nils-herrmann/clean_scirepeval huggingface dataset:
Levels of plasma and fecal glucocorticoid metabolites following an ACTH challenge in male and female coyotes (Canis latrans)
Venue: Journal of Comparative Physiology B

Knowledge of endocrine stress responses can be advantageous for understanding how animals respond to their environment. One tool in wildlife endocrinology is to measure the adrenocortical activity as a parameter of disturbance of animals. Fecal glucocorticoid metabolites (GCMs) provide a noninvasive assessment of adrenocortical activity. Using an adrenocorticotropic hormone (ACTH) challenge administered to 28 captive coyotes (Canis latrans), we measured the levels of plasma cortisol, and fecal cortisol and corticosterone metabolites (i.e., GCMs). Our goal was to determine the dose-response in the plasma and fecal samples following the injection and determine if there were effects of sex, age, and time of day. Specifically, animals were anesthetized for ~ 90 min with treatment animals intravenously injected with exogenous ACTH and control animals receiving saline. We collected blood samples prior to injection and at 4 different time points post-injection. We also collected fecal samples 2 days pre- and 2 days post-injection to measure fecal GCMs and determine if an endocrine stress response could be detected in fecal samples. We found a definite response in cortisol levels in the plasma for coyotes to the ACTH challenge. There was a response in fecal corticosterone 1 day post-injection, but the control males showed a similar response indicating a handling effect. Fecal cortisol levels did not indicate a response to the ACTH challenge, and were significantly lower than corticosterone concentrations. We also found significant sex, but not age or diurnal, differences in fecal GCMs. Radioimmunoassays for fecal corticosterone levels appeared to be a reliable indicator of physiological stress in coyotes.
Phylogenetic analysis of standard metabolic rate of snakes: a new proposal for the understanding of interspecific variation in feeding behavior
Venue: Journal of Comparative Physiology B

The current proposal about the variation of standard metabolic rates (SMR) in snakes predicts that SMR is influenced by the feeding frequency (frequent or infrequent feeders). However, feeding frequency in snakes is poorly studied and hard to quantify under natural conditions. Alternatively, foraging strategy was studied for a large number of species and is usually related to the feeding frequency. In this work, we performed a meta-analysis on the SMR of compiled data from 74 species of snakes obtained from the literature and five more different species of lanceheads (genus Bothrops), after categorization according to the foraging mode (ambush or active foraging) and regarding their phylogenetic history. We tested the hypothesis that foraging mode (FM) is a determinant factor on the interspecific variation of SMR despite the phylogenetic relationship among species. We demonstrated that FM predicted SMR, but there is also a partial phylogenetic structuration of SMR in snakes. We also detected that evolution rates of SMR in active foragers seem to be higher than ambush-hunting snakes. We suggested that foraging mode has a major effect over the evolution of SMR in snakes, which could represent an ecophysiological co-adaptation, since ambush hunters (with low feeding rates) present a lower maintenance energetic cost (SMR) when compared to active foragers. The higher SMR evolution rates for active foraging snakes could be related to a higher heterogeny in the degree of activity during hunting by active foragers when compared to ambush-hunting snakes.
Combined effects of drought and cold acclimation on phospholipid fatty acid composition and cold-shock tolerance in the springtail Protaphorura fimata
Venue: Journal of Comparative Physiology B

Terrestrial arthropods’ ability to survive sub-zero winter temperatures is an important factor influencing their abundance and geographic distribution. It is, therefore, important to understand their physiological mechanisms of low-temperature survival. Acclimation to moderate–low temperature can improve cold tolerance, and pre-acclimation to mild desiccation can also improve survival of a subsequent cold exposure. However, very few studies have assessed the combined actions of cold and drought acclimations. In the present study, we combined cold acclimation with drought acclimation making it possible to assess the interactions between effects of these two stressors using the springtail Protaphorura fimata as a model organism. We investigated the interacting effects of drought and cold acclimation on body fluid osmolality, membrane phospholipid fatty acid (PLFA) composition, and cold-shock tolerance. Acclimation to mild drought (− 2.46 MPa) increased body fluid osmolality from 0.33 to 1.25 Osm at all acclimation temperatures (5, 10, 15, or 20 °C) likely due to accumulation of the compatible osmolytes, trehalose, and alanine. Interestingly, the expected positive effect of drought acclimation on cold-shock tolerance was only evident at high acclimation temperature (20 °C), whereas at intermediate temperatures (10 and 15 °C), there was an interaction between acclimation temperature and drought. At 5 °C, no effect of drought acclimation on cold-shock tolerance was observed despite high osmolality. The positive effect of drought acclimation at 20 °C on subsequent cold-shock survival coincided with a drought-induced effect on PLFA composition only detectable at high temperature. We discuss the possible roles of drought-induced compatible osmolytes and an altered PLFA composition in the cold-shock tolerance of arthropods.
Effects of seasonal acclimatization on thermal tolerance of inward currents in roach (Rutilus rutilus) cardiac myocytes
Venue: Journal of Comparative Physiology B

To test the hypothesis of temperature-dependent deterioration of electrical excitability (TDEE) (Vornanen,  2016), the role of sodium (INa) and calcium (ICa) currents in heat tolerance of cardiac excitability was examined in a eurythermic fish, the roach (Rutilus rutilus). Densities of cardiac ICa and INa and their acute heat tolerance were measured in winter-acclimatized (WiR) and summer-acclimatized (SuR) fish maintained in the laboratory at 4 ± 1 and 18 ± 1 °C, respectively. A robust L-type Ca2+ current (ICaL), but no T-type Ca2+ current, was present in roach atrial and ventricular myocytes. Peak density of ICaL was smaller in atrial (− 1.97 ± 0.14 and − 1.75 ± 0.19 pA/pF for WiR and SuR, respectively) than ventricular myocytes (− 4.00 ± 0.59 and − 2.88 ± 0.47 pA/pF for WiR and SuR, respectively) (p < 0.05), but current density and heat tolerance of ICaL did not change between seasons in either cell type. In contrast to ICa, marked differences appeared in INa between WiR and SuR. INa density was 38% higher in WiR than SuR atrial myocytes (− 80.03 ± 5.92 vs. − 49.77 ± 4.72 pA/pF; p < 0.05) and 48% higher in WiR than SuR ventricular myocytes (− 39.25 ± 3.06 vs. − 20.03 ± 1.79 pA/pF; p < 0.05). The winter increase in INa density was associated with 55% (1.70 ± 0.27 vs. 0.77 ± 0.12) and 54% (1.08 ± 0.19 vs. 0.50 ± 0.10) up-regulation of the total Na+ channel (scn4 + scn5 + scn8) transcripts in atrium and ventricle, respectively (p < 0.05). Heat tolerance of atrial INa was lower in WiR with a breakpoint temperature of 20.3 ± 1.2 °C than in SuR (23.8 ± 0.7 °C) (p < 0.05). The response of INa to seasonal acclimatization conforms to the TDEE hypothesis. The lower heat tolerance of INa in WiR is consistent with the lower heat tolerance of in vivo heart rate in WiR in comparison to SuR, but the match is not quantitatively perfect, suggesting that other factors in addition to INa may be involved.
Plasticity of skin water permeability and skin thickness in the amphibious mangrove rivulus Kryptolebias marmoratus
Venue: Journal of Comparative Physiology B

The skin of amphibious fishes is a multipurpose organ, important for gas and ion exchange and nitrogen excretion when fish are out of water (emersed). We tested the hypothesis that skin permeability is altered to maintain water balance through changes in water permeability and skin thickness during salinity acclimation and/or when fish emerse, using the euryhaline, amphibious fish Kryptolebias marmoratus as a model. We first recorded the behaviour of fish out of water to determine which part of the cutaneous surface was in contact with the substrate. Fish spent about 70% of their time on their ventral surface when out of water. Osmotic permeability of the skin was assessed in fish acclimated to 0.3 or 45‰ using 3H2O fluxes in an in vitro micro-Ussing chamber setup. In freshwater-acclimated fish, 3H2O influx across the skin was significantly higher compared to hypersaline-acclimated fish, with no significant changes in efflux. Prolonged emersion (7 days) resulted in an increase in skin 3H2O influx, but not efflux in fish acclimated to a moist 45‰ substrate. In a separate experiment, dorsal epidermal skin thickness increased while the ventral dermis thickness decreased in fish emersed for over a week. However, there was no link between regional skin thickness and water flux in our experiments. Taken together, these findings suggest that K. marmoratus alter skin permeability to maximize water uptake while emersed in hypersaline conditions, adjustments that probably help them survive months of emersion during the dry season when drinking to replace water loss is not possible.
Octopaminergic innervation and a neurohaemal release site in the antennal heart of the locust Schistocerca gregaria
Venue: Journal of Comparative Physiology A

A detailed account is given by the octopaminergic innervation of the antennal heart in Schistocerca gregaria using various immunohistochemical methods. Anterograde axonal filling illustrates the unilateral innervation on the medial ventral surface of the pumping muscle of the antennal heart via the paired corpora cardiaca nerve III. In addition, antibody staining revealed that ascending axons of this nerve terminate at the ampullae of the antennal heart forming synaptoid structures and extensive neurohaemal release sites. Due to the innervation by two dorsal unpaired median neurons, the presence of the biogenic amines octopamine and tyramine could be visualized by immunocytochemistry in an insect antennal heart for the first time. The data suggest that tyramine acts as a precursor and not purely as an independent transmitter. While the octopaminergic fibers innervating the pumping muscle of the antennal heart indicate a cardioregulatory role, we conclude that octopamine released from the neurohaemal area is pumped into the antennae and an involvement in the modulation of the antennal sensory sensitivity is discussed.
Honey bees possess a polarity-sensitive magnetoreceptor
Venue: Journal of Comparative Physiology A

Honey bees, Apis mellifera, exploit the geomagnetic field for orientation during foraging and for alignment of their combs within hives. We tested the hypothesis that honey bees sense the polarity of magnetic fields. We created an engineered magnetic anomaly in which the magnetic field generally either converged toward a sugar reward in a watch glass, or away from it. After bees in behavioral field studies had learned to associate this anomaly with a sugar water reward, we subjected them to two experiments performed in random order. In both experiments, we presented bees with two identical sugar water rewards, one of which was randomly marked by a magnetic field anomaly. During the control experiment, the polarity of the magnetic field anomaly was maintained the same as it was during the training session. During the treatment experiment, it was reversed. We predicted that bees would not respond to the altered anomaly if they were sensitive to the polarity of the magnetic field. Our findings that bees continued to respond to the magnetic anomaly when its polarity was in its unaltered state, but did not respond to it when its polarity was reversed, support the hypothesis that honey bees possess a polarity-sensitive magnetoreceptor.
The effects of protein and fiber content on gut structure and function in zebrafish (Danio rerio)
Venue: Journal of Comparative Physiology B

Chemical reactor theory (CRT) suggests that the digestive tract functions as a chemical reactor for processing food. Presumably, gut structure and function should match diet to ensure adequate nutrient and energy uptake to maintain performance. Within CRT, dietary biochemical composition is the most important factor affecting gut structure and function in vertebrates. We fed Danio rerio (zebrafish) diets ranging from high- to moderate- to low-quality (i.e., ranging from high-protein, low-fiber to low-protein, high-fiber), and observed how gut length and surface area, as well as the activity levels of digestive enzymes (amylase, maltase, trypsin, aminopeptidase, and lipase) shifted in response to these dietary changes. Fish on the low-quality diet had the longest guts with the largest intestinal epithelial surface area and enterocyte cellular volumes. Fish on the moderate-quality diet had intermediate values of most of these parameters, and fish on the high-quality diet, the lowest. These data largely support CRT. Digestive enzyme activity levels were generally elevated in fish fed the moderate- and low-quality diets, but were highest in the fish fed the moderate-quality diet, suggesting that a diet with protein levels closest to that of the natural diet of D. rerio (they are omnivorous in nature) may elicit the best gut performance. However, fish fed the carnivore diet reached the largest terminal body size. Our results support CRT in terms of gut structure; however, our enzyme results do not necessarily agree with CRT and largely depend on which enzyme is discussed. In particular, the evidence for lipase activities being elevated in the fish fed the low-protein, high-fiber diet perhaps reflects a lipid-scavenging mechanism in fish consuming high-fiber foods rather than CRT.
Comparing the face inversion effect in crows and humans
Venue: Journal of Comparative Physiology A

Humans show impaired recognition of faces that are presented upside down, a phenomenon termed face inversion effect, which is thought to reflect the special relevance of faces for humans. Here, we investigated whether a phylogenetically distantly related avian species, the carrion crow, with similar socio-cognitive abilities to human and non-human primates, exhibits a face inversion effect. In a delayed matching-to-sample task, two crows had to differentiate profiles of crow faces as well as matched controls, presented both upright and inverted. Because crows can discriminate humans based on their faces, we also assessed the face inversion effect using human faces. Both crows performed better with crow faces than with human faces and performed worse when responding to inverted pictures in general compared to upright pictures. However, neither of the crows showed a face inversion effect. For comparative reasons, the tests were repeated with human subjects. As expected, humans showed a face-specific inversion effect. Therefore, we did not find any evidence that crows—like humans—process faces as a special visual stimulus. Instead, individual recognition in crows may be based on cues other than a conspecific’s facial profile, such as their body, or on processing of local features rather than holistic processing.
Behavioral responses to visual overstimulation in the cockroach Periplaneta americana L.
Venue: Journal of Comparative Physiology A

In the visual systems of insects, different types of photoreceptors contribute to specialized visual channels that mediate distinct functions and behaviors. Large compound eyes of Periplaneta americana contain photoreceptors of two spectral classes, broadband green-sensitive photoreceptors and narrow-band UV-sensitive photoreceptors. Here, we investigated how visual stimulation by UV and green light affects locomotor, resting, and grooming behaviors in P. americana under conditions when light avoidance is not possible. We show that green but not UV light stimulates locomotor activity, inducing paradoxical positive masking. Duration of resting and grooming decreased with increasing light intensity, consistent with development of behavioral stress in response to visual overstimulation. A reaction of full immobility is described under UV light and at higher intensities of green light, with relative periods of immobility and grooming strongly negatively correlated. Low-intensity UV was more effective than low-intensity green light in suppressing grooming and inducing immobility. Our results suggest that locomotor activity in P. americana is mainly regulated by green-sensitive photoreceptors, and that dim UV light can trigger behavioral immobility, whereas both wavelengths induce stress-like reactions at high intensities. Considering the intrinsic UV sensitivity of green-sensitive photoreceptors, the contrasting behavioral responses indicate antagonistic interactions between UV and green visual channels.
High contrast sensitivity for visually guided flight control in bumblebees
Venue: Journal of Comparative Physiology A

Many insects rely on vision to find food, to return to their nest and to carefully control their flight between these two locations. The amount of information available to support these tasks is, in part, dictated by the spatial resolution and contrast sensitivity of their visual systems. Here, we investigate the absolute limits of these visual properties for visually guided position and speed control in Bombus terrestris. Our results indicate that the limit of spatial vision in the translational motion detection system of B. terrestris lies at 0.21 cycles deg−1 with a peak contrast sensitivity of at least 33. In the perspective of earlier findings, these results indicate that bumblebees have higher contrast sensitivity in the motion detection system underlying position control than in their object discrimination system. This suggests that bumblebees, and most likely also other insects, have different visual thresholds depending on the behavioral context.
The path to colour discrimination is S-shaped: behaviour determines the interpretation of colour models
Venue: Journal of Comparative Physiology A

Most of our current understanding on colour discrimination by animal observers is built on models. These typically set strict limits on the capacity of an animal to discriminate between colour stimuli imposed by physiological characteristics of the visual system and different assumptions about the underlying mechanisms of colour processing by the brain. Such physiologically driven models were not designed to accommodate sigmoidal-type discrimination functions as those observed in recent behavioural experiments. Unfortunately, many of the fundamental assumptions on which commonly used colour models are based have been tested against empirical data for very few species and many colour vision studies solely rely on physiological measurements of these species for predicting colour discrimination processes. Here, we test the assumption of a universal principle of colour discrimination only mediated by physiological parameters using behavioural data from four closely related hymenopteran species, considering two frequently used models. Results indicate that there is not a unique function describing colour discrimination by closely related bee species, and that this process is independent of specific model assumptions; in fact, different models produce comparable results for specific test species if calibrated against behavioural data.
Short-term peripheral sensitization by brief exposure to pheromone components in Spodoptera littoralis
Venue: Journal of Comparative Physiology A

In insects, the olfactory system displays a high degree of plasticity. In Spodoptera littoralis, pre-exposure of males to the sex pheromone has been shown to increase the sensitivity of the olfactory sensory neurons at peripheral level. In this study, we have investigated this sensitization effect by recording the electroantennographic responses of male antennae to the major sex pheromone component (Z,E)-9,11-tetradecadienyl acetate and to the minor components (Z,E)-9,12-tetradecadienyl acetate and (Z)-9-tetradecenyl acetate. Responses to the conjugated diene acetate at 1 and 10 µg and to the unconjugated ester at 10 µg at three different times (11, 22 and 33 min) after pre-exposure (T = 0 min) were significantly higher than those at T = 0, whereas no increase of sensitivity to the pheromone was elicited by any dose of the minor monoene acetate. In addition, pre-exposed antennae to sub-threshold amounts (0.1, 1 and 10 ng) of the major pheromone component also induced an increased response to the chemical at different times (5 and 15 min) after exposure. Our results revealed that pre-exposed isolated antennae display a short-term higher sensitivity at the peripheral level when compared to naive antennae. In addition, we provide evidence of a peripheral sensitization mediated not only by the major pheromone component, but also by the minor unconjugated diene acetate, and the induction of this sensitivity appears to be dependent on the pre-exposure dose and the time span between pre-exposure and subsequent recordings. Possible implications of the sensitization effect displayed by the minor component for a more effective discrimination of the pheromone bouquets of other closely related species are highlighted.
Take time: odor coding capacity across sensory neurons increases over time in Drosophila
Venue: Journal of Comparative Physiology A

Due to the highly efficient olfactory code, olfactory sensory systems are able to reliably encode enormous numbers of olfactory stimuli. The olfactory code consists of combinatorial activation patterns across sensory neurons, thus its capacity exceeds the number of involved classes of sensory neurons by a manifold. Activation patterns are not static but vary over time, caused by the temporally complex response dynamics of the individual sensory neuron responses. We systematically analyzed the temporal dynamics of olfactory sensory neuron responses to a diverse set of odorants. We find that response dynamics depend on the combination of sensory neuron and odorant and that information about odorant identity can be extracted from the time course of the response. We also show that new response dynamics can arise when mixing two odorants. Our data show that temporal dynamics of odorant responses are able to significantly enhance the coding capacity of olfactory sensory systems.
The effects of stimulus parameters on auditory evoked potentials of Carassius auratus
Venue: Journal of Comparative Physiology A

Whole-brain responses to sound are easily measured through auditory evoked potentials (AEP), but it is unclear how differences in experimental parameters affect these responses. The effect of varying parameters is especially unclear in fish studies, the majority of which use simple sound types and then extrapolate to natural conditions. The current study investigated AEPs in goldfish (Carassius auratus) using sounds of different durations (5, 10, and 20 ms) and frequencies (200, 500, 600 and 700 Hz) to test stimulus effects on latency and thresholds. We quantified differences in latency and threshold in comparison to a 10-ms test tone, a duration often used in AEP fish studies. Both response latency and threshold were significantly affected by stimulus duration, with latency patterning suggesting that AEP fires coincident with a decrease in stimulus strength. Response latency was also significantly affected by presentation frequency. These results show that stimulus type has important effects on AEP measures of hearing and call for clearer standards across different measures of AEP. Duration effects also suggest that AEP measures represent summed responses of duration-detecting neural circuit, but more effort is needed to understand the neural drivers of this commonly used technique.