a case study
           on the phototactic behaviour of sea lice (Lepeophtheirus salmonis) during
           sound and ultrasound stimuli [METHODS AND TECHNIQUES]
    • Authors: Solvang, T; Hagemann, A.
      Abstract: Torfinn Solvang and Andreas Hagemann

      Machine vision represents an accurate and easily verifiable method for observing live organisms and this technology is constantly evolving in terms of accessibility and cost. Motivated by the complexity of observing small-sized aquatic organisms in experimental systems, and the difficulties related to real-time observation, sampling and counting without interfering with the organisms, we here present a new method for observing behaviour and dispersion of non-sessile zooplankton organisms using a custom-made tank with an associated machine vision system. The system was used in an experiment where the aim was to assess the effect of sound and ultrasound on the phototactic behaviour of copepodite stages of the salmon louse (Lepeophtheirus salmonis). The experimental set-up is described, including a triangular test tank designed to create a sound pressure gradient, a mechanized camera movement system and a vision system with dedicated image processing software.
      PubDate: 2018-09-06T07:26:29-07:00
      DOI: 10.1242/jeb.183277
      Issue No: Vol. 221, No. 17 (2018)
  • Avian thermoregulation in the heat: is evaporative cooling more economical
           in nocturnal birds' [RESEARCH ARTICLE]
    • Authors: O'Connor, R. S; Smit, B, Talbot, W. A, Gerson, A. R, Brigham, R. M, Wolf, B. O, McKechnie, A. E.
      Abstract: Ryan S. O'Connor, Ben Smit, William A. Talbot, Alexander R. Gerson, R. Mark Brigham, Blair O. Wolf, and Andrew E. McKechnie

      Evaporative cooling is a prerequisite for avian occupancy of hot, arid environments, and is the only avenue of heat dissipation when air temperatures (Ta) exceed body temperature (Tb). Whereas diurnal birds can potentially rehydrate throughout the day, nocturnal species typically forgo drinking between sunrise and sunset. We hypothesized that nocturnal birds have evolved reduced rates of evaporative water loss (EWL) and more economical evaporative cooling mechanisms compared with diurnal species, permitting nocturnal species to tolerate extended periods of intense heat without becoming lethally dehydrated. We used phylogenetically informed regressions to compare EWL and evaporative cooling efficiency [ratio of evaporative heat loss (EHL) and metabolic heat production (MHP); EHL/MHP] among nocturnal and diurnal birds at high Ta. We analyzed variation in three response variables: (1) slope of EWL at Ta between 40 and 46°C, (2) EWL at Ta=46°C and (3) EHL/MHP at Ta=46°C. Nocturnality emerged as a weak, negative predictor, with nocturnal species having slightly shallower slopes and reduced EWL compared with diurnal species of similar mass. In contrast, nocturnal activity was positively correlated with EHL/MHP, indicating a greater capacity for evaporative cooling in nocturnal birds. However, our analysis also revealed conspicuous differences among nocturnal taxa. Caprimulgids and Australian owlet-nightjars had shallower slopes and reduced EWL compared with similarly sized diurnal species, whereas owls had EWL rates comparable to those of diurnal species. Consequently, our results did not unequivocally demonstrate more economical cooling among nocturnal birds. Owls predominately select refugia with cooler microclimates, but the more frequent and intense heat waves forecast for the 21st century may increase microclimate temperatures and the necessity for active heat dissipation, potentially increasing owls' vulnerability to dehydration and hyperthermia.
      PubDate: 2018-09-06T07:13:59-07:00
      DOI: 10.1242/jeb.181420
      Issue No: Vol. 221, No. 17 (2018)
  • Correction: The reluctant visitor: an alkaloid in toxic nectar can reduce
           olfactory learning and memory in Asian honey bees (doi:10.1242/jeb.168344)
    • Authors: Zhang, J; Wang, Z, Wen, P, Qu, Y, Tan, K, Nieh, J. C.
      Abstract: Junjun Zhang, Zhengwei Wang, Ping Wen, Yufeng Qu, Ken Tan, and James C. Nieh

      PubDate: 2018-09-06T07:13:59-07:00
      DOI: 10.1242/jeb.191478
      Issue No: Vol. 221, No. 17 (2018)
  • Cooler snakes respond more strongly to infrared stimuli, but we have no
           idea why [RESEARCH ARTICLE]
    • Authors: Bakken, G. S; Schraft, H. A, Cattell, R. W, Tiu, D. B, Clark, R. W.
      Abstract: George S. Bakken, Hannes A. Schraft, Robert W. Cattell, Donna B. Tiu, and Rulon W. Clark

      The pit organ defining pit vipers (Crotalinae) contains a membrane covered with temperature receptors that detect thermal radiation from environmental surfaces. Temperature is both the environmental parameter being sensed and the mechanism by which the pit membrane detects the signal. As snakes are ectotherms, temperature also has a strong influence on neurological and locomotor responses to the signal. This study of Pacific rattlesnakes (Crotalus oreganus) systematically examined the effect of body, target and background temperatures on response to a moving target. We presented each snake with a moving pendulum bob regulated at a series of six temperatures against a uniform background regulated at one of three temperatures. Snake body temperatures varied from 18 to 36°C. As expected, we found stronger responses to positive contrasts (target warmer than background) than to negative contrasts, and stronger responses to greater contrasts. However, the effect of body temperature was contrary to expectations based on studies of the TRPA1 ion channel (believed to be the molecular basis for pit membrane temperature receptors) and typical thermal reaction norms for neural and motor performance. These predict (1) no response below the threshold where the TRPA1 channel opens, (2) response increasing as temperature increases, peaking near preferred body temperature, and (3) declining thereafter. Remarkably, this behavioral response decreased as body temperature increased from 18 to 36°C, with no threshold or peak in this range. We review various possible physiological mechanisms related to body temperature proposed in the literature, but find none that can satisfactorily explain this result.
      PubDate: 2018-09-05T01:13:19-07:00
      DOI: 10.1242/jeb.182121
      Issue No: Vol. 221, No. 17 (2018)
  • Scaling of morphology and ultrastructure of hearts among wild African
           antelope [RESEARCH ARTICLE]
    • Authors: Snelling, E. P; Maloney, S. K, Farrell, A. P, Meyer, L. C. R, Izwan, A, Fuller, A, Mitchell, D, Haw, A, Costello, M.-A, Seymour, R. S.
      Abstract: Edward P. Snelling, Shane K. Maloney, Anthony P. Farrell, Leith C. R. Meyer, Adian Izwan, Andrea Fuller, Duncan Mitchell, Anna Haw, Mary-Ann Costello, and Roger S. Seymour

      The hearts of smaller mammals tend to operate at higher mass-specific mechanical work rates than those of larger mammals. The ultrastructural characteristics of the heart that allow for such variation in work rate are still largely unknown. We have used perfusion-fixation, transmission electron microscopy and stereology to assess the morphology and anatomical aerobic power density of the heart as a function of body mass across six species of wild African antelope differing by approximately 20-fold in body mass. The survival of wild antelope, as prey animals, depends on competent cardiovascular performance. We found that relative heart mass (g kg–1 body mass) decreases with body mass according to a power equation with an exponent of –0.12±0.07 (±95% confidence interval). Likewise, capillary length density (km cm–3 of cardiomyocyte), mitochondrial volume density (fraction of cardiomyocyte) and mitochondrial inner membrane surface density (m2 cm–3 of mitochondria) also decrease with body mass with exponents of –0.17±0.16, –0.06±0.05 and –0.07±0.05, respectively, trends likely to be associated with the greater mass-specific mechanical work rate of the heart in smaller antelope. Finally, we found proportionality between quantitative characteristics of a structure responsible for the delivery of oxygen (total capillary length) and those of a structure that ultimately uses that oxygen (total mitochondrial inner membrane surface area), which provides support for the economic principle of symmorphosis at the cellular level of the oxygen cascade in an aerobic organ.
      PubDate: 2018-09-05T01:13:19-07:00
      DOI: 10.1242/jeb.184713
      Issue No: Vol. 221, No. 17 (2018)
  • Fin and body neuromuscular coordination changes during walking and
           swimming in Polypterus senegalus [RESEARCH ARTICLE]
    • Authors: Foster, K. L; Dhuper, M, Standen, E. M.
      Abstract: Kathleen L. Foster, Misha Dhuper, and Emily M. Standen

      The ability to modulate the function of muscle is integral to an animal's ability to function effectively in the face of widely disparate challenges. This modulation of function can manifest through short-term changes in neuromuscular control, but also through long-term changes in force profiles, fatiguability and architecture. However, the relative extent to which shorter-term modulation and longer-term plasticity govern locomotor flexibility remains unclear. Here, we obtain simultaneously recorded kinematic and muscle activity data of fin and body musculature of an amphibious fish, Polypterus senegalus. After examining swimming and walking behaviour in aquatically raised individuals, we show that walking behaviour is characterized by greater absolute duration of muscle activity in most muscles when compared with swimming, but that the magnitude of recruitment during walking is only increased in the secondary bursts of fin muscle and in the primary burst of the mid-body point. This localized increase in intensity suggests that walking in P. senegalus is powered in a few key locations on the fish, contrasting with the more distributed, low intensity muscle force that characterizes the stroke cycle during swimming. Finally, the increased intensity in secondary, but not primary, bursts of the fin muscles when walking probably underscores the importance of antagonistic muscle activity to prevent fin collapse, add stabilization and increase body support. Understanding the principles that underlie the flexibility of muscle function can provide key insights into the sources of animal functional and behavioural diversity.
      Keywords: Comparative biomechanics of movement
      PubDate: 2018-09-03T01:26:20-07:00
      DOI: 10.1242/jeb.168716
      Issue No: Vol. 221, No. 17 (2018)
  • Limits to sustained energy intake XXIX: the case of the golden hamster
           (Mesocricetus auratus) [RESEARCH ARTICLE]
    • Authors: Ohrnberger, S. A; Hambly, C, Speakman, J. R, Valencak, T. G.
      Abstract: S. A. Ohrnberger, C. Hambly, J. R. Speakman, and T. G. Valencak

      Golden hamster females have the shortest known gestation period among placental mammals and at the same time raise very large litters of up to 16 offspring, which are born in a naked and blind state and are able to pick up food from days 12-14 only. We quantified energy metabolism and milk production in female golden hamsters raising offspring under cold (8°C), normal (22°C) and hot (30°C) ambient temperature conditions. We monitored energy intake, subcutaneous body temperature, daily energy expenditure, litter size and pup masses over the course of lactation. Our results show that, in line with the concept of heat dissipation limitation, female golden hamsters had the largest energy intake under the coldest conditions and a significantly lower intake at 30° (partial for influence of ambient temperature: F2,403=5.6; p= 0.004). Metabolisable energy intake as well as milk energy output showed the same pattern and were significantly different between the temperatures (partial for milk energy production: F1,40= 86.4; p
      PubDate: 2018-09-18T03:32:39-07:00
      DOI: 10.1242/jeb.183749
  • An exercise-induced improvement in isolated skeletal muscle contractility
           does not affect the performance-enhancing benefit of 70{mu}M caffeine
           treatment [SHORT COMMUNICATION]
    • Authors: Tallis, J; Higgins, M. F, Cox, V. M, Duncan, M. J, James, R. S.
      Abstract: Jason Tallis, Matthew F. Higgins, Val M. Cox, Michael J. Duncan, and Rob S. James

      This study aimed to examine the effects of exercise-induced increases in skeletal muscle contractile performance on isolated skeletal muscle caffeine sensitivity. 30-week old CD1 mice (n=28) either acted as controls or underwent eight weeks of voluntary wheel running. Following the treatment intervention, whole soleus (SOL) or a section of the costal diaphragm (DIA) was isolated from each mouse and tested to determine the effect of 70μM caffeine on work loop power output. Although caffeine elicited a significant increase in power of both the SOL and the DIA, relative to a non-caffeine control, the effect was not different between the experimental groups, despite the muscles of the trained group producing significantly greater muscle power. There was no significant relationship between training volume or baseline work loop power and the caffeine response. These results indicate that an exercise-induced increase in muscle performance did not influence the performance-enhancing effects of caffeine.
      PubDate: 2018-09-17T07:41:03-07:00
      DOI: 10.1242/jeb.190132
  • Electrical interactions between photoreceptors in the compound eye of
           Periplaneta americana [RESEARCH ARTICLE]
    • Authors: Saari, P; Immonen, E.-V, French, A. S, Torkkeli, P. H, Liu, H, Heimonen, K, Frolov, R. V.
      Abstract: Paulus Saari, Esa-Ville Immonen, Andrew S. French, Päivi H. Torkkeli, Hongxia Liu, Kyösti Heimonen, and Roman V. Frolov

      The compound eye of Periplaneta americana contains two spectral classes of photoreceptors: narrow-band UV-sensitive and broad-band green-sensitive. In intracellular recordings, stimulation of green-sensitive photoreceptors with flashes of relatively bright UV/violet light produced anomalous delayed depolarization after the end of the normal light response, whereas stimulation of UV-sensitive photoreceptors with green light elicited biphasic responses characterized by initial transient hyperpolarization followed by prolonged delayed depolarization. To explore the basis for these findings, we used RNA interference to selectively suppress expression of the genes coding either green opsin (GO1) or UV opsin (UVO) or both. The hyperpolarizing component in UV-sensitive photoreceptors was eliminated and the delayed depolarization reduced after GO1 knock-down, suggesting that the hyperpolarization represents fast inhibitory interactions between green- and UV-sensitive photoreceptors. Green-sensitive photoreceptor responses of GO1 knockdowns to flashes of UV/violet were almost exclusively biphasic, while residual responses to green had normal kinetics. Knock-down of UVO reduced the responses of UV-sensitive photoreceptors but had minor effects on delayed depolarization in green-sensitive photoreceptors. Angular sensitivity analysis indicated that delayed depolarization of green-sensitive photoreceptors by violet light originates from excitation of (an)other photoreceptor(s) in the same ommatidium. The angle at which the maximal delayed depolarization was observed in green-sensitive photoreceptors stimulated with violet light did not match the angle of the maximal transient depolarization. In contrast, no significant mismatch was observed for delayed depolarization elicited by green light. These results suggest that the cellular sources of the normal transient and additional delayed depolarization by violet light are separate and distinct.
      PubDate: 2018-09-17T07:41:03-07:00
      DOI: 10.1242/jeb.189340
  • Ultrasound avoidance by flying antlions (Myrmeleontidae) [RESEARCH
    • Authors: Holderied, M. W; Thomas, L. A, Korine, C.
      Abstract: Marc W. Holderied, Liam A. Thomas, and Carmi Korine

      The acoustic arms race between insectivorous bats and their invertebrate prey has led to the convergent evolution of ultrasound hearing in seven orders of nocturnal insects. Upon hearing the echolocation calls of an approaching bat such insects take defensive action. Here we document an unknown sense of ultrasound hearing and phonotactic flight behaviour in the neuropteran family Myrmeleontidae (antlions). The antlion Myrmeleon hyalinus was presented with sound pulses at ultrasonic frequencies used by echolocating bats and its response thresholds in tethered flight determined. Behaviours included abdominal twitches, wing-flicks, brief pauses in flight and flight cessation. Such behaviours create erratic evasive flight manoeuvres in other eared insects, particularly mantids and lacewings. Antlions responded best to ultrasound between 60-80 kHz (75 dB peSPL at 80 kHz) showing response thresholds similar to the related lacewings (Neuroptera, Chrysopidae). Yet at lower ultrasonic frequencies (20-50 kHz) antlions were far less sensitive than lacewings. Based on calculated response distances we conclude that antlions respond only after having been detected by bats rather than using early evasive flights. We argue that the high response threshold for low frequency ultrasound is adaptive for an insect that is mainly active close to and within vegetation, because a behavioural response to the lower ultrasonic frequencies used by high-flying bats would result in evasive action in the absence of actual predation risk.
      PubDate: 2018-09-17T07:41:03-07:00
      DOI: 10.1242/jeb.189308
  • Dietary canthaxanthin reduces xanthophyll uptake and red coloration in
           adult red-legged partridges [RESEARCH ARTICLE]
    • Authors: Alonso-Alvarez, C; Garcia-de Blas, E, Mateo, R.
      Abstract: C. Alonso-Alvarez, E. Garcia-de Blas, and R. Mateo

      Carotenoids give color to conspicuous animal signals that are often the product of sexual selection. To know the mechanisms involved in carotenoid-based signaling is critical to understand how these traits evolve. However, these mechanisms remain partially understood. Carotenoids are usually viewed as scarce dietary antioxidants whose allocation to ornaments may trade against health. This trade-off would assure its reliability as individual quality signals. In the case of red (keto)carotenoids, the literature suggests that some species may show constraints in their uptake. Canthaxanthin is one of the most common ketocarotenoids in red ornaments of animals. It is often commercially used as a dietary supplement to obtain redder birds (e.g. poultry). We increased the dietary canthaxanthin levels in captive red-legged partridges (Alectoris rufa). This species shows red bare parts mostly pigmented by another common ketocarotenoid: astaxanthin. We studied the impact on the uptake of carotenoids, vitamins and, finally, on coloration. We also tested the potential protecting effect of canthaxanthin when exposing birds to a free radical generator (diquat). Canthaxanthin did not apparently protect birds from oxidative stress, but interfered with the absorption of yellow carotenoids (lutein and zeaxanthin). Zeaxanthin is a precursor of astaxanthin in enzymatic pathways, and their values in tissues and eggs were lower in canthaxanthin-supplied birds. This led to lower astaxanthin levels in ornaments and paler colorations. As far as we know, this is the first report of a carotenoid supplementation decreasing animal coloration. The results have implications for understanding carotenoid-based signaling evolution, but also for improving husbandry/experimental procedures.
      PubDate: 2018-09-17T07:41:03-07:00
      DOI: 10.1242/jeb.185074
  • Impacts of differences in nutritional quality of wingless and winged
           aphids on parasitoid fitness [RESEARCH ARTICLE]
    • Authors: Pirotte, J. A.- L. M; Lorenzi, A, Foray, V, Hance, T.
      Abstract: Jennifer A.-L. M. Pirotte, Ange Lorenzi, Vincent Foray, and Thierry Hance

      Winged aphids are described as hosts of lesser quality for parasitoids because a part of their resources is used to produce wings and associated muscles during their development. Host lipid content is particularly important for parasitoid larvae as they lack lipogenesis, therefore, they rely entirely on the host for this resource. The goal of this study is to determine in what extent winged and wingless aphids differ from the nutritional point of view and if these differences impact the parasitoid fitness notably the lipid content. We analysed the energetic budget (proteins, lipids and carbohydrates) of aphids of different ages (third, fourth instars and adults) according to the morph (winged or wingless). We also compared fitness indicators for parasitoids emerging from winged and wingless aphids (third and fourth instars). We found that in third instars, parasitoids are able to inhibit wing development whereas not in fourth instars. Both winged instars allow the production of heavier and fattier parasitoids. The presence of wings in aphids seems to have little effect on the fitness of emerging parasitoids and did not modify female choice for oviposition. Finally, we demonstrate that Aphidius colemani, used as a biological control agent is able to parasite wingless as well as winged Myzus persicae at least the juvenile stages. If the parasitism occurs in third instars, the parasitoid will prevent the aphid from flying, which could in turn reduce the virus transmission.
      PubDate: 2018-09-11T03:34:41-07:00
      DOI: 10.1242/jeb.185645
  • Aquatic versus terrestrial crab skeletal support: morphology, mechanics,
           molting and scaling [RESEARCH ARTICLE]
    • Authors: Taylor; J. R. A.
      Abstract: Jennifer R. A. Taylor

      The transition from aquatic to terrestrial environments places significant mechanical challenges on skeletal support systems. Crabs have made this transition multiple times and are the largest arthropods to inhabit both environments. Furthermore, they alternate between rigid and hydrostatic skeletons, making them an interesting system to examine mechanical adaptations in skeletal support systems. I hypothesized that terrestrial crabs have modified morphology to enhance mechanical stiffness and that rigid and hydrostatic skeletons scale differently from each other, with stronger allometric relationships on land. Using the aquatic blue crab, Callinectes sapidus, and the terrestrial blackback land crab, Gecarcinus lateralis, I measured and compared body mass, merus morphology (dimensions, cuticle thickness, and I) and mechanics (EI, E, critical stress, and hydrostatic pressure) of rigid and hydrostatic stage crabs encompassing a range of sizes (C. sapidus: 1.5-133 g, N≤24; G. lateralis: 22-70 g, N≤15). Results revealed that rigid G. lateralis has similar morphology (L/D and T/D) than C. sapidus, but the mechanics and most scaling relationships are the same. Hydrostatic land crabs differ from aquatic crabs by having different morphology (thinner cuticle), mechanics (greater internal pressures), and scaling relationship (cuticle thickness). These results suggest that the rigid crab body plan is inherently overbuilt and sufficient to deal with the greater gravitational loading that occurs on land, while mechanical adaptations are important for hydrostatically supported crabs. Compared to other arthropods and hydrostatic animals, crabs possess distinct strategies for adapting mechanically to life on land.
      PubDate: 2018-09-07T06:51:37-07:00
      DOI: 10.1242/jeb.185421
  • Controlled feeding experiments with diets of different abrasiveness reveal
           slow development of mesowear signal in goats (Capra aegagrus hircus)
    • Authors: Ackermans, N. L; Winkler, D. E, Schulz-Kornas, E, Kaiser, T. M, Müller, D. W. H, Kircher, P. R, Hummel, J, Clauss, M, Hatt, J.-M.
      Abstract: Nicole L. Ackermans, Daniela E. Winkler, Ellen Schulz-Kornas, Thomas M. Kaiser, Dennis W. H. Müller, Patrick R. Kircher, Jürgen Hummel, Marcus Clauss, and Jean-Michel Hatt

      Dental mesowear is applied as a proxy to determine the general diet of mammalian herbivores based on tooth-cusp shape and occlusal relief. Low, blunt cusps are considered typical for grazers and high, sharp cusps typical for browsers. However, how internal or external abrasives impact mesowear, and the time frame the wear signature takes to develop, still need to be explored. Four different pelleted diets of increasing abrasiveness (lucerne, grass, grass and rice husks, grass, rice husks and sand) were fed to four groups of a total of 28 adult goats in a controlled feeding experiment over a six-month period. Tooth morphology was captured by medical CT scans at the beginning and end of the experiment. These scans, as well as the crania obtained postmortem, were scored using the mesowear method. Comparisons between diet groups only showed few significant differences after six months, irrespective of whether CT scans or the real teeth were scored. Only when assessing the difference in signal between start and end did relevant, significant diet-specific effects emerge. Diets containing lower phytolith content caused a more pronounced change in mesowear towards sharper cusps/higher reliefs, while the feed containing sand did not result in more extreme changes in mesowear when compared to the same feed without sand. Our experiment suggests that the formation of a stable and hence reliable mesowear signal requires more time to develop than six months.
      PubDate: 2018-09-07T06:36:19-07:00
      DOI: 10.1242/jeb.186411
  • Head width influences flow sensing by the lateral line canal system in
           fishes [RESEARCH ARTICLE]
    • Authors: Yanagitsuru, Y. R; Akanyeti, O, Liao, J. C.
      Abstract: Yuzo R. Yanagitsuru, Otar Akanyeti, and James C. Liao

      The architecture of the cephalic lateral line canal system, with distinct lines for the supraorbital, infraorbital, and mandibular canals, is highly conserved among fish species. Because these canals lay on a cranial platform, the sensory input they receive is expected to change based on how flow interacts with the head and how the canal pores are spatially distributed. In this study, we explore how head width, a trait that can vary greatly between species and across ontogeny, affects flow sensing. We inserted pressure sensors into physical fish head models of varying widths (narrow, intermediate, and wide) and placed these models in steady and vortical flows. We measured sensory performance in terms of detecting flow parameters (flow speed, vortex shedding frequency, and cylinder diameter), sensitivity, (change in pressure gradient as a function of flow speed) and signal-to-noise ratio (strength of vortex shedding frequency with respect to background). Our results show that in all model heads the amount of hydrodynamic information was maximized at the anterior region regardless of what metric we used to evaluate the sensory performance. In addition, we discovered that all model heads had the highest signal-to-noise ratios (SNR) for vortices at the intermediate flow speeds but that each head width passively optimized the SNR for different sized vortices, which may have implications for refuge and prey seeking. Our results provide insight into the sensory ecology of fishes and has implications for the design of autonomous underwater vehicles.
      PubDate: 2018-09-07T06:36:19-07:00
      DOI: 10.1242/jeb.180877
  • Differences in motor cortical control of the Soleus and Tibialis [RESEARCH
    • Authors: Lauber, B; Gollhofer, A, Taube, W.
      Abstract: Benedikt Lauber, Albert Gollhofer, and Wolfgang Taube

      The tibialis anterior (TA) and the soleus (SOL) are both ankle joint muscles with functionally very different tasks. Thus, differences in motor cortical control between the TA and the SOL have been debated. This study compared the activity of the primary motor cortex during dynamic plantar- and dorsiflexions and compared this with measures obtained during rest. Single- and paired-pulse transcranial magnetic stimulations known as short-interval intracortical inhibition (SICI) were applied to the cortical representation of either the soleus or the tibialis muscle. The results show that the range of SICI from rest to activity is significantly greater in the TA compared with the SOL. Furthermore, when the TA acts as the agonist muscle during dorsiflexions of the ankle, SICI is almost absent (2.9%). When acting as the antagonist during plantarflexions, intracortical inhibition is significantly increased (28.7%). This task-specific modulation is far less pronounced in the SOL, which displayed higher levels of SICI when acting as agonist (10.9%) during plantarflexion, but there was no significant inhibition (6.5%) as antagonist during dorsiflexion. Furthermore, the cortical silent period (CSP) during plantarflexions was significantly longer in the SOL compared with the TA during dorsiflexions, accompanied by a greater corticospinal excitability in the TA. Thus, cortical control considerably differs between the SOL and the TA in a way that inhibitory cortical control (SICI and CSP) of the TA is task-specifically adapted in a broader range of movements, whereas inhibition in the SOL muscle is less specific and more limited in its magnitude of modulation.
      PubDate: 2018-09-07T06:36:19-07:00
      DOI: 10.1242/jeb.174680
  • Effects of both cold and heat stresses on the liver of giant spiny frog
           Quasipaa spinosa: stress response and histological changes [RESEARCH
    • Authors: Liu, Z.-P; Gu, W.-B, Tu, D.-D, Zhu, Q.-H, Zhou, Y.-L, Wang, C, Wang, L.-Z, Shu, M.-A.
      Abstract: Ze-Peng Liu, Wen-Bin Gu, Dan-Dan Tu, Qi-Hui Zhu, Yi-Lian Zhou, Cong Wang, Lan-Zhi Wang, and Miao-An Shu

      Ambient temperature associated stress can affect the normal physiological functions in ectotherms. To assess the effects of cold or heat stress on amphibians, the giant spiny frogs, Quasipaa spinosa, were acclimated at 22 °C followed by being treated at 5 °C or 30 °C for 0, 3, 6, 12, 24 and 48 h, respectively. Histological alterations, apoptotic index, mitochondrial reactive oxygen species (ROS) generation, antioxidant activity indices and stress-response gene expressions in frog livers were subsequently determined. Results showed that many fat droplets appeared after 12 h of heat stress. Percentage of melanomacrophages centres significantly changed during 48 h at both stress conditions. Furthermore, the mitochondrial ROS levels were elevated in a time-dependent manner up to 6 h and 12 h in the cold and heat stress groups, respectively. The activities of superoxide dismutase, glutathione peroxidase and catalase were successively increased along the cold or heat exposure, and most of their gene expression levels showed similar changes at both stress conditions. Most tested HSP genes were sensitive to temperature exposure, and the expression profiles of most apoptosis-related genes was significantly up-regulated at 3 and 48 h under cold and heat stress, respectively. Apoptotic index at 48 h under cold stress was significantly higher than that under heat stress. Notably, lipid droplets, HSP30, HSP70 and HSP110 might be suitable bioindicators of heat stress. The results of these alterations at physiological, biochemical and molecular levels might contribute to a better understanding of the stress response of Q. spinosa and even amphibians under thermal stresses.
      PubDate: 2018-09-06T02:15:29-07:00
      DOI: 10.1242/jeb.186379
  • The yellow specialist: dronefly Eristalis tenax prefers different yellow
           colours for landing and proboscis extension [RESEARCH ARTICLE]
    • Authors: An, L; Neimann, A, Eberling, E, Algora, H, Brings, S, Lunau, K.
      Abstract: Lina An, Alexander Neimann, Eugen Eberling, Hanna Algora, Sebastian Brings, and Klaus Lunau

      Droneflies, imagoes of the hoverfly Eristalis tenax, are known to possess a preference for yellow flowers, i.e. they prefer to visit yellow flowers and prefer to extend the proboscis to yellow colours. In this study we disentangle these colour preferences by investigating the landing reaction and proboscis reflex with particular reference to intensity, spectral purity and dominant wavelength of colour stimuli and their UV-reflection properties. In multiple choice tests naïve and non-trained flies prefer to land on yellow colours independent of its UV-reflection, but also accept blue, white and pink colours if UV-absorbing and of effectual brightness. Flies trained to land on other colours than yellow still prefer yellow colours to some extent. Moreover, the flies prefer bright over dark yellow colours even if trained to dark yellow ones. The flies refuse to land on dark colours of all colour hues. Naïve flies exhibit the proboscis reflex only to pure yellow pollen. These experiments show for the first time that landing in Droneflies is triggered by yellow colours independent of UV-reflection properties, but the proboscis extension by strongly UV- and blue-absorbing yellow colours. The ability to discriminate colours is better than predicted by the categorical colour vision model. The colour preferences in E. tenax seem a fine-tuned ability to visit yellow flowers displaying an ultraviolet bull's eye colour pattern.
      PubDate: 2018-09-06T02:15:29-07:00
      DOI: 10.1242/jeb.184788
  • Dietary antioxidants, but not courtship effort, affect oxidative balance
           in the testes and muscles of crickets [RESEARCH ARTICLE]
    • Authors: Simmons, L. W; Lovegrove, M, Lymbery, S. J.
      Abstract: Leigh W. Simmons, Maxine Lovegrove, and Samuel J. Lymbery

      Recent interest has focused on the role of reactive oxygen species (ROS) as universal constraints in life-history evolution. Empirical studies have examined the oxidative costs of reproduction for females, with little work conducted on males. The male germline is thought to be particularly susceptible to oxidative damage because the testes, and sperm themselves, can be prolific producers of ROS. We tested the hypothesis that protection of the male germline from oxidative damage represents a cost of reproduction for males. We fed male crickets, Teleogryllus oceanicus, with one of two experimental diets in which we manipulated the availability of dietary antioxidants and induced variation in their expenditure on courtship effort by manipulating access to females. We measured the total antioxidant capacity, levels of ROS production and the amount of oxidative damage to proteins in both testis and thoracic muscle tissues. Dietary antioxidants contributed to positive oxidative balance in both tissue types. Although testes had greater antioxidant defences than muscle tissue, they also produced considerably higher levels of ROS and sustained higher levels of oxidative damage. Courtship effort had no impact on any measure of oxidative balance. Our data confirm that the male germline is especially susceptible to oxidative stress and that dietary antioxidants can alleviate this oxidative cost of reproduction.
      PubDate: 2018-09-06T02:15:29-07:00
      DOI: 10.1242/jeb.184770
  • Aerobic capacities and swimming performance of Polar cod (Boreogadus saida
           Lepechin) under ocean acidification and warming conditions [RESEARCH
    • Authors: Kunz, K. L; Claireaux, G, Pörtner, H.-O, Knust, R, Mark, F. C.
      Abstract: Kristina Lore Kunz, Guy Claireaux, Hans-Otto Pörtner, Rainer Knust, and Felix Christopher Mark

      Polar cod, Boreogadus saida, is an important prey species in the Arctic ecosystem, yet its habitat is changing rapidly: Climate change, through rising seawater temperatures and CO2 concentrations, is projected to be most pronounced in Arctic waters. This study aimed at investigating the influence of ocean acidification and warming on maximum performance parameters of B. saida as indicators for the species’ acclimation capacities under environmental conditions projected for the end of this century. After four months at four acclimation temperatures (0, 3, 6, 8°C) each combined with two PCO2 levels (390 and 1170 µatm), aerobic capacities and swimming performance of B. saida were recorded following a Ucrit protocol. At both CO2 levels, standard metabolic rate (SMR) was elevated at the highest acclimation temperature indicating thermal limitations. Maximum metabolic rate (MMR) increased continuously with temperature, suggesting an optimum temperature for aerobic scope for exercise (ASex) at 6°C. Aerobic swimming performance (Ugait) increased with acclimation temperature irrespective of CO2 levels, while critical swimming speed (Ucrit) did not reveal any clear trend with temperature. Hypercapnia evoked an increase in MMR (and thereby ASex). However, swimming performance (both Ugait and Ucrit) was impaired under elevated near-future PCO2 conditions, indicating reduced efficiencies of oxygen turnover. The contribution of anaerobic metabolism to swimming performance was overall very low, and further reduced under hypercapnia. Our results revealed high sensitivities of maximum performance parameters (MMR, Ugait, Ucrit) of B. saida to ocean acidification. Impaired swimming capacity under ocean acidification may reflect reduced future competitive strength of B. saida.
      PubDate: 2018-09-06T02:15:29-07:00
      DOI: 10.1242/jeb.184473
  • Physiological responses of ionotropic histamine receptors, PxHCLA and
           PxHCLB, to neurotransmitter candidates in a butterfly, Papilio xuthus
    • Authors: Akashi, H. D; Chen, P.-J, Akiyama, T, Terai, Y, Wakakuwa, M, Takayama, Y, Tominaga, M, Arikawa, K.
      Abstract: Hiroshi D. Akashi, Pei-Ju Chen, Tokiho Akiyama, Yohey Terai, Motohiro Wakakuwa, Yasunori Takayama, Makoto Tominaga, and Kentaro Arikawa

      Histamine is the only known neurotransmitter released by arthropod photoreceptors. Synaptic transmission from photoreceptors to second order neurons is mediated by the activation of histamine-gated chloride channels (HCLs). These histaminergic synapses have been assumed to be conserved among insect visual systems. However, our understanding of the channels in question has thus far been based on studies in flies. In the butterfly Papilio xuthus, we have identified two candidate histamine-gated chloride channels, PxHCLA and PxHCLB, and studied their physiological properties using a whole-cell patch-clamp technique. We studied the responses of channels expressed in cultured cells to histamine as well as to other neurotransmitter candidates, namely GABA, tyramine, serotonin, D-/L- glutamate, and glycine. We found that histamine and GABA activated both PxHCLA and PxHCLB, while the other molecules did not. The sensitivity to histamine and GABA was consistently higher in PxHCLB than in PxHCLA. Interestingly, simultaneous application of histamine and GABA activated both PxHCLA and PxHCLB more strongly than either neurotansmitter individually; histamine and GABA may have synergistic effects on PxHCLs in the regions where they colocalize. Our results suggest that the physiological properties of the histamine receptors are basically conserved among insects, but that the response to GABA differs between butterflies and flies, implying variation in early visual processing among species.
      PubDate: 2018-09-06T02:15:29-07:00
      DOI: 10.1242/jeb.183129
  • Insect fat body cell morphology and response to cold stress is modulated
           by acclimation [RESEARCH ARTICLE]
    • Authors: Des Marteaux, L. E; Stetina, T, Kostal, V.
      Abstract: Lauren E. Des Marteaux, Tomas Stetina, and Vladimir Kostal

      Mechanistic understanding about the nature of cellular cryoinjury and mechanisms by which some animals survive freezing while others do not, is currently lacking. Here we exploited the broadly-manipulable freeze tolerance of larval malt flies (Chymomyza costata) to uncover cell and tissue morphological changes associated with freeze mortality. Diapause induction, cold acclimation, and dietary proline supplementation generate malt fly variants ranging from weakly to extremely freeze tolerant. Using confocal microscopy and immunostaining of the fat body, Malpighian tubules, and anterior midgut we described tissue and cytoskeletal (F-actin and α-tubulin) morphologies among these variants after exposure to various cold stresses (from chilling at -5°C to extreme freezing at -196°C), and upon recovery from cold exposure. Fat body tissue appeared to be the most susceptible to cryoinjury; freezing caused coalescence of lipid droplets, loss of α-tubulin structure, and apparent aggregation of F-actin. A combination of diapause and cold acclimation substantially lowered the temperature at which these morphological disruptions occurred. Larvae that recovered from a freezing challenge repaired F-actin aggregation but repaired neither lipid droplet coalescence nor α-tubulin structure. Our observations indicate that lipid coalescence and damage to α-tubulin are non-lethal forms of freeze injury, and suggest that repair or removal (rather than protection) of actin proteins is a potential mechanism of acquired freeze tolerance.
      PubDate: 2018-09-06T02:15:28-07:00
      DOI: 10.1242/jeb.189647
  • No short-term physiological costs of offspring care in a cooperatively
           breeding bird [RESEARCH ARTICLE]
    • Authors: Guindre-Parker, S; Rubenstein, D. R.
      Abstract: Sarah Guindre-Parker and Dustin R. Rubenstein

      The cost of reproduction results in a life-history trade-off where investment in current reproduction via costly parental care decreases subsequent fitness. Although this trade-off is thought to occur ubiquitously across animals, there is equivocal evidence that parental care behaviours are costly. A major challenge of studying the cost of parental care has been a lack of consensus over which physiological mechanisms underlie this trade-off. Here we compare four traits believed to mediate the cost of parental care by examining whether glucocorticoids, oxidative stress, immune function, or body condition represent a cost of performing offspring care and shape subsequent fitness. We use a 4-year dataset collected in free-living cooperatively breeding superb starlings (Lamprotornis superbus), a species in which parental and alloparental care effort varies widely among individuals and across years. Our results showed that within-individual change in physiology was unrelated to investment in offspring care, and physiological state during chick-rearing did not predict the likelihood that an individual would breeding in subsequent seasons. Instead, individuals that had elevated baseline corticosterone during incubation performed more nest guarding, suggesting that this hormone may play a preparatory role for investing in offspring care. Together, our results indicate that superb starlings modify their investment in offspring care according to their physiological state during incubation, despite no evidence of a short-term physiological cost of parental or alloparental care. Thus, breeding cooperatively appears to provide individuals with the flexibility to adjust their investment in offspring care and overcome any potential costs of reproduction.
      PubDate: 2018-09-06T02:15:28-07:00
      DOI: 10.1242/jeb.186569
  • Environmental temperature alters the digestive performance and gut
           microbiota of a terrestrial amphibian [RESEARCH ARTICLE]
    • Authors: Fontaine, S. S; Novarro, A. J, Kohl, K. D.
      Abstract: Samantha S. Fontaine, Alexander J. Novarro, and Kevin D. Kohl

      Environmental temperature and gut microbial communities can both have profound impacts on the digestive performance of ectothermic vertebrates. Additionally, the diversity, composition, and function of gut microbial communities themselves are influenced by temperature. It is typically assumed that the temperature-dependent nature of ectotherm digestive performance is due to factors such as host physiological changes and adaptation to local climatic conditions. However, it is also possible that temperature-induced alterations to gut microbiota may influence the relationship between temperature and digestion. To explore the connections between these three factors, we compared digestive performance and gut microbial community diversity and composition in red-backed salamanders housed at three experimental temperatures—10°C, 15°C, and 20°C. We also investigated associations between specific bacterial taxa and temperature, or salamander digestive performance. We found that salamander digestive performance was greatest at 15°C, while gut microbial diversity was reduced at 20°C. Further, gut microbial community composition differed among the three temperature treatments. The relative abundances of 25 bacterial genera were dependent on temperature, with high temperatures being associated with reductions in relative abundance of disease-resistant bacteria and increases in pathogenic taxa. The relative abundances of four bacterial genera were correlated with salamander energy assimilation, two of which are known to digest chitin, a main component of the red-backed salamander diet. These findings suggest that gut microbiota may mediate the relationship between temperature and digestion in ectotherms. We discuss how global climate change may impact ectotherms by altering host-microbe interactions.
      PubDate: 2018-08-31T02:24:43-07:00
      DOI: 10.1242/jeb.187559
  • Effects of temperature on juvenile Dungeness crab, Metacarcinus magister
           (Dana): survival, moulting, and mTOR signalling and neuropeptide gene
           expression in eyestalk ganglia, moulting gland (Y-organ), and heart
    • Authors: Wittmann, A. C; Benrabaa, S. A. M, Lopez-Ceron, D. A, Chang, E. S, Mykles, D. L.
      Abstract: Astrid C. Wittmann, Samiha A. M. Benrabaa, Diego Alejandro Lopez-Ceron, Ernest S. Chang, and Donald L. Mykles

      Mechanistic target of rapamymcin (mTOR) is a highly conserved protein kinase that controls cellular protein synthesis and energy homeostasis. We hypothesize that mTOR integrates intrinsic signals (moulting hormones) and extrinsic signals (thermal stress) to regulate moulting and growth in decapod crustaceans. The effects of temperature on survival, moulting, and mRNA levels of mTOR signalling genes (Mm-Rheb, Mm-mTOR, Mm-AMPKα, Mm-S6K, and Mm-AKT) and neuropeptides (Mm-CHH and Mm-MIH) were quantified in juvenile Metacarcinus magister. Crabs at different moult stages (12 d, 18 d or 26 d postmoult) were transferred from ambient temperature (~15°C) to temperatures between 5 and 30°C for up to 14 days. Survival was 97-100% from 5 to 20°C, but none survived at 25°C and 30°C. Moult stage progression accelerated from 5 to 15°C, but not further at 20°C. In eyestalk ganglia, Mm-Rheb, Mm-AMPKα, and Mm-AKT mRNA levels decreased with increasing temperatures. Mm-MIH and Mm-CHH mRNA levels were lowest in the eyestalk ganglia of mid-premoult animals at 20°C. In Y-organ, Mm-Rheb mRNA level decreased with increasing temperature and increased during premoult and was positively correlated with haemolymph ecdysteroid titre. In heart, moult stage had no effect on mTOR signalling gene mRNA levels; only Mm-Rheb, Mm-S6K, and Mm-mTOR mRNA levels were higher in intermoult animals at 10°C. These data suggest that temperature compensation of neuropeptide and mTOR signalling gene expression in eyestalk ganglia and Y-organ contributes to regulate moulting in the 10°C to 20°C range. The limited warm compensation in heart may contribute to mortality at temperatures above 20°C.
      PubDate: 2018-08-31T02:24:43-07:00
      DOI: 10.1242/jeb.187492
  • Identification of the role of Rh protein in ammonia excretion of swimming
           crab Portunus trituberculatus [RESEARCH ARTICLE]
    • Authors: Si, L; Pan, L, Wang, H, Zhang, X.
      Abstract: Lingjun Si, Luqing Pan, Hongdan Wang, and Xin Zhang

      In Portunus trituberculatus, a full-length cDNA of Rhesus-like glycoprotein (Rh protein), the whole 478 amino acids, has been identified in gills, which plays an essential role in ammonia (NH3 /NH4+) excretion. Phylogenetic analysis of the Rh-like proteins from crabs was clustered, showing high conservation of the ammonium transporter domain and transmembrane segments essential to the function of Rh protein. Rh protein of P. trituberculatus (PtRh) was detected in all tested tissues, and showed the highest expression in gills. To further characterize the role of PtRh in ammonia metabolism and excretion, a double-stranded RNA-mediated RNA interference of PtRh was employed. The knockdown of PtRh up-regulated mRNA expression of ammonia excretion related genes aquaporin (AQP), K+-channel, vesicle associated membrane protein (VAMP), increased activities of Na+ /K+ -ATPase (NKA) and V-type H+-ATPase (V-ATPase), whereas the Na+/H+-exchanger (NHE) expression reduced firstly and then elevated. dsRNA-mediated reductions in PtRh significantly reduced ammonia excretion rate and increased ammonia and glutamine (Gln) levels in hemolymph, together with increase of glutamate dehydrogenase (GDH) and glutamine synthetase (GS) activites, indicating a central role for PtRh in ammonia excretion and detoxification mechanisms. Taken together, we conclude that the Rh protein is a primary contributor to ammonia excretion of P. trituberculatus, which may be the basis of their ability to inhabit benthic water with high ammonia levels.
      PubDate: 2018-08-31T02:24:43-07:00
      DOI: 10.1242/jeb.184655
  • Acoustic communication in marine shallow waters: testing the acoustic
           adaptive hypothesis in sand gobies [RESEARCH ARTICLE]
    • Authors: Amorim, M. C. P; Vasconcelos, R. O, Bolgan, M, Pedroso, S. S, Fonseca, P. J.
      Abstract: M. C. P. Amorim, R. O. Vasconcelos, M. Bolgan, S. S. Pedroso, and P. J. Fonseca

      Acoustic communication is an important part of social behaviour of fish species that live or breed in shallow noisy waters. Previous studies have shown that some fish species exploit a quiet window in the background noise for communication. However, it remains to be examined if hearing abilities and sound production of fish are adapted to marine habitats presenting high hydrodynamism. Here we investigated whether the communication system of the painted (Pomatoschistus pictus) and the marbled (P. marmoratus) gobies is adapted to enhance sound transmission and reception in Atlantic shallow water environments. We recorded and measured the sound pressure levels of social vocalizations of both species, as well as snapshots of ambient noise of habitats characterised by different hydrodynamism. Hearing thresholds (in terms of both sound pressure and particle acceleration) and responses to conspecific signals were determined using the Auditory Evoked Potential recording technique. We found that the peak frequency range (100-300 Hz) of acoustic signals matched the best hearing sensitivity in both species and appeared well adapted for short-range communication in Atlantic habitats. Sandy/rocky exposed beaches presented a quiet window, observable even during the breaking of moderate waves, coincident with the main sound frequencies and best hearing sensitivities of both species. Our data demonstrates that the hearing abilities of these gobies are well suited to detect conspecific sounds within typical interacting distances (few body-lengths) in Atlantic shallow waters. These findings lend support to the acoustic adaptive hypothesis, under the sensory drive framework, proposing that signals and perception systems coevolve to be effective within local environment constraints.
      PubDate: 2018-08-31T02:24:43-07:00
      DOI: 10.1242/jeb.183681
  • Sperm pre-fertilization thermal environment shapes offspring phenotype and
           performance [RESEARCH ARTICLE]
    • Authors: Kekäläinen, J; Oskoei, P, Janhunen, M, Koskinen, H, Kortet, R, Huuskonen, H.
      Abstract: Jukka Kekäläinen, Parastu Oskoei, Matti Janhunen, Heikki Koskinen, Raine Kortet, and Hannu Huuskonen

      Sperm pre-fertilization environment has recently been suggested to mediate remarkable transgenerational consequences for offspring phenotype (transgenerational plasticity, TGB), but the adaptive significance of the process has remained unclear. Here, we studied the transgenerational effects of sperm pre-fertilization thermal environment in a cold-adapted salmonid, the European whitefish (Coregonus lavaretus L.). We used a full-factorial breeding design where the eggs of five females were fertilized with the milt of 10 males that had been pre-incubated at two different temperatures (3.5°C and 6.5°C) for 15 hours prior to fertilization. Thermal manipulation did not affect sperm motility, cell size, fertilization success or embryo mortality. However, offspring that were fertilized with warm-treated milt were smaller and had poorer swimming performance than their full-siblings that had been fertilized with cold-treated milt. Furthermore, the effect of milt treatment on embryo mortality varied among different females (treatmentxfemale interaction) and male-female combinations (treatmentxfemalexmale interaction). Together these results indicate that sperm pre-fertilization thermal environment shapes offspring phenotype and post-hatching performance and modify both the magnitude of female (dam) effects and the compatibility of the gametes. Generally, our results suggest that short-term changes in sperm thermal conditions may have negative impact for offspring fitness. Thus, sperm thermal environment may have an important role in determining the adaptation potential of organisms to climate change. Detailed mechanism(s) behind our findings require further attention.
      PubDate: 2018-08-31T02:24:43-07:00
      DOI: 10.1242/jeb.181412
  • Comparing the impacts of macronutrients on life-history traits in larval
           and adult Drosophila melanogaster: the use of nutritional geometry and
           chemically defined diets [RESEARCH ARTICLE]
    • Authors: Jang, T; Lee, K. P.
      Abstract: Taehwan Jang and Kwang Pum Lee

      Protein and carbohydrate are the two major macronutrients that exert profound influences over fitness in many organisms, including Drosophila melanogaster. Our understanding of how these macronutrients shape the components of fitness in D. melanogaster has been greatly enhanced by the use of nutritional geometry, but most nutritional geometric analyses on this species have been conducted using semi-synthetic diets that are not chemically well-defined. Here we combined the use of nutritional geometry and chemically defined diets to compare the patterns of larval and adult life-history traits expressed across 34 diets systematically varying in protein:carbohydrate (P:C) ratio and in protein plus carbohydrate (P+C) concentration. The shape of the response surfaces constructed for all larval and adult traits differed significantly from one another, with the nutritional optima being identified at P:C 1:4 for lifespan (P+C 120 g l–1), 1:2 for egg-to-adult viability (120 g l–1), 1:1 for female body mass at adult eclosion (240 g l–1) and lifetime fecundity (360 g l–1), 2:1 for larval developmental rate (60 g l–1), and 8:1 for egg production rate (120 g l–1). Such divergence in nutritional optima among life-history traits indicates that D. melanogaster confined to a single diet cannot maximize the expression of these traits simultaneously and thus may face a life-history trade-off. Our data provide the most comprehensive and nutritionally explicit analysis of the impacts of macronutrients on life-history traits in D. melanogaster and support the emerging notion that the fundamental trade-offs among life-history traits are mediated by macronutrients.
      PubDate: 2018-08-31T02:24:43-07:00
      DOI: 10.1242/jeb.181115
  • How temperature influences the viscosity of hornworm hemolymph [RESEARCH
    • Authors: Kenny, M. C; Giarra, M. N, Granata, E, Socha, J. J.
      Abstract: Melissa C. Kenny, Matthew N. Giarra, Ellen Granata, and John J. Socha

      Hemolymph is responsible for the transport of nutrients and metabolic waste within the insect circulatory system. Circulation of hemolymph is governed by viscosity, a physical property, which is well known to be influenced by temperature. However, the effect of temperature on hemolymph viscosity is unknown. We used Manduca sexta larvae to measure hemolymph viscosity across a range of physiologically relevant temperatures. Measurements were taken from 0 to 45°C using a cone and plate viscometer in a sealed environmental chamber. Hemolymph viscosity decreased with increasing temperature, showing a 6.4x change (11.08 to 1.74 cP) across the temperature range. Viscosity values exhibited two behaviors, changing rapidly from 0 to 15°C and slowly from 17.5 to 45°C. To test the effects of large particulates (e.g. cells) on viscosity, we also tested hemolymph plasma alone. Plasma viscosity also decreased as temperature increased, but did not exhibit two slope regimes, suggesting that particulates strongly influence low-temperature shifts in viscosity values. These results suggest that as environmental temperatures decrease, insects experience dramatic changes in hemolymph viscosity, leading to altered circulatory flows or increased energetic input to maintain similar flows. Such physical effects represent a previously unrecognized factor in the thermal biology of insects.
      PubDate: 2018-08-30T06:48:32-07:00
      DOI: 10.1242/jeb.186338
  • ArHsp40 and ArHsp40-2 contribute to stress tolerance and longevity in
           Artemia franciscana, but only ArHsp40 influences diapause entry [RESEARCH
    • Authors: Rowarth, N. M; MacRae, T. H.
      Abstract: Nathan M. Rowarth and Thomas H. MacRae

      Embryos of the crustacean, Artemia franciscana, develop either ovoviviparously or oviparously, respectively yielding swimming larvae (nauplii) or encysted gastrulae (cysts). Nauplii molt several times and become adults whereas cysts enter diapause, a state of dormancy characterized by exceptionally low metabolism and high stress tolerance. Synthesis of molecular chaperones such as the J-domain proteins, ArHsp40 and ArHsp40-2 occurs during embryo development and post-diapause growth of A. franciscana and they influence development and stress tolerance. To further investigate J-domain protein function ArHsp40 and ArHsp40-2 were each knocked down by RNA interference. Reductions in ArHsp40 and ArHsp40-2 had no effect on adult survival, time to release of cysts and nauplii from females and first brood size. However, knockdown of both A. franciscana J-domain proteins reduced the longevity and heat tolerance of nauplii with the loss of ArHsp40 having a greater effect. The knockdown of ArHsp40, but not of ArHsp40-2, caused approximately 50% of cysts to abort diapause entry and hatch without exposure to an exogenous signal such as low temperature and/or desiccation. Cysts lacking ArHsp40 that entered diapause exhibited decreased stress tolerance as did cysts with reduced ArHsp40-2, the latter to a lesser degree. The longevity of nauplii hatching prematurely from cysts was less than for nauplii arising by other means. The results expand our understanding of Hsp40 function during A. franciscana stress tolerance and development, especially during diapause, and they provide the first example of a molecular chaperone that influences diapause entry.
      PubDate: 2018-08-29T04:59:45-07:00
      DOI: 10.1242/jeb.189001
  • A new approach for measuring temperature inside turtle eggs [METHODS [amp
           ] TECHNIQUES]
    • Authors: Tezak, B. M; Sifuentes-Romero, I, Wyneken, J.
      Abstract: Boris M. Tezak, Itzel Sifuentes-Romero, and Jeanette Wyneken

      For turtles, the thermal environment experienced during development plays critical roles in many biological processes. While the temperature inside an egg is assumed to match substrate temperature, many factors like evaporative cooling, metabolic heating, and insulating properties of extra-embryonic components can lead to thermal differences. However, no method, to date, allowed for measurement of embryonic temperature in live chelonian eggs. We designed a thermocouple-based technique to measure embryonic temperature achieving 94 percent survival in Trachemys scripta. This methodology may be applicable to other reptile species. We found that, while temperature in the substrate adjacent to the eggshell accurately reflects internal egg temperature, it differs from air temperature (~ 2 °C) in a moisture-dependent manner. Our results demonstrate that external egg, but not air temperature is suitable for assessing the effects of temperature on biological processes, critical when considering that the TSD mechanism in turtles occur within a 4° C window.
      PubDate: 2018-08-29T04:59:45-07:00
      DOI: 10.1242/jeb.188698
  • Adult-larvae vibrational communication in paper wasps: the role of
           abdominal wagging in Polistes dominula [RESEARCH ARTICLE]
    • Authors: Pepiciello, I; Cini, A, Nieri, R, Mazzoni, V, Cervo, R.
      Abstract: Irene Pepiciello, Alessandro Cini, Rachele Nieri, Valerio Mazzoni, and Rita Cervo

      Communication through vibrational signals is widespread among social insects and regulates crucial social activities. Females of the social wasp Polistes dominula (Christ, 1791) produce substrate-borne vibrations on the combs by performing a conspicuous abdominal oscillatory behavior, known as abdominal wagging. Several studies have reported correlative evidence in support of its signaling role, but direct evidence is still lacking. Because abdominal wagging is strictly associated with the presence of larvae in the nest and with cell inspection, it has been suggested that it could be involved in adult–larvae communication. According to this hypothesis, abdominal wagging vibrations would have short-term effects related to food and trophallactic exchanges between adult and larvae by modulating salivary secretion (decreasing its amount, to prepare larvae to receive food, or stimulating the release of larval saliva to adults). Here, by using an electro-magnetic shaker, we assessed, for the first time, the short-term effect of abdominal wagging on larval behavior by recording larval response and by measuring the amount of saliva released immediately after abdominal wagging playback. Our results show that larvae are able to perceive the substrate-borne vibrations produced by abdominal wagging and react by increasing the movement of their body, possibly in order to attract the attention of adult females during feeding nest inspection. Yet, we found that vibrations neither increase nor decrease the release of larval saliva. Our results support the hypothesis of the alleged role of vibrations in adult–larvae communications; however, they do not support the long-lasting hypothesis of salivary release modulation.
      PubDate: 2018-08-29T04:59:45-07:00
      DOI: 10.1242/jeb.186247
  • Extreme physiological plasticity in a hibernating basoendothermic mammal,
           Tenrec ecaudatus [RESEARCH ARTICLE]
    • Authors: Treat, M. D; Scholer, L, Barrett, B, Khachatryan, A, McKenna, A. J, Reyes, T, Rezazadeh, A, Ronkon, C. F, Samora, D, Santamaria, J. F, Silva Rubio, C, Sutherland, E, Richardson, J, Lighton, J. R. B, van Breukelen, F.
      Abstract: Michael D. Treat, Lori Scholer, Brandon Barrett, Artur Khachatryan, Austin J. McKenna, Tabitha Reyes, Alhan Rezazadeh, Charles F. Ronkon, Dan Samora, Jeremy F. Santamaria, Claudia Silva Rubio, Evan Sutherland, Jeffrey Richardson, John R. B. Lighton, and Frank van Breukelen

      Physiological plasticity allows organisms to respond to diverse conditions. However, can being too plastic actually be detrimental' Malagasy common tenrecs, Tenrec ecaudatus, have many plesiomorphic traits and may represent a basal placental mammal. We established a laboratory population of T. ecaudatus and found extreme plasticity in thermoregulation and metabolism, a novel hibernation form, variable annual timing, and remarkable growth and reproductive biology. For instance, tenrec body temperature (Tb) may approximate ambient temperature to as low as 12°C even when tenrecs are fully active. Conversely, tenrecs can hibernate with Tbs of 28°C. During the active season, oxygen consumption may vary 25-fold with little or no changes in Tb. During the Austral winter, tenrecs are consistently torpid but the depth of torpor may be variable. A righting assay revealed that Tb contributes to but does not dictate activity status. Homeostatic processes are not always linked e.g. a hibernating tenrec experienced a ~34% decrease in heart rate while maintaining constant body temperature and oxygen consumption rates. Tenrec growth rates vary but young may grow ~40-fold in the 5 weeks until weaning and may possess indeterminate growth as adults. Despite all of this profound plasticity, tenrecs are surprisingly intolerant to extremes in ambient temperature (34°C). We contend that while plasticity may confer numerous energetic advantages in consistently moderate environments, environmental extremes may have limited the success and distribution of plastic basal mammals.
      PubDate: 2018-08-29T04:59:45-07:00
      DOI: 10.1242/jeb.185900
  • Short term colour vision plasticity on the reef: Changes in opsin
           expression under varying light conditions differ between ecologically
           distinct reef fish species [RESEARCH ARTICLE]
    • Authors: Luehrmann, M; Stieb, S. M, Carleton, K. L, Pietzker, A, Cheney, K. L, Marshall, N. J.
      Abstract: Martin Luehrmann, Sara M. Stieb, Karen L. Carleton, Alisa Pietzker, Karen L. Cheney, and N. Justin Marshall

      Vision mediates important behavioural tasks such as mate choice, escape from predators and foraging. In fish, photoreceptors are generally tuned to specific visual tasks and/or to their light environment according to depth or water colour to ensure optimal performance. Evolutionary mechanisms acting on opsin genes, the protein component of the photopigment, can influence the spectral sensitivity of photoreceptors. Opsin genes are known to respond to environmental conditions on a number of time scales including shorter time frames due to seasonal variation, or through longer term evolutionary tuning. There is also evidence for ‘on-the-fly’ adaptations in adult fish in response to rapidly changing environmental conditions, however, results are contradictory. Here we investigated the ability of three reef fish species that belong to two ecologically distinct families, Yellow-striped cardinalfish, Ostorhinchus cyanosoma, Ambon damselfish, Pomacentrus amboinensis, and Lemon damselfish, Pomacentrus moluccensis, to alter opsin-gene expression as an adaptation to short-term (weeks to months) changes of environmental light conditions, and attempted to characterize the underlying expression regulation principles. We report the ability for all species to alter opsin gene expression within months and even a few weeks, suggesting that opsin expression in adult reef fish is not static. Furthermore, we found that opsin expression changes in single cones generally occurred more rapidly than in double cones, and identified different responses of RH2 opsin gene expression between the ecologically distinct reef fish families. Quantum catch correlation analysis suggested different regulation mechanisms for opsin expression dependent on gene class.
      PubDate: 2018-08-29T04:59:45-07:00
      DOI: 10.1242/jeb.175281
  • Nosemosis control in European honey bees Apis mellifera by silencing the
           gene encoding Nosema ceranae polar tube protein 3 [RESEARCH ARTICLE]
    • Authors: Rodriguez-Garcia, C; Evans, J. D, Li, W, Branchiccela, B, Li, J. H, Heerman, M. C, Banmeke, O, Zhao, Y, Hamilton, M, Higes, M, Martin-Hernandez, R, Chen, Y. P.
      Abstract: Cristina Rodriguez-Garcia, Jay D. Evans, Wenfeng Li, Belen Branchiccela, Jiang Hong Li, Matthew C. Heerman, Olubukola Banmeke, Yazhou Zhao, Michele Hamilton, Mariano Higes, Raquel Martin-Hernandez, and Yan Ping Chen

      RNA interference (RNAi) is a post-transcriptional gene silencing mechanism triggered by double-stranded RNA (dsRNA) that is homologous in sequence to the silenced gene and is conserved in a wide range of eukaryotic organisms. The RNAi mechanism has provided unique opportunities in combating honey bee diseases caused by various parasites and pathogens. Nosema ceranae is a microsporidian parasite of European honey bees, Apis mellifera, and has been associated with honey bee colony losses in some regions of the world. Here we explored the possibility of silencing the expression of a N. ceranae putative virulence factor encoding polar tube protein 3 (ptp3) which is involved in host cell invasion as a therapeutic strategy for controlling Nosema parasites in honey bees. Our studies showed that the oral ingestion of a dsRNA corresponding to the sequences of N. ceranae ptp3 could effectively suppress the expression of the ptp3 gene in N. ceranae infected bees and reduce Nosema load. In addition to the knockdown of ptp3 gene expression, ingestion of ptp3-dsRNA also led to improved innate immunity in bees infected with N. ceranae along with an improvement in physiological performance and lifespan compared to untreated control bees. These results strongly suggest that RNAi-based therapeutics hold real promise for the effective treatment of honey bee diseases in the future and warrant further investigation.
      PubDate: 2018-08-22T02:31:48-07:00
      DOI: 10.1242/jeb.184606
  • Influence of flow on locomotion, feeding behaviour and spatial
           distribution of a suspension-feeding sea cucumber [RESEARCH ARTICLE]
    • Authors: Sun, J; Hamel, J.-F, Mercier, A.
      Abstract: Jiamin Sun, Jean-Francois Hamel, and Annie Mercier

      While movement in response to environmental conditions represents a fundamental link between animal behaviour and population ecology, it is rarely investigated in suspension feeders because they are generally perceived as sessile. Here, the interplay between water flow and fine locomotor and feeding behaviours was experimentally investigated for the first time in a free-moving suspension-feeding sea cucumber (Echinodermata: Holothuroidea) using time-lapse videography in a mesocosm setting. Individuals moved away from static conditions in the weakest flow treatment and fled the strongest flows>40 cm s–1 in the more dynamic treatments. The tentacles of individuals located in areas with flows of ≥40 cm s–1 was aligned with the direction of the current, whereas in flows 40 cm s–1, and active rolling occurred randomly at flows between 0-120 cm s–1. Overall, the flow regime favoured by Cucumaria frondosa was determined to be between 21-40 cm s–1, under which an optimal balance between efficient food capture and energy expenditure for attachment to the bottom was presumably found. These findings provide insight into the distribution and population dynamics of suspension-feeding holothuroids, and may also assist the fisheries management and aquaculture development of commercial species.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.189597
  • Glyphosate impairs learning in mosquito larvae (Aedes aegypti) at
           field-realistic doses [RESEARCH ARTICLE]
    • Authors: Baglan, H; Lazzari, C. R, Guerrieri, F. J.
      Abstract: Hugo Baglan, Claudio R. Lazzari, and Fernando J. Guerrieri

      Glyphosate is the most widely used herbicide in the world. In the last years, the number of studies revealing deleterious effects of glyphosate on non-target species has been increasing. We studied the impact of glyphosate at field-realistic doses on learning in mosquito larvae (Aedes aegypti). Larvae of A. aegypti live in small water bodies and perform a stereotyped escape response when a moving object projects its shadow on the water surface. Repeated presentations of an innocuous visual stimulus induce a decrease in response due to habituation, a non-associative form of learning. In this study, different groups of larvae were reared in water containing different concentrations of glyphosate that can be found in the field (50 µg/l, 100 µg/l, 210 µg/l and 2 mg/l). Larvae reared in a glyphosate solution of 2 mg/l could complete their development. However, glyphosate impaired habituation. The higher the dose, the stronger the deleterious effects on learning abilities. This protocol opens new avenues to further studies aiming at understanding how glyphosate affects non-target organisms as insects. Habituation in mosquito larvae could serve as a parameter for testing the impact of pollutants in water bodies.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.187518
  • Context-dependent behavioural lateralization in the European pond turtle
           Emys orbicularis (Testudines, Emydidae) [RESEARCH ARTICLE]
    • Authors: Pellitteri-Rosa, D; Gazzola, A.
      Abstract: Daniele Pellitteri-Rosa and Andrea Gazzola

      Lateralization presents clear advantages in ecological contexts since dominance of one brain side prevents the simultaneous activation of contrasting responses in organisms with laterally located eyes. This is crucial in selecting a safe refuge during a predatory attack and may strongly affect predator–prey interactions. We explored the possible presence of lateralization in the antipredatory behaviour of European pond turtles, considering their escape facing a possible predatory attack. Thirty individuals (17 males, 13 females) were exposed to three different environmental situations of gradual increasing predatory threat: escape underwater from an unsafe shelter, diving into the water from a basking site, righting after being overturned. All turtles were tested 20 times for each of the three experiments (60 trials per individual and 1800 overall trials). We recorded multiple behavioural responses in the general context of predation risk. This was done in order to assess both the existence of lateralization and possible correlations among different behaviours as function of lateralization. The number of significant responses to the left side was always prevalent in each of the three simulated anti-predatory situations, suggesting the existence of a lateralized behaviour in this species. At the individual level, the differences we found in the three experiments could be related to different ecological contexts and consequent risk of predation. Our findings, among the few on Chelonians, support the possible involvement of the right hemisphere activity and, most importantly, reveal how the complexity of a general predatory context can affect the laterality of escape behaviour.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.186775
  • The choreography of learning walks in the Australian jack jumper ant
           Myrmecia croslandi [RESEARCH ARTICLE]
    • Authors: Jayatilaka, P; Murray, T, Narendra, A, Zeil, J.
      Abstract: Piyankarie Jayatilaka, Trevor Murray, Ajay Narendra, and Jochen Zeil

      We provide a detailed analysis of the learning walks performed by Myrmecia croslandi ants at the nest during which they acquire visual information on its location. Most learning walks of 12 individually marked naïve ants took place in the morning with a narrow time window separating the first two learning walks, which most often occurred on the same day. Naïve ants performed between 2 to 7 walks over up to 4 consecutive days before heading out to forage. On subsequent walks naïve ants tend to explore the area around the nest in new compass directions. During learning walks ants move along arcs around the nest while performing oscillating scanning movements. In a regular temporal sequence, the ants’ gaze oscillates between the nest direction and the direction pointing away from the nest. Ants thus experience a sequence of views roughly across the nest and away from the nest from systematically spaced vantage points around the nest. We show further that ants leaving the nest for a foraging trip often walk in an arc around the nest on the opposite side to the intended foraging direction, performing a scanning routine indistinguishable from that of a learning walk. These partial learning walks are triggered by disturbance around the nest and may help returning ants with reorienting when overshooting the nest, which they frequently do. We discuss what is known about learning walks in different ant species and their adaptive significance for acquiring robust navigational memories.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.185306
  • Differences in spatial resolution and contrast sensitivity of flight
           control in the honeybees Apis cerana and Apis mellifera [RESEARCH ARTICLE]
    • Authors: Chakravarthi, A; Rajus, S, Kelber, A, Dacke, M, Baird, E.
      Abstract: Aravin Chakravarthi, Santosh Rajus, Almut Kelber, Marie Dacke, and Emily Baird

      Visually-guided behaviour is constrained by the capacity of the visual system to resolve detail. This is, in turn, limited by the spatial resolution and contrast sensitivity of the underlying visual system. Because these properties are interdependent and vary non-uniformly, it is only possible to fully understand the limits of a specific visually guided behaviour when they are investigated in combination. To understand the visual limits of flight control in bees, which rely heavily on vision to control flight, and to explore whether they vary between species, we tested how changes in spatial resolution and contrast sensitivity affect the speed and position control of the Asian and European honeybees (Apis cerana and A. mellifera). Despite their apparent similarity, we found some interesting and surprising differences between the visual limits of these species. While the effect of spatial frequency and contrast on position control is similar between the species, ground speed is differently affected by these variables. A comparison with published data from the bumblebee Bombus terrestris reveals further differences. The visual resolution that limits the detection and use of optic flow for flight control in both species of honeybees is lower than previously anatomically determined resolution and differs from object detection limits of A. mellifera, providing evidence that the limits of spatial resolution and contrast sensitivity are highly tuned to the particular behavioural task of a species.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.184267
  • Evidence for spatial vision in Chiton tuberculatus, a chiton with eyespots
    • Authors: Kingston, A. C. N; Chappell, D. R, Speiser, D. I.
      Abstract: Alexandra C. N. Kingston, Daniel R. Chappell, and Daniel I. Speiser

      To better understand relationships between the structures and functions of the distributed visual systems of chitons, we are comparing how morphological differences between the light-sensing structures of these animals relate to their visually-guided behaviors. All chitons have sensory organs – termed aesthetes – embedded within their protective shell plates. In some species, the aesthetes are interspersed with small, image-forming eyes. In other species, the aesthetes are paired with pigmented eyespots. Previously, we compared the visually-influenced behaviors of chitons with aesthetes to those of chitons with both aesthetes and eyes. Here, we characterize the visually-influenced behaviors of chitons with aesthetes and eyespots. We find that chitons with eyespots engage in behaviors consistent with spatial vision, but appear to use spatial vision for different tasks than chitons with eyes. Unlike chitons with eyes, Chiton tuberculatus and C. marmoratus fail to distinguish between sudden appearances of overhead objects and equivalent, uniform changes in light levels. We also find that C. tuberculatus orients to static objects with angular sizes as small as 10°. Thus, C. tuberculatus demonstrates spatial resolution that is at least as fine as that demonstrated by chitons with eyes. The eyespots of Chiton are smaller and more numerous than the eyes found in other chitons and they are separated by angles of
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.183632
  • The insensitive dormouse: reproduction skipping is not caused by chronic
           stress in Glis glis [RESEARCH ARTICLE]
    • Authors: Cornils, J. S; Hoelzl, F, Huber, N, Zink, R, Gerritsmann, H, Bieber, C, Schwarzenberger, F, Ruf, T.
      Abstract: Jessica S. Cornils, Franz Hoelzl, Nikolaus Huber, Richard Zink, Hanno Gerritsmann, Claudia Bieber, Franz Schwarzenberger, and Thomas Ruf

      Entire populations of edible dormice (Glis glis) can skip reproduction in years without mast seeding of deciduous trees (particularly beech or oak seed), because juveniles require high caloric seeds for growth and fattening prior to hibernation. We hypothesized that, in mast failure years, female dormice may be forced to spend larger amounts of time foraging for low-quality food, which should increase their exposure to predators, mainly owls. This may lead to chronic stress, i.e., long-term increased secretion of Glucocorticoids (GC), which can have inhibitory effects on reproductive function in both female and male mammals. We monitored reproduction in free-living female dormice over three years with varying levels of food availability, and performed a supplemental feeding experiment. To measure stress hormone levels, we determined fecal GC metabolite (GCM) concentrations collected during the day, which reflect hormone secretion rates in the previous nocturnal activity phase. We found that year-to-year differences in beech mast significantly affected fecal GCM levels and reproduction. However, contrary to our hypothesis, GCM levels were lowest in a non-mast year without reproduction, and significantly elevated in full-mast and intermediate years, as well as under supplemental feeding. Variation in owl density in our study area had no influence on GCM levels. Consequently, we conclude that down-regulation of gonads and reproduction skipping in mast-failure years in this species is not caused by chronic stress. Thus, in edible dormice, delayed reproduction apparently is profitable in response to the absence of energy-rich food in non-mast years, but not in response to chronic stress.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.183558
  • Individual differences in heart rate reveal a broad range of autonomic
           phenotypes in a free-living seabird population [SHORT COMMUNICATION]
    • Authors: Müller, M. S; Vyssotski, A. L, Yamamoto, M, Yoda, K.
      Abstract: Martina S. Müller, Alexei L. Vyssotski, Maki Yamamoto, and Ken Yoda

      Animals in the same population consistently differ in their physiology and behaviour, but the underlying mechanisms remain poorly understood. As the autonomic nervous system regulates wide-ranging physiological functions, many of these phenotypic differences may be generated by autonomic activity. We investigated for the first time in a free-living animal population (the long-lived seabird Streaked Shearwater, Calonectris leucomelas), whether individuals consistently differ in autonomic activity, over time and across contexts. We repeatedly recorded electrocardiograms from individual shearwaters, and from heart rate and heart rate variability quantified sympathetic activity, which drives the ‘fight-or-flight’ response, and parasympathetic activity, which promotes ‘rest-and-digest’ processes. We found a broad range of autonomic phenotypes that persisted even across years: heart rate consistently differed among individuals during stress and non-stress and these differences were driven by parasympathetic activity, thus identifying the parasympathetic ‘rest-and-digest’ system as a central mechanism that can drive broad phenotypic variation in natural animal populations.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.182758
  • Oxidative cost of interspecific hybridization: a case study of two
           Triturus species and their hybrids [RESEARCH ARTICLE]
    • Authors: Prokic, M. D; Despotovic, S. G, Vucic, T. Z, Petrovic, T. G, Gavric, J. P, Gavrilovic, B. R, Radovanovic, T. B, Saicic, Z. S.
      Abstract: Marko D. Prokic, Svetlana G. Despotovic, Tijana Z. Vucic, Tamara G. Petrovic, Jelena P. Gavric, Branka R. Gavrilovic, Tijana B. Radovanovic, and Zorica S. Saicic

      Oxidative stress has most recently been suggested as one of possible mechanisms responsible for reduced fitness of hybrids. To explore possible oxidative cost of hybridization, we examined antioxidant defense system parameters (superoxide dismutase, catalase, glutathione peroxidase, glutathione s-transferase, glutathione reductase, glutathione, SH groups), their interconnectedness (index of integration), and levels of oxidative damage (concentrations of lipid peroxides-TBARS) in lab-reared newt species, Triturus macedonicus and T. ivanbureschi, and their hybrid. Our results showed that parental species differed in antioxidant defense system parameters, but not in the levels of integration of the whole system and oxidative damage. Individuals of T. ivanbureschi had higher activities of superoxide dismutase, glutathione s-transferase and concentrations of glutathione. Hybrid individuals of crested newts displayed higher levels of the antioxidant defense system (higher superoxide dismutase, catalase, glutathione peroxidase activities and concentrations of SH groups), and a lower overall correlation of antioxidant system (lower index of integration) in comparison to both parental species, suggesting that they may possess a less efficient antioxidant defense system and a higher investment in maintaining oxidative balance. The higher investment in the antioxidant system could divert limited resources away from other functions and affect further hybrid fitness. The presented findings contribute to a better understanding of the antioxidant defense system of crested newts and their interspecies differences, and support the hypothesis that oxidative stress is one of the costs of interspecific hybridization.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.182055
  • Terrestrial locomotion of the northern elephant seal (Mirounga
           angustirostris): limitation of large aquatically adapted seals on
           land' [RESEARCH ARTICLE]
    • Authors: Tennett, K. A; Costa, D. P, Nicastro, A. J, Fish, F. E.
      Abstract: Kelsey A. Tennett, Daniel P. Costa, Anthony J. Nicastro, and Frank E. Fish

      The aquatic specializations of phocid seals have restricted their ability to locomote on land. The amphibious northern elephant seal, Mirounga angustirostris, is the second largest phocid seal in the world with males reaching 2,700 kg. Although elephant seals are proficient swimmers and deep divers, their extreme size and aquatic specializations limits terrestrial movement. The kinematics of terrestrial locomotion in northern elephant seals were analyzed from video recordings of animals observed on the beach of Año Nuevo State Reserve, CA. The seals moved using a series of rhythmic undulations produced by dorsoventral spinal flexion. The traveling spinal wave moved anteriorly along the dorsal margin of the body with the chest, pelvic region, and foreflippers serving as the main points of contact with the ground. The hind flippers were not used. The spinal wave and foreflippers were used to lift the chest off the ground as the body was pushed forward from the pelvis as the foreflippers were retracted to pull the body forward. Seals moved over land at 0.41-2.56 m s–1 (0.12-0.71 BL s–1). The frequency and amplitude of spinal flexions both displayed a direct increase with increasing speed. The duty factor for the pelvic region decreased with increasing velocity while the duty factor of the foreflipper remained constant. Kinematic data for elephant seals and other phocids were used in a biomechanical model to calculate the mechanical energy expended during terrestrial locomotion. The elephant seals were found to expend more energy when traveling over land for their size than smaller phocids. The unique method of terrestrial movement also exhibited greater energy expenditure on land than large quadrupeds. The trade-off for the northern elephant seal has been that its massive size and morphology have well adapted it to an aquatic existence, but limited its locomotor performance (i.e., speed, endurance) on land.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.180117
  • Foot-propelled swimming kinematics and turning strategies in common loons
    • Authors: Clifton, G. T; Biewener, A. A.
      Abstract: Glenna T. Clifton and Andrew A Biewener

      Loons (Gaviiformes) are arguably one of the most successful groups of swimming birds. As specialist foot-propelled swimmers, loons are capable of diving up to 70 meters, remaining underwater for several minutes, and capturing fish. Despite the swimming prowess of loons, their undomesticated nature has prevented prior quantitative analysis. Our study used high-speed underwater cameras to film healthy common loons (Gavia immer) at the Tufts Wildlife Clinic in order to analyze their swimming and turning strategies. Loons swim by synchronously paddling their feet laterally at an average of 1.8 Hz. Combining flexion-extension of the ankle with rotation at the knee, loon swimming resembles grebe swimming and likely generates lift forces for propulsion. Loons modulate swimming speed by altering power stroke duration and use head-bobbing to enhance underwater vision. We observed that loons execute tight but slow turns compared to other aquatic swimmers, potentially associated with hunting by flushing fish from refuges at short range. To execute turns, loons use several strategies. Loons increase the force produced on the outside of the turn by increasing the speed of the outboard foot, which also begins its power stroke before the inboard foot. During turns, loons bank their body away from the turn and alter the motion of the feet to maintain the turn. Our findings demonstrate that foot-propelled swimming has evolved convergently in loon and grebes, but divergently from cormorants. The swimming and turning strategies used by loons that allow them to capture fish could inspire robotic designs or novel paddling techniques.
      PubDate: 2018-08-20T07:20:45-07:00
      DOI: 10.1242/jeb.168831
  • How does the environment affect fighting' The interaction between
           extrinsic fighting ability and resource value during contests [RESEARCH
    • Authors: Lane, S. M; Briffa, M.
      Abstract: Sarah M. Lane and Mark Briffa

      An individual's performance during a fight is influenced by a combination of their capacity and willingness to compete. While willingness to fight is known to be determined by both intrinsic and extrinsic drivers, an individual's capacity to fight is generally thought of as solely intrinsic, being driven by a host of physiological factors. However, evidence indicates that variation in fighting ability can also be generated through exposure to different environmental conditions. Environmental contributions to fighting ability may be particularly important for animals living in spatially and temporally heterogeneous habitats, in which fights can occur between rivals recently exposed to different environmental conditions. The rapidly changing environment experienced within intertidal zones, for example, means that seawater parameters, including dissolved oxygen content and temperature, can vary across small spatial and temporal scales. Here we investigate the relative importance of these extrinsic contributions to fighting ability and resource value on contest dynamics in the beadlet sea anemone Actinia equina. We manipulate the extrinsic fighting ability of both opponents (through dissolved oxygen concentration prior to fights) and resource value (through seawater flow rate during the fight). Our results indicate that the extrinsic fighting ability of both opponents can interact with resource value to drive escalation patterns and that extrinsic drivers can be more important in determining contest dynamics than the intrinsic traits commonly studied. Our study highlights the need to combine data on intrinsic state and extrinsic conditions in order to gain a more holistic view of the factors driving contest behaviour.
      PubDate: 2018-08-16T05:24:10-07:00
      DOI: 10.1242/jeb.187740
  • Ocean acidification does not limit squid metabolism via blood oxygen
           supply [RESEARCH ARTICLE]
    • Authors: Birk, M. A; McLean, E. L, Seibel, B. A.
      Abstract: Matthew A. Birk, Erin L. McLean, and Brad A. Seibel

      Ocean acidification is hypothesized to limit the performance of squids due to their exceptional oxygen demand and pH-sensitivity of blood-oxygen binding, which may reduce oxygen supply in acidified waters. The critical oxygen partial pressure (Pcrit), the PO2 below which oxygen supply cannot match basal demand, is a commonly reported index of hypoxia tolerance. Any CO2-induced reduction in oxygen supply should be apparent as an increase in Pcrit. In this study, we assessed the effects of CO2 (46-143 Pa; 455-1410 μatm) on the metabolic rate and Pcrit of two squid species - Dosidicus gigas and Doryteuthis pealeii - through manipulative experiments. We also developed a model, with inputs for hemocyanin pH-sensitivity, blood PCO2, and buffering capacity that simulates blood oxygen supply under varying seawater CO2 partial pressures. We compare model outputs to measured Pcrit in squids. Using blood-O2 parameters from the literature for model inputs, we estimated that, in the absence of blood acid-base regulation, an increase in seawater PCO2 to 100 Pa ( 1000 μatm) would result in a maximum drop in arterial hemocyanin-O2 saturation by 1.6% at normoxia and a Pcrit increase of 0.5 kPa. Our live-animal experiments support this supposition, as CO2 had no effect on measured metabolic rate or Pcrit in either squid species.
      PubDate: 2018-08-15T02:04:57-07:00
      DOI: 10.1242/jeb.187443
  • Wing inertia as a cause of aerodynamically uneconomical flight with high
           angles-of-attack in hovering insects [RESEARCH ARTICLE]
    • Authors: Phan, H. V; Park, H. C.
      Abstract: Hoang Vu Phan and Hoon Cheol Park

      Flying insects can maintain maneuverability in the air by flapping their wings, and to save energy, the wings should operate following the optimal kinematics. However, unlike conventional rotary wings, insects operate their wings at aerodynamically uneconomical and high angles-of-attack (AoAs). Although insects have continuously received attention from biologists and aerodynamicists, the high AoA operation in insect flight has not been clearly explained. Here, we use a theoretical blade-element model to examine the impact of wing inertia on the power requirement and flapping AoA, based on three-dimensional free-hovering flight wing kinematics of a horned beetle, Alloymyrina dichotoma. The relative simplicity of the model allows us to search for the best AoAs distributed along the wingspan, which generate the highest vertical force per unit power. We show that, although elastic elements may be involved in flight muscles to store and save energy, the insect still has to spend substantial power to accelerate its wings, because inertial energy stores should be used to overcome aerodynamic drag before being stored elastically. At the same flapping speed, a wing operating at a higher AoA requires lower inertial torque, and therefore lower inertial power output, at the stroke reversals than a wing operating at an aerodynamically-optimal low AoA. An interactive aerodynamic-inertial effect thereby enables the wing to flap at sufficiently high AoAs, which causes an aerodynamically uneconomical flight in an effort to minimize the net flight energy.
      PubDate: 2018-08-15T02:04:57-07:00
      DOI: 10.1242/jeb.187369
  • Do squids breathe through their skin' [RESEARCH ARTICLE]
    • Authors: Birk, M. A; Dymowska, A. K, Seibel, B. A.
      Abstract: Matthew A. Birk, Agnieszka K. Dymowska, and Brad A. Seibel

      Squids are thought to obtain a large portion of their oxygen via simple diffusion across the skin in addition to uptake at the gills. Although this hypothesis has support from indirect evidence and is widely accepted, no empirical examinations have been conducted to assess the validity of this hypothesis. In this study, we examined cutaneous respiration in two squid species, Doryteuthis pealeii and Lolliguncula brevis, by using a divided chamber to physically separate the mantle cavity and gills from the outer mantle surface. We measured oxygen consumption and ammonia excretion rates in the two compartments and found that, at rest, squids only obtain enough oxygen cutaneously to meet demand of the skin tissue locally (12% of total) and excrete little ammonia across the skin. The majority of oxygen is obtained via the traditional branchial pathway. In light of these findings, we re-examine and discuss the indirect evidence that has supported the cutaneous respiration hypothesis.
      PubDate: 2018-08-15T02:04:57-07:00
      DOI: 10.1242/jeb.185553
  • Channeling vorticity: Modeling the filter-feeding mechanism in silver carp
           using {mu}CT and 3D PIV [RESEARCH ARTICLE]
    • Authors: Cohen, K. E; Hernandez, L. P, Crawford, C. H, Flammang, B. E.
      Abstract: Karly E. Cohen, L. Patricia Hernandez, Callie H. Crawford, and Brooke E. Flammang

      Invasive silver carp are thriving within eutrophic environments in the United States due in part to their highly efficient filter-feeding mechanism. Like many filter feeding fishes, silver carp utilize modified gill rakers to capture a specific range of food; however, the greatly modified filtering morphology of silver carp allows them to feed on phytoplankton and zooplankton ranging in size from 4-85μm. The filtering apparatus of silver carp is comprised of rigid filtering plates where the outer anatomy of these plates is characterized by long parallel channels (riddled with openings of different sizes) that change in orientation along the length of the plate. Here we investigate the underlying morphology and concomitant hydrodynamics that support the filtration mechanisms of silver and bighead carp. Bighead carp are also invasive filter feeders but their filtering apparatus is morphologically distinct from silver carp composed of thin, flattened individual rakers more similar to that of filter feeders such as Brevoortia sp. or Anchoa sp. Gill rakers from adult silver and bighead carp were scanned using a micro CT scanner at 15.2 micron and 17.0 micron voxel resolution, respectively. Scans were segmented and reconstructed in 3D, printed as a 3D structure in resin, and placed in a 2200 L recirculating flow tank (into which 50 micron buoyant particles had been added) with water flowing across the model in an anteroposterior direction. Using 3D PIV, we determined how particles and fluid interact with the surface of the gill rakers/plates. Filtering plates in silver carp induce strong directed vortical flow whereas the filtering apparatus of bighead carp resulted in a type of haphazard crossflow filtration. The organized vortical flow established by silver carp likely increased the number of interactions that the particle-filled water has with the filtering membrane. This strong vortical organization is maintained only at 0.75BL(body lengths)/s and vortical flow is poorly developed and maintained at slower and faster speeds. Moreover, we found that absolute vorticity magnitude in silver carp is an order of magnitude greater than in bighead carp. Vortical flow established in the silver carp model suggests that this species is a more effective and likely efficient filter feeder than bighead carp, perhaps explaining the success of silver carp as an invasive species.
      PubDate: 2018-08-15T02:04:57-07:00
      DOI: 10.1242/jeb.183350
  • Corticosterone implants make stress hyporesponsive birds [RESEARCH
    • Authors: Torres-Medina, F; Cabezas, S, Marchant, T. A, Wikelski, M, Romero, L. M, Hau, M, Carrete, M, Tella, J. L, Blas, J.
      Abstract: Fernando Torres-Medina, Sonia Cabezas, Tracy A. Marchant, Martin Wikelski, L. Michael Romero, Michaela Hau, Martina Carrete, Jose L. Tella, and Julio Blas

      In birds, the use of corticosterone (Cort) implants is a frequent tool aimed at simulating systemic elevations of this hormone and studying effects on biological traits (e.g. physiology, morphology, behavior). This manipulation may alter adrenocortical function, potentially changing both baseline (BAS-Cort) and stress-induced (STRESS-Cort) plasma Cort levels. However, implant effects on the latter trait are rarely measured, disregarding downstream consequences of potentially altered stress responses. Here we analyzed the effects of Cort implants on both BAS-Cort and STRESS-Cort in nestling and adult European white storks Ciconia ciconia. In addition, we performed a review of 50 studies using Cort implants in birds during the last two decades to contextualize stork results, assess researchers' patterns of use and infer current study biases. High and low doses of Cort implants resulted in a decrease of both BAS-Cort (31-71% below controls) and STRESS-Cort (63-79% below controls) in storks. Our review revealed that BAS-Cort generally increases (72% of experiments) while STRESS-Cort decreases (78% of experiments) following implant treatment in birds. Our results challenge and expand the prevailing assumption that CORT implants increase circulating BAS-Cort levels because: (i) BAS-Cort levels show a quadratic association with implant dose across bird species, and decreased levels may occur at both high and low implant doses, and (ii) Cort implants also decrease STRESS-Cort levels, thus producing stress hyporesponsive phenotypes. It is time to work towards a better understanding of the effects of Cort implants on adrenocortical function, before addressing downstream links to variation in other biological traits.
      PubDate: 2018-08-15T02:04:57-07:00
      DOI: 10.1242/jeb.173864
  • Aerodynamic characteristics along the wing span of a dragonfly Pantala
           Flavescens [RESEARCH ARTICLE]
    • Authors: Hefler, C; Qiu, H, Shyy, W.
      Abstract: Csaba Hefler, Huihe Qiu, and Wei Shyy

      We investigate the characteristics of inter-wing aerodynamic interactions across the span of the high-aspect-ratio, flexible wings of dragonflies under tethered and free-flying conditions. The effects of the interactions on the hindwings vary across four spanwise regions. (I) Close to the wing root, a trailing-edge vortex (TEV) is formed by each stroke, while the formation of a leading-edge vortex (LEV) is limited by the short translational distance of the hindwing and suppressed by the forewing-induced flow. (II) In the region away from the wing root but not quite up to midspan, the formation of the hindwing LEV is influenced by that of the forewing LEV. This vortex synergy can increase the circulation of the hindwing LEV in the corresponding cross-section by 22% versus that the hindwing in isolation. (III) The region about half way between the wing root and wing tip is there is a transition dominated by downwash from the forewing resulting in flow attached to the hindwing. (IV) An LEV is developed in the remaining, outer region of the wing at the end of a stroke when the hindwing captures the vortex shed by the forewing. The interaction effects depend not only on the wing phasing, but also the flapping offset and flight direction. The aerodynamics of the hindwings vary substantially from the wing root to the wing tip. For a given phasing, this spanwise variation in the aerodynamics can be exploited in the design of artificial wings to achieve greater agility and higher efficiency.
      PubDate: 2018-08-14T01:29:16-07:00
      DOI: 10.1242/jeb.171199
  • Blood pressure in the Greenland shark as estimated from ventral aortic
           elasticity [SHORT COMMUNICATION]
    • Authors: Shadwick, R. E; Bernal, D, Bushnell, P. G, Steffensen, J. F.
      Abstract: Robert E. Shadwick, Diego Bernal, Peter G. Bushnell, and John F. Steffensen

      We conducted in vitro inflations of freshly excised ventral aortas of the Greenland shark, Somniosus microcephalus, and used pressure-diameter data to estimate the point of transition from high to low compliance, which has been shown to occur at the mean blood pressure in other vertebrates including fishes. We also determined the pressure at which the modulus of elasticity of the aorta reached 0.4MPa, as occurs at the compliance transition in other species. From these analyses we predict the average ventral aortic blood pressure in S. microcephalus to be about 2.3-2.8kPa, much lower than reported for other sharks. Our results support the idea that this species is slow moving and has a relatively low aerobic metabolism. Histological investigation of the ventral aorta show that elastic fibres are present in relatively low abundance and loosely connected, consistent with this aorta to have high compliance at a relatively low blood pressure.
      PubDate: 2018-08-13T01:02:49-07:00
      DOI: 10.1242/jeb.186957
  • Anti-diuretic activity of a CAPA neuropeptide can compromise Drosophila
           chill tolerance [RESEARCH ARTICLE]
    • Authors: MacMillan, H. A; Nazal, B, Wali, S, Yerushalmi, G. Y, Misyura, L, Donini, A, Paluzzi, J.-P.
      Abstract: Heath A. MacMillan, Basma Nazal, Sahr Wali, Gil Y. Yerushalmi, Lidiya Misyura, Andrew Donini, and Jean-Paul Paluzzi

      For insects, chilling injuries that occur in the absence of freezing are often related to a systemic loss of ion and water balance that leads to extracellular hyperkalemia, cell depolarization, and the triggering of apoptotic signalling cascades. The ability of insect ionoregulatory organs (e.g. the Malpighian tubules) to maintain ion balance in the cold has been linked to improved chill tolerance, and many neuroendocrine factors are known to influence ion transport rates of these organs. Injection of micromolar doses of CAPA (an insect neuropeptide) have been previously demonstrated to improve Drosophila cold tolerance, but the mechanisms through which it impacts chill tolerance are unclear, and low doses of CAPA have been previously demonstrated to cause anti-diuresis in insects, including dipterans. Here, we provide evidence that low (fM) and high (µM) doses of CAPA impair and improve chill tolerance, respectively, via two different effects on Malpighian tubule ion and water transport. While low doses of CAPA are anti-diuretic, reduce tubule K+ clearance rates and reduce chill tolerance, high doses facilitate K+ clearance from the haemolymph and increase chill tolerance. By quantifying CAPA peptide levels in the central nervous system, we estimated the maximum achievable hormonal titres of CAPA, and found further evidence that CAPA may function as an anti-diuretic hormone in Drosophila melanogaster. We provide the first evidence of a neuropeptide that can negatively affect cold tolerance in an insect, and further evidence of CAPA functioning as an anti-diuretic peptide in this ubiquitous insect model.
      PubDate: 2018-08-13T01:02:49-07:00
      DOI: 10.1242/jeb.185884
  • Multiple optic gland signaling pathways implicated in octopus maternal
           behaviors and death [RESEARCH ARTICLE]
    • Authors: Wang, Z. Y; Ragsdale, C. W.
      Abstract: Z. Yan Wang and Clifton W. Ragsdale

      Post-reproductive life in the female octopus is characterized by an extreme pattern of maternal care: the mother cares for her clutch of eggs without feeding until her death. These maternal behaviors are eradicated if the optic glands, the octopus analog of the vertebrate pituitary gland, are removed from brooding females. Despite the optic gland's importance in regulating maternal behavior, the molecular features underlying optic gland function are unknown. Here, we identify major signaling systems of the Octopus bimaculoides optic gland. Through behavioral analyses and transcriptome sequencing, we report that the optic gland undergoes remarkable molecular changes that coincide with transitions between behavioral stages. These include the dramatic up- and down-regulation of catecholamine, steroid, insulin, and feeding peptide pathways. Transcriptome analyses in other tissues demonstrate that these molecular changes are not generalized markers of senescence, but instead, specific features of the optic glands. Our study expands the classic optic gland-pituitary gland analogy and more specifically, it indicates that, rather than a single "self-destruct" hormone, the maternal optic glands employ multiple pathways as systemic hormonal signals of behavioral regulation.
      PubDate: 2018-08-13T01:02:49-07:00
      DOI: 10.1242/jeb.185751
  • Effects of temperature on the timing of breeding and molt transitions in
           house finches [RESEARCH ARTICLE]
    • Authors: Watts, H. E; Jimenez, D, Pacheco, V, Vilgalys, T. P.
      Abstract: Heather E. Watts, Daniela Jimenez, Veronica Pacheco, and Tauras P. Vilgalys

      Temperature-correlated shifts in reproductive timing are now well documented in numerous bird species. However, whether temperature directly influences reproductive timing or if its effects are mediated by an intermediate environmental cue, such as plant phenology, remains poorly understood. In this study, we investigated the direct effects of temperature on reproductive timing in house finches (Haemorhous mexicanus), which have a range and breeding diet not well represented in previous studies of temperature and reproductive timing. We conducted experiments with captive male house finches in which temperature was elevated within realistic ranges and the effects on the timing of preparations for reproduction, as well as on the termination of reproduction and the onset of prebasic feather molt were examined. We found no adjustments in the timing of reproductive preparations of males in direct response to temperature. However, elevated temperature did advance the breeding-molt transition. Our results suggest elevated temperatures in the range tested here do not directly impact physiological preparations for reproduction in male house finches, but may constrain the timing of the breeding-molt transition in this species.
      PubDate: 2018-08-13T01:02:49-07:00
      DOI: 10.1242/jeb.185058
  • Effects of organism and substrate size on burial mechanics of English
           sole, Parophrys vetulus [RESEARCH ARTICLE]
    • Authors: Corn, K. A; Farina, S. C, Summers, A. P, Gibb, A. C.
      Abstract: Katherine A. Corn, Stacy C. Farina, Adam P. Summers, and Alice C. Gibb

      Flatfishes use cyclic body undulations to force water into the sediment and fluidize substrate particles, displacing them into the water column. When water velocity decreases, suspended particles settle back onto the fish, hiding it from view. Burial may become more challenging as flatfishes grow because the area to be covered increases exponentially with the second power of length. In addition, particle size is not uniform in naturally occurring substrates, and larger particles require higher water velocities for fluidization. We quantified the effects of organism and particle-size scaling on burial behavior of English Sole, Parophrys vetulus. We recorded burial events from a size range of individuals (5-32 cm TL), while maintaining constant substrate grain-size. Larger fish used lower cycle frequencies and took longer to bury, but overall burial performance was maintained (~100% coverage). To test the effect of particle size on burial performance, individuals of similar lengths (5.7-8.1 cm TL) were presented with different substrate sizes (0.125–0.710 mm). Particle size did not affect cycle frequency or time to burial, but fish did not achieve 100% coverage with the largest particles because they could not fluidize this substrate. Taken together, these results suggest that both body size and substrate grain size can potentially limit the ability of flatfishes to bury: a very large fish (>150 cm) may move too slowly to fluidize all but the smallest substrate particles and some particles are simply too large for smaller individuals to fluidize.
      PubDate: 2018-08-13T01:02:49-07:00
      DOI: 10.1242/jeb.176131
  • Influence of temperature and pearl rotation on biomineralization in the
           pearl oyster Pinctada margaritifera [RESEARCH ARTICLE]
    • Authors: Le Moullac, G; Schuck, L, Chabrier, S, Belliard, C, Lyonnard, P, Broustal, F, Soyez, C, Saulnier, D, Brahmi, C, Ky, C.-L, Beliaeff, B.
      Abstract: Gilles Le Moullac, Lucie Schuck, Sebastien Chabrier, Corinne Belliard, Pierre Lyonnard, Floriane Broustal, Claude Soyez, Denis Saulnier, Chloe Brahmi, Chin-Long Ky, and Benoit Beliaeff

      The objective of this study was to observe the impact of temperature on pearl formation using an integrative approach describing the rotation of the pearls, the rate of nacre deposition, the thickness of the aragonite tablets and the biomineralizing potential of the pearl sac tissue though the expression level of some key genes. Fifty pearl oysters were grafted with magnetized nuclei to allow the rotation of the pearls to be described. Four months later, 32 of these pearl oysters were exposed to four temperatures (22, 26, 30 and 34°C) for 2 weeks. Results showed that the rotation speed differed according to the movement direction: pearls with axial movement (AM) had a significantly higher rotation speed than those with random movement (RM). Pearl growth rate was influenced by temperature, with a maximum between 26 and 30°C but almost no growth at 34°C. Lastly, among the nine genes implicated in the biomineralization process, the Pmarg-Pif177 expression was significantly modified by temperature. These results showed that the rotation speed of the pearls was not linked to pearl growth or to the expression profiles of biomineralizing genes targeted in this study. On the basis of our results, we consider that pearl rotation is a more complex process than formerly thought. Mechanisms involved could include a strong environmental forcing in immediate proximity to the pearl. Another implication of our findings is that, in the context of ocean warming, pearl growth and quality can be expected to decrease in pearl oysters exposed to temperatures above 30°C.
      PubDate: 2018-08-02T03:05:24-07:00
      DOI: 10.1242/jeb.186858
  • Thermal physiological traits and plasticity of metabolism are sensitive to
           biogeographic breaks in a rock-pool marine shrimp [RESEARCH ARTICLE]
    • Authors: Barria, A. M; Bacigalupe, L. D, Lagos, N. A, Lardies, M. A.
      Abstract: Aura M. Barria, Leonardo D. Bacigalupe, Nelson A. Lagos, and Marco A. Lardies

      Populations of broadly distributed species commonly exhibit latitudinal variation in thermal tolerance and physiological plasticity. This variation can be interrupted when biogeographic breaks occur across the range of a species, which are known to affect patterns of community structure, abundance, and recruitment dynamics. Coastal biogeographic breaks often impose abrupt changes in environmental characteristics driven by oceanographic processes and can affect the physiological responses of populations inhabiting these areas. Here we examined thermal limits, performances for heart rate and plasticity for metabolic rate of the intertidal shrimp Betaeus emarginatus from seven populations along its latitudinal range (~ 3000 km). The distribution of this species encompass two breaks at the southeastern Pacific coast of Chile: the northern break is characterized by sharp discontinuities in upwelling regimes, and the southern break, constitutes a major discontinuity in water conditions (temperature, pH, dissolved oxygen and nutrients), coastline topography, and divergence of main oceanographic currents. For B. emarginatus, we found higher plasticity of metabolism in the sites sampled at the biogeographic breaks, and at the site subjected to seasonal upwelling. The variation of metabolic rate was not consistent with increasing latitude and it was not affected by breaks. The lower and upper thermal limits were lower in populations around breaks, although the optimum temperature decreased towards higher latitudes. Overall, while thermal limits and plasticity of metabolism are related to biogeographic breaks, metabolic rate is not related with increasing latitude or the presence of breaks in the sampled range.
      PubDate: 2018-08-02T03:05:24-07:00
      DOI: 10.1242/jeb.181008
  • Limping following limb loss increases locomotor stability [RESEARCH
    • Authors: Wilshin, S; Shamble, P. S, Hovey, K. J, Harris, R, Spence, A. J, Hsieh, S. T.
      Abstract: Simon Wilshin, Paul S. Shamble, Kyle J. Hovey, Ryan Harris, Andrew J. Spence, and S. Tonia Hsieh

      Although many arthropods have the ability to voluntarily lose limbs, how these animals rapidly adapt to such an extreme perturbation remains poorly understood. It is thought that moving with certain gaits can enable efficient, stable locomotion; however, switching gaits requires complex information flow between and coordination of an animal's limbs. We show here that upon losing two legs, spiders can switch to a novel, more statically stable gait, or use temporal adjustments without a gait change. The resulting gaits have higher overall static stability than the gaits that would be imposed by limb loss. By decreasing the time spent in a low-stability configuration—effectively "limping" over less stable phases of the stride—spiders increased the overall stability of the less statically-stable gait with no observable reduction in speed, as compared to the intact condition. Our results shed light on how voluntary limb loss could have persisted evolutionarily among many animals, and provide bioinspired solutions for robots when they break or lose limbs.
      PubDate: 2018-08-02T03:05:24-07:00
      DOI: 10.1242/jeb.174268
  • Convective oxygen transport during development in embryos of the snapping
           turtle Chelydra serpentina [RESEARCH ARTICLE]
    • Authors: Sartori, M. R; Kohl, Z. F, Taylor, E. W, Abe, A. S, Crossley, D. A.
      Abstract: Marina R. Sartori, Zachary F. Kohl, Edwin W. Taylor, Augusto S. Abe, and Dane A. Crossley II

      This study investigated the maturation of convective oxygen transport in embryos of the snapping turtle (Chelydra serpentina). Measurements included: mass, oxygen consumption (VO2), heart rate (fH), blood oxygen content and affinity and blood flow distribution at 50%, 70% and 90% of the incubation period. Body mass increased exponentially, paralleled by increased cardiac mass and metabolic rate. Heart rate was constant from 50% to 70% of incubation but was significantly reduced at 90%. Hematocrit (Hct) and hemoglobin concentration (Hb) were constant at the three points of development studied but arteriovenous difference (A-V diff) doubled from 50 to 90% of incubation. Oxygen affinity was lower early in 50% of incubation compared to all other age groups. Blood flow was directed predominantly to the embryo but highest to the CAM at 70% incubation and was directed away from the yolk as it was depleted at 90% incubation. The findings indicate that the plateau or reduction in egg VO2 characteristic of the late incubation period of turtle embryos may be related to an overall reduction in mass-specific VO2 that is correlated with decreasing relative heart mass and plateaued CAM blood flow. Importantly, if the blood properties remain unchanged prior to hatching, as they did during the incubation period studied in the current investigation, this could account for the pattern of VO2 previously reported for embryonic snapping turtles prior to hatching.
      PubDate: 2018-07-31T01:17:16-07:00
      DOI: 10.1242/jeb.185967
  • Accumulation and excretion of manganese ion in the kidney of the Mytilus
           galloprovincialis [RESEARCH ARTICLE]
    • Authors: Wakashin, H; Seo, E, Seo, Y.
      Abstract: Hidefumi Wakashin, Eriko Seo, and Yoshiteru Seo

      T1-weighted magnetic resonance imaging (T1w-MRI) was employed to detect the accumulation of manganese ion (Mn2+) in urine in the kidney of Mytilus galloprovincialis, and the longitudinal relaxation rates (1/T1=R1) were measured. When the mussel exposed to seawater containing 10 µM Mn2+, the T1w-MR image intensity and R1 of the kidney, stomach and digestive glands were increased. Mn2+ might be taken into the hemolymph via the gastrointestinal tract, and then filtrated into the pericardium via the auricles. While the image intensity in the pericardium was not affected by manganese, an image intensity enhancement was observed in the distal part of the renopericardial communication canals between the pericardium and kidneys, indicating Mn2+ concentration in the excretion pathway. As the seawater Mn2+ concentration ([Mn2+]SW) was increased from 3 to 50 µM, R1 of the kidney (R1K) were elevated. When the mussels were immersed in 3 - 10 µM [Mn2+]SW for 24 hrs, the Mn2+ concentration in the kidney ([Mn2+]K) increased by 15 fold, compared to the ambient [Mn2+]SW concentration. In the range of [Mn2+]SW from 10 to 50 µM, R1K reached a plateau level that corresponded to 200 µM [Mn2+]K. As [Mn2+]K fell transiently, voluntary excretion of urine from the kidney was assumed. The decreases in intensity were not synchronized between the right and left kidneys, and the closure of the shells might not essential for the urinary excretion. The voluntary excretion suggested an additional explanation for the large variety of metal concentration in the kidneys of the mussel.
      PubDate: 2018-07-31T01:17:16-07:00
      DOI: 10.1242/jeb.185439
  • What determines the metabolic cost of human running across a wide range of
           velocities' [RESEARCH ARTICLE]
    • Authors: Kipp, S; Grabowski, A. M, Kram, R.
      Abstract: Shalaya Kipp, Alena M. Grabowski, and Rodger Kram

      The cost of generating force hypothesis proposes that the metabolic rate during running is determined by the rate of muscle force development (1/tc, tc=contact time) and the volume of active leg muscle. A previous study assumed a constant recruited muscle volume and reported that the rate of force development alone explained ~70% of the increase in metabolic rate for human runners across a moderate velocity range (2-4 m s–1). We hypothesized that over a wider range of velocities, the effective mechanical advantage (EMA) of the lower limb joints would overall decrease, necessitating a greater volume of active muscle recruitment. Ten high-caliber male human runners ran on a force-measuring treadmill at 8, 10, 12, 14, 16 and 18 km hr–1 while we analyzed their expired air to determine metabolic rates. We measured ground reaction forces and joint kinematics to calculate contact time and estimate active muscle volume. From 8 to 18 km hr–1, metabolic rate increased 131% from 9.28 to 21.44 W kg–1. Contact time (tc) decreased from 0.280 sec to 0.190 sec, and thus the rate of force development (1/tc) increased by 48%. Ankle EMA decreased by 19.7±11%, knee EMA increased by 11.1±26.9% and hip EMA decreased by 60.8±11.8%. Estimated active muscle volume per leg increased 52.8% from 1663±152 cm3 to 2550±169 cm3. Overall, 98% of the increase in metabolic rate across the velocity range was explained by just two factors: the rate of generating force and the volume of active leg muscle.
      PubDate: 2018-07-31T01:17:16-07:00
      DOI: 10.1242/jeb.184218
  • Symbiont photosynthesis in giant clams is promoted by V-type H+-ATPase
           from host cells [RESEARCH ARTICLE]
    • Authors: Armstrong, E. J; Roa, J. N, Stillman, J. H, Tresguerres, M.
      Abstract: Eric J. Armstrong, Jinae N. Roa, Jonathon H. Stillman, and Martin Tresguerres

      Giant clams (genus Tridacna) are the largest living bivalves and, like reef-building corals, host symbiotic dinoflagellate algae (Symbiodinium) that significantly contribute to their energy budget. In turn, Symbiodinium rely on the host to supply inorganic carbon (Ci) for photosynthesis. In corals, host "proton pump" vacuolar-type H+-ATPase (VHA) is part of a carbon concentrating mechanism (CCM) that promotes Symbiodinium photosynthesis. Here, we report that VHA in the small giant clam (Tridacna maxima) similarly promotes Symbiodinium photosynthesis. VHA was abundantly expressed in the apical membrane of epithelial cells of T. maxima’s siphonal mantle tubule system which harbors Symbiodinium. Furthermore, application of the highly specific pharmacological VHA inhibitors bafilomycin A1 and concanamycin A significantly reduced photosynthetic O2 production by ~40%. Together with our observation that exposure to light increased holobiont aerobic metabolism ~five-fold, and earlier estimates that translocated fixed carbon exceeds metabolic demand, we conclude that VHA activity in the siphonal mantle confers strong energetic benefits to the host clam through increased supply of Ci to algal symbionts and subsequent photosynthetic activity. The convergent role of VHA in promoting Symbiodinium photosynthesis in the giant clam siphonal mantle tubule system and coral symbiosome suggests VHA-driven CCM is a common exaptation in marine photosymbioses that deserves further investigation in other taxa.
      PubDate: 2018-07-31T01:17:16-07:00
      DOI: 10.1242/jeb.177220
  • Changes in the material properties of the shell during simulated aquatic
           hibernation in the anoxia-tolerant painted turtle [RESEARCH ARTICLE]
    • Authors: Odegard, D. T; Sonnenfelt, M. A, Bledsoe, J. G, Keenan, S. W, Hill, C. A, Warren, D. E.
      Abstract: Dean T. Odegard, Michael A. Sonnenfelt, J. Gary Bledsoe, Sarah W. Keenan, Craig A. Hill, and Daniel E. Warren

      Western painted turtles (Chrysemys picta bellii) tolerate anoxic submergence longer than any other tetrapod, surviving more than 170 days at 3°C. This ability is due, in part, to the shell and skeleton simultaneously releasing calcium and magnesium carbonates, and sequestering lactate and H+ to prevent lethal decreases in body fluid pH. We evaluated the effects of anoxic submergence at 3°C on various material properties of painted turtle bone after 60, 130, and 167-170 days, and compared them to normoxic turtles held at the same temperature for the same time periods. To assess changes in the mechanical properties, beams (4x25 mm) were milled from the plastron and broken in a three-point flexural test. Bone mineral density, CO2 concentration (a measure of total bone HCO3–/CO32-), and elemental composition were measured using microCT, HCO3–/CO32- titration, and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Tissue mineral density of the sampled bone beams were not significantly altered by 167-170 days of aquatic overwintering in anoxic or normoxic water, but bone CO2 and Mg were depleted in anoxic compared normoxic turtles. At this time point, the plastron beams from anoxic turtles yielded at stresses that were significantly smaller and strains significantly greater than the plastron beams of normoxic turtles. When data from anoxic and normoxic turtles were pooled, plastron beams had a diminished elastic modulus after 167-170 days compared to control turtles sampled on Day 1, indicating an effect of prolonged housing of the turtles in 3°C water without access to basking sites. There were no changes in the mechanical properties of the plastron beams at any of the earlier time points in either group. We conclude that anoxic hibernation can weaken the painted turtle's plastron, but likely only after durations that exceed what it might naturally experience. The duration of aquatic overwintering, regardless of oxygenation state, is likely to be an important factor determining the mechanical properties of the turtle shell during spring emergence.
      PubDate: 2018-07-31T01:17:16-07:00
      DOI: 10.1242/jeb.176990
  • Silencing cuticular pigmentation genes enables RNA FISH in intact insect
           appendages [METHODS [amp ] TECHNIQUES]
    • Authors: Pentzold, S; Grabe, V, Ogonkov, A, Schmidt, L, Boland, W, Burse, A.
      Abstract: Stefan Pentzold, Veit Grabe, Andrei Ogonkov, Lydia Schmidt, Wilhelm Boland, and Antje Burse

      Optical imaging of gene expression by fluorescence in situ hybridisation (FISH) in insects is often impeded by their pigmented cuticle. Since most chemical bleaching agents are incompatible with FISH, we developed a RNA interference-based method for clearing cuticular pigmentation which enables using whole-mount body appendages for RNA FISH. Silencing laccase2 or tyrosine hydroxylase in two leaf beetles species (Chrysomela populi, Phaedon cochleariae) cleared their pigmented cuticle and decreased light absorbance. Subsequently, intact appendages (palps, antennae, legs) from RNAi-cleared individuals were used to image expression and spatial distribution of antisense mRNA of two chemosensory genes (gustatory receptor, odorant-binding protein). Imaging did neither work for RNAi-controls due to retained pigmentation, nor for FISH-controls (sense mRNA). Several bleaching agents were incompatible with FISH, either due to degradation of RNA, lack of clearing efficacy or long incubation times. Overall, silencing pigmentation genes is a significant improvement over bleaching agents enabling FISH in intact appendages.
      PubDate: 2018-07-19T00:25:41-07:00
      DOI: 10.1242/jeb.185710
  • How the egg rolls: a morphological analysis of avian egg shape in the
           context of displacement dynamics [RESEARCH ARTICLE]
    • Authors: Hays, I. R; Hauber, M. E.
      Abstract: Ian R. Hays and Mark E. Hauber

      Very little is known about how morphology affects the motion, spatial stability, and resulting viability of avian eggs. The limited existing research focuses on the uniquely pyriform egg shapes found in the Alcidae bird family. This unusual shell shape was originally thought to suppress displacement and prevent egg loss on the cliffside nesting habitat of the Uria genus. Unfortunately, these early studies never isolated or quantified the specific morphological features (elongation, asymmetry, and conicality) of these pyriform eggs, which limits their applicability to other taxa and has hampered a robust proof of concept. We isolated each feature as an enumerated variable, produced model 3D printed eggs with incremental expressions of a single variable and then with all three features covarying simultaneously. Recorded motion (egg-rolling) trials were conducted to test the individual and combined effects of each morphological characteristic on displacement over a range of inclines representative of the conditions found in nesting habitats. Increasing elongation and asymmetry significantly increased displacement, whereas increased conicality decreased displacement in the single-variable egg models. In the multivariable egg models, only conicality consistently suppressed displacement, while lower levels of asymmetry significantly increased displacement. Our findings broadly support previous studies’ assertions of the adaptive value of the pyriform eggs while providing methodology and comparative data for future analyses of the interactions between nesting habitat, behavior, and egg shape, beyond the confines of a handful of focal species.
      PubDate: 2018-07-19T00:25:41-07:00
      DOI: 10.1242/jeb.178988
  • Parameters of motion vision in low-light in the hawkmoth, Manduca sexta
    • Authors: Parthasarathy, K; Willis, M. A.
      Abstract: K. Parthasarathy and M. A. Willis

      The hawkmoth Manduca sexta, is nocturnally active, beginning its flight activity at sunset, and executing rapid controlled maneuvers to search for food and mates in dim light conditions. This moth's visual system has been shown to trade off spatial and temporal resolution for increased sensitivity in these conditions. The study presented here uses tethered flying moths to characterize the flight performance envelope of M. sexta's wide-field-motion-triggered steering response in low light conditions by measuring attempted turning in response to wide-field visual motion. Moths were challenged with a horizontally oscillating sinusoidal grating at a range of luminance, from daylight to starlight conditions. The impact of luminance on response to a range of temporal frequencies and spatial wavelengths was assessed across a range of pattern contrasts. The optomotor response decreased as a function of decreasing luminance, and the lower limit of the moth's contrast sensitivity was found to be between 1% to 5%. The preferred spatial frequency for M. sexta increased from 0.06 to 0.3 cycles/degree as the luminance decreased, but the preferred temporal frequency remained stable at 4.5 Hz across all conditions. The relationship between the optomotor response time to the temporal frequency of the pattern movement did not vary significantly with luminance levels. Taken together, these results suggest that the behavioral response to wide-field visual input in M. sexta is adapted to operate during crepuscular to nocturnal luminance levels, and the decreasing light levels experienced during that period changes visual acuity and does not affect their response time significantly.
      PubDate: 2018-07-18T05:45:40-07:00
      DOI: 10.1242/jeb.173344
  • Heterogeneity of neuromasts in a fish without lateral line canals: the
           pufferfish (Takifugu obscurus, Abe, 1949) model [RESEARCH ARTICLE]
    • Authors: Li, C; Wang, X, Wu, J, Zhang, X, Fan, C, Guo, H, Song, J.
      Abstract: Chao Li, Xiaojie Wang, Jianyong Wu, Xuguang Zhang, Chunxin Fan, Hongyi Guo, and Jiakun Song

      Fish detect water motions with their mechanosensory lateral line. The basic functional unit of the lateral line is the neuromast. In most fish species neuromasts are located in lateral line canals (canal neuromasts) or on the skin (superficial neuromasts). In this paper we describe the lateral line system of pufferfish, Takifugu obscurus. If threatened, this fish inflates its body by sucking water into the esophagus. Pufferfish lack a canal system but have neuromasts located directly on the skin or in open grooves. Each groove houses Tall, Medium, and Short Neuromasts, based on the height of their pedestal. One or more Medium neuromasts were always located between two Tall neuromasts, and the Short neuromasts were scattered between them. Tall neuromasts showed phasic responses to water jets, similar to the canal neuromasts of other fish species. In contrast, the Medium and Short neuromasts showed tonic responses to water jets. The response properties of nerve fibers that innervated the latter two types of neuromasts were similar to the response properties of the superficial neuromasts found in other fish species. Our results suggest that each groove of a pufferfish has two functional groups of neuromasts. This may allow pufferfish to extract spatial and temporal hydrodynamic information, despite the changes in body shape that occur during and after inflation. The short neuromasts at the bottom of a groove most likely supplement the medium neuromasts when the body is maximally inflated.
      PubDate: 2018-07-11T03:03:20-07:00
      DOI: 10.1242/jeb.186163
  • Optomotor steering and flight control requires a specific sub-section of
           the compound eye in the hawkmoth, Manduca sexta [RESEARCH ARTICLE]
    • Authors: Copley, S; Parthasarathy, K, Willis, M. A.
      Abstract: Sean Copley, Kalyanasundaram Parthasarathy, and Mark A. Willis

      While tracking odor plumes, male hawkmoths use optic flow cues to stabilize their flight movements with respect to their environment. We studied the responses of freely flying moths tracking odor plumes in a laboratory wind tunnel and tethered moths in an optomotor flight simulator to determine the locations on the compound eye on which critical optic flow cues are detected. In these behavioral experiments, we occluded specific regions of the compound eye and systematically examined the moths’ behavior for specific deficits in optic flow processing. Freely flying moths with the dorsal half of the compound eye painted were unable to maintain stable flight and track the wind-borne odor plume. However, the plume tracking performance of moths with the ventral half of their compound eyes painted was the same as unpainted controls. In a matched set of experiments, we presented tethered moths with moving vertically-oriented sinusoidal gratings and found that individuals with their eyes unpainted, ventrally-painted, and medially-painted all responded by attempting optomotor-driven turns in the same proportion. In contrast, individuals with their compound eyes, dorsally-painted, laterally-painted, and totally-painted showed no optomotor turning response. We decreased the contrast of the visual stimulus and found that this relationship was consistent down to a contrast level of 2.5%. We conclude that visual input from the dorso-lateral region of the animal's visual world is critical for successful maintenance of flight stability and that this species’ visual environment must meet or exceed a contrast ratio of 2.5% to support visual flight control.
      PubDate: 2018-07-02T02:52:41-07:00
      DOI: 10.1242/jeb.178210
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