nils-herrmann/clean_scirepeval huggingface dataset:
The ability of the Antarctic nematode Panagrolaimus davidi to survive intracellular freezing is dependent upon nutritional status
Venue: Journal of Comparative Physiology B

The Antarctic nematode Panagrolaimus davidi is the best documented example of an animal surviving intracellular freezing and the only animal so far shown to survive such freezing throughout its tissues. However, a recent study found that after exposure to a freezing stress that produced intracellular freezing in a proportion of nematodes, the resulting survival levels could be explained if those nematodes that froze intracellularly had died. We have thus re-examined the survival of intracellular freezing in this nematode. The ability to survive a freezing exposure that is likely to produce intracellular freezing (freezing at −10 °C) declines with culture age. In cultures that are fed regularly, the ability to survive freezing at −10 °C increases, but in starved cultures freezing survival declines. Survival of intracellular freezing in fed cultures was confirmed using cryomicroscopy, staining of cells with vital dyes and by freeze substitution and transmission electron microscopy. We have thus confirmed that P. davidi can survive intracellular freezing and shown that this ability is dependent upon them being well fed. The effect of culture conditions on the nutrient status of the nematodes should thus be an important factor in the design of experiments.
Discontinuous ammonia excretion and glutamine storage in littoral Oniscidea (Crustacea: Isopoda): testing tidal and circadian models
Venue: Journal of Comparative Physiology B

A key evolutionary development facilitating land colonization in terrestrial isopods (Isopoda: Oniscidea) is the intermittent liberation of waste nitrogen as volatile ammonia. Intermittent ammonia release exploits glutamine (Gln) as an intermediary nitrogen store. Here, we explore the relationship between temporal patterns of ammonia release and Gln accumulation in three littoral oniscideans from Southern California. Results are interpreted in terms of water availability, habitat, activity patterns, and ancestry. A two-way experimental design was used to test whether ammonia excretion and Gln accumulation follow a tidal or diel periodicity. Ammonia excretion was studied in the laboratory using chambers with or without available seawater and using an acid trap to collect volatile ammonia. Ligia occidentalis releases ammonia directly into seawater and accumulates Gln during low tide (48.9 ± 6.5 μmol g−1 at low tide, 24.1 ± 3.0 μmol g−1 at high tide), indicating that excretion is tidally constrained. Alloniscus perconvexus and Tylos punctatus can excrete ammonia directly into seawater or utilize volatilization. Both species burrow in sand by day and show a diel excretory pattern, accumulating Gln nocturnally (31.8 ± 2.7 μmol g−1 at dawn and 21.8 ± 2.3 μmol g−1 at dusk for A. perconvexus; 85.7 ± 15.1 μmol g−1 at dawn and 25.4 ± 2.9 μmol g−1 at dusk for T. punctatus) and liberating ammonia diurnally. Glutaminase shows higher activity in terrestrial (0.54–0.86 U g−1) compared to intertidal (0.25–0.31 U g−1) species, consistent with the need to generate high PNH3 for volatilization. The predominant isoform in Armadillidium vulgare is phosphate dependent and maleate independent; phosphate is a plausible regulator in vivo.
Interspecifc variation in eye shape and retinal topography in seven species of galliform bird (Aves: Galliformes: Phasianidae)
Venue: Journal of Comparative Physiology A

Eye morphology and the retinal topography of animals that live in either ‘open’ (e.g., grassland) or ‘enclosed’ (e.g., forest) terrestrial habitats show common adaptations to constraints imposed by these different habitat types. Although relationships between habitat and the visual system are well documented in most vertebrates, relatively few studies have examined this relationship in birds. Here, we compare eye shape and retinal topography across seven species from the family Phasianidae (Galliformes) that are diurnally active in either open or enclosed habitats. Species from enclosed habitats have significantly larger corneal diameters, relative to transverse diameters, than species from open habitats, which we predict serves to enhance visual sensitivity. Retinal topography, however, was similar across all seven species and consisted of a centrally positioned area centralis and a weak horizontal visual streak, with no discernible fovea. In the Japanese quail (Coturnix japonica), there was also a dorso-temporal extension of increased neuron density and, in some specimens, a putative area dorsalis. The total number of neurons in the retinal ganglion cell layer was correlated with retinal whole-mount area. Average and peak neuron densities were similar across species, with the exception of the Japanese quail, which had greater average and peak densities. Peak anatomical spatial resolving power was also similar among species, ranging from approximately 10–13 cycles/°. Overall, the pattern of retinal topography we found in phasianids is associated with ground-foraging in birds and presumably facilitates the identification of small food items on the ground as well as other visually guided behaviors, irrespective of habitat type.
Effects of aversive experience on the behavior within a custom-made plus maze in the short-tailed fruit bat, Carollia perspicillata
Venue: Journal of Comparative Physiology A

Stress exposure evokes a variety of physiological and behavioral responses in an organism, enabling it to cope with stressful situations and changes in the environment. In a previous study, we found that subjecting individuals of Carollia perspicillata to a chronic immobilization stress paradigm resulted in a significant increase of fecal cortisol concentrations. In the present study, we investigated the influence of stress on the behavior of C. perspicillata, by adapting a commonly used behavioral paradigm for characterizing coping styles of animals (i.e., the elevated-plus maze) to bats. Adult bats were subjected 1 h/day to immobilization over a period of 10 days. On the subsequent day, the behavior of each animal was analyzed in a custom-made plus maze, consisting of four arms (two open and two enclosed ones) and designed 3D because of the bats’ ability to fly. In this newly invented design, we compared the behaviors of stressed animals and controls. Changes in locomotor and exploratory behavior suggest two divergent adaptive behaviors in C. perspicillata following the chronic stress paradigm, possibly indicating different stress coping styles.
Echolocation behavior of the Japanese horseshoe bat in pursuit of fluttering prey
Venue: Journal of Comparative Physiology A

Echolocation sounds of Rhinolophus ferrumequinum nippon as they approached a fluttering moth (Goniocraspidum pryeri) were investigated using an on-board telemetry microphone (Telemike). In 40 % of the successful moth-capture flights, the moth exhibited distinctive evasive flight behavior, but the bat pursued the moth by following its flight path. When the distance to the moth was approximately 3–4 m, the bats increased the duration of the pulses to 65–95 ms, which is 2–3 times longer than those during landing flight (30–40 ms). The mean of 5.8 long pulses were emitted before the final buzz phase of moth capture, without strengthening the sound pressure level. The mean duration of long pulses (79.9 ± 7.9 ms) corresponded to three times the fluttering period of G. pryeri (26.5 × 3 = 79.5 ms). These findings indicate that the bats adjust the pulse duration to increase the number of temporal repetitions of fluttering information rather than to produce more intense sonar sounds to receive fine insect echoes. The bats exhibited Doppler-shift compensation for echoes returning from large static objects ahead, but not for echoes from target moths, even though the bats were focused on capturing the moths. Furthermore, the echoes of the Telemike recordings from target moths showed spectral glints of approximately 1–1.5 kHz caused by the fluttering of the moths but not amplitude glints because of the highly acoustical attenuation of ultrasound in the air, suggesting that spectral information may be more robust than amplitude information in echoes during moth capturing flight.
A comparative meta-analysis of maximal aerobic metabolism of vertebrates: implications for respiratory and cardiovascular limits to gas exchange
Venue: Journal of Comparative Physiology B

Maximal aerobic metabolic rates (MMR) in vertebrates are supported by increased conductive and diffusive fluxes of O2 from the environment to the mitochondria necessitating concomitant increases in CO2 efflux. A question that has received much attention has been which step, respiratory or cardiovascular, provides the principal rate limitation to gas flux at MMR? Limitation analyses have principally focused on O2 fluxes, though the excess capacity of the lung for O2 ventilation and diffusion remains unexplained except as a safety factor. Analyses of MMR normally rely upon allometry and temperature to define these factors, but cannot account for much of the variation and often have narrow phylogenetic breadth. The unique aspect of our comparative approach was to use an interclass meta-analysis to examine cardio-respiratory variables during the increase from resting metabolic rate to MMR among vertebrates from fish to mammals, independent of allometry and phylogeny. Common patterns at MMR indicate universal principles governing O2 and CO2 transport in vertebrate cardiovascular and respiratory systems, despite the varied modes of activities (swimming, running, flying), different cardio-respiratory architecture, and vastly different rates of metabolism (endothermy vs. ectothermy). Our meta-analysis supports previous studies indicating a cardiovascular limit to maximal O2 transport and also implicates a respiratory system limit to maximal CO2 efflux, especially in ectotherms. Thus, natural selection would operate on the respiratory system to enhance maximal CO2 excretion and the cardiovascular system to enhance maximal O2 uptake. This provides a possible evolutionary explanation for the conundrum of why the respiratory system appears functionally over-designed from an O2 perspective, a unique insight from previous work focused solely on O2 fluxes. The results suggest a common gas transport blueprint, or Bauplan, in the vertebrate clade.
Water absorption and bicarbonate secretion in the intestine of the sea bream are regulated by transmembrane and soluble adenylyl cyclase stimulation
Venue: Journal of Comparative Physiology B

In the marine fish intestine luminal, HCO3− can remove divalent ions (calcium and magnesium) by precipitation in the form of carbonate aggregates. The process of epithelial HCO3− secretion is under endocrine control, therefore, in this study we aimed to characterize the involvement of transmembrane (tmACs) and soluble (sACs) adenylyl cyclases on the regulation of bicarbonate secretion (BCS) and water absorption in the intestine of the sea bream (Sparus aurata). We observed that all sections of sea bream intestine are able to secrete bicarbonate as measured by pH–Stat in Ussing chambers. In addition, gut sac preparations reveal net water absorption in all segments of the intestine, with significantly higher absorption rates in the anterior intestine that in the rectum. BCS and water absorption are positively correlated in all regions of the sea bream intestinal tract. Furthermore, stimulation of tmACs (10 μM FK + 500 μM IBMX) causes a significant decrease in BCS, bulk water absorption and short circuit current (Isc) in a region dependent manner. In turn, stimulation of sACs with elevated HCO3− results in a significant increase in BCS, and bulk water absorption in the anterior intestine, an action completely reversed by the sAC inhibitor KH7 (200 μM). Overall, the results reveal a functional relationship between BCS and water absorption in marine fish intestine and modulation by tmACs and sAC. In light of the present observations, it is hypothesized that the endocrine effects on intestinal BCS and water absorption mediated by tmACs are locally and reciprocally modulated by the action of sACs in the fish enterocyte, thus fine-tuning the process of carbonate aggregate production in the intestinal lumen.
K+-dependent 3H-d-glucose transport by hepatopancreatic brush border membrane vesicles of a marine shrimp
Venue: Journal of Comparative Physiology B

The effects of sodium, potassium, sugar inhibitors, and membrane potential on 3H-d-glucose uptake by hepatopancreatic epithelial brush border membrane vesicles (BBMV) of the Atlantic marine shrimp, Litopenaeus setiferus, were investigated. Brush border membrane vesicles were prepared using a MgCl2/EGTA precipitation method and uptake experiments were conducted using a high speed filtration technique. 3H-d-Glucose uptake was stimulated by both sodium and potassium and these transport rates were almost doubled in the presence of an inside-negative-induced membrane potential. Kinetics of 3H-d-glucose influx were hyperbolic functions of both external Na+ or K+, and an induced membrane potential increased influx Jmax and lowered Km in both salts. 3H-d-Glucose influx versus [glucose] in both Na+ or K+ media also displayed Michaelis–Menten properties that were only slightly affected by induced membrane potential. Phloridzin was a poor inhibitor of 0.5 mM 3H-d-glucose influx, requiring at least 5 mM in NaCl and 10 mM in KCl to significantly reduce hexose transport. Several sugars (d-galactose, α-methyl-d-gluco-pyranoside, unlabeled d-glucose, d-fructose, and d-mannose) were used at 75 mM as potential inhibitors of 0.1 mM 3H-d-glucose influx. Only unlabeled d-glucose, d-fructose, and d-mannose significantly (p < 0.05) reduced labeled glucose transport. An additional experiment using increasing concentrations of d-mannose (0, 10, 25, 75, and 100 mM) showed this hexose to be an effective inhibitor of 0.1 mM 3H-d-glucose uptake at concentrations of 75 mM and higher. As a whole these results suggest that 3H-d-glucose transport by hepatopancreatic BBMV occurs by a carrier system that is able to use both Na+ and K+ as drivers, is enhanced by membrane potential, is relatively refractory to phloridzin, and is only inhibited by itself, d-fructose, and d-mannose. These properties are similar to those exhibited by the mammalian SLC5A9/SGLT4 transporter, suggesting that an invertebrate analogue of this protein may occur in shrimp.
Increased bursting glutamatergic neurotransmission in an auditory forebrain area of the zebra finch (Taenopygia guttata) induced by auditory stimulation
Venue: Journal of Comparative Physiology A

The caudomedial nidopallium (NCM) is a telencephalic area involved in auditory processing and memorization in songbirds, but the synaptic mechanisms associated with auditory processing in NCM are largely unknown. To identify potential changes in synaptic transmission induced by auditory stimulation in NCM, we used a slice preparation for path-clamp recordings of synaptic currents in the NCM of adult zebra finches (Taenopygia guttata) sacrificed after sound isolation followed by exposure to conspecific song or silence. Although post-synaptic GABAergic and glutamatergic currents in the NCM of control and song-exposed birds did not present any differences regarding their frequency, amplitude and duration after song exposure, we observed a higher probability of generation of bursting glutamatergic currents after blockade of GABAergic transmission in song-exposed birds as compared to controls. Both song-exposed males and females presented an increase in the probability of the expression of bursting glutamatergic currents, however bursting was more commonly seen in males where they appeared even without blocking GABAergic transmission. Our data show that song exposure changes the excitability of the glutamatergic neuronal network, increasing the probability of the generation of bursts of glutamatergic currents, but does not affect basic parameters of glutamatergic and GABAergic synaptic currents.
Ontogeny of hypoxic modulation of cardiac performance and its allometry in the African clawed frog Xenopus laevis
Venue: Journal of Comparative Physiology B

The ontogeny of cardiac hypoxic responses, and how such responses may be modified by rearing environment, are poorly understood in amphibians. In this study, cardiac performance was investigated in Xenopus laevis from 2 to 25 days post-fertilization (dpf). Larvae were reared under either normoxia or moderate hypoxia (PO2 = 110 mmHg), and each population was assessed in both normoxia and acute hypoxia. Heart rate (fh) of normoxic-reared larvae exhibited an early increase from 77 ± 1 beats min−1 at 2 dpf to 153 ± 1 beats min−1 at 4 dpf, followed by gradual decreases to 123 ± 3 beats min−1 at 25 dpf. Stroke volume (SV), 6 ± 1 nl, and cardiac output (CO), 0.8 ± 0.1 μl min−1, at 5 dpf both increased by more than 40-fold to 25 dpf with rapid larval growth (~30-fold increase in body mass). When exposed to acute hypoxia, normoxic-reared larvae increased fh and CO between 5 and 25 dpf. Increased SV in acute hypoxia, produced by increased end-diastolic volume (EDV), only occurred before 10 dpf. Hypoxic-reared larvae showed decreased acute hypoxic responses of EDV, SV and CO at 7 and 10 dpf. Over the period of 2–25 dpf, cardiac scaling with mass showed scaling coefficients of −0.04 (fh), 1.23 (SV) and 1.19 (CO), contrary to the cardiac scaling relationships described in birds and mammals. In addition, fh scaling in hypoxic-reared larvae was altered to a shallower slope of −0.01. Collectively, these results indicate that acute cardiac hypoxic responses develop before 5 dpf. Chronic hypoxia at a moderate level can not only modulate this cardiac reflex, but also changes cardiac scaling relationship with mass.
Osmoregulatory response to low salinities in the European sea bass embryos: a multi-site approach
Venue: Journal of Comparative Physiology B

Embryonic osmoregulation effected by embryonic ionocytes in the European sea bass Dicentrarchus labrax has been studied at several sites, including the yolk sac membrane, the first gill slits and the gut ionocytes. D. labrax embryos, spawned in seawater (SW) (39 ‰), were exposed to dilute seawater (DSW) (5 ‰) during 48 h, from stage 10 pairs of somites (10S) to hatching time (HT). Control embryos originating from the same spawn were maintained in SW. Both SW and DSW embryos were examined after 24- and 48-h exposure. Nanoosmometric measurements of the embryonic fluids osmolality suggest that late embryos are confronted with the variations in external salinity and that they were able to slightly regulate their osmolality. Immunolocalization of Na+/K+ ATPase, NKCC and CFTR has shown that DSW-exposed embryos can limit ion losses due to compensatory physiological mechanisms. CFTR and NKCC were not observed in DSW embryos in the yolk sac ionocytes and in the tegumentary ionocytes of the gill slits. The quantification of mRNA indicated that NKA, NKCC1 and CFTR transcript levels increased from stage 10S to stage HT. At stage HT, following 48 h of DSW- or SW-exposure, different responses were observed according to salinity. These results, when compared to those obtained in D. labrax juveniles and adults long-term exposed to fresh water (FW), show that in embryos the physiological response following a short-term DSW exposure is different. The mechanisms of hyper-osmoregulation observed in D. labrax embryos, although not fully efficient, allow their survival for several days in DSW.
Interspecific variation in thermoregulation among three sympatric bats inhabiting a hot, semi-arid environment
Venue: Journal of Comparative Physiology B

Bats in hot roosts experience some of the most thermally challenging environments of any endotherms, but little is known about how heat tolerance and evaporative cooling capacity vary among species. We investigated thermoregulation in three sympatric species (Nycteris thebaica, Taphozous mauritianus and Sauromys petrophilus) in a hot, semi-arid environment by measuring body temperature (Tb), metabolic rate and evaporative water loss (EWL) at air temperatures (Ta) of 10–42 °C. S. petrophilus was highly heterothermic with no clear thermoneutral zone, and exhibited rapid increases in EWL at high Ta to a maximum of 23.7 ± 7.4 mg g−1 h−1 at Ta ≈ 42 °C, with a concomitant maximum Tb of 43.7 ± 1.0 °C. T. mauritianus remained largely normothermic at Tas below thermoneutrality and increased EWL to 14.7 ± 1.3 mg g−1 h−1 at Ta ≈ 42 °C, with a maximum Tb of 42.9 ± 1.6 °C. In N. thebaica, EWL began increasing at lower Ta than in either of the other species and reached a maximum of 18.6 ± 2.1 mg g−1 h−1 at Ta = 39.4 °C, with comparatively high maximum Tb values of 45.0 ± 0.9 °C. Under the conditions of our study, N. thebaica was considerably less heat tolerant than the other two species. Among seven species of bats for which data on Tb as well as roost temperatures in comparison to outside Ta are available, we found limited evidence for a correlation between overall heat tolerance and the extent to which roosts are buffered from high Ta.
Hepatic carbamoyl phosphate synthetase (CPS) I and urea contents in the hylid tree frog, Litoria caerulea: transition from CPS III to CPS I
Venue: Journal of Comparative Physiology B

The complete cDNA sequence of CPS I obtained from the liver of the hylid tree frog, Litoria caerulea, consisted of 4,485 bp which coded for 1,495 amino acids with an estimated molecular mass of 163.7 kDa. The deduced CPS I consisted of a mitochondrial targeting sequence of 33 amino acid residues, a glutaminase amidotransferase component spanning from tyrosine 95 to leucine 425, and a methylglyoxal synthetase-like component spanning from valine 441 to lysine 1566. It also comprised two cysteine residues (cysteine 1360 and cysteine 1370) that are characteristic of N-acetyl-l-glutamate dependency. Similar to the CPS I of Ranacatesbeiana and Cps III of lungfishes and teleosts, it contained the Cys–His–Glu catalytic triad (cysteine 304, histidine 388 and glutamate 390). All Cps III contain methionine 305 and glutamine 308, which are essential for the Cys–His–Glu triad to react with glutamine, but the CPS I of R.catesbeiana contains lysine 305 and glutamate 308, and therefore cannot effectively utilize glutamine as a substrate. However, the CPS I of L. caerulea, unlike that of R.catesbeiana, contained besides glutamate 308, methionine 305 instead of lysine 305, and thus represented a transitional form between Cps III and CPS I. Indeed, CPS I of L. caerulea could utilize glutamine or NH4+ as a substrate in vitro, but the activity obtained with glutamine + NH4+ reflected that obtained with NH4+ alone. Furthermore, only <5 % of the glutamine synthetase activity was present in the hepatic mitochondria, indicating that CPS I of L. caerulea did not have an effective supply of glutamine in vivo. Hence, our results confirmed that the evolution of CPS I from Cps III occurred in amphibians. Since L. caerulea contained high levels of urea in its muscle and liver, which increased significantly in response to desiccation, its CPS I had the dual functions of detoxifying ammonia to urea and producing urea to reduce evaporative water loss.