nils-herrmann/clean_scirepeval huggingface dataset:
Do frog-eating bats perceptually bind the complex components of frog calls?
Venue: Journal of Comparative Physiology A

The mating calls of male túngara frogs, Physalaemus pustulosus, attract intended (conspecific females) and unintended (eavesdropping predators and parasites) receivers. The calls are complex, having two components: a frequency-modulated “whine” followed by 0–7 harmonic bursts or “chucks”. The whine is necessary and sufficient to elicit phonotaxis from females and the chuck enhances call attractiveness when it follows a whine. Although chucks are never made alone, females perceptually bind the whine and chuck when they are spatially separated. We tested whether an unintended receiver with independent evolution of phonotaxis, the frog-eating bat, Trachops cirrhosus, has converged with frogs in its auditory grouping of the call components. In contrast to frogs, bats approached chucks broadcast alone; when the chuck was spatially separated from the whine the bats preferentially approached the whine, and bats were sensitive to whine–chuck temporal sequence. This contrast suggests that although disparate taxa may be selected to respond to the same signals, different evolutionary histories, selective regimes, and neural and cognitive architectures may result in different weighting and grouping of signal components between generalist predators and conspecific mates.
Noninvasive diffusive optical imaging of the auditory response to birdsong in the zebra finch
Venue: Journal of Comparative Physiology A

Songbirds communicate by learned vocalizations with concomitant changes in neurophysiological and genomic activities in discrete parts of the brain. Here, we tested a novel implementation of diffusive optical imaging (also known as diffuse optical imaging, DOI) for monitoring brain physiology associated with vocal signal perception. DOI noninvasively measures brain activity using red and near-infrared light delivered through optic fibers (optodes) resting on the scalp. DOI does not harm subjects, so it raises the possibility of repeatedly measuring brain activity and the effects of accumulated experience in the same subject over an entire life span, all while leaving tissue intact for further study. We developed a custom-made apparatus for interfacing optodes to the zebra finch (Taeniopygia guttata) head using 3D modeling software and rapid prototyping technology, and applied it to record responses to presentations of birdsong in isoflurane-anesthetized zebra finches. We discovered a subtle but significant difference between the hemoglobin spectra of zebra finches and mammals which has a major impact in how hemodynamic responses are interpreted in the zebra finch. Our measured responses to birdsong playback were robust, highly repeatable, and readily observed in single trials. Responses were complex in shape and closely paralleled responses described in mammals. They were localized to the caudal medial portion of the brain, consistent with response localization from prior gene expression, electrophysiological, and functional magnetic resonance imaging studies. These results define an approach for collecting neurophysiological data from songbirds that should be applicable to diverse species and adaptable for studies in awake behaving animals.
The ClC-3 chloride channel and osmoregulation in the European Sea Bass, Dicentrarchus labrax
Venue: Journal of Comparative Physiology B

Dicentrarchus labrax migrates between sea (SW), brackish and fresh water (FW) where chloride concentrations and requirements for chloride handling change: in FW, fish absorb chloride and restrict renal losses; in SW, they excrete chloride. In this study, the expression and localization of ClC-3 and Na+/K+-ATPase (NKA) were studied in fish adapted to SW, or exposed to FW from 10 min to 30 days. In gills, NKA-α1 subunit expression transiently increased from 10 min and reached a stabilized intermediate expression level after 24 h in FW. ClC-3 co-localized with NKA in the basolateral membrane of mitochondria-rich cells (MRCs) at all conditions. The intensity of MRC ClC-3 immunostaining was significantly higher (by 50 %) 1 h after the transfer to FW, whereas the branchial ClC-3 protein expression was 30 % higher 7 days after the transfer as compared to SW. This is consistent with the increased number of immunopositive MRCs (immunostained for NKA and ClC-3). However, the ClC-3 mRNA expression was significantly lower in FW gills. In the kidney, after FW transfer, a transient decrease in NKA-α1 subunit expression was followed by significantly higher stable levels from 24 h. The low ClC-3 protein expression detected at both salinities was not observed by immunocytochemistry in the SW kidney; ClC-3 was localized in the basal membrane of the collecting ducts and tubules 7 and 30 days after transfer to FW. Renal ClC-3 mRNA expression, however, seemed higher in SW than in FW. The potential role of this chloride channel ClC-3 in osmoregulatory and osmosensing mechanisms is discussed.
Springs, steroids, and slingshots: the roles of enhancers and constraints in animal movement
Venue: Journal of Comparative Physiology B

Whole-body movement is an essential part of life for many animal species, and is used to evade predators, capture prey, and perform many other behaviors. In many cases, the ability to perform rapid movements may be crucial to fitness as doing so may allow animals to do things like effectively capture an elusive prey or to elude a chasing predator. A significant body of research has been devoted toward the musculoskeletal and neurobiological basis of animal movement, with large reviews and volumes written on locomotion and feeding. Biologists have also defined how movement can be quantified and compared among different species. Arnold ( 1983) first clearly explained that the ability to perform an ecologically important task could be labeled and quantified as maximum performance abilities, a point that is elaborated upon later (Garland and Losos, Ecological morphology: integrative organismal biology. University of Chicago Press, Chicago, 1994; Irschick et al.,  2008). Some commonly examined performance traits include maximum sprint speed, maximum acceleration or deceleration, maneuverability, maximum aerobic capacity (VO2max), bite force, and rapidity of tongue projection, among other examples. Although the ability to perform such movements can be limited by muscle physiology, there are several situations in which the limits of muscle physiology are circumvented with a range of specializations. Here, we synthesize the literature dealing with movement (primarily ballistic) enhancers. Our goal is both to encapsulate the current state of knowledge of enhancers, and also to provide a broader evolutionary framework that might explain in which ecological contexts they have evolved, and how they can be studied in the future. Some common mechanisms for enhancing movement include elastic energy storage (e.g., tendons and other materials) in vertebrates and invertebrates, or hormonal changes (e.g., increased testosterone levels).
Seasonal variations of cellular stress response of the gilthead sea bream (Sparus aurata)
Venue: Journal of Comparative Physiology B

The present study aimed to investigate the seasonal cellular stress response in vital organs, like the heart, the liver, the whole blood and the skeletal (red and white) muscles of the Mediterranean fish Sparus aurata during a 1-year acclimatization period in the field, in two examined depths (0–2 m and 10–12 m). Processes studied included heat shock protein expression and protein kinase activation. Molecular responses were addressed through the expression of Hsp70 and Hsp90, the phosphorylation of stress-activated protein kinases and particularly p38 mitogen-activated protein kinase (p38 MAPK), the extracellular signal-regulated kinases (ERK-1/2) and c-Jun N-terminal kinases (JNK1/2/3). The induction of Hsp70 and Hsp90 and the phosphorylation of p38 MAPK, JNKs and ERKs in the examined five tissues of the gilthead sea bream indicated a cellular stress response under the prism of a seasonal pattern which was characterized by distinct tissue specificity. Specifically, Hsp induction and MAPK activation occurred before peak summer water temperatures, with no further increases in their levels despite increases in water temperatures. Moreover, although water temperature did not vary significantly with depth of immersion, significant effects of depth on cellular stress response were observed, probably caused by different light regime. The expression and the activation of these certain proteins can be used as tools to define the extreme thermal limits of the gilthead sea bream.
Effect of age and diet composition on activity of pancreatic enzymes in birds
Venue: Journal of Comparative Physiology B

Digestive enzymes produced by the pancreas and intestinal epithelium cooperate closely during food hydrolysis. Therefore, activities of pancreatic and intestinal enzymes processing the same substrate can be hypothesized to change together in unison, as well as to be adjusted to the concentration of their substrate in the diet. However, our knowledge of ontogenetic and diet-related changes in the digestive enzymes of birds is limited mainly to intestinal enzymes; it is largely unknown whether they are accompanied by changes in activities of enzymes produced by the pancreas. Here, we analyzed age- and diet-related changes in activities of pancreatic enzymes in five passerine and galloanserine species, and compared them with simultaneous changes in activities of intestinal enzymes. Mass-specific activity of pancreatic amylase increased with age in young house sparrows but not in zebra finches, in agreement with changes in typical dietary starch content and activity of intestinal maltase. However, we found little evidence for the presence of adaptive, diet-related modulation of pancreatic enzymes in both passerine and galloanserine species, even though in several cases the same birds adaptively modulated activities of their intestinal enzymes. In general, diet-related changes in mass-specific activities of pancreatic and intestinal enzymes were not correlated. We conclude that activity of pancreatic enzymes in birds is under strong genetic control, which enables evolutionary adjustment to typical diet composition but is less adept for short term, diet-related flexibility.
Summer heterothermy in Rafinesque’s big-eared bats (Corynorhinus rafinesquii) roosting in tree cavities in bottomland hardwood forests
Venue: Journal of Comparative Physiology B

Many small mammals are heterothermic endotherms capable of maintaining an elevated core body temperature or reducing their thermoregulatory set point to enter a state of torpor. Torpor can confer substantial energy savings, but also incurs ecological costs, such as hindering allocation of energy towards reproduction. We placed temperature-sensitive radio transmitters on 44 adult Rafinesque’s big-eared bats (Corynorhinus rafinesquii) and deployed microclimate dataloggers inside 34 day roosts to compare the use of torpor by different sex and reproductive classes of bats during the summer. We collected 324 bat-days of skin-temperature data from 36 females and 4 males. Reproductive females employed fewer torpor bouts per day than non-reproductive females and males (P < 0.0001), and pregnant and lactating females had higher average (P < 0.0001) and minimum (P < 0.0001) skin temperatures than non-reproductive females. Pregnant females spent less time torpid (P < 0.0001) than non-reproductive females, but lactating females used relatively deep, long torpor bouts. Microclimates varied inside tree species with different configurations of entrances to the roost cavity (P < 0.0001). Bats spent more time torpid when roosting in water tupelo (Nyssa aquatica) trees possessing only a basal entrance to the cavity (P = 0.001). Of the tree species used as roosts, water tupelo cavities exhibited the least variable daytime and nighttime temperatures. These data demonstrate that use of summer torpor is not uniform among sex and reproductive classes in Rafinesque’s big-eared bat, and variation in microclimate among tree roosts due to species and structural characteristics facilitates the use of different thermoregulatory strategies in these bats.
A review of gastric processing in decapod crustaceans
Venue: Journal of Comparative Physiology B

This article reviews the mechanical processes associated with digestion in decapod crustaceans. The decapod crustacean gut is essentially an internal tube that is divided into three functional areas, the foregut, midgut, and hindgut. The foregut houses the gastric mill apparatus which functions in mastication (cutting and grinding) of the ingested food. The processed food passes into the pyloric region of the foregut which controls movement of digesta into the midgut region and hepatopancreas where intracellular digestion takes place. The movements of the foregut muscles and gastric mill are controlled via nerves from the stomatogastric ganglion. Contraction rates of the gastric mill and foregut muscles can be influenced by environmental factors such as salinity, temperature, and oxygen levels. Gut contraction rates depend on the magnitude of the environmental perturbation and the physiological ability of each species. The subsequent transit of the digesta from the foregut into the midgut and through the hindgut has been followed in a wide variety of crustaceans. Transit rates are commonly used as a measure of food processing rates and are keys in understanding strategies of adaptation to trophic conditions. Transit times vary from as little as 30 min in small copepods to over 150 h in larger lobsters. Transit times can be influenced by the size and the type of the meal, the size and activity level of an animal and changes in environmental temperature, salinity and oxygen tension. Ultimately, changes in transit times influence digestive efficiency (the amount of nutrients absorbed across the gut wall). Digestive efficiencies tend to be high for carnivorous crustaceans, but somewhat lower for those that consume plant material. A slowing of the transit rate allows more time for nutrient absorption but this may be confounded by changes in the environment, which may reduce the energy available for active transport processes. Given the large number of articles already published on the stomatogastric ganglion and its control mechanisms, this area will continue to be of interest to scientists. There is also a push towards studying animals in a more natural environment or even in the field and investigation of the energetic costs of the components of digestion under varying biotic and environmental conditions will undoubtedly be an area that expands in the future.
Sarcoplasmic reticulum: a key factor in cardiac contractility of sea bass Dicentrarchus labrax and common sole Solea solea during thermal acclimations
Venue: Journal of Comparative Physiology B

This study investigated the effects of acclimation temperature upon (i) contractility of ventricular strips (ii) calcium movements in ventricular cardiomyocytes during excitation–contraction coupling (ECC), and (iii) the role of the sarcoplasmic reticulum (SR) in myocardial responses, in two marine teleosts, the sea bass (Dicentrarchus labrax) and the common sole (Solea solea). Because of the different sensitivities of their metabolism to temperature variation, both species were exposed to different thermal ranges. Sea bass were acclimated to 10, 15, 20, and 25 °C, and common sole to 6, 12, 18, and 24 °C, for 1 month. Isometric tension developed by ventricular strips was recorded over a range of physiological stimulation frequencies, whereas the depolarization-induced calcium transients were recorded on isolated ventricular cells through hyperpotassic solution application (at 100 mM). The SR contribution was assessed by ryanodine (RYAN) perfusion on ventricular strips and by caffeine application (at 10 mM) on isolated ventricular cells. Rates of contraction and relaxation of ventricular strip, in both species, increased with increasing acclimation temperature. At a low range of stimulation frequency, ventricular strips of common sole developed a positive force–frequency relationship at high acclimation temperature. In both the species, SR Ca2+-cycling was dependent on fish species, acclimation temperature and pacing frequency. The SR contribution was more important to force development at low acclimation temperatures in sea bass but at high acclimation temperatures in common sole. The results also revealed that high acclimation temperature causes an increase in the maximum calcium response amplitude on ventricular cells in both the species. Although sea bass and common sole occupy similar environments and tolerate similar environmental temperatures, this study indicated that sea bass and common sole can acclimatize to new thermal conditions, adjusting their cellular process in a different manner.
Quantification of cuttlefish (Sepiaofficinalis) camouflage: a study of color and luminance using in situ spectrometry
Venue: Journal of Comparative Physiology A

Cephalopods are renowned for their ability to adaptively camouflage on diverse backgrounds. Sepia officinalis camouflage body patterns have been characterized spectrally in the laboratory but not in the field due to the challenges of dynamic natural light fields and the difficulty of using spectrophotometric instruments underwater. To assess cuttlefish color match in their natural habitats, we studied the spectral properties of S. officinalis and their backgrounds on the Aegean coast of Turkey using point-by-point in situ spectrometry. Fifteen spectrometry datasets were collected from seven cuttlefish; radiance spectra from animal body components and surrounding substrates were measured at depths shallower than 5 m. We quantified luminance and color contrast of cuttlefish components and background substrates in the eyes of hypothetical di- and trichromatic fish predators. Additionally, we converted radiance spectra to sRGB color space to simulate their in situ appearance to a human observer. Within the range of natural colors at our study site, cuttlefish closely matched the substrate spectra in a variety of body patterns. Theoretical calculations showed that this effect might be more pronounced at greater depths. We also showed that a non-biological method (“Spectral Angle Mapper”), commonly used for spectral shape similarity assessment in the field of remote sensing, shows moderate correlation to biological measures of color contrast. This performance is comparable to that of a traditional measure of spectral shape similarity, hue and chroma. This study is among the first to quantify color matching of camouflaged cuttlefish in the wild.
Time disparity sensitive behavior and its neural substrates of a pulse-type gymnotiform electric fish, Brachyhypopomus gauderio
Venue: Journal of Comparative Physiology A

Roles of the time coding electrosensory system in the novelty responses of a pulse-type gymnotiform electric fish, Brachyhypopomus, were examined behaviorally, physiologically, and anatomically. Brachyhypopomus responded with the novelty responses to small changes (100 μs) in time difference between electrosensory stimulus pulses applied to different parts of the body, as long as these pulses were given within a time period of ~500 μs. Physiological recording revealed neurons in the hindbrain and midbrain that fire action potentials time-locked to stimulus pulses with short latency (500–900 μs). These time-locked neurons, along with other types of neurons, were labeled with intracellular and extracellular marker injection techniques. Light and electron microscopy of the labeled materials revealed neural connectivity within the time coding system. Two types of time-locked neurons, the pear-shaped cells and the large cells converge onto the small cells in a hypertrophied structure, the mesencephalic magnocellular nucleus. The small cells receive a calyx synapse from a large cell at their somata and an input from a pear-shaped cell at the tip of their dendrites via synaptic islands. The small cells project to the torus semicircularis. We hypothesized that the time-locked neural signals conveyed by the pear-shaped cells and the large cells are decoded by the small cells for detection of time shifts occurring across body areas.
Torpor as an emergency solution in Galago moholi: heterothermy is triggered by different constraints
Venue: Journal of Comparative Physiology B

The expression of heterothermy in the African lesser bushbaby, Galago moholi, seems to be strikingly different to most other heterotherms: G. moholi uses its ability to enter torpor only rarely and torpor is only used by a small fraction of the population. The aim of this study was, therefore, to summarize the parameters of torpor use in G. moholi to conclude the general patterns and discuss them in comparison to other heterotherms to elucidate possible causes and constraints that underlie these differences in deployment of heterothermy. Our study was carried out on wild animals using temperature loggers and open-flow respirometry for measurements of body temperature and metabolic rate, respectively. G. moholi uses torpor only as a last resort and not as a routine, seasonal behavior. Nevertheless, we found that the general physiological patterns of torpor, e.g., torpor bout duration or entry and arousal times from torpor, were mainly consistent with those described for other nocturnal daily heterotherms. The greatest difference found was the unusual low rewarming rates during arousal from torpor, probably due to already depleted internal energy stores and thus inability to mobilize sufficient energy for endogenous heating. We therefore conclude that while general physiological parameters of heterothermy seem to have remained conserved in heterotherms, the underlying causes which elicit this physiological response, and thus the extent of expression and timing of heterothermy, have evolved very differently in different groups, depending on body mass and the specific habitat and lifestyle of the species.
Seasonal plasticity of gut morphology and small intestinal enzymes in free-living Mongolian gerbils
Venue: Journal of Comparative Physiology B

The phenotypic plasticity of the digestive system may determine the diversity of animal diets and, thus, their niche width. This study examines the effects of seasonal fluctuations in food quality and temperature on the gut morphology and the activity of sucrase, maltase, and aminopeptidase-N in the small intestinal brush-border membrane of male Mongolian gerbils (Meriones unguiculatus). Based on the adaptive modulation hypothesis and the principle of optimal gut function design, we hypothesize that the gut size, tissue-specific activity, and total hydrolytic capacity of intestinal digestive enzyme are upregulated in winter and downregulated in summer in response to diet shifts and energy demand in free-living Mongolian gerbils. Various seasonal modulation patterns in digestive enzyme activity in different regions of the small intestines were observed. The results show that male gerbils have the longest and heaviest small intestines in winter. This mechanism may be adapted to increase their food intake during winter. Male gerbils also exhibit the highest tissue-specific and total sucrase, maltase, and aminopeptidase-N activity in winter and in spring. Seasonal modulations are more distinct in the jejunum than in the duodenum and the ileum of the small intestines. The digestive phenotypic flexibility of male gerbils effectively corresponded with seasonal diet shifts and temperature fluctuations.