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Journal of Experimental Biology

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https://www.readbyqxmd.com/read/28213397/regional-differences-in-the-preferred-e-vector-orientation-of-honeybee-ocellar-photoreceptors
#1
Yuri Ogawa, Willi Ribi, Jochen Zeil, Jan M Hemmi
In addition to compound eyes, honeybees (Apis mellifera) possess three single lens eyes called ocelli located on the top of the head. Ocelli are involved in head-attitude control and in some insects have been shown to provide celestial compass information. Anatomical and early electrophysiological studies have suggested that UV and blue-green photoreceptors in ocelli are polarization sensitive. However, their retinal distribution and receptor characteristics have not been documented. Here, we used intracellular electrophysiology to determine the relationship between the spectral and polarization sensitivity of photoreceptors and their position within the visual field of the ocelli...
February 17, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28209806/short-term-and-long-term-effects-of-transient-exogenous-cortisol-manipulation-on-oxidative-stress-in-juvenile-brown-trout
#2
Kim Birnie-Gauvin, Kathryn S Peiman, Martin H Larsen, Kim Aarestrup, William G Willmore, Steven J Cooke
In the wild, animals are exposed to a growing number of stressors with increasing frequency and intensity, as a result of human activities and human-induced environmental change. To fully understand how wild organisms are affected by stressors, it is crucial to understand the physiology that underlies an organism's response to a stressor. Prolonged levels of elevated glucocorticoids are associated with a state of chronic stress and decreased fitness. Exogenous glucocorticoid manipulation reduces an individual's ability to forage, avoid predators and grow, thereby limiting the resources available for physiological functions like the defence against oxidative stress...
February 16, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28209805/effects-of-photophase-illuminance-on-locomotor-activity-urine-production-and-urinary-6-sulfatoxymelatonin-in-nocturnal-and-diurnal-south-african-rodents
#3
Ingrid van der Merwe, Maria K Oosthuizen, Andre Ganswindt, Abraham Haim, Nigel C Bennett
Effects of photophase illuminance (1, 10, 100 and 330 lux of white incandescent lighting) on daily rhythms of locomotor activity, urine production and 6-sulfatoxymelatonin (6-SMT; 10 lux vs. 330 lux) were studied in nocturnal Namaqua rock mice (Micaelamys namaquensis) and diurnal four striped field mice (Rhabdomys pumilio). Micaelamys namaquensis was consistently nocturnal (∼90-94% nocturnal activity), whereas considerable individual variation marked activity profiles in R. pumilio, but with activity mostly pronounced around twilight (∼55-66% diurnal activity)...
February 16, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28202587/it-s-cool-to-be-dominant-social-status-alters-short-term-risks-of-heat-stress
#4
Susan J Cunningham, Michelle L Thompson, Andrew E McKechnie
Climate change has potential to trigger social change. As a first step towards understanding mechanisms determining the vulnerability of animal societies to rising temperatures, we investigated interactions between social rank and thermoregulation in three arid-zone bird species: fawn-coloured lark (Mirafra africanoides, territorial); African red-eyed bulbul (Pycnonotus nigricans, loosely social) and sociable weaver (Philetairus socius, complex cooperative societies). We assessed relationships between body temperature (Tb), air temperature (Ta) and social rank in captive groups in the Kalahari Desert...
February 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28202586/waveform-sensitivity-of-electroreceptors-in-the-pulse-weakly-electric-fish-gymnotus-omarorum
#5
Alejo Rodríguez-Cattaneo, Pedro A Aguilera, Angel A Caputi
As in most sensory systems electrosensory images in weakly electric fish are encoded in two parallel pathways, fast and slow. From the work on wave type electric fish these pathways are thought to encode the time and amplitude of electrosensory signals respectively. This article focuses on the primary afferents giving origin to the slow path of the pulse type weakly electric fish Gymnotus omarorum We found that burst duration coders respond with a high-frequency train of spikes to each electric organ discharge...
February 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28202585/is-human-achilles-tendon-deformation-greater-in-regions-where-cross-sectional-area-is-smaller
#6
Neil D Reeves, Glen Cooper
The Achilles is a long tendon varying in cross-sectional area (CSA) considerably along its length. For the same force, a smaller CSA would experience higher tendon stress and we hypothesised that these areas would therefore undergo larger transverse deformations. A novel magnetic resonance imaging-based approach was implemented to quantify changes in tendon CSA from rest along the length of the Achilles tendon under load conditions corresponding to 10, 20 and 30% of isometric plantar flexor maximum voluntary contraction (MVC)...
February 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28202584/comparison-of-human-gastrocnemius-forces-predicted-by-hill-type-muscle-models-and-estimated-from-ultrasound-images
#7
Taylor J M Dick, Andrew A Biewener, James M Wakeling
Hill-type models are ubiquitous in the field of biomechanics, providing estimates of a muscle's force as a function of its activation state and its assumed force-length and force-velocity properties. However, despite their routine use, the accuracy with which Hill-type models predict the forces generated by muscles during submaximal, dynamic tasks remains largely unknown. This study compared human gastrocnemii forces predicted by Hill-type models to the forces estimated from ultrasound-based measures of tendon length changes and stiffness during cycling, over a range of loads and cadences...
February 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28202583/acoustic-measurements-of-post-dive-cardiac-responses-in-southern-elephant-seals-mirounga-leonina-during-surfacing-at-sea
#8
Louise Day, Joffrey Jouma'a, Julien Bonnel, Christophe Guinet
Measuring physiological data in free-ranging marine mammals remains challenging, owing to their far-ranging foraging habitat. Yet, it is important to understand how these divers recover from effort expended underwater, as marine mammals can perform deep and recurrent dives. Among them, southern elephant seals (Mirounga leonina) are one of the most extreme divers, diving continuously at great depth and for long duration while travelling over large distances within the Southern Ocean. To determine how they manage post-dive recovery, we deployed hydrophones on four post-breeding female southern elephant seals...
February 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28202582/dynamic-changes-in-cardiac-mitochondrial-metabolism-during-warm-acclimation-in-rainbow-trout
#9
Nicolas Pichaud, Andreas Ekström, Kim Hellgren, Erik Sandblom
Although the mitochondrial metabolism responses to warm acclimation have been widely studied in fish, the time course of this process is less understood. Here, we characterise changes of rainbow trout (Oncorhyncus mykiss) cardiac mitochondrial metabolism during acute warming from 10 to 16°C, and during the subsequent warm acclimation for 39 days (D). We repeatedly measured mitochondrial O2 consumption in cardiac permeabilized fibers and functional integrity of mitochondria (i.e. mitochondrial coupling and cytochrome c effect) at two assay temperatures (10 and 16°C), as well as citrate synthase (CS) and lactate dehydrogenase (LDH) activities at room temperature...
February 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28193637/jumping-performance-of-flea-hoppers-and-other-mirid-bugs-hemiptera-miridae
#10
M Burrows, M Dorosenko
The order Hemiptera includes jumping insects with the fastest take-off velocities, all generated by catapult mechanisms. It also contains the large family Miridae or plant bugs. Here we analysed the jumping strategies and mechanisms of six mirid species from high speed videos and from the anatomy of their propulsive legs and conclude that they use a different mechanism in which jumps are powered by the direct contractions of muscles. Three strategies were identified. First, jumping was propelled only by movements of the middle and hind legs which were respectively 140% and 190% longer than the front legs...
February 13, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28183870/visual-acuity-in-ray-finned-fishes-correlates-with-eye-size-and-habitat
#11
Eleanor M Caves, Tracey T Sutton, Sönke Johnsen
Visual acuity (the ability to resolve spatial detail) is highly variable across fishes. However, little is known about the evolutionary pressures underlying this variation. We reviewed published literature to create an acuity database for 159 species of ray-finned fishes (Actinopterygii). Within a subset of those species for which we had phylogenetic information and anatomically-measured acuity data (n=81), we examined relationships between acuity and both morphological (eye size and body size) and ecological (light level, water turbidity, habitat spatial complexity, and diet) variables...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28183869/behavioral-and-physiological-traits-of-migrant-and-resident-white-crowned-sparrows-a-common-garden-approach
#12
Marilyn Ramenofsky, Andrew W Campion, Jonathan H Pérez, Jesse S Krause, Zoltán Németh
: To accommodate a migratory life history, migrants express a greater number of physiological and behavioral stages per annum than residents and are thus considered to have higher finite state diversity (FSD). To investigate the physiological mechanisms and constraints associated with migration, direct comparison of two subspecies of White-crowned Sparrow - migrant, Zonotrichia leucophrys gambelii and resident, Z.l.nuttalli - were made under common garden conditions of photoperiod and housing, as birds progressed from winter through the vernal life history stages...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28183868/separation-of-different-pollen-types-by-chemotactile-sensing-in-bombus-terrestris
#13
Fabian A Ruedenauer, Sara D Leonhardt, Fabian Schmalz, Wolfgang Rössler, Martin F Strube-Bloss
When tasting food, animals rely on chemical and tactile cues, which determine the animal's decision on whether or not to eat food. As food nutritional composition has enormous consequences for the survival of animals, food items should generally be tasted before they are eaten or collected for later consumption. Even though recent studies confirmed the importance of e.g. gustatory cues, compared to olfaction only little is known about the representation of chemotactile stimuli at the receptor level (let alone higher brain centers) in animals other than vertebrates...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28183867/propulsion-in-hexapod-locomotion-how-do-desert-ants-traverse-slopes
#14
Toni Wöhrl, Lars Reinhardt, Reinhard Blickhan
The employment of an alternating tripod gait to traverse uneven terrains is a common characteristic shared among many hexapoda. Since this could be one specific cause for their ecological success, we examined the alternating tripod gait of the desert ant Cataglyphis fortis together with their ground reaction forces and weight-specific leg impulses for level locomotion and on moderate (±30°) and steep (±60°) slopes in order to understand mechanical functions of individual legs during inclined locomotion...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28183866/self-fertilization-sex-allocation-and-spermatogenesis-kinetics-in-the-hypodermically-inseminating-flatworm-macrostomum-pusillum
#15
Athina Giannakara, Steven A Ramm
The free-living flatworm genus Macrostomum is an emerging model system for studying the links between sex allocation, sexual selection and mating system evolution, as well as the underlying developmental and physiological mechanisms responsible for wide intra- and inter-specific variability in reproductive phenotypes. Despite compelling comparative morphological evidence of sexual diversity, detailed experimental work on reproductive behaviour and physiology in Macrostomum has so far been largely limited to just two species, M...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28183865/compass-cues-used-by-a-nocturnal-bull-ant-myrmecia-midas
#16
Cody A Freas, Ajay Narendra, Ken Cheng
Ants use both terrestrial landmarks and cues derived from path integration to navigate to and from their nest location. These cues persist even as light levels drop during the twilight/night. Here we determined the compass cues used by a nocturnal bull ant, Myrmecia midas, in which the majority of the individuals begin foraging during the evening twilight period. Foragers of M. midas with vectors of≤5 m when displaced to unfamiliar locations did not follow the home vector, but instead showed random heading directions...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28183864/odorant-organization-in-the-olfactory-bulb-of-the-sea-lamprey
#17
Warren W Green, Karl Boyes, Charrie McFadden, Gheylen Daghfous, François Auclair, Huiming Zhang, Weiming Li, Réjean Dubuc, Barbara S Zielinski
Olfactory sensory neurons innervate the olfactory bulb, where responses to different odorants generate a chemotopic map of increased neural activity within different bulbar regions. In this study, insight into the basal pattern of neural organization of the vertebrate olfactory bulb was gained by investigating the lamprey. Retrograde labeling established that lateral and dorsal bulbar territories receive the axons of sensory neurons broadly distributed in the main olfactory epithelium and that the medial region receives sensory neuron input only from neurons projecting from the accessory olfactory organ...
February 9, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28167809/exercise-training-reveals-trade-offs-among-endurance-performance-and-immune-function-but-not-growth-in-juvenile-lizards
#18
Jerry F Husak, Jordan C Roy, Matthew B Lovern
Acquired energetic resources allocated to a particular trait cannot then be re-allocated to a different trait. This often results in a trade-off between survival and reproduction for the adults of many species, but such a trade-off may be manifested differently in juveniles not yet capable of reproduction. Whereas adults may allocate resources to current and/or future reproduction, juveniles can only allocate to future reproduction. Thus, juveniles should allocate resources toward traits that increase survival and their chances of future reproductive success...
February 6, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28167808/how-do-individuals-cope-with-stress-behavioural-physiological-and-neuronal-differences-between-proactive-and-reactive-coping-styles-in-fish
#19
Marco A Vindas, Marnix Gorissen, Erik Höglund, Gert Flik, Valentina Tronci, Børge Damsgård, Per-Ove Thörnqvist, Tom O Nilsen, Svante Winberg, Øyvind Øverli, Lars O E Ebbesson
Despite the use of fish models to study human mental disorders and dysfunctions, knowledge of regional telencephalic responses in non-mammalian vertebrates expressing alternate stress coping styles is poor. Since perception of salient stimuli associated with stress coping in mammals is mainly under forebrain limbic control, we tested region-specific forebrain neural (i.e mRNA abundance and monoamine neurochemistry) and endocrine responses at basal and acute stress conditions for previously characterised proactive and reactive Atlantic salmon...
February 6, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28167807/flipper-stroke-rate-and-venous-oxygen-levels-in-free-ranging-california-sea-lions
#20
Michael S Tift, Luis A Hückstädt, Birgitte I McDonald, Philip H Thorson, Paul J Ponganis
The depletion rate of the blood oxygen store, development of hypoxemia, and dive capacity are dependent on the distribution and rate of blood oxygen delivery to tissues while diving. Although blood oxygen extraction by working muscle would increase the blood oxygen depletion rate in a swimming animal, there is little information on the relationship between muscle workload and blood oxygen depletion during dives. Therefore, we examined flipper stroke rate, a proxy of muscle workload, and posterior vena cava oxygen profiles in four adult female California sea lions (Zalophus californianus) during foraging trips at sea...
February 6, 2017: Journal of Experimental Biology
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