nils-herrmann/clean_scirepeval huggingface dataset:
Egocentric and geocentric navigation during extremely long foraging paths of desert ants
Venue: Journal of Comparative Physiology A

Desert ants, Cataglyphis fortis, navigate individually in the salt pans of Tunisia by means of path integration. However, as path integration is error-prone, the ants in addition use visual and olfactory cues to pinpoint their nest entrance. It has been shown that the accuracy of the path integrator as well as the ants’ confidence in that egocentric navigational tool decreases with increasing foraging distance. Here, we show that despite the accumulating errors, even after far-reaching foraging runs path integration provides the ants with surprisingly accurate information regarding the nest position. However, in addition, the ants take into account distant visual cues that are most probably provided by the patterns along the horizon line behind the nest entrance.
Warming up and shipping out: arousal and emergence timing in hibernating little brown bats (Myotis lucifugus)
Venue: Journal of Comparative Physiology B

Phenology refers to the timing of events in the annual cycle of organisms. For temperate-zone mammals, hibernation is one such event, but little is known about its phenology. Hibernation consists of energy-saving torpor bouts interspersed with energetically expensive arousals to normothermic Tb, and hibernators should benefit from mechanisms which reduce arousal costs and help them time arousals to coincide with foraging opportunities. In a previous study, we showed that, in contrast to hibernating bats from warmer climates, little brown bats (Myotis lucifugus) from central Canada abandon a circadian pattern to arousal in the middle of winter when there is no chance of feeding. Here, we used temperature telemetry to test whether they would re-synchronize arousals with normal foraging time (i.e. sunset) during late winter as the chance of foraging or emergence opportunities improves, and whether they would synchronize arousals with conspecifics, possibly to exploit social thermoregulation. We also used passive transponders to test whether energy reserves and/or sex differences in reproductive timing influence phenology and the sensitivity of emergence timing to environmental cues. In contrast to patterns in mid-winter, after 7 April 2013, bats synchronized arousals with sunset and with conspecifics. Females emerged earlier than males, and females in the best condition emerged first while body condition had no influence on male emergence timing. Both male and female bats appeared to time emergence with falling barometric pressure, a cue that predicts favourable foraging conditions for bats but which, unlike outside temperature, would have been readily detectable by bats inside the hibernaculum. Our results highlight hibernation traits associated with extreme winter energy limitation for insect-eating bats in cold climates and illustrate the influence of reproductive timing and environmental conditions on hibernation energetics and phenology.
Neural response in vestibular organ of Helix aspersa to centrifugation and re-adaptation to normal gravity
Venue: Journal of Comparative Physiology A

Gravity plays a key role in shaping the vestibular sensitivity (VS) of terrestrial organisms. We studied VS changes in the statocyst of the gastropod Helix aspersa immediately after 4-, 16-, and 32-day exposures to a 1.4G hypergravic field or following a 7-day recovery period. In the same animals we measured latencies of behavioral “negative gravitaxis” responses to a head-down pitch before and after centrifugation and found significant delays after 16- and 32-day runs. In an isolated neural preparation we recorded the electrophysiological responses of the statocyst nerve to static tilt (±19°) and sinusoids (±12°; 0.1 Hz). Spike sorting software was used to separate individual sensory cells’ patterns out of a common trace. In correspondence with behavior we observed a VS decrease in animals after 16- (p < 0.05) and 32-day (p < 0.01) centrifugations. These findings reveal the capability of statoreceptors to adjust their sensitivity in response to a prolonged change in the force of gravity. Interestingly, background discharge rate increased after 16 and 32 days in hypergravity and continued to rise through the recovery period. This result indicates that adaptive mechanisms to novel gravity levels were long lasting, and re-adaptation from hypergravity is a more complex process than just “return to normal”.
Nitrogen metabolism, acid–base regulation, and molecular responses to ammonia and acid infusions in the spiny dogfish shark (Squalus acanthias)
Venue: Journal of Comparative Physiology B

Although they are ureotelic, marine elasmobranchs express Rh glycoproteins, putative ammonia channels. To address questions raised by a recent study on high environmental ammonia (HEA) exposure, dogfish were intravascularly infused for 24 h at 3 ml kg−1 h−1 with isosmotic NaCl (500 mmol l−1, control), NH4HCO3 (500 mmol l−1), NH4Cl (500 mmol l−1), or HCl (as 125 mmol l−1 HCl + 375 mmol l−1 NaCl). While NaCl had no effect on arterial acid–base status, NH4HCO3 caused mild alkalosis, NH4Cl caused strong acidosis, and HCl caused lesser acidosis, all predominantly metabolic in nature. Total plasma ammonia (TAmm) and excretion rates of ammonia (JAmm) and urea-N (JUrea-N) were unaffected by NaCl or HCl. However, despite equal loading rates, plasma TAmm increased to a greater extent with NH4Cl, while JAmm increased to a greater extent with NH4HCO3 due to much greater increases in blood-to-water PNH3 gradients. As with HEA, both treatments caused large (90 %) elevations of JUrea-N, indicating that urea-N synthesis by the ornithine-urea cycle (OUC) is driven primarily by ammonia rather than HCO3−. Branchial mRNA expressions of Rhbg and Rhp2 were unaffected by NH4HCO3 or NH4Cl, but v-typeH+-ATPase was down-regulated by both treatments, and Rhbg and Na+/H+ exchanger NHE2 were up-regulated by HCl. In the kidney, Rhbg was unresponsive to all treatments, but Rhp2 was up-regulated by HCl, and the urea transporter UT was up-regulated by HCl and NH4Cl. These responses are discussed in the context of current ideas about branchial, renal, and OUC function in this nitrogen-limited predator.
Biochemical characteristics and modulation by external and internal factors of aminopeptidase-N activity in the hepatopancreas of a euryhaline burrowing crab
Venue: Journal of Comparative Physiology B

Strikingly, in spite of its physiological importance, information about occurrence, biochemical characteristics and mechanisms of regulation of aminopeptidase-N (APN) in the hepatopancreas of intertidal euryhaline crabs is still lacking. In this work, we determined the occurrence, biochemical characteristics, response to environmental salinity and dopamine of APN in the hepatopancreas of the euryhaline crab Neohelice granulata (Dana 1851) from the open mudflat of Mar Chiquita coastal lagoon (Buenos Aires province, Argentina). APN activity was maximal at pH and temperature range of 7.6–9.0 and 37–45 °C, respectively. APN activity exhibited Michaelis–Menten kinetics (apparent Km = 0.19 ± 0.10 mM) (pH 7.6, 37 °C) and appeared to be sensitive to bestatin (I50 = 15 mM) and EDTA (I50 = 9 mM). In crabs acclimated to 10 psu (hyper-regulation conditions) and 37 psu (hypo-regulation conditions), APN activity was about 45 and 160 % higher, respectively, than in 35 psu (osmoconformation). APN activity in the hepatopancreas was stimulated in vitro (about 137 %) by 10−4 M dopamine. Higher dopamine concentrations produced a similar extent of increase. The responses of APN activity to salinity and dopamine in vitro suggest the role of APN in digestive adjustments upon hyper and hypo-regulatory conditions and its modulation via direct mechanisms on hepatopancreas by dopamine.
Timing matters: corticosterone injections 4 h before ovulation bias sex ratios towards females in chickens
Venue: Journal of Comparative Physiology B

Birds have the ability to influence offspring sex prior to egg laying and may use hormones to mediate these skews. Corticosterone is of particular interest as a mediator of offspring sex because, as the primary stress hormone in birds, it regulates responses to environmental and social stimuli that trigger sex ratio biases. In previous studies in birds, chronic elevations of corticosterone stimulated female-biased sex ratios while acute pharmacological elevations that were provided 5 h prior to the expected time of ovulation stimulated male-biased sex ratios. Here, we aimed to determine the magnitude of corticosterone necessary to influence offspring sex and to further pinpoint the timing of the hormonal influence. Because high-dose injections of corticosterone stimulated male-biased sex ratios in hens, we hypothesized that females receiving acute pharmacological elevations of corticosterone would produce more male offspring while females with acute physiological elevations would produce an intermediate proportion of males compared to controls. We tested our hypotheses in laying hens by elevating corticosterone in the physiological or pharmacological range through injections of corticosterone administered 4 or 5 h prior to the expected time of ovulation. Contrary to our hypothesis, a physiological dose of corticosterone provided 5 h prior to the expected time of ovulation did not bias offspring sex ratios when compared to controls. Further, when corticosterone injections were given at 4 h prior to the expected time of ovulation, sex ratios were instead biased towards females. These results suggest that the timing and magnitude of the corticosterone elevation are both critical not only to whether a sex ratio bias occurs, but also the direction of the bias.
Acute and chronic temperature effects on cardiovascular regulation in the red-eared slider (Trachemys scripta)
Venue: Journal of Comparative Physiology B

Acute and chronic changes in ambient temperature alter several aspects of reptilian physiology. We investigated the effects of each type of temperature change on reptilian cardiovascular regulation in red-eared slider turtles (Trachemys scripta), a species known to experience marked seasonal changes in ambient temperature. Turtles were instrumented with occlusive catheters in the femoral artery and vein. Following an acclimation period of 10 days at 13 °C (131), cardiovascular responses to adrenaline, and the cardiac limb of the baroreflex were quantified. Ambient temperature was then reduced 1 °C day−1 until 3 °C was reached (31). Turtles were maintained at this temperature for 1-week before cardiovascular responses were reassessed. Turtles were then gradually (1 °C day−1) returned to an ambient temperature of 13 °C, (132). After a 1-week re-acclimation period, cardiovascular responses were again determined. Finally, 1-week post-pharmacological manipulation of turtles in the 132 treatment, ambient temperature was reduced to 3 °C over 24 h (32), and cardiovascular responses were again assessed. Temperature reduction from 131 to 31 decreased mean arterial blood pressure (Pm) and heart rate (fH) by ~38 and ~63 %, respectively. Acute temperature reduction, from 132 to 32, decreased fH similarly, ~66 %; however, while Pm decreased ~28 %, this was not significantly different than Pm at 132. The adrenaline injections increased fH ranging from 90 to 170 % at 13 °C which was a greater change than that observed at 3 °C ranging from a 40 to 70 % increase. The increase in Pm at the lowest dose of adrenaline did not differ across the temperature treatment groups. The operational point (set-point) Pm of the baroreflex was decreased similarly by both methods of temperature reduction (31 or 32). Further, a hypertensive cardiac baroreflex was absent in the majority of the animals studied independent of temperature. Baroreflex gain and normalized gain based on individual estimates of the relationship were decreased by temperature reduction similarly. Collectively, the data suggest that red-eared slider turtles modulate (down-regulate) some cardiovascular control mechanisms during reduced ambient temperature.
Species-specificity of temporal processing in the auditory midbrain of gray treefrogs: interval-counting neurons
Venue: Journal of Comparative Physiology A

Interval-counting neurons (ICNs) respond after a threshold number of sound pulses have occurred with specific intervals; a single aberrant interval can reset the counting process. Female gray treefrogs, Hyla chrysoscelis and H. versicolor, discriminate against synthetic ‘calls’ possessing a single interpulse interval 2–3 three times the optimal value, suggesting that ICNs are important for call recognition. The calls of H. versicolor consist of pulses that are longer in duration, rise more slowly in amplitude and are repeated at a slower rate than those of H. chrysoscelis. Results of recordings from midbrain auditory neurons in these species include: (1) ICNs were found in both species and their temporal selectivity appeared to result from interplay between excitation and inhibition; (2) band-pass cells in H. versicolor were tuned to slower pulse rates than those in H. chrysoscelis; (3) ICNs that were selective for slow-rise pulse shape were found almost exclusively in H. versicolor, but fast-rise-selective neurons were found in both species, and (4) band-suppression ICNs in H. versicolor showed response minima at higher pulse rates than those in H. chrysoscelis. Selectivity of midbrain ICNs for pulse rise time and repetition rate thus correlate well with discriminatory abilities of these species that promote reproductive isolation.
Effect of the small-world structure on encoding performance in the primary visual cortex: an electrophysiological and modeling analysis
Venue: Journal of Comparative Physiology A

The biological networks have been widely reported to present small-world properties. However, the effects of small-world network structure on population’s encoding performance remain poorly understood. To address this issue, we applied a small world-based framework to quantify and analyze the response dynamics of cell assemblies recorded from rat primary visual cortex, and further established a population encoding model based on small world-based generalized linear model (SW-GLM). The electrophysiological experimental results show that the small world-based population responses to different topological shapes present significant variation (t test, p < 0.01; effect size: Hedge’s g > 0.8), while no significant variation was found for control networks without considering their spatial connectivity (t test, p > 0.05; effect size: Hedge’s g < 0.5). Furthermore, the numerical experimental results show that the predicted response under SW-GLM is more accurate and reliable compared to the control model without small-world structure, and the decoding performance is also improved about 10 % by taking the small-world structure into account. The above results suggest the important role of the small-world neural structure in encoding visual information for the neural population by providing electrophysiological and theoretical evidence, respectively. The study helps greatly to well understand the population encoding mechanisms of visual cortex.
Comparative histology of the adult electric organ among four species of the genus Campylomormyrus (Teleostei: Mormyridae)
Venue: Journal of Comparative Physiology A

The electric organ (EO) of weakly electric mormyrids consists of flat, disk-shaped electrocytes with distinct anterior and posterior faces. There are multiple species-characteristic patterns in the geometry of the electrocytes and their innervation. To further correlate electric organ discharge (EOD) with EO anatomy, we examined four species of the mormyrid genus Campylomormyrus possessing clearly distinct EODs. In C. compressirostris, C. numenius, and C. tshokwe, all of which display biphasic EODs, the posterior face of the electrocytes forms evaginations merging to a stalk system receiving the innervation. In C. tamandua that emits a triphasic EOD, the small stalks of the electrocyte penetrate the electrocyte anteriorly before merging on the anterior side to receive the innervation. Additional differences in electrocyte anatomy among the former three species with the same EO geometry could be associated with further characteristics of their EODs. Furthermore, in C. numenius, ontogenetic changes in EO anatomy correlate with profound changes in the EOD. In the juvenile the anterior face of the electrocyte is smooth, whereas in the adult it exhibits pronounced surface foldings. This anatomical difference, together with disparities in the degree of stalk furcation, probably contributes to the about 12 times longer EOD in the adult.
Motion cues improve the performance of harnessed bees in a colour learning task
Venue: Journal of Comparative Physiology A

The proboscis extension conditioning (PER) is a successful behavioural paradigm for studying sensory and learning mechanisms in bees. Whilst mainly used with olfactory and tactile stimuli, more recently reliable PER conditioning has been achieved with visual stimuli such as colours and looming stripes. However, the results reported in different studies vary quite strongly, and it remains controversially discussed how to best condition visual PER. It is particularly striking that visual PER leads to more limited performance as compared to visual conditioning of free-flying bees. It could be that visual PER learning is affected by the lack of movement and that the presence of visual motion cues could compensate for it. We tested whether bees would show differences in learning performances when conditioned either with a colour and motion stimulus in combination or with colour alone. Colour acquisition was improved in the presence of the motion stimulus. The result is consistent with the idea that visual learning might be tightly linked to movement in bees, given that they use vision predominantly during flight. Our results further confirm recent findings that successful visual PER conditioning in bees is achievable without obligatorily removing the antennae.
Hearing thresholds of swimming Pacific bluefin tuna Thunnus orientalis
Venue: Journal of Comparative Physiology A

Pacific bluefin tuna (Thunnus orientalis) is a highly migratory, commercially valuable species potentially vulnerable to acoustic noise generated from human activities which could impact behavior and fitness. Although significant efforts have been made to understand hearing abilities of fishes, the large size and need to continuously swim for respiration have hindered investigations with tuna and other large pelagic species. In this study, Pacific bluefin tuna were trained to respond to a pure tone sound stimulus ranging 325–800 Hz and their hearing abilities quantified using a staircase psychophysical technique. Hearing was most sensitive from 400 to 500 Hz in terms of particle motion (radial acceleration −88 dB re 1 m s−2; vertical acceleration −86 dB re 1 m s−2) and sound pressure (83 dB re 1 μPa). Compared to yellowfin tuna (Thunnus albacares) and kawakawa (Euthynnus affinis), Pacific bluefin tuna has a similar bandwidth of hearing and best frequency, but greater sensitivity overall. Careful calibration of the sound stimulus and experimental tank environment, as well as the adoption of behavioral methodology, demonstrates an experimental approach highly effective for the study of large fish species in the laboratory.
Level-tolerant duration selectivity in the auditory cortex of the velvety free-tailed bat Molossus molossus
Venue: Journal of Comparative Physiology A

It has been reported previously that in the inferior colliculus of the bat Molossus molossus, neuronal duration tuning is ambiguous because the tuning type of the neurons dramatically changes with the sound level. In the present study, duration tuning was examined in the auditory cortex of M. molossus to describe if it is as ambiguous as the collicular tuning. From a population of 174 cortical 104 (60 %) neurons did not show duration selectivity (all-pass). Around 5 % (9 units) responded preferentially to stimuli having longer durations showing long-pass duration response functions, 35 (20 %) responded to a narrow range of stimulus durations showing band-pass duration response functions, 24 (14 %) responded most strongly to short stimulus durations showing short-pass duration response functions and two neurons (1 %) responded best to two different stimulus durations showing a two-peaked duration–response function. The majority of neurons showing short- (16 out of 24) and band-pass (24 out 35) selectivity displayed “O-shaped” duration response areas. In contrast to the inferior colliculus, duration tuning in the auditory cortex of M. molossus appears level tolerant. That is, the type of duration selectivity and the stimulus duration eliciting the maximum response were unaffected by changing sound level.
Salt concentration and solar orientation in two supralittoral sandhoppers: Talitrus saltator (Montagu) and Talorchestia ugolinii Bellan Santini and Ruffo
Venue: Journal of Comparative Physiology A

The influence of salt concentration in the seawater on solar orientation in Talitrus saltator and Talorchestia ugolinii was studied in a confined environment (transparent plexiglass bowls). Sodium and calcium concentrations strongly affect both sea–land orientation and the sun compass mechanism in T.saltator, whereas the behaviour of T. ugolinii is less influenced. The absence of Na+ does not influence the sun compass mechanism, but causes an inversion in the mean direction of orientation in T. saltator. In T. ugolinii, there was no influence on the compass mechanism for solar orientation and no inversion in the directional choice. In the absence of Ca2+, a photonegative tendency was observed for T saltator together with marked reduction in the capacity to go in any direction. However, the effect of Ca2+ absence on the orientation capacity of T. saltator is reversible and the orientation capacity can be reduced in a few minutes. The different behaviour of the two species of sandhoppers is discussed.
The effect of light intensity on prey detection behavior in two Lake Malawi cichlids, Aulonocara stuartgranti and Tramitichromis sp.
Venue: Journal of Comparative Physiology A

Two sand-dwelling cichlids from Lake Malawi (Aulonocara stuartgranti, Tramitichromis sp.) that feed on benthic invertebrates, but have different lateral line phenotypes, use lateral line and/or visual cues to detect prey under light versus dark conditions. The current study examined how ecologically relevant variation in light intensity [0–800 lux (lx)] influences detection of prey (mobile, immobile) in each species by analyzing six behavioral parameters. Both species fed at light intensities ≥1 lx and trends in behavior among light intensities were informative. However, prey type and/or time of day (but not light intensity) predicted all four parameters analyzed with generalized linear mixed models in A. stuartgranti, whereas the interaction of light intensity and time of day predicted three of these parameters in Tramitichromis sp. Data suggest that the critical light intensity is 1–12 lx for both species, that the integration of visual and lateral line input explains differences in detection of mobile and immobile prey and behavioral changes at the transition from 1 to 0 lx in A. stuartgranti, and that Tramitichromis sp. likely uses binocular vision to locate prey. Differences in the sensory biology of species that exploit similar prey will have important implications for the trophic ecology of African cichlid fishes.