nils-herrmann/clean_scirepeval huggingface dataset:
Phenotypic flexibility of energetics in acclimated Siberian hamsters has a narrower scope in winter than in summer
Venue: Journal of Comparative Physiology B

As photoperiod shortens with the approach of winter, small mammals should reduce their energy expenditure to survive periods of food limitation. However, within seasons, animals should balance their energy budgets as abiotic conditions change, sometimes unpredictably; cold spells should increase heat production, while warm spells should do the opposite. Therefore, we addressed specific questions about the possible interactions between seasonal acclimatization and the intra-seasonal phenotypic flexibility of metabolic rate. We hypothesized that phenotypic flexibility in small mammals differs seasonally and is greater in summer than in winter, and predicted that seasonal adjustments in energetics, which are driven by photoperiod, overwhelm the influence of variations in the thermal environment. We measured body mass, basal metabolic rate (BMR), facultative non-shivering thermogenesis (fNST), body temperature, and calculated minimum thermal conductance in Siberian hamsters Phodopus sungorus. Animals were acclimated to winter-like, and then to summer-like conditions and, within each season, were exposed twice, for 3 weeks to 10, 20 or 28 °C. We used differences between values measured after these short acclimation periods as a measure of the scope of phenotypic flexibility. After winter acclimation, hamsters were lighter, had lower whole animal BMR, higher fNST than in summer, and developed heterothermy. After these short acclimations to the above-mentioned temperatures, hamsters showed reversible changes in BMR and fNST; however, these traits were less flexible in winter than in summer. We conclude that seasonal acclimation affects hamster responses to intra-seasonal variations in the thermal environment. We argue that understanding seasonal changes in phenotypic flexibility is crucial for predicting the biological consequences of global climate changes.
Src family tyrosine kinase inhibitors suppress Nav1.1 expression in cultured rat spiral ganglion neurons
Venue: Journal of Comparative Physiology A

Src family kinases regulate neuronal voltage-gated Na+ channels, which generate action potentials. The mechanisms of action, however, remain poorly understood. The aim of the present study was to further elucidate the effects of Src family kinases on Nav1.1 mRNA and protein expression in spiral ganglion neurons. Immunofluorescence staining techniques detected Nav1.1 expression in the spiral ganglion neurons. Additionally, quantitative PCR and western blot techniques were used to analyze Nav1.1 mRNA and protein expression, respectively, in spiral ganglion neurons following exposure to Src family kinase inhibitors PP2 (1 and 10 μM) and SU6656 (0.1 and 1 μM) for different lengths of time (6 and 24 h). In the spiral ganglion neurons, Nav1.1 protein expression was detected in the somas and axons. The Src family kinase inhibitors PP2 and SU6665 significantly decreased Nav1.1 mRNA and protein expression (p < 0.05), respectively, in the spiral ganglion neurons, and changes in expression were not dependent on time or dose (p > 0.05).
Temporal encoding precision of bat auditory neurons tuned to target distance deteriorates on the way to the cortex
Venue: Journal of Comparative Physiology A

During echolocation, bats estimate distance to avoid obstacles and capture moving prey. The primary distance cue is the delay between the bat’s emitted echolocation pulse and the return of an echo. In the bat’s auditory system, echo delay-tuned neurons that only respond to pulse–echo pairs having a specific echo delay serve target distance calculation. Accurate prey localization should benefit from the spike precision in such neurons. Here we show that delay-tuned neurons in the inferior colliculus of the mustached bat respond with higher temporal precision, shorter latency and shorter response duration than those of the auditory cortex. Based on these characteristics, we suggest that collicular neurons are best suited for a fast and accurate response that could lead to fast behavioral reactions while cortical neurons, with coarser temporal precision and longer latencies and response durations could be more appropriate for integrating acoustic information over time. The latter could be important for the formation of biosonar images.
Spectral absorption of visual pigments in stomatopod larval photoreceptors
Venue: Journal of Comparative Physiology A

Larval stomatopod eyes appear to be much simpler versions of adult compound eyes, lacking most of the visual pigment diversity and photoreceptor specializations. Our understanding of the visual pigment diversity of larval stomatopods, however, is based on four species, which severely limits our understanding of stomatopod eye ontogeny. To investigate several poorly understood aspects of stomatopod larval eye function, we tested two hypotheses surrounding the spectral absorption of larval visual pigments. First, we examined a broad range of species to determine if stomatopod larvae generally express a single, spectral class of photoreceptor. Using microspectrophotometry (MSP) on larvae captured in the field, we found data which further support this long-standing hypothesis. MSP was also used to test whether larval species from the same geographical region express visual pigments with similar absorption spectra. Interestingly, despite occupation of the same geographical location, we did not find evidence to support our second hypothesis. Rather, there was significant variation in visual pigment absorption spectra among sympatric species. These data are important to further our understanding of larval photoreceptor spectral diversity, which is beneficial to ongoing investigations into the ontogeny, physiology, and molecular evolution of stomatopod eyes.
Molecular, behavioral, and performance responses of juvenile largemouth bass acclimated to an elevated carbon dioxide environment
Venue: Journal of Comparative Physiology B

Aquatic hypercarbia, either naturally occurring or anthropogenically induced, can have extensive impacts on aquatic environments and resident organisms. While the impact of acute hypercarbia exposure on the behavior and physiology of fishes has been well studied, relatively little work has examined the physiological impact and acclimation capacity of fishes to chronic hypercarbia. To better understand the impacts of prolonged hypercarbia exposure, largemouth bass were held at ambient CO2 (13 mg L−1) and elevated CO2 (31 mg L−1; ≈21,000 µatm) for 58 days. Following this acclimation period, fish were subjected to three separate, yet complementary, experiments: (1) acute hypercarbia challenge of 120 mg L−1 CO2 for 1 h to quantify physiological and molecular responses; (2) hypercarbia avoidance challenge to compare CO2 agitation and avoidance responses; and (3) swim performance challenge to quantify burst swimming performance. Acclimation to 31 mg L−1 CO2 resulted in a significant constitutive upregulation of c-fos expression in erythrocytes, combined with significant constitutive expression of hsp70 in both gill and erythrocytes, relative to controls. Largemouth bass acclimated to elevated CO2 also had a reduced glucose response (relative to controls) following an acute CO2 exposure, indicating a reduced stress response to CO2 stressors. In addition, largemouth bass acclimated to elevated CO2 conditions required 50 % higher CO2 concentrations to illicit agitation behaviors and displayed prolonged burst swimming abilities in high CO2 environments relative to controls. Together, results demonstrate that largemouth bass exposed to chronic hypercarbia may possess a physiological advantage during periods of elevated CO2 relative to naïve fish, which may permit increased performance in hypercarbia.
Four photoreceptor classes in the open rhabdom eye of the red palm weevil, Rynchophorus ferrugineus Olivier
Venue: Journal of Comparative Physiology A

The red palm weevil (RPW) is a severe palm pest with high dispersal capability. Its visual sense allows it to navigate long distances and to discriminate among differently colored traps. We investigated the RPW compound eyes with anatomical and electrophysiological methods. The ommatidia are composed of eight photoreceptor cells in an open rhabdom arrangement with six peripheral and two central photoreceptors. The photoreceptor signals are relatively slow and noisy. The majority of recorded photoreceptors have broad spectral sensitivity with a peak in the green, at 536 nm. Three minor classes of photoreceptors have narrower spectral sensitivities with maxima in the UV (366 nm), green (520 nm) and yellow (564 nm). Sensitivity below 350 nm is very low due to filtering by the UV-absorbing cornea. The set of photoreceptors represents the retinal substrate for putative trichromatic color vision.
Professor Matti Weckström (1959–2015)
Venue: Journal of Comparative Physiology A

efforts in Oulu and later at the University of Cambridge, where he worked as a visiting researcher in 1988–1989. Matti was appointed as Docent of Neurophysiology at the University of Oulu in 1990. Since 1998, he held professorships at the University of Oulu in Biophysics, and in 2004 he was appointed to the post permanently. Biophysics was Matti’s great scientific love. He enjoyed exploring nature’s biological systems with a physics toolbox, quantifying and making sense of its complexity. Matti’s infectious enthusiasm and determination to improve biophysics research and teaching in Finland made the University of Oulu its major seat of learning in Finland. Matti was an accomplished and talented researcher, who was comfortable with both experiments and theory, and driven by his inherent curiosity. His research was at the interface of physiology, neuroethology, and biophysics, and most often focussed upon how the visual world is encoded into neural signals within the eye. He used different microelectrode techniques to record and characterise electrical response properties and signalling performance of individual photoreceptor cells and visual interneurones in many different insect species. A key early breakthrough in his research involved the first characterisation of voltagesensitive potassium channels in graded potential neurones in insect eyes. In his most recent, and ongoing studies he pioneered the development of patch-clamp preparations from photoreceptors of numerous and ecologically diverse insect species, with the goal of understanding how membrane conductances (such as light-sensitive channels and voltage-sensitive K channels) were tuned to visual performance. Matti was also involved in studying the biophysical properties of mammalian heart cells and their electromechanical functions. Characteristically, his research often encompassed the development of experimental and theoretical tools for bioelectrical measurements and signal Professor Matti Tapani Weckström, who was a frequent contributor to this journal, died of a sudden illness on 24 October 2015 at the age of 56 years. Matti was born in Helsinki, Finland on 3rd July 1959, but spent most of his youth in the northern town of Rovaniemi, in the Arctic Circle. After his high-school matriculation, Matti was accepted to study medicine at the University of Oulu, Finland, in 1985. While successfully completing his medical studies, Matti still found time for neurophysiology research in the Department of Physiology, where he defended his Ph.D. thesis concerning blowfly (Calliphora vicina) vision in 1987. He then continued his research
The effects of acute cold exposure on morphology and gene expression in the heart of neonatal chicks
Venue: Journal of Comparative Physiology B

Cold exposure induces an increase in blood flow and blood pressure, and long-term exposure to cold causes cardiac hypertrophy. Neonatal chicks (Gallus gallus domesticus) are highly sensitive to cold exposure, because their capacity for thermogenesis is immature until 1 week after hatching. Hence, we hypothesized that the heart of chicks at around 1 week of age acutely responds to cold environment. To investigate the effect of acute (24 h) and long-term (2 weeks) cold on the heart of chicks, 7-day-old chicks were exposed to cold temperature (4 °C) or kept warm (30 °C). Chicks exposed to the cold showed cardiac hypertrophy with marked left ventricular (LV) chamber dilation and wall thickening. On the other hand, long-term cold exposure (2 weeks from 7-day-old) induced an increase in total ventricular mass, but not in LV morphological parameters. Then, we investigated the details of acute cardiac hypertrophy in chicks. Electron microscopy revealed that cardiomyocytes in the hypertrophied LV had enlarged mitochondria with less dense cristae. Although the mRNA expression of lipoprotein lipase in the LV of the cold-exposed chicks significantly increased, the mRNA expression of genes involved in fatty acid β-oxidation did not change in response to cold exposure. In addition, the mRNA expression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha, which enhances mitochondrial biogenesis and function under physiological cardiac hypertrophy, increased in LV of cold-exposed chicks. The study found that acute cold exposure to neonatal chicks induces LV hypertrophy. However, these results suggest that acute cold exposure to chicks might induce both adaptive and maladaptive responses of the LV.
Physiology of reproductive worker honey bees (Apis mellifera): insights for the development of the worker caste
Venue: Journal of Comparative Physiology A

Reproductive and behavioural specialisations characterise advanced social insect societies. Typically, the honey bee (Apis mellifera) shows a pronounced reproductive division of labour between worker and queen castes, and a clear division of colony roles among workers. In a queenless condition, however, both of these aspects of social organisation break down. Queenless workers reproduce, forage and maintain their colony operating in a manner similar to communal bees, rather than as an advanced eusocial group. This plasticity in social organisation provides a natural experiment for exploring physiological mechanisms of division of labour. We measured brain biogenic amine (BA) levels and abdominal fat body vitellogenin gene expression levels of workers in queenright and queenless colonies. Age, ovary activation and social environment influenced brain BA levels in honey bees. BA levels were most influenced by ovary activation state in queenless bees. Vitellogenin expression levels were higher in queenless workers than queenright workers, but in both colony environments vitellogenin expression was lower in foragers than non-foragers. We propose this plasticity in the interacting signalling systems that influence both reproductive and behavioural development allows queenless workers to deviate significantly from the typical worker bee reaction norm and develop as reproductively active behavioural generalists.
Short day-triggered quiescence promotes water conservation in the American dog tick, Dermacentorvariabilis
Venue: Journal of Comparative Physiology B

A short day–long day exposure comparison of water balance characteristics throughout the life history of the American dog tick, Dermacentorvariabilis, was conducted to examine how this tick survives winter-associated dryness. Larvae, nymphs, and adults under potential diapause-inducing conditions (short day, 20 °C) have low water loss rates compared to long day exposed ticks. Above the critical equilibrium activity, these nonfed ticks show greater water gain from lower water vapor activities. In contrast to nonfed stages, eggs and blood-engorged stages (fed larva, fed nymph) were enhanced for water conservation independent of short day exposure and did not display reduced water loss rates under short day conditions. This short day-prompted response in nonfed ticks was distinguished from a genetically programmed diapause as noted in other arthropods by: (1) reduction in water loss was temporary and could be reversed quickly by transferring to long day for only a single day, then re-triggered by returning to short day conditions; (2) switch between low and high water loss rates could be induced multiple times and for multiple different stages; and (3) response by ticks was to the photoperiod they were under, not the condition that was experienced by previous fed stages or in the mother in the case of eggs. Furthermore, short day had no impact on altering body water content, dehydration tolerance limit, instar yields, or developmental stadia. We conclude that a short day-triggered quiescence reduces desiccation stress associated with overwintering in nonfed ticks. This effect on water conservation due to short day exposure is more pronounced for subadults and is likely due to their increased sensitivity to water loss as a result of their smaller size, which is critical to prevent dehydration during the dry winter periods.
Regulatory roles of biogenic amines and juvenile hormone in the reproductive behavior of the western tarnished plant bug (Lygus hesperus)
Venue: Journal of Comparative Physiology B

Mating induces behavioral and physiological changes in the plant bug Lygus hesperus Knight (Hemiptera: Miridae). After receiving seminal products, which include the systemic regulator juvenile hormone (JH), females enter a post-mating period lasting several days during which they enhance their oviposition rate and lose interest in remating. To elucidate the regulation of these behavioral changes in L. hesperus, biogenic amines were quantified in the heads of females at 5 min, 1 h and 24 h after copulation and compared to levels in virgins using high-performance liquid chromatography coupled with electrochemical detection. Mating significantly increased dopamine (DA) after 1 and 24 h, and decreased octopamine (OA) after 5 min and 1 h. Serotonin did not change with mating, but tyramine was significantly reduced after 5 min. While injection of amines into virgin females did not influence sexual receptivity, OA caused a decrease in oviposition during the 24 h following injection. Topical application of the JH analog methoprene to virgins caused an increase in DA, and a decline in mating propensity, but did not influence other amines or the oviposition rate. The results suggest the decline in OA observed immediately after mating may promote egg laying, and that male-derived JH may induce an increase in DA that could account for the post-mating loss of sexual receptivity.
Vulnerability to climate warming of Liolaemus pictus (Squamata, Liolaemidae), a lizard from the cold temperate climate in Patagonia, Argentina
Venue: Journal of Comparative Physiology B

The vulnerability of populations and species to global warming depends not only on the environmental temperatures, but also on the behavioral and physiological abilities to respond to these changes. In this sense, the knowledge of an organism’s sensitivity to temperature variation is essential to predict potential responses to climate warming. In particular, it is interesting to know how close species are to their thermal limits in nature and whether physiological plasticity is a potential short-term response to warming climates. We exposed Liolaemus pictus lizards, from northern Patagonia, to either 21 or 31 °C for 30 days to compare the effects of these treatments on thermal sensitivity in 1 and 0.2 m runs, preferred body temperature (Tpref), panting threshold (Tpant), and critical minimum temperature (CTMin). Furthermore, we measured the availability of thermal microenvironments (operative temperatures; Te) to measure how close L. pictus is, in nature, to its optimal locomotor performance (To) and thermal limits. L. pictus showed limited physiological plasticity, since the acclimation temperature (21 and 31 °C) did not affect the locomotor performance nor did it affect Tpref, the Tpant, or the CTMin. The mean Te was close to To and was 17 °C lower than the CTMax. The results suggest that L. pictus, in a climate change scenario, could be vulnerable to the predicted temperature increment, as this species currently lives in an environment with temperatures close to their highest locomotor temperature threshold, and because they showed limited acclimation capacity to adjust to new thermal conditions by physiological plasticity. Nevertheless, L. pictus can run at 80 % or faster of its maximum speed across a wide range of temperatures near To, an ability which would attenuate the impact of global warming.
Involvement of the crustacean hyperglycemic hormone (CHH) in the physiological compensation of the freshwater crayfish Cherax quadricarinatus to low temperature and high salinity stress
Venue: Journal of Comparative Physiology B

This study was aimed at determining the role of the crustacean hyperglycemic hormone (CHH) in the physiological compensation to both saline and thermal stress, in the freshwater crayfish Cherax quadricarinatus. By determining the expression of the CHH gene in the eyestalk of juvenile crayfish, we found that maximal induction of CHH was induced at high salinity (10 g/L) and low temperature (20 °C). In order to investigate the role of CHH in the physiological compensation to such stressful conditions, recombinant CHH was supplied to stressed animals. CHH-injected crayfish showed increased hemolymphatic levels of glucose, in accordance with a significant utilization of glycogen reserves from the hepatopancreas. Furthermore, CHH administration allowed stressed animals to regulate hemolymphatic sodium and potassium at more constant levels than controls. Taken together, these results suggest a relevant role of CHH in increasing the energy available intended for processes involved in the physiological compensation of C. quadricarinatus to both saline and thermal stress.
13C-Breath testing in animals: theory, applications, and future directions
Venue: Journal of Comparative Physiology B

The carbon isotope values in the exhaled breath of an animal mirror the carbon isotope values of the metabolic fuels being oxidized. The measurement of stable carbon isotopes in carbon dioxide is called 13C-breath testing and offers a minimally invasive method to study substrate oxidation in vivo. 13C-breath testing has been broadly used to study human exercise, nutrition, and pathologies since the 1970s. Owing to reduced use of radioactive isotopes and the increased convenience and affordability of 13C-analyzers, the past decade has witnessed a sharp increase in the use of breath testing throughout comparative physiology—especially to answer questions about how and when animals oxidize particular nutrients. Here, we review the practical aspects of 13C-breath testing and identify the strengths and weaknesses of different methodological approaches including the use of natural abundance versus artificially-enriched 13C tracers. We critically compare the information that can be obtained using different experimental protocols such as diet-switching versus fuel-switching. We also discuss several factors that should be considered when designing breath testing experiments including extrinsic versus intrinsic 13C-labelling and different approaches to model nutrient oxidation. We use case studies to highlight the myriad applications of 13C-breath testing in basic and clinical human studies as well as comparative studies of fuel use, energetics, and carbon turnover in multiple vertebrate and invertebrate groups. Lastly, we call for increased and rigorous use of 13C-breath testing to explore a variety of new research areas and potentially answer long standing questions related to thermobiology, locomotion, and nutrition.