nils-herrmann/clean_scirepeval huggingface dataset:
Overwinter body temperature patterns in captive jerboas (Jaculus orientalis): influence of sex and group
Venue: Journal of Comparative Physiology B

The jerboa (Jaculus orientalis) has been described in the past as a hibernator, but no reliable data exist on the daily and seasonal rhythmicity of body temperature (Tb). In this study, Tb patterns were determined in different groups of jerboas (isolated males and females, castrated males and grouped animals) maintained in captivity during autumn and winter, and submitted to natural variations of light and ambient temperature (Ta). Tb and Ta variations were recorded with surgically implanted iButton temperature loggers at 30-min intervals for two consecutive years. About half (6/13) of isolated female jerboas hibernated with a Tb < 33°C, with hibernation bouts interspersed with short periods of normothermy from November to February. Hibernation bout durations were longer (4–5 days) than those of normothermia phases (1–4 days). During hibernation, the minimum Tb was low (Tbmin ~10.7°C). In contrast, one of the 12 isolated males showed short hibernation bouts of ca. 2 days late in the hibernation season, February–March. The males had Tbmin values of 15.1°C. In contrast to predictions, no castrated males hibernated. When jerboas were grouped, females and males exhibited concomitant torpor bouts. In males, the longest bouts were observed during the late hibernation season. These data suggest complex regulation of hibernation in jerboas.
Feeding into old age: long-term effects of dietary fatty acid supplementation on tissue composition and life span in mice
Venue: Journal of Comparative Physiology B

Smaller mammals, such as mice, possess tissues containing more polyunsaturated fatty acids (PUFAs) than larger mammals, while at the same time live shorter lives. These relationships have been combined in the ‘membrane pacemaker hypothesis of aging’. It suggests that membrane PUFA content might determine an animal’s life span. PUFAs in general and certain long-chain PUFAs in particular, are highly prone to lipid peroxidation which brings about a high rate of reactive oxygen species (ROS) production. We hypothesized that dietary supplementation of either n-3 or n-6 PUFAs might affect (1) membrane phospholipid composition of heart and liver tissues and (2) life span of the animals due to the altered membrane composition, and subsequent effects on lipid peroxidation. Therefore, we kept female laboratory mice from the C57BL/6 strain on three diets (n-3 PUFA rich, n-6 PUFA rich, control) and assessed body weights, life span, heart, and liver phospholipid composition after the animals had died. We found that while membrane phospholipid composition clearly differed between feeding groups, life span was not directly affected. However, we were able to observe a positive correlation between monounsaturated fatty acids in cardiac muscle and life span.
Intra- and extracellular osmotic regulation in the hololimnetic Caridea and Anomura: a phylogenetic perspective on the conquest of fresh water by the decapod Crustacea
Venue: Journal of Comparative Physiology B

We investigate extra- and intracellular osmoregulatory capability in two species of hololimnetic Caridea and Anomura: Macrobrachium brasiliense, a palaemonid shrimp, and Aegla franca, an aeglid anomuran, both restricted to continental waters. We also appraise the sharing of physiological characteristics by the hololimnetic Decapoda, and their origins and role in the conquest of fresh water. Both species survive salinity exposure well. While overall hyperosmoregulatory capability is weak in A. franca and moderate in M. brasiliense, both species strongly hyporegulate hemolymph [Cl−] but not osmolality. Muscle total free amino acids (FAA) increase slowly but markedly in response to the rapid rise in hemolymph osmolality consequent to hyperosmotic challenge: 3.5-fold in A. franca and 1.9-fold in M. brasiliense. Glycine, taurine, arginine, alanine and proline constitute ≈85% of muscle FAA pools in fresh water; taurine, arginine, alanine each contribute ≈22% in A. franca, while glycine predominates (70%) in M. brasiliense. These FAA also show the greatest increases on salinity challenge. Muscle FAA titers correlate strongly (R = 0.82) with hemolymph osmolalities across the main decapod sub/infraorders, revealing that marine species with high hemolymph osmolalities achieve isosmoticity of the intra- and extracellular fluids partly through elevated intracellular FAA concentrations; freshwater species show low hemolymph osmolalities and exhibit reduced intracellular FAA titers, consistent with isosmoticity at a far lower external osmolality. Given the decapod phylogeny adopted here and their multiple, independent invasions of fresh water, particularly by the Caridea and Anomura, our findings suggest that homoplastic strategies underlie osmotic and ionic homeostasis in the extant freshwater Decapoda.
Vasotocin- and mesotocin-induced increases in short-circuit current across tree frog skin
Venue: Journal of Comparative Physiology B

In adult amphibian skin, Na+ crosses from outside to inside. This Na+ transport can be measured as the amiloride-blockable short-circuit current (SCC) across the skin. We investigated the effects of arginine vasotocin (AVT) and mesotocin (MT), and those of antagonists of the vasopressin and oxytocin receptors, on the SCC across Hyla japonica skin. (1) Both AVT (100 pmol/L or more) and MT (1 nmol/L or more) increased the SCC. (2) The AVT- and MT-induced increases in SCC recovered with time (downregulation). (3) These AVT/MT-induced effects were blocked by application of OPC-31260 (vasopressin V2-receptor antagonist). (4) The OPC-31260 concentration needed to block the AVT-induced response was lower upon post-application (after application of agonist) than upon pre-application (before application of agonist), suggesting the number of receptors may have decreased after AVT application. (5) Upon repeated application of AVT (100 pmol/L), the induced SCC increase did not differ significantly between the 1st and 2nd applications. (6) The time to reach the half-maximum value of the AVT-induced or MT-induced increase in SCC was not significantly different between washout and post-application of OPC-31260, suggesting that post-application of OPC-31260 cleared AVT and MT from their receptors. The effects of AVT, MT, and their antagonists in H. japonica, which is adapted to a terrestrial habitat, are compared with our previously published data on Rana catesbeiana (=Lithobates catesbeianus), which is adapted to a semiaquatic habitat.
Contrast sensitivity in a harbor seal (Phoca vitulina)
Venue: Journal of Comparative Physiology A

In this study, the contrast sensitivity function (CSF) of one harbor seal was determined behaviorally in a go-/no-go-experiment at an ambient light of 0.9 lx in air. Contrast sensitivity was assessed as the reciprocal value of the threshold contrast for spatial frequencies varying between 0.03 and 1.5 cycles/deg, which were displayed with contrast ranging from 0.02 to 1 on a TFT monitor with a mean luminance of 3.8 cd/m². The CSF of the harbor seal shows the general characteristics described for other species with a peak at an intermediate frequency, a low frequency roll-off and a high frequency cut-off towards the harbor seal’s resolution limit determined in a previous study. The position of the CSF’s peak lies at approximately 0.5 cycles/deg and adopts an absolute height of 40. These results compare well with the cat’s CSF assessed at a comparable adaptation light which might reflect similarities in lifestyle and optics.
Epithelial remodeling and claudin mRNA abundance in the gill and kidney of puffer fish (Tetraodon biocellatus) acclimated to altered environmental ion levels
Venue: Journal of Comparative Physiology B

In water of varying ion content, the gills and kidney of fishes contribute significantly to the maintenance of salt and water balance. However, little is known about the molecular architecture of the tight junction (TJ) complex and the regulation of paracellular permeability characteristics in these tissues. In the current studies, puffer fish (Tetraodon biocellatus) were acclimated to freshwater (FW), seawater (SW) or ion-poor freshwater (IPW) conditions. Following acclimation, alterations in systemic endpoints of hydromineral status were examined in conjunction with changes in gill and kidney epithelia morphology/morphometrics, as well as claudin TJ protein mRNA abundance. T. biocellatus were able to maintain endpoints of hydromineral status within relatively tight limits across the broad range of water ion content examined. Both gill and kidney tissue exhibited substantial alterations in morphology as well as claudin TJ protein mRNA abundance. These responses were particularly pronounced when comparing fish acclimated to SW versus those acclimated to IPW. TEM observations of IPW-acclimated fish gills revealed the presence of cells that exhibited the typical characteristics of gill mitochondria-rich cells (e.g. voluminous, Na+-K+-ATPase-immunoreactive, exposed to the external environment at the apical surface), but were not mitochondria-rich. To our knowledge, this type of cell has not previously been described in hyperosmoregulating fish gills. Furthermore, modifications in the morphometrics and claudin mRNA abundance of kidney tissue support the notion that spatial alterations in claudin TJ proteins along the nephron of fishes will likely play an important role in the regulation of salt and water balance in these organisms.
Morphological and physiological regeneration in the auditory system of adult Mecopoda elongata (Orthoptera: Tettigoniidae)
Venue: Journal of Comparative Physiology A

Orthopterans are suitable model organisms for investigations of regeneration mechanisms in the auditory system. Regeneration has been described in the auditory systems of locusts (Caelifera) and of crickets (Ensifera). In this study, we comparatively investigate the neural regeneration in the auditory system in the bush cricket Mecopoda elongata. A crushing of the tympanal nerve in the foreleg of M. elongata results in a loss of auditory information transfer. Physiological recordings of the tympanal nerve suggest outgrowing fibers 5 days after crushing. An anatomical regeneration of the fibers within the central nervous system starts 10 days after crushing. The neuronal projection reaches the target area at day 20. Threshold values to low frequency airborne sound remain high after crushing, indicating a lower regeneration capability of this group of fibers. However, within the central target area the low frequency areas are also innervated. Recordings of auditory interneurons show that the regenerating fibers form new functional connections starting at day 20 after crushing.
Views, landmarks, and routes: how do desert ants negotiate an obstacle course?
Venue: Journal of Comparative Physiology A

The Australian desert ant Melophorus bagoti often follows stereotypical routes through a cluttered landscape containing both distant panoramic views and obstacles (plants) to navigate around. We created an artificial obstacle course for the ants between a feeder and their nest. Landmarks comprised natural objects in the landscape such as logs, branches, and tussocks. Many ants travelled stereotypical routes home through the obstacle course in training, threading repeatedly the same gaps in the landmarks. Manipulations altering the relations between the landmarks and the surrounding panorama, however, affected the routes in two major ways. Both interchanging the positions of landmarks (transpositions) and displacing the entire landmark set along with the starting position of the ants (translations) (1) reduced the stereotypicality of the route, and (2) increased turns and meanders during travel. The ants might have used the entire panorama in view-based travel, or the distal panorama might prime the identification and use of landmarks en route. Despite the large data set, both options (not mutually exclusive) remain viable.
Response properties of visual neurons in the turtle nucleus isthmi
Venue: Journal of Comparative Physiology A

The optic tectum holds a central position in the tectofugal pathway of non-mammalian species and is reciprocally connected with the nucleus isthmi. Here, we recorded from individual nucleus isthmi pars parvocellularis (Ipc) neurons in the turtle eye-attached whole-brain preparation in response to a range of computer-generated visual stimuli. Ipc neurons responded to a variety of moving or flashing stimuli as long as those stimuli were small. When mapped with a moving spot, the excitatory receptive field was of circular Gaussian shape with an average half-width of less than 3°. We found no evidence for directional sensitivity. For moving spots of varying sizes, the measured Ipc response-size profile was reproduced by the linear Difference-of-Gaussian model, which is consistent with the superposition of a narrow excitatory center and an inhibitory surround. Intracellular Ipc recordings revealed a strong inhibitory connection from the nucleus isthmi pars magnocellularis (Imc), which has the anatomical feature to provide a broad inhibitory projection. The recorded Ipc response properties, together with the modulatory role of the Ipc in tectal visual processing, suggest that the columns of Ipc axon terminals in turtle optic tectum bias tectal visual responses to small dark changing features in visual scenes.
Changes of globin expression in the Japanese medaka (Oryzias latipes) in response to acute and chronic hypoxia
Venue: Journal of Comparative Physiology B

Fishes live in an aquatic environment with low or temporally changing O2 availability. Variations in O2 levels require many anatomical, behavioral, physiological, and biochemical adaptations that ensure the uptake of an adequate amount of O2. Some fish species are comparatively well adapted to tolerate low O2 partial pressure (hypoxia). The Japanese ricefish medaka (Oryzias latipes) is an important model organism for biomedical research that shows remarkable tolerance towards hypoxia. We have investigated the regulation and role of globins under hypoxia. We applied four different regimes of chronic hypoxia (24 and 48 h at PO2 = 2 or 4 kPa) as well as acute hypoxia (2 h at PO2 = 0.5 kPa) to adult male medaka. Changes of mRNA levels of seven globin genes (adult hemoglobin α and β, myoglobin, neuroglobin, cytoglobin 1 and 2, globin X), three hypoxia-response genes (lactate dehydrogenase b, phosphoglycerate kinase, adrenomedullin 1) and two putative reference genes (cyclophilin, acidic ribosomal phosphoprotein P0) were monitored by means of quantitative real-time reverse-transcription PCR. We observed strong upregulation of myoglobin, which is also expressed in the medaka brain, as previously demonstrated for carp, goldfish and zebrafish. The hemoglobin chains were found upregulated, whereas earlier studies found down-regulation of hemoglobin in hypoxic zebrafish. By contrast, neuroglobin mRNA was not affected by hypoxia in medaka, but had been found upregulated in zebrafish. Globin X is induced in medaka brain, but down-regulated in zebrafish. Thus, the patterns of hypoxia response of globins are strikingly different in various fish species, which can be interpreted as indication for different roles of the various globins in hypoxia response and for alternative metabolic strategies of fish species in coping with O2 deprivation.
Hydrodynamic trail following in a California sea lion (Zalophus californianus)
Venue: Journal of Comparative Physiology A

The mystacial vibrissae of pinnipeds constitute a sensory system for active touch and detection of hydrodynamic events. Harbour seals (Phoca vitulina) and California sea lions (Zalophus californianus) can both detect hydrodynamic stimuli caused by a small sphere vibrating in the water (hydrodynamic dipole stimuli). Hydrodynamic trail following has only been shown in harbour seals. Hydrodynamical and biomechanical studies of single vibrissae of the two species showed that the specialized undulated structure of harbour seal vibrissae, as opposed to the smooth structure of sea lion vibrissae, suppresses self-generated noise in the actively moving animal. Here we tested whether also sea lions were able to perform hydrodynamic trail following in spite of their non-specialized hair structure. Hydrodynamic trails were generated by a remote-controlled miniature submarine. Linear trails could be followed with high accuracy, comparable to the performance of harbour seals, but in contrast, increasing delay resulted in a reduced performance as compared to harbour seals. The results of this study are consistent with the hypothesis that structural differences in the vibrissal hair types of otariid compared to phocid pinnipeds lead to different sensitivity of the vibrissae during forward swimming, but still reveal a good performance even in the species with non-specialized hair type.
Arboreal habitat structure affects route choice by rat snakes
Venue: Journal of Comparative Physiology A

In arboreal habitats gaps between branches and branch structure profoundly affect the ability of animals to move; hence, an ability to perceive such attributes could facilitate choosing routes that enhance the speed and ease of locomotion. Although many snakes are arboreal, no previous study has determined whether they can perceive structural variation of branches that is mechanically relevant to their locomotion. We tested whether the gap distance, location, and attributes of two destination perches on the far side of a crossable gap affected the route travelled by North American rat snakes (Pantherophis), which are proficient climbers. Snakes usually chose routes with shorter gaps. Within a horizontal plane, the snakes usually went straight rather than crossing an equal distance gap with a 90° turn, which was consistent with our finding that crossing a straight gap was easier. However, decreasing the distance of the gap with a 90° turn eliminated the preference for going straight. Additional factors, such as the width of the landing surface and the complexity of branching of the destination perches, resulted in non-random route choice. Thus, many of the observed biases in route choice suggested abilities to perceive structural variation and select routes that are mechanically beneficial.
Between-species jamming avoidance in Pipistrelles?
Venue: Journal of Comparative Physiology A

Past studies have reported that bats modify the spectral–temporal features of their vocalizations to avoid interference from the vocalizations of conspecifics (jamming avoidance). We tested for within, and between-species jamming avoidance in two sympatrically occurring species of vespertilionid bats, Pipistrellus pipistrellus and Pipistrellus nathusii. In both species the peak frequencies of the narrowband frequency component from samples of bats flying with conspecifics varied more than those from samples of bats flying alone, indicating intraspecific jamming avoidance. If individuals of the two species were recorded together, we found no reaction of P. nathusii. P. pipistrellus, however, used significantly higher frequencies than when recorded alone. As the narrowband frequency of this species normally overlaps with the frequency modulated (FM) part of P. nathusii calls, this can be interpreted as an interspecific jamming avoidance response.
Air-permeable hole-pattern and nose-droop control improve aerodynamic performance of primary feathers
Venue: Journal of Comparative Physiology A

Primary feathers of soaring land birds have evolved into highly specialized flight feathers characterized by morphological improvements affecting aerodynamic performance. The foremost feathers in the cascade have to bear high lift-loading with a strong bending during soaring flight. A challenge to the study of feather aerodynamics is to understand how the observed low drag and high lift values in the Reynolds (Re) regime from 1.0 to 2.0E4 can be achieved. Computed micro-tomography images show that the feather responds to high lift-loading with an increasing nose-droop and profile-camber. Wind-tunnel tests conducted with the foremost primary feather of a White Stork (Ciconia ciconia) at Re = 1.8E4 indicated a surprisingly high maximum lift coefficient of 1.5 and a glide ratio of nearly 10. We present evidence that this is due to morphologic characteristics formed by the cristae dorsales as well as air-permeable arrays along the rhachis. Measurements of lift and drag forces with open and closed pores confirmed the efficiency of this mechanism. Porous structures facilitate a blow out, comparable to technical blow-hole turbulators for sailplanes and low speed turbine-blades. From our findings, we conclude that the mechanism has evolved in order to affect the boundary layer and to reduce aerodynamic drag of the feather.
Interval-counting neurons in the anuran auditory midbrain: factors underlying diversity of interval tuning
Venue: Journal of Comparative Physiology A

In anurans, the temporal patterning of sound pulses is the primary information used for differentiating between spectrally similar calls. One class of midbrain neurons, referred to as ‘interval-counting’ cells, appears to be particularly important for discriminating among calls that differ in pulse repetition rate (PRR). These cells only respond after several pulses are presented with appropriate interpulse intervals. Here we show that the range of selectivity and sharpness of interval tuning vary considerably across neurons. Whole-cell recordings revealed that neurons showing temporally summating excitatory postsynaptic potentials (EPSPs) with little or no inhibition or activity-dependent enhancement of excitation exhibited low-pass or band-pass tuning to slow PRRs. Neurons that showed inhibition and rate-dependent enhancement of excitation, however, were band-pass or high-pass to intermediate or fast PRRs. Surprisingly, across cells, interval tuning based on membrane depolarization and spike rate measures were not significantly correlated. Neurons that lacked inhibition showed the greatest disparities between these two measures of interval tuning. Cells that showed broad membrane potential-based tuning, for example, varied considerably in their spike rate-based tuning; narrow spike rate-based tuning resulted from ‘thresholding’ processes, whereby only the largest depolarizations triggered spikes. The potential constraints associated with generating interval tuning in this manner are discussed.
A central pacemaker that underlies the production of seasonal and sexually dimorphic social signals: anatomical and electrophysiological aspects
Venue: Journal of Comparative Physiology A

Our long-term goal is to approach the understanding of the anatomical and physiological bases for communication signal diversity in gymnotiform fishes as a model for vertebrate motor pattern generation. Brachyhypopomus gauderio emits, in addition to its electric organ discharge (EOD) at basal rate, a rich repertoire of rate modulations. We examined the structure of the pacemaker nucleus, responsible for the EOD rate, to explore whether its high output signal diversity was correlated to complexity in its neural components or regional organization. We confirm the existence of only two neuron types and show that the previously reported dorsal–caudal segregation of these neurons is accompanied by rostral–caudal regionalization. Pacemaker cells are grouped dorsally in the rostral half of the nucleus, and relay cells are mainly ventral and more abundant in the caudal half. Relay cells are loosely distributed from the center to the periphery of the nucleus in correlation to somata size. Our findings support the hypothesis that regional organization enables a higher diversity of rate modulations, possibly offering distinct target areas to modulatory inputs. Since no anatomical or electrophysiological seasonal or sexual differences were found, we explored these aspects from a functional point of view in a companion article.