nils-herrmann/clean_scirepeval huggingface dataset:
Characterization and modelling of looming-sensitive neurons in the crab Neohelice
Venue: Journal of Comparative Physiology A

Looming-sensitive neurons (LSNs) are motion-sensitive neurons tuned for detecting imminent collision. Their main characteristic is the selectivity to looming (a 2D representation of an object approach), rather than to receding stimuli. We studied a set of LSNs by performing surface extracellular recordings in the optic nerve of Neohelice granulata crabs, and characterized their response against computer-generated visual stimuli with different combinations of moving edges, highlighting different components of the optical flow. In addition to their selectivity to looming stimuli, we characterized other properties of these neurons, such as low directionality; reduced response to sustained excitement; and an inhibition phenomenon in response to visual stimuli with dense optical flow of expansion, contraction, and translation. To analyze the spatio-temporal processing of these LSNs, we proposed a biologically plausible computational model which was inspired by previous computational models of the locust lobula giant motion detector (LGMD) neuron. The videos seen by the animal during electrophysiological experiments were applied as an input to the model which produced a satisfactory fit to the measured responses, suggesting that the computation performed by LSNs in a decapod crustacean appears to be based on similar physiological processing previously described for the LGMD in insects.
Mass scaling of the resting and maximum metabolic rates of the black carp
Venue: Journal of Comparative Physiology B

We investigated the body mass (M) scaling of resting metabolic rate (RMR), maximum metabolic rate (MMR), excess post-exercise oxygen consumption (EPOC), blood parameters, and organ masses of black carp (Mylopharyngoden piceus). The results showed that RMR scaled with M of the fish by an exponent (b) of 0.833 (bR), which was significantly larger than 0.75. MMR scaled with M by a power of 0.775 (bM), which was significantly lower than 1 and may be due to a small size proportion of red muscle. No difference between bR and bM or correlation between factorial aerobic scope and M was found. However, EPOC scaled positively with M by a power of 1.231, suggesting a constant aerobic capacity and an enhanced anaerobic capacity with fish growth. Mass of the inactive organs scaled with M by a power of 1.005, which was significantly larger than 1 and was negatively correlated with RMR, suggesting that the proportion of inactive organs increases with fish growth, which may contribute to the negative scaling of RMR. Red blood cell surface area (S) did not increase with increasing M, suggesting that the ontogenetic decrease in the surface area to volume ratio of cells may not contribute to the negative scaling of RMR. The predicted bR value (0.846) by the average S (1.746 µm²) differs by only 1.62% from the observed bR value using our previously reported S − bR function in carp, suggesting that the species-specific cell size, rather than its ontogenetic change, affects the metabolic scaling of a species.
Heat flux in manatees: an individual matter and a novel approach to assess and monitor the thermal state of Florida manatees (Trichechus manatus latirostris)
Venue: Journal of Comparative Physiology B

Florida manatees (Trichechus manatus latirostris) possess an unusual suite of adaptations to accommodate both a fully aquatic lifestyle and an herbivorous diet, including a low metabolic rate and a very limited thermoneutral zone. Their relatively high lower critical temperature of around 20 °C suggests strong sensitivity to cold, thereby limiting their distribution to tropical and subtropical waters. “Cold stress syndrome” affects and kills Florida manatees every year during intense or prolonged cold weather, posing one of the major threats to manatees. However, knowledge regarding manatee thermoregulation is sparse, but essential for effective conservation and management of this threatened species. We measured heat flux in two captive Florida manatees at multiple times of the year, at 41 sites distributed across the entire body surface of each manatee. Heat flux differed significantly between individuals, and among body sites and times of the year. The pectoral flippers and axillae were identified as areas with highest heat exchange. Despite exposure to constant water temperature throughout the year, the manatees in this study had significantly lower heat flux in winter than in summer. We used the measured heat flux values to calculate total heat dissipation in individual manatees. The values estimated this way correspond well with the low metabolic rates estimated in previous studies, confirming the reliability of our novel approach. Our method provides simple and useful options for enhancing manatee welfare by monitoring the animals’ thermal state during potentially stressful activities such as during medical treatment, capture restraints and transportation.
The cryoprotectant system of Cope’s gray treefrog, Dryophytes chrysoscelis: responses to cold acclimation, freezing, and thawing
Venue: Journal of Comparative Physiology B

Cope’s gray treefrog (Dryophytes chrysoscelis) is one of few freeze-tolerant frogs that mobilize glycerol as a cryoprotectant, yet cold and freezing-induced accumulation of this and other osmolytes has received little attention in this species. This study investigated the development of freeze tolerance in D. chrysoscelis, analyzing the response of the cryoprotectant system to cold acclimation, freezing, and thawing. Glycerol production was low and unresponsive to acclimation temperature, or duration of acclimation to 5 °C, except for one cold-acclimated frog that presented elevated glycerol in plasma, liver, and skeletal muscle. Curiously, glycerol concentration in skeletal muscle was higher than that of plasma and liver, in both warm- and cold-acclimated frogs, suggesting glycerol synthesis in muscle. Urea concentration in plasma doubled in response to cold acclimation but did not change during freezing. Freezing induced hepatic glycogen catabolism and an increase in glycerol and glucose in several tissues, although the mobilization dynamics differed between these cryoprotectants, possibly as a result of different transport mechanisms. Although hepatic glucose mobilization was of considerable magnitude, glucose accumulation in peripheral tissues was low and was surpassed by that of glycerol and urea. The muscle production of glycerol and the cold-induced accumulation of urea imply a role for skeletal muscle metabolism in the mobilization of cryoprotective solutes in D. chrysoscelis. The cryoprotectant system of D. chrysoscelis is complex, highly variable, and unique, with glycerol, glucose, and likely urea serving as cryoprotectants.
Ventilatory responses of the clown knifefish, Chitala ornata, to hypercarbia and hypercapnia
Venue: Journal of Comparative Physiology B

The aim of the present study was to determine the roles of externally versus internally oriented CO2/H+-sensitive chemoreceptors in promoting cardiorespiratory responses to environmental hypercarbia in the facultative air-breathing fish, Chitala ornata (the clown knifefish). Fish were exposed to environmental acidosis (pH ~ 6.0) or hypercarbia (≈ 30 torr PCO2) that produced changes in water pH equal to the pH levels of the acidotic water to distinguish the relative roles of CO2 versus H+. We also injected acetazolamide to elevate arterial levels of PCO2 and [H+] in fish in normocarbic water to distinguish between internal and external stimuli. We measured changes in gill ventilation frequency, air breathing frequency, heart rate and arterial blood pressure in response to each treatment as well as the changes produced in arterial PCO2 and pH. Exposure to normocarbic water of pH 6.0 for 1 h did not produce significant changes in any measured variable. Exposure to hypercarbic water dramatically increased air breathing frequency, but had no effect on gill ventilation. Hypercarbia also produced a modest bradycardia and fall in arterial blood pressure. Injection of acetazolamide produced similar effects. Both hypercarbia and acetazolamide led to increases in arterial PCO2 and falls in arterial pH although the changes in arterial PCO2/pH were more modest following acetazolamide injection as were the increases in air breathing frequency. The acetazolamide results suggest that the stimulation of air breathing was due, at least in part, to stimulation of internally oriented CO2/H+ chemoreceptors monitoring blood gas changes.
De novo transcriptomics reveal distinct phototransduction signaling components in the retina and skin of a color-changing vertebrate, the hogfish (Lachnolaimus maximus)
Venue: Journal of Comparative Physiology A

Across diverse taxa, an increasing number of photoreceptive systems are being discovered in tissues outside of the eye, such as in the skin. Dermal photoreception is believed to serve a variety of functions, including rapid color change via specialized cells called chromatophores. In vitro studies of this system among color-changing fish have suggested the use of a phototransduction signaling cascade that fundamentally differs from that of the retina. Thus, the goal of this study was to identify phototransduction genes and compare their expression in the retina and skin of a color-changing fish, the hogfish Lachnolaimus maximus. De novo transcriptomics revealed the expression of genes that may underlie distinct, yet complete phototransduction cascades in L. maximus retina and skin. In contrast to the five visual opsin genes and cGMP-dependent phototransduction components expressed in the retina of L. maximus, only a single short-wavelength sensitive opsin (SWS1) and putative cAMP-dependent phototransduction components were expressed in the skin. These data suggest a separate evolutionary history of phototransduction in the retina and skin of certain vertebrates and, for the first time, indicate an expression repertoire of genes that underlie a non-retinal phototransduction pathway in the skin of a color-changing fish.
Tyraminergic modulation of agonistic outcomes in crayfish
Venue: Journal of Comparative Physiology A

Octopamine, a biogenic amine, modulates various behaviors, ranging from locomotion and aggression to learning and memory in invertebrates. Several studies recently demonstrated that tyramine, the biological precursor of octopamine, also affects behaviors independent of octopamine. Here we investigated the involvement of tyramine in agonistic interaction of the male crayfish Procambarus clarkii. When male crayfish fight, larger animals (3–7% difference in body length) are more likely to win. By contrast, direct injection of tyramine or octopamine counteracted the physical advantage of larger animals. Tyramine or octopamine-injected naive large animals were mostly beaten by untreated smaller naive animals. This pharmacological effect was similar to the loser effect in which subordinate larger animals are frequently beaten by smaller animals. Furthermore, loser effects were partly eliminated by either injection of epinastine, an octopamine blocker, or yohimbine, a tyramine blocker, and significantly diminished by injection of a mixture of both blockers. We also observed that tyramine levels in the subesophageal ganglion were remarkably increased in subordinate crayfish after losing a fight. These results suggest that tyramine modulates aggressive levels of crayfish and contributes to the loser effect in parallel with octopamine.
Candidate genes for cooperation and aggression in the social wasp Polistes dominula
Venue: Journal of Comparative Physiology A

Cooperation and aggression are ubiquitous in social groups, and the genetic mechanisms underlying these behaviours are of great interest for understanding how social group formation is regulated and how it evolves. In this study, we used a candidate gene approach to investigate the patterns of expression of key genes for cooperation and aggression in the brain of a primitively eusocial wasp, Polistes dominula, during colony founding, when multiple foundresses can join the same nest and establish subtle hierarchies of dominance. We used a comparative approach to select candidate genes for cooperation and aggression looking at two previously published studies on global gene expression in wasps and ants. We tested the expression of these genes in P. dominula wasps that were either displaying aggressive behaviour (dominant and single foundresses) or cooperation (subordinate foundresses and workers) towards nestmates. One gene in particular, the egg yolk protein vitellogenin, known for its reproductive role in insects, displayed patterns of expression that strongly matched wasp social rank. We characterize the genomic context of vitellogenin by building a head co-expression gene network for P. dominula, and we discuss a potential role for vitellogenin as a mediator of social interactions in wasps.
Scaling of work and power in a locomotor muscle of a frog
Venue: Journal of Comparative Physiology B

Muscle work and power are important determinants of movement performance in animals. How these muscle properties scale determines, in part, the scaling of performance during movements, such as jump height or distance. Muscle-mass-specific work is predicted to remain constant across a range of scales, assuming geometric similarity, while muscle-mass-specific power is expected to decrease with increasing scale. We tested these predictions by examining muscle morphology and contractile properties of plantaris muscles from frogs ranging in mass from 1.28 to 20.60 g. Scaling of muscle work and power was examined using both linear regression on log10-transformed data (LR) and non-linear regressions on untransformed data (NLR). Results depended on the method of regression not because of large changes in scaling slopes, but because of changing levels of statistical significance using corrections for multiple tests, demonstrating the importance of careful consideration of statistical methods when analyzing patterns of scaling. In LR, muscle-mass-specific work decreased with increasing scale, but an accompanying positive allometry of muscle mass predicts constant movement performance at all scales. These relationships were non-significant in NLR, though scaling with geometric similarity also predicts constant jump performance across scales, because of proportional increases in available muscle energy and body mass. Both intrinsic shortening velocity and muscle-mass-specific power were positively allometric in both types of analysis. Nonetheless, scale accounts for little variation in contractile properties overall over the range examined, indicating that other sources of intraspecific variation may be more important in determining muscle performance and its effects on movement.
Interaction of interaural cues and their contribution to the lateralisation of Mongolian gerbils (Meriones unguiculatus)
Venue: Journal of Comparative Physiology A

The main sound localisation cues in the horizontal plane are interaural time and level differences (ITDs and ILDs, respectively). ITDs are thought to be the dominant cue in the low-frequency range, ILDs the dominant cue in the high-frequency range. ITDs and ILDs co-occur. Their interaction and contribution to the lateralisation of pure tones by Mongolian gerbils was investigated behaviourally using cross-talk cancellation techniques for presenting ITDs and ILDs independently. First, ITDs were applied to pure tones with frequencies ≤ 2 kHz to the ongoing waveform, at the onsets and offsets, or in both the ongoing waveform and at the onsets and offsets. Gerbils could lateralise tones only if ongoing ITDs were present indicating that ongoing ITDs are decisive for the lateralisation of low-frequency tones. Second, an ITD was added to 2-to-6-kHz tones with varying ILD. Gerbils’ lateralisation was unaffected by the ITD indicating that a large ILD provides a strong lateralisation cue at those frequencies. Finally, small ILDs were applied to 2-kHz tones with an ongoing ITD, pointing either to the same or opposing sides as the ITD. Gerbils’ lateralisation was driven by the ITD but strongly affected by the ILD indicating that both interaural cues contribute to the lateralisation.
Sex-specific thermal sensitivities of performance and activity in the asian house gecko, Hemidactylus frenatus
Venue: Journal of Comparative Physiology B

Studies of sexual selection primarily focus on morphological traits such as body size and secondary trait dimorphism, with less attention been given to the functional differences between the sexes and even more so their thermal performance capacities. Each sex may benefit from possessing different thermal performance capacities that would allow them to maximise their fitness relative to their different reproductive roles; especially when performances are closely related to reproductive success. Here, we examine sexual divergence in thermal sensitivities of performance across three populations of the Asian house gecko (Hemidactylus frenatus) over an extensive latitudinal cline. Using analyses of the thermal sensitivity of routine activity, bite force and sprint speed, we explored whether: (i) males and females differed in their optimal temperatures for performance, (ii) the sexes differed in their thermal sensitivities of performance, and (iii) the degree of sexual divergence in thermal sensitivity varied among the populations. Because male H. frenatus are highly aggressive and frequently engage in combat to gain territories and mating opportunities, we expected males would be active over a wider range of temperatures than females and this would favour broad thermal sensitivity curves for males. In addition, we expected a greater divergence between the sexes in thermal sensitivities for the temperate populations that experience greater daily and seasonal thermal variation. We found that males were more active, and had greater bite forces and faster sprint speeds than females, independent of body size. In addition, we found differences between the sexes in thermal sensitivities for the tropical population; female H. frenatus were less active and possessed lower sprint speeds at higher temperatures than males. Although H. frenatus from the most variable thermal environments also displayed the broadest thermal performance range, it was the more stable tropical population that exhibited the greatest divergence between the sexes in thermal sensitivity of performance. The divergence in thermal physiology that we detected between the sexes of H. frenatus is consistent with the idea that males will derive mating and territorial advantages for maintaining function over a broader range of temperatures.
Electrophysiological differences in cholinergic signaling between the hearts of summer and winter frogs (Rana temporaria)
Venue: Journal of Comparative Physiology B

The striking seasonal difference in sensitivity of frog cardiac muscle to acetylcholine or stimulation of parasympathetic nervous fibers has been noted almost a century ago, although its electrophysiological basis has never been revealed. The present study compares the effects of the muscarinic agonist carbamylcholine chloride (CCh 10−8–10−5 M) on electrical activity in isolated atrial and ventricular preparations from dormant frogs (Rana temporaria) caught in January (winter-acclimatized, WA) and from active frogs caught in July (summer-acclimatized, SA). Seasonal differences in the density of potassium acetylcholine-dependent current (IKACh) were also studied in atrial and ventricular myocytes from both summer and winter groups. In atrial myocardium, CCh produced concentration-dependent shortening of action potentials (APs). CCh concentration producing a 50% reduction of AP duration was lower in WA (1.03 × 10−7 M) than SA atria (2.7 × 10−7 M). 10−6 M CCh induced drastic reduction of AP amplitude rendering the tissue unexcitable in both WA or SA atrial preparations. Ventricular preparations showed greater seasonal difference in CCh sensitivity. While 10−6 M induced inexcitability in 50% of tested WA preparations, in SA preparations even 10−5 M CCh was without effect. This striking difference between cholinergic effects in SA and WA frog ventricle could be explained by seasonal changes in the IKACh density. The density of IKACh induced by 10−5 M CCh and measured at 0 mV was 14.4 ± 3.45 pA/pF in WA, but only 1.5 ± 0.4 pA/pF in SA atrial cells. In ventricular cells, the respective values were 2.61 ± 0.56 and 0.71 ± 0.09 pA/pF. Thus, hibernating winter frog has a much greater electrophysiological cholinergic response than active summer frog due to up-regulation of IKACh.
Cardiovascular adjustments with egg temperature at 90% incubation in embryonic American alligators, Alligator mississippiensis
Venue: Journal of Comparative Physiology B

American alligators (Alligator mississippiensis) deposit eggs in a mound nest, potentially subjecting embryos to daily variations in temperature. Whilst adult crocodilian cardiovascular responses to changes in temperature have been investigated, similar studies in alligator embryos are limited. We investigated cardiovascular function of embryonic alligators during heating and cooling as well as at different temperatures. We measured arterial blood pressure (Pm) and heart rate (fH) in response to cooling (30–26 °C), heating (26–36 °C), followed by a reciprocal cooling event (36–26 °C) and assessed the cardiac baroreflex at 30 and 36 °C. Embryonic fH increased during heating events and decreased during cooling events, while embryos were hypotensive at 26 and 36 °C, although Pm did not differ between heating or cooling events. There was a clear temperature-dependent heart rate hysteresis at a given embryo’s temperature, depending on whether embryos were cooling or heating. Cardiovascular regulation through the cardiac limb of the baroreflex was not affected by temperature, despite previous studies suggesting that vagal tone is present at both low and high temperatures.
Immune challenges decrease biliverdin concentration in the spleen of northern Bobwhite quail, Colinus virginianus
Venue: Journal of Comparative Physiology B

Most antioxidants have multiple functions; in addition to minimizing oxidative damage, many antioxidants have immune-modulating properties. For example, biliverdin is produced in the liver and spleen from the breakdown of heme, and has putative immune-suppressing and antioxidant properties. However, the majority of these properties have been investigated in vitro or in mammalian models, in which biliverdin reductase converts virtually all biliverdin to bilirubin. Thus, biliverdin’s physiological roles remain largely untested. Here, we investigated whether biliverdin has immunomodulating roles by injecting Northern Bobwhite quail (Colinus virginianus) with either a vehicle control, lysed and rinsed pig red blood cells (pRBC) that contain erythrocyte antigens but no heme, or intact pRBC that contain both erythrocyte antigens and hemoglobin, thus increasing the amount of heme that can be converted to biliverdin. We then quantified hemagglutination and hemolysis ability, and biliverdin concentration in the liver and spleen, on 3, 6, and 9 days post-injection. We found that hemagglutination was greater in individuals that received intact pRBC, but not in those injected with heme-removed pRBC, demonstrating that biliverdin does not suppress immune function at this dosage. Biliverdin levels of liver and spleen were correlated within individuals, suggesting organism-level variation in biliverdin production. Lastly, individuals injected with intact pRBC had a reduced biliverdin concentration in the spleen, suggesting that immune challenges may reduce biliverdin production or accumulation. This initial investigation demonstrated that biliverdin may have more nuanced physiological roles than previously reported, supporting the value of further investigations into the physiology of biliverdin.