nils-herrmann/clean_scirepeval huggingface dataset:
Taste-mediated behavioral and electrophysiological responses by the predatory fish Ariopsis felis to deterrent pigments from Aplysia californica ink
Venue: Journal of Comparative Physiology A

Chemical defenses are used by many organisms to avoid predation, and these defenses may function by stimulating predators’ chemosensory systems. Our study examined detection mechanisms for components of defensive ink of sea hares, Aplysia californica, by predatory sea catfish, Ariopsis felis. Behavioral analyses show aplysioviolin and phycoerythrobilin are detected intra-orally and by barbels and are deterrent at concentrations as low as 0.1% full strength. We performed electrophysiological recordings from the facial–trigeminal nerve complex innervating the maxillary barbel and tested aplysioviolin, phycoerythrobilin, amino acids, and bile salts in cross-adaptation experiments. Amino acids and bile salts are known stimulatory compounds for teleost taste systems. Our results show aplysioviolin and phycoerythrobilin are equally stimulatory and completely cross-adapt to each other’s responses. Adaptation to aplysioviolin or phycoerythrobilin reduced but did not eliminate responses to amino acids or bile salts. Adaptation to amino acids or bile salts incompletely reduced responses to aplysioviolin or phycoerythrobilin. The fact that cross-adaptations with aplysioviolin and phycoerythrobilin were not completely reciprocal indicates there are amino acid and bile salt sensitive fibers insensitive to aplysioviolin and phycoerythrobilin. These results indicate two gustatory pathways for aplysioviolin and phycoerythrobilin: one independent of amino acids and bile salts and another shared with some amino acids.
Seasonal leptin resistance is associated with impaired signalling via JAK2-STAT3 but not ERK, possibly mediated by reduced hypothalamic GRB2 protein
Venue: Journal of Comparative Physiology B

The Siberian hamster, Phodopus sungorus, undergoes a striking seasonal cycle of leptin sensitivity and body weight regulation, but the molecular mechanism and relevance to human leptin insensitivity are unknown. Here we show that nuclear translocation of phospho-STAT3 in the hypothalamus is rapidly stimulated by leptin to a greater extent in hamsters held in short-day length (SD) as compared to long-day length (LD). Intriguingly, effects of leptin on STAT3 appeared to be in part limited to nuclear translocation of phospho-STAT3 associated with the cell surface rather than phosphorylation of STAT3. The number of phospho-ERK cells within the hypothalamus was unaffected by either photoperiod or leptin. However, proximal to ERK phosphorylation, hypothalamic SH2-containing tyrosine phosphatase (SHP2) and the small growth factor receptor-binding protein (GRB2), which act as competitive negative modulators on binding of SOCS3 to leptin receptor (LRb)-associated Tyr985, were increased in SD compared to LD. Our findings suggest that activation of STAT3 by leptin may be dependent on interaction of stimulatory SHP2/GRB2 as well as inhibitory SOCS3 on the level of competitive binding to LRb-associated Tyr985. This hypothetical mechanism may represent the molecular identity of seasonally induced adjustments in leptin sensitivity and may be applied to investigating leptin sensitivity in other rodent models.
Particle motion is broadly represented in the vestibular medulla of the bullfrog across larval development
Venue: Journal of Comparative Physiology A

In their shallow-water habitats, bullfrog (Rana catesbeiana) tadpoles are exposed to both underwater and airborne sources of acoustic stimulation. We probed the representation of underwater particle motion throughout the tadpole’s dorsal medulla to determine its spatial extent over larval life. Using neurobiotin-filled micropipettes, we recorded neural activity to z-axis particle motion (frequencies of 40–200 Hz) in the medial vestibular nucleus, lateral vestibular nucleus, dorsal medullary nucleus (DMN), and along the dorsal arcuate pathway. Sensitivity was comparable in the medial and lateral vestibular nuclei, with estimated thresholds between 0.016 and 12.5 μm displacement. Neither best responding frequency nor estimated threshold varied significantly over larval stage. Transport of neurobiotin from active recording sites was also stable over development. The DMN responded poorly to z-axis particle motion, but did respond to low-frequency pressure stimulation. These data suggest that particle motion is represented widely and stably in the tadpole’s vestibular medulla. This is in marked contrast to the representation of pressure stimulation in the auditory midbrain, where a transient “deaf period” of non-responsiveness and decreased connectivity occurs immediately prior to metamorphic climax. We suggest that, in bullfrogs, sensitivity to particle motion and to pressure follows different developmental trajectories.
Nuclear DNA content variation associated with muscle fiber hypertrophic growth in fishes
Venue: Journal of Comparative Physiology B

Muscle fiber hypertrophic growth can lead to an increase in the myonuclear domain (MND), leading to greater diffusion distances within the cytoplasmic volume that each nucleus services. We tested the hypothesis that hypertrophic growth in the white muscle of fishes was associated with increases in the mean DNA content of nuclei, which may be a strategy to offset increasing diffusion constraints. DAPI-stained chicken erythrocytes standards and image analysis were used to estimate nuclear DNA content in erythrocytes and muscle fibers from 17 fish species. Mean diploid (2C) values in fish erythrocytes ranged from 0.78 to 7.2 pg. Erythrocyte 2C values were used to determine ploidy level in muscle tissue of small and large size classes of each species. Within each species, mean muscle fiber diameter was greater in the large size class than the small size class, and MND was significantly greater in larger fibers for 11 of the 17 species. Nuclear DNA content per species in muscle ranged from 2 to 64C. Fiber-size dependent increases in ploidy were observed in nine species, which is consistent with our hypothesis and indicates that endoreduplication is occurring during fiber growth. However, two species exhibited significantly lower ploidy in the larger size class, and the mechanistic basis and potential advantage of this ploidy shift is unclear. These results suggest that increases in ploidy may be a common mechanism to compensate for increases in MND associated with fiber hypertrophy in fishes, although it is likely that other factors also affect ploidy changes that occur in muscle during animal growth.
Both seawater acclimation and environmental ammonia exposure lead to increases in mRNA expression and protein abundance of Na+:K+:2Cl− cotransporter in the gills of the climbing perch, Anabas testudineus
Venue: Journal of Comparative Physiology B

The freshwater climbing perch, Anabas testudineus, is an obligatory air-breathing teleost which can acclimate to seawater, survive long period of emersion, and actively excrete ammonia against high concentrations of environmental ammonia. This study aimed to clone and sequence the Na+:K+:2Cl− cotransporter (nkcc) from the gills of A. testudineus, and to determine the effects of seawater acclimation or exposure to 100 mmol l−1 NH4Cl in freshwater on its branchial mRNA expression. The complete coding cDNA sequence of nkcc from the gills of A. testudineus consisted of 3,495 bp, which was translated into a protein with 1,165 amino acid residues and an estimated molecular mass of 127.4 kDa. A phylogenetic analysis revealed that the translated Nkcc of A. testudineus was closer to fish Nkcc1a than to fish Nkcc1b or Nkcc2. After a progressive increase in salinity, there were significant increases in the mRNA expression and protein abundance of nkcc1a in the gills of fish acclimated to seawater as compared with that of the freshwater control. Hence, it can be concluded that similar to marine teleosts, Cl− excretion through basolateral Nkcc1 of mitochondrion-rich cells (MRCs) was essential to seawater acclimation in A. testudineus. Exposure of A. testudineus to 100 mmol l−1 NH4Cl for 1 or 6 days also resulted in significant increases in the mRNA expression of nkcc1a in the gills, indicating a functional role of Nkcc1a in active ammonia excretion. It is probable that NH4+ enter MRCs through basolateral Nkcc1a before being actively transported across the apical membrane. Since the operation of Nkcc1a would lead to an increase in the intracellular Na+ concentration, it can be deduced that an upregulation of basolateral Na+/K+-ATPase (Nka) activity would be necessary to compensate for the increased influx of Na+ into MRCs during active NH4+ excretion. This would imply that the main function of Nka in active NH4+ excretion is to maintain intracellular Na+ and K+ homeostasis instead of transporting NH4+ directly into MRCs as proposed previously. In conclusion, active salt secretion during seawater acclimation and active NH4+ excretion during exposure to ammonia in freshwater could involve similar transport mechanisms in the gills of A. testudineus.
The activity of leech motoneurons during motor patterns is regulated by intrinsic properties and synaptic inputs
Venue: Journal of Comparative Physiology A

The activity of motoneurons during motor patterns depends on their intrinsic properties and on synaptic inputs. This study analyzed the properties of two leech motoneurons: the excitors of dorsal longitudinal muscles (DE-3) and of dorsal and ventral longitudinal muscles (MN-L) in basal conditions (normal and high Mg2+ saline) and during crawling. The voltage–current relationships in DE-3 and MN-L were similar. The curves exhibited the largest slope around resting potential, showed marked inward and outward rectification, and were not affected by high Mg2+. In response to 5-s pulses, DE-3 exhibited a fast initial adaptation, a slow recovery and a very slow late adaptation. High Mg2+ abolished the initial high frequency. The frequency–voltage relationship for the rest of the response was highly similar in normal and in high Mg2+ saline. MN-L exhibited a minor initial adaptation and then fired steadily. High Mg2+ diminished the frequency–voltage relationship. During crawling DE-3 and MN-L fired in phase and their frequency–voltage curves overlapped with the lower end of the curves obtained in basal conditions. The results suggest that the activity of these motoneurons during crawling was regulated, to a large extent, by synaptic inputs.
The physiology of the honey possum, Tarsipes rostratus, a small marsupial with a suite of highly specialised characters: a review
Venue: Journal of Comparative Physiology B

Field and laboratory studies of the iconic nectarivorous and ‘pollenivorous’ honey possum, Tarsipes rostratus, are reviewed with the aim of identifying aspects of its physiology that are as yet poorly understood and needed to implement management strategies for its long-term conservation. Dietary specialisations include the loss of teeth, a modified gut with a high rate of passage, exceptionally low minimum nitrogen requirements, an apparently high basal metabolic rate and a permanently polyuric kidney. In contrast, its reproductive physiology is plesiomorphic, combining aspects such as a post-partum oestrus, embryonic diapause, photoperiodicity and extended maternal care that are usually separate characteristics of other marsupial groups. In common with a number of other marsupials, the honey possum has the potential for trichromatic colour vision and has been the subject of several studies attempting to correlate visual quality with ecological realities. Field physiological studies have established its high rates of nectar and pollen intake needed to maintain energy balance and highlight the need for a constant intake from floral sources. Early allometric studies suggesting that the honey possum’s relatively low reproductive rate may be linked to a diet limited in protein have not been supported and nitrogen intakes in the field exceed by a factor of 10 the animal’s basic requirements for balance. Measurements of rates of protein turnover in field-caught lactating females suggest that they divert nitrogen from the protein pool to milk production by reducing rates of degradation, rather than by increasing rates of synthesis of protein. Although not yet an endangered species, the honey possum’s habitat has been drastically reduced since European occupation of Australia and future-targeted research on the animal’s unique physiology and habitat linkage is needed that can be translated into effective management practices. Only then will its long-term survival be assured.
Analysis of GABA-induced inhibition of spontaneous firing in chick accessory lobe neurons
Venue: Journal of Comparative Physiology A

It has been hypothesized that chick accessory lobes (ALs) contain functional neurons and act as a sensory organ of equilibrium. It was reported that neurons located in an outer layer of ALs showed γ-aminobutyric acid (GABA)- and glutamic acid decarboxylase (GAD)-like immunoreactivity more strongly than centrally located neurons, which were surrounded by the GAD-immunoreactive terminals. We investigated effects of GABA on the electrical activity of AL neurons. About 50% of embryonic AL neurons exhibited spontaneous firing. In the on-cell recording, GABA, muscimol, and GABA in combination with CGP35348 inhibited this firing. In whole-cell voltage clamp recordings, GABA and muscimol evoked a transient current. The mean reversal potential of GABA-evoked currents was close to the theoretical reversal potential of Cl−. These results indicate that GABA exerts the inhibitory effect on the firing through the activation of GABAA receptors. In addition, the intracellular concentration of Cl− was estimated to be about 16 mM in measurements with the gramicidin-perforated configuration, indicating the physiological reversal potential of the GABA current was about −60 mV. In conclusion, AL neurons have an intrinsic mechanism to evoke the spontaneous firing, which can be arrested by the inhibitory mechanism through the activation of the GABAA receptors.
Serotonin modulates worker responsiveness to trail pheromone in the ant Pheidole dentata
Venue: Journal of Comparative Physiology A

As social insect workers mature, outside-nest tasks associated with foraging and defense are typically performed at higher frequencies. Foraging in ants is often a pheromonally mediated collective action performed by mature workers; age-dependent differences in olfactory response thresholds may therefore proximately regulate task repertoire development. In the ant Pheidole dentata, foraging activity increases with chronological age in minor workers, and is chemically controlled. The onset of foraging in minor workers is accompanied by marked neuroanatomical and neurochemical changes, including synaptic remodeling in olfactory regions of the brain, proliferation of serotonergic neurons, and increased brain titers of monoamines, notably serotonin. We examined the linkage of serotonin and olfactory responsiveness by assaying trail-following performance in mature P. dentata minor workers with normal serotonin levels, or serotonin levels experimentally lowered by oral administration of the serotonin synthesis inhibitor α-methyltryptophan (AMTP). By assessing responsiveness to standardized pheromone trails, we demonstrate that trail-following behaviors are significantly reduced in serotonin-depleted workers. AMTP-treated individuals were less likely to initiate trail following, and oriented along pheromone trails for significantly shorter distances than untreated, similar-age workers. These results demonstrate for the first time that serotonin modulates olfactory processes and/or motor functions associated with cooperative foraging in ants.
Warming up for dinner: torpor and arousal in hibernating Natterer’s bats (Myotis nattereri) studied by radio telemetry
Venue: Journal of Comparative Physiology B

The frequency and function of arousals during hibernation in free-living mammals are little known. We used temperature-sensitive radio transmitters to measure patterns of torpor, arousal and activity in wild Natterer’s bats Myotis nattereri during hibernation. Duration of torpor bouts ranged from 0.06 to 20.4 days with individual means ranging from 0.9 to 8.9 days. Arousals from torpor occurred most commonly coincident with the time (relative to sunset) typical for bats emerging from summer roosts to forage. Bats with lower body condition indices had a shorter average duration of their torpor bouts. We found a non-linear relationship between duration of torpor bout and ambient temperature: the longest average torpor bouts were at temperatures between 2 and 4°C with shorter bouts at lower and higher ambient temperatures. One individual was radio-tracked for ten nights, remained active for an average of 297 min each night and was active for longer on warmer nights. Our results suggest that vespertilionid bats use relatively short torpor bouts during hibernation in a location with a maritime climate. We hypothesise that Natterer’s bats time arousals to maximise opportunities for potential foraging during winter although winter feeding is not the sole determinant of arousal as bats still arouse at times when foraging is unlikely.
Regionalization in the eye of the grapsid crab Neohelice granulata (=Chasmagnathus granulatus): variation of resolution and facet diameters
Venue: Journal of Comparative Physiology A

Crabs have panoramic compound eyes, which can show marked regional specializations of visual acuity. These specializations are thought to be related to the particular features of the animal’s ecological environment. Modern knowledge on the neuroanatomy and neurophysiology of the crabs’ visual system mainly derives from studies performed in the grapsid crab Neohelice granulata (=Chasmagnathus granulatus). However, the organization of the visual sampling elements across the eye surface of this animal had not yet been addressed. We analyzed the sampling resolution across the eye of Neohelice by measuring the pseudopupil displacement with a goniometer. In addition, we measured the facet sizes in the different regions of the eye. We found that Neohelice possesses an acute band of high vertical resolution around the eye equator and an increase in horizontal sampling resolution and lenses diameter towards the lateral side of the eye. Therefore, the analysis of the optical apparatus indicates that this crab possesses greater visual acuity around the equator and at the lateral side of the eye. These specializations are compared with those found in different species of crabs and are discussed in connection to the particular ecological features of Neohelice’s habitat.
Signalling plasticity and energy saving in a tropical bushcricket
Venue: Journal of Comparative Physiology A

Males of the tropical bushcricket Mecopoda elongata synchronize their acoustic advertisement signals (chirps) in interactions with other males. However, synchrony is not perfect and distinct leader and follower roles are often maintained. In entrainment experiments in which conspecific signals were presented at various rates, chirps displayed as follower showed notable signal plasticity. Follower chirps were shortened by reducing the number and duration of syllables, especially those of low and medium amplitude. The degree of shortening depended on the time delay between leader and follower signals and the sound level of the entraining stimulus. The same signal plasticity was evident in male duets, with the effect that the last syllables of highest amplitude overlapped more strongly. Respiratory measurements showed that solo singing males producing higher chirp rates suffered from higher metabolic costs compared to males singing at lower rates. In contrast, respiratory rate was rather constant during a synchronous entrainment to a conspecific signal repeated at various rates. This allowed males to maintain a steady duty cycle, associated with a constant metabolic rate. Results are discussed with respect to the preference for leader signals in females and the possible benefits males may gain by overlapping their follower signals in a chorus.
Photic induction of locomotor activity is correlated with photic habitat in Anolis lizards
Venue: Journal of Comparative Physiology A

A variety of ecologically important behaviors, including circadian rhythms and seasonal reproduction, are influenced by non-visual responses to light, yet very little is known about the relationship between photic habitat and non-visual photoreception. Puerto Rican Anolis lizards have diverged into multiple photic niches, making them a good model for non-visual photosensory ecology. We investigated the photic induction of locomotor activity, a non-visual response to light, in four species of Anolis comprising two pairs of closely related, ecomorphologically similar species whose microhabitats differ in solar irradiance. We developed a device for continuous, automated detection and recording of anole locomotor activity, and used it to characterize activity under 12:12 h light–dark cycles. Next, we administered a series of 2-h light pulses during the dark period of the light–dark cycle and measured the increase in locomotor activity relative to baseline dark activity. Five different irradiances (ranging from very dim to daytime levels) were given to each individual lizard on separate nights. As expected, light caused an irradiance-dependent increase in locomotor activity in all four species. The responses at the highest irradiances were significantly greater in species occupying relatively more shaded habitats, suggesting that non-visual photoreception may be adapted to habitat light in Anolis lizards.
Temporal resolution for calling song signals by female crickets, Gryllus bimaculatus
Venue: Journal of Comparative Physiology A

A behavioural gap detection paradigm was used to determine the temporal resolution for song patterns by female crickets, Gryllus bimaculatus. For stimuli with a modulation depth of 100% the critical gap duration was 6–8 ms. A reduction of the modulation depth of gaps to 50% led either to an increase or a decrease of the critical gap duration. In the latter case, the critical gap duration dropped to 3–4 ms indicating a higher sensitivity of auditory processing. The response curve for variation of pulse period was not limited by temporal resolution. However, the reduced response to stimuli with a high duty cycle, and thus short pause durations, was in accordance with the limits of temporal resolution. The critical duration of masking pulses inserted into pauses was 4–6 ms. An analysis of the songs of males revealed that gaps (5.8 ms) and masking pulses (6.9 ms) were at detectable time scales for the auditory pathway of female crickets. However, most of the observed temporal variation of song patterns was tolerated by females. Critical cues such as pulse period and pulse duty cycle provided little basis for inter-individual selection by females.