nils-herrmann/clean_scirepeval huggingface dataset:
Seasonal changes of cholinergic response in the atrium of Arctic navaga cod (Eleginus navaga)
Venue: Journal of Comparative Physiology B

Fishes of north-temperate latitudes exhibit marked seasonal changes in electrical excitability of the heart partly as an outcome of temperature-dependent changes in the density of major K+ ion currents: delayed rectifiers (IKr, IKs) and background inward rectifier (IK1). In the arctic teleost, navaga cod (Eleginus navaga), IKr and IK1 are strongly up-regulated in winter. The current study tests the hypothesis that the ligand-gated K+ current, the acetylcholine-activated inward rectifier, IKACh, is also modified by seasonal acclimatization in atrial myocytes of navaga. In sinoatrial preparations of the summer-acclimatized (SA) navaga, 10−6 M carbamylcholine chloride (CCh) caused slowing of heart rate, shortening of atrial action potential (AP) duration and a drastic reduction of AP amplitude, eventually resulting in inexcitability. In winter-acclimatized (WA) atria CCh slowed HR and reduced AP duration, but reduction of AP amplitude was modest and never resulted in inexcitability. The difference in cholinergic response between SA and WA navaga is explained by seasonal changes in IKACh density. The peak density of IKACh, induced by 10−5 M CCh, at the common experimental temperature (+6 °C) was 0.97 ± 0.28 pA/pF in SA navaga but only 0.183 ± 0.013 pA/pF in WA navaga (a 5.3-fold difference, P < 0.05). At acclimatization temperatures of the fish IKACh density was 2.8 ± 0.50 (at +12 °C) and 0.11 ± 0.06 pA/pF (at +3 °C) (a 26-fold difference, P < 0.05) for SA and WA navaga, respectively. Thus, acclimatization to summer induces a drastic up-regulation of the atrial IKACh, which effectively shortens atrial AP. The reverse temperature compensation of the atrial IKACh may be advantageous in summer under variable water temperatures and oxygen concentrations by reducing workload of the heart.
Rapid mapping of compound eye visual sampling parameters with FACETS, a highly automated wide-field goniometer
Venue: Journal of Comparative Physiology A

A highly automated goniometer instrument (called FACETS) has been developed to facilitate rapid mapping of compound eye parameters for investigating regional visual field specializations. The instrument demonstrates the feasibility of analyzing the complete field of view of an insect eye in a fraction of the time required if using non-motorized, non-computerized methods. Faster eye mapping makes it practical for the first time to employ sample sizes appropriate for testing hypotheses about the visual significance of interspecific differences in regional specializations. Example maps of facet sizes are presented from four dipteran insects representing the Asilidae, Calliphoridae, and Stratiomyidae. These maps provide the first quantitative documentation of the frontal enlarged-facet zones (EFZs) that typify asilid eyes, which, together with the EFZs in male Calliphoridae, are likely to be correlated with high-spatial-resolution acute zones. The presence of EFZs contrasts sharply with the almost homogeneous distribution of facet sizes in the stratiomyid. Moreover, the shapes of EFZs differ among species, suggesting functional specializations that may reflect differences in visual ecology. Surveys of this nature can help identify species that should be targeted for additional studies, which will elucidate fundamental principles and constraints that govern visual field specializations and their evolution.
The influence of natural photoperiod on seasonal torpor expression of two opportunistic marsupial hibernators
Venue: Journal of Comparative Physiology B

Many mammals use torpor throughout the year but the individual contributions of environmental variables to seasonal changes in torpor expression are often difficult to tease apart. In many mammals, torpor is most often used opportunistically in response to decreased ambient temperature (Ta) and food availability, but information on how seasonally changing photoperiod per se influences torpor patterns is scant. Therefore, we quantified patterns of torpor use in response to natural photoperiod in captive marsupial pygmy-possums held at near-constant Ta with a stable food supply over a period of 19 months. Western pygmy-possums (Cercartetus concinnus) and eastern pygmy-possums (C. nanus) used spontaneous torpor in every month of the year; in total we measured >1100 individual torpor bouts. Torpor bout duration was >60 % longer in winter than in summer and increased with decreasing day length for both species. Interestingly, the duration of torpor appeared to be adjusted at both the beginning and end of bouts because the time of entry into and rewarming from torpor relative to sunrise and sunset, respectively, changed with season. We propose that this reflects a synchronisation of torpor timing with foraging periods in the wild, which would enable animals to maintain a high body mass year-round by maximising both energy savings via torpor and energy input via food consumption. Our study suggests that photoperiod makes a significant contribution to the seasonal change in torpor bout duration of small hibernating mammals that use torpor throughout the year.
How females of chirping and trilling field crickets integrate the ‘what’ and ‘where’ of male acoustic signals during decision making
Venue: Journal of Comparative Physiology A

In crickets acoustic communication serves mate selection. Female crickets have to perceive and integrate male cues relevant for mate choice while confronted with several different signals in an acoustically diverse background. Overall female decisions are based on the attractiveness of the temporal pattern (informative about the ‘what’) and on signal intensity (informative about the ‘where’) of male calling songs. Here, we investigated how the relevant cues for mate choice are integrated during the decision process by females of five different species of chirping and trilling field crickets. Using a behavioral design, female preferences in no-choice and choice situations for male calling songs differing in pulse rate, modulation depth, intensities, chirp/trill arrangements and temporal shifts were examined. Sensory processing underlying decisions in female field crickets is rather similar as combined evidence suggested that incoming song patterns were analyzed separately by bilaterally paired networks for pattern attractiveness and pattern intensity. A downstream gain control mechanism leads to a weighting of the intensity cue by pattern attractiveness. While remarkable differences between species were observed with respect to specific processing steps, closely related species exhibited more similar preferences than did more distantly related species.
Avian axons undergo Wallerian degeneration after injury and stress
Venue: Journal of Comparative Physiology A

The integrity of long axons is essential for neural communication. Unfortunately, relatively minor stress to a neuron can cause extensive loss of this integrity. Axon degeneration is the cell-intrinsic program that actively deconstructs an axon after injury or damage. Although ultrastructural examination has revealed signs of axon degeneration in vivo, the occurrence and progression of axon degeneration in avian species have not yet been documented in vitro. Here, we use a novel cell culture system with primary embryonic zebra finch retinal ganglion cells to interrogate the properties of avian axon degeneration. First, we establish that both axotomy and a chemically induced injury (taxol and vincristine) are sufficient to initiate degeneration. These events are dependent on a late influx of calcium. In addition, as in mammals, the NAD pathway is involved, since a decrease in NMN with FK866 can reduce degeneration. Importantly, these retinal ganglion cell axons were sensitive to a pressure-induced injury, which may mimic the effect of high intraocular pressure associated with glaucoma. We have demonstrated that avian neurons undergo Wallerian degeneration in response to both physical and chemical injury. Subsequent avian studies will investigate whether blocking the degeneration pathway can protect individuals from neurodegenerative disease.
Effects of aging on the food intake in the feeding behavior of Aplysia kurodai
Venue: Journal of Comparative Physiology A

In wild Aplysia, the birthdate of animals can typically not be determined. Therefore, we sought a reliable index of old age by taking into consideration the distinguished Japanese seasons. Large amounts of eggs and dead bodies were present on the coast during and after the second half of May (MayS). Body mass decreased after May. We roughly classified animals collected before and after the MayS as mature and old animals. Plots of internalized shell length (S) against body mass (B) gave distinct best-fit curves for mature and old animals. The B/S significantly decreased in the second half of June, suggesting that body mass decreases with age but shell length is maintained in each animal. Therefore, the collected animals were classified into mature and old animals using the best-fit curves for animals classified by the collection period. We examined the amount of food intake every 2 h up to 8 h after providing food. The amounts increased linearly, and the rate was significantly lower in old animals than in mature animals. The amount of 1-day food intake was also significantly lower in old animals. These results suggest that food intake may decline with age and this may cause mass loss in old animals.
Does diet influence salivary enzyme activities in elephant species?
Venue: Journal of Comparative Physiology B

Asian elephants (Elephas maximus) and African elephants (Loxodonta africana) are herbivore generalists; however, Asian elephants might ingest a higher proportion of grasses than Africans. Although some studies have investigated nutrition-specific morphological adaptations of the two species, broader studies on salivary enzymes in both elephant species are lacking. This study focuses on the comparison of salivary enzymes activity profiles in the two elephant species; these enzymes are relevant for protective and digestive functions in humans. We aimed to determine whether salivary amylase (sAA), lysozyme (sLYS), and peroxidase (sPOD) activities have changed in a species-specific pattern during evolutionary separation of the elephant genera. Saliva samples of 14 Asian and eight African elephants were collected in three German zoos. Results show that sAA and sLYS are salivary components of both elephant species in an active conformation. In contrast, little to no sPOD activity was determined in any elephant sample. Furthermore, sAA activity was significantly higher in Asian compared with African elephants. sLYS and sPOD showed no species-specific differences. The time of food provision until sample collection affected only sAA activity. In summary, the results suggest several possible factors modulating the activity of the mammal-typical enzymes, such as sAA, sLYS, and sPOD, e.g., nutrition and sampling procedure, which have to be considered when analyzing differences in saliva composition of animal species.
Beyond thermoregulation: metabolic function of cetacean blubber in migrating bowhead and beluga whales
Venue: Journal of Comparative Physiology B

The processes of lipid deposition and utilization, via the gene leptin (Lep), are poorly understood in taxa with varying degrees of adipose storage. This study examines how these systems may have adapted in marine aquatic environments inhabited by cetaceans. Bowhead (Balaena mysticetus) and beluga whales (Delphinapterus leucas) are ideal study animals—they possess large subcutaneous adipose stores (blubber) and undergo bi-annual migrations concurrent with variations in food availability. To answer long-standing questions regarding how (or if) energy and lipid utilization adapted to aquatic stressors, we quantified variations in gene transcripts critical to lipid metabolism related to season, age, and blubber depth. We predicted leptin tertiary structure conservation and assessed inter-specific variations in Lep transcript numbers between bowheads and other mammals. Our study is the first to identify seasonal and age-related variations in Lep and lipolysis in these cetaceans. While Lep transcripts and protein oscillate with season in adult bowheads reminiscent of hibernating mammals, transcript levels reach up to 10 times higher in bowheads than any other mammal. Data from immature bowheads are consistent with the hypothesis that short baleen inhibits efficient feeding. Lipolysis transcripts also indicate young Fall bowheads and those sampled during Spring months limit energy utilization. These novel data from rarely examined species expand the existing knowledge and offer unique insight into how the regulation of Lep and lipolysis has adapted to permit seasonal deposition and maintain vital blubber stores.
Desiccation enhances rapid cold-hardening in the flesh fly Sarcophaga bullata: evidence for cross tolerance between rapid physiological responses
Venue: Journal of Comparative Physiology B

Many insects use rapid cold-hardening (RCH), a physiological response to sub-lethal exposure to stressors, such as chilling and desiccation, to enhance their cold tolerance within minutes. Recently, drought-induced RCH, triggered by brief, mild desiccation, was described in larvae of the freeze-tolerant gall fly (Eurosta solidaginis). However, its prevalence and ecological significance in other insects is not known. Consequently, we used a freeze-intolerant model, the flesh fly, Sarcophaga bullata, to investigate the effects and mechanisms of drought-induced RCH. In addition, we investigated how drought- and cold-induced RCH interact by exposing flies to both desiccation and chilling. Desiccation for 3 h increased larval pupariation after cold shock from 28 to 40 %—the first example of drought-induced RCH in both a freeze-intolerant insect and in a non-overwintering life stage. We also found that desiccation and chilling together enhanced the cold hardiness of larvae and adults more than either did separately, suggesting that drought and cold trigger distinct physiological mechanisms that interact to afford greater cold tolerance. These results suggest that drought-induced RCH is a highly conserved response used by insects with diverse life history strategies. Furthermore, the protective interaction between drought- and cold-induced RCH suggests that, in nature, insects use multiple cues and physiological mechanisms to fine-tune their response to changing ambient conditions.
Species-specific control of acoustic gaze by echolocating bats, Rhinolophus ferrumequinum nippon and Pipistrellus abramus, during flight
Venue: Journal of Comparative Physiology A

Based on the characteristics of the ultrasounds they produce, echolocating bats can be categorized into two main types: broadband FM (frequency modulated) and narrowband CF (constant frequency) echolocators. In this study, we recorded the echolocation behavior of a broadband FM (Pipistrellus abramus) and a narrowband CF echolocator species (Rhinolophus ferrumequinum nippon) while they explored an unfamiliar space in a laboratory chamber. During flight, P. abramus smoothly shifted its acoustic gaze in relation to its flight direction, whereas R. ferrumequinum nippon frequently shifted its acoustic gaze from side to side. The distribution of the acoustic gazes of R. ferrumequinum nippon was twice as wide as that of P. abramus. Furthermore, R. ferrumequinum nippon produced double pulses twice as often as P. abramus. Because R. ferrumequinum nippon has a horizontal beam width (−6 dB off-axis angle) half as wide (±20.8 ± 6.0°) as that of P. abramus (±38.3 ± 6.0°), it appears to double the width of its acoustical field of view by shifting its acoustic gaze further off-axis and emitting direction-shifted double pulses. These results suggest that broadband FM and narrowband CF bats actively control their acoustic gazes in a species-specific manner based on the acoustic features of their echolocation signals.
Visual motion detection and habitat preference in Anolis lizards
Venue: Journal of Comparative Physiology A

The perception of visual stimuli has been a major area of inquiry in sensory ecology, and much of this work has focused on coloration. However, for visually oriented organisms, the process of visual motion detection is often equally crucial to survival and reproduction. Despite the importance of motion detection to many organisms’ daily activities, the degree of interspecific variation in the perception of visual motion remains largely unexplored. Furthermore, the factors driving this potential variation (e.g., ecology or evolutionary history) along with the effects of such variation on behavior are unknown. We used a behavioral assay under laboratory conditions to quantify the visual motion detection systems of three species of Puerto Rican Anolis lizard that prefer distinct structural habitat types. We then compared our results to data previously collected for anoles from Cuba, Puerto Rico, and Central America. Our findings indicate that general visual motion detection parameters are similar across species, regardless of habitat preference or evolutionary history. We argue that these conserved sensory properties may drive the evolution of visual communication behavior in this clade.
Nitrogen metabolism in tambaqui (Colossoma macropomum), a neotropical model teleost: hypoxia, temperature, exercise, feeding, fasting, and high environmental ammonia
Venue: Journal of Comparative Physiology B

The total rate of N-waste excretion (MN) in juvenile tambaqui living in ion-poor Amazonian water comprised 85 % ammonia-N (MAmm-N) and 15 % urea-N (MUrea-N). Both occurred mainly across the gills with only ~5 % of MAmm-N and ~39 % of MUrea-N via the urine. Tambaqui were not especially tolerant to high environmental ammonia (HEA), despite their great resistance to other environmental factors. Nevertheless, they were able to maintain a continued elevation of MAmm-N during and after 48-h exposure to 2.5 mmol L−1 HEA. The normally negative transepithelial potential (−18 mV) increased to −9 mV during the HEA period, which would help to reduce branchial NH4+ entry. During 3 h of acute environmental hypoxia (30 % saturation), MAmm-N declined, and recovered thereafter, similar to the response seen in other hypoxia-tolerant teleosts; MUrea-N did not change. However, during gradual hypoxia, MAmm-N remained constant, but MUrea-N eventually fell. The acute temperature sensitivities of MAmm-N and MN were low from 28 °C (acclimation) to 33 °C (Q10 ~1.5), but high (~3.8) from 33 to 38 °C, relative to $$ M_{{{\text{O}}_ }} $$MO2 (~1.9 throughout). In contrast, MUrea-N exhibited a different pattern over these temperature ranges (Q10 2.6 and 2.1, respectively). The nitrogen quotient (NQ = 0.16–0.23) was high at all temperatures, indicating a 60–85 % reliance on protein to fuel aerobic metabolism in these fasting animals. During steady-state aerobic exercise, $$ M_{{{\text{O}}_ }} $$MO2 and MUrea-N increased in parallel with velocity (up to 3.45 body lengths s−1), but MAmm (and thus MN) remained approximately constant. Therefore, the NQ fell progressively, indicating a decreasing reliance on protein-based fuels, as work load increased. In group feeding trials using 45 % protein commercial pellets, tambaqui excreted 82 % (range 39–170 %) of the dietary N within 24 h; N-retention efficiency was inversely related to the ration voluntarily consumed. MAmm-N peaked at 4–6 h, and MUrea-N at 6–9-h post-feeding, with an additional peak in MAmm-N only at 21 h. During subsequent fasting, MN stabilized at a high endogenous rate from 2 through 8 days post-feeding. Possible reasons for the high wasting of protein-N during both fasting and feeding are discussed.
Metabolic compartmentation in rainbow trout cardiomyocytes: coupling of hexokinase but not creatine kinase to mitochondrial respiration
Venue: Journal of Comparative Physiology B

Rainbow trout (Oncorhynchus mykiss) cardiomyocytes have a simple morphology with fewer membrane structures such as sarcoplasmic reticulum and t-tubules penetrating the cytosol. Despite this, intracellular ADP diffusion is restricted. Intriguingly, although diffusion is restricted, trout cardiomyocytes seem to lack the coupling between mitochondrial creatine kinase (CK) and respiration. Our aim was to study the distribution of diffusion restrictions in permeabilized trout cardiomyocytes and verify the role of CK. We found a high activity of hexokinase (HK), which led us to reassess the situation in trout cardiomyocytes. We show that diffusion restrictions are more prominent than previously thought. In the presence of a competitive ADP-trapping system, ADP produced by HK, but not CK, was channeled to the mitochondria. In agreement with this, we found no positively charged mitochondrial CK in trout heart homogenate. The results were best fit by a simple mathematical model suggesting that trout cardiomyocytes lack a functional coupling between ATPases and pyruvate kinase. The model simulations show that diffusion is restricted to almost the same extent in the cytosol and by the outer mitochondrial membrane. Furthermore, they confirm that HK, but not CK, is functionally coupled to respiration. In perspective, our results suggest that across a range of species, cardiomyocyte morphology and metabolism go hand in hand with cardiac performance, which is adapted to the circumstances. Mitochondrial CK is coupled to respiration in adult mammalian hearts, which are specialized to high, sustained performance. HK associates with mitochondria in hearts of trout and neonatal mammals, which are more hypoxia-tolerant.
A broader look at ammonia production, excretion, and transport in fish: a review of impacts of feeding and the environment
Venue: Journal of Comparative Physiology B

For nearly a century, researchers have studied ammonia production and excretion in teleost fish. Stemming from past investigations a body of knowledge now exists on various aspects including biochemical mechanisms of ammonia formation and specific routes and tissues used for ammonia transport, culminating in a current detailed theoretical model of branchial transport, including the molecular identities of the moieties involved. However, typical studies examining ammonia balance use routine laboratory conditions and fasted fish. While avoiding additional variables that influence nitrogen balance, these studies are arguably idealistic and do not reflect the natural variety of conditions that fish encounter. Further studies have revealed the impacts of extrinsic factors (e.g. salinity, pH, temperature) on ammonia handling in fasted fish whereas others have explored intrinsic factors, such as life history and developmental impacts. One routine challenge for ammonia balance that fish encounter is feeding and digestion. Fortunately, many new studies have revealed the impact of feeding and digestion on several aspects of ammonia balance; from production to excretion and to transport, and several have done so incorporating supplemental extrinsic and/or intrinsic factors. Together, these complex studies reveal realistic responses to multifactorial challenges encountered by animals in the wild and begin to provide a holistic view of ammonia balance in freshwater teleost fish.