nils-herrmann/clean_scirepeval huggingface dataset:
The metabolic responses and acid–base status after feeding, exhaustive exercise, and both feeding and exhaustive exercise in Chinese catfish (Silurus asotus Linnaeus)
Venue: Journal of Comparative Physiology B

Feeding and exhaustive exercise are known to elevate metabolism. However, acid–base status may be oppositely affected by the two processes. In this study, we first investigated the acid–base response of Chinese catfish to feeding (the meal size was about 8% of body mass) to test whether an alkaline tide (a metabolic alkalosis created by gastric HCl secretion after feeding) would occur. We then determined the combined effects of feeding and exhaustive exercise on excess post-exercise oxygen consumption and acid–base status to determine whether the alkaline tide induced by feeding protects against acid–base disturbance during exhaustive exercise and affects subsequent recovery. Arterial blood pH increased from 7.74 ± 0.02 before feeding to 7.88 ± 0.02 and plasma [HCO3−]pl increased from 5.42 ± 0.29 to 7.83 ± 0.37 mmol L−1 6 h after feeding, while feeding had no significant effect on $$ P_{{{\text{CO}}_{2} }} $$. Exhaustive exercise led to a significant reduction in pH by 0.46 units and a reduction of [HCO3−]pl by ~3 mmol L−1. Lactate concentrations in white muscle and plasma increased by 2.4 mmol L−1 and 13.4 μmol g−1, respectively. Fed fish had a higher pH and [HCO3−]pl than fasting fish at rest, and the reductions in pH (0.36 units) and [HCO3−]pl (~2 mmol L−1) were thus lower after exhaustive exercise. However, the recovery of acid–base status and metabolites were similar in digesting and fasting fish. Overall, a significant alkaline tide was found in Chinese catfish after feeding. The alkaline tide elicited by feeding significantly prevented the decreases in pH and [HCO3−]pl immediately after exhaustive exercise, but recovery from exhaustive exercise was not affected by digestion.
Physiological and behavioural responses to seasonal changes in environmental temperature in the Australian spiny crayfish Euastacus sulcatus
Venue: Journal of Comparative Physiology B

The strategies used by ectotherms to minimise the detrimental effects of suboptimal thermal environments on physiological performance are often related to whether they inhabit a terrestrial or aquatic environment. Most terrestrial ectotherms use thermoregulatory strategies to maintain body temperature within an optimal range, while many aquatic ectotherms utilise thermal acclimation to maintain performance over varying seasonal temperatures. This study aimed to elucidate the relative contributions of acclimation and behavioural thermoregulation to maintaining whole-animal performance over varying seasonal temperatures in the semi-terrestrial Lamington spiny crayfish (Euastacus sulcatus). Crayfish activity and surface temperatures were determined by means of radio tracking and behavioural observations. Field studies demonstrated that E. sulcatus is exposed to stable daily temperatures, varying only between seasons from 10°C in late winter to over 20°C in summer. Also, terrestrial behaviour corresponded to a small portion of crayfish time (1.13%), much lower than predicted, indicating that E. sulcatus has limited opportunity for behavioural thermoregulation. We also tested the effect of acclimation to either 10 or 20°C on chela strength and stamina. We found acclimation had a more marked effect on chela stamina than maximum strength measures; however, overall acclimatory capacity was limited in E. sulcatus. Thus, we found that the semi-terrestrial crayfish E. sulcatus used neither thermoregulatory behaviours nor physiological strategies to deal with seasonal changes in environmental temperature.
The role of succinate dehydrogenase and oxaloacetate in metabolic suppression during hibernation and arousal
Venue: Journal of Comparative Physiology B

Hibernation elicits a major reduction in whole-animal O2 consumption that corresponds with active suppression of liver mitochondrial electron transport capacity at, or downstream of, succinate dehydrogenase (SDH). During arousal from the torpor phase of hibernation this suppression is reversed and metabolic rates rise dramatically. In this study, we used the 13-lined ground squirrel (Ictidomys tridecemlineatus) to assess isolated liver mitochondrial respiration during the torpor phase of hibernation and various stages of arousal to elucidate a potential role of SDH in metabolic suppression. State 3 and state 4 respiration rates were seven- and threefold lower in torpor compared with the summer-active and interbout euthermic states. Respiration rates increased during arousal so that when body temperature reached 30°C in late arousal, state 3 and state 4 respiration were 3.3- and 1.8-fold greater than during torpor, respectively. SDH activity was 72% higher in interbout euthermia than in torpor. Pre-incubating with isocitrate [to alleviate oxaloacetate (OAA) inhibition] increased state 3 respiration rate during torpor by 91%, but this rate was still fourfold lower than that measured in interbout euthermia. Isocitrate pre-incubation also eliminated differences in SDH activity among hibernation bout stages. OAA concentration correlated negatively with both respiration rates and SDH activity. These data suggest that OAA reversibly inhibits SDH in torpor, but cannot fully account for the drastic metabolic suppression observed during this hibernation phase.
Anatomy and physics of the exceptional sensitivity of dolphin hearing (Odontoceti: Cetacea)
Venue: Journal of Comparative Physiology A

During the past 50 years, the high acoustic sensitivity and the echolocation behavior of dolphins and other small odontocetes have been studied thoroughly. However, understanding has been scarce as to how the dolphin cochlea is stimulated by high frequency echoes, and likewise regarding the ear mechanics affecting dolphin audiograms. The characteristic impedance of mammalian soft tissues is similar to that of water, and thus no radical refractions of sound, nor reflections of sound, can be expected at the water/soft tissue interfaces. Consequently, a sound-collecting terrestrial pinna and an outer ear canal serve little purpose in underwater hearing. Additionally, compared to terrestrial mammals whose middle ear performs an impedance match from air to the cochlea, the impedance match performed by the odontocete middle ear needs to be reversed to perform an opposite match from water to the cochlea. In this paper, we discuss anatomical adaptations of dolphins: a lower jaw collecting sound, thus replacing the terrestrial outer ear pinna, and a thin and large tympanic bone plate replacing the tympanic membrane of terrestrial mammals. The paper describes the lower jaw anatomy and hypothetical middle ear mechanisms explaining both the high sensitivity and the converted acoustic impedance match.
Thermal strategies and energetics in two sympatric colubrid snakes with contrasted exposure
Venue: Journal of Comparative Physiology B

The thermoregulatory strategy of reptiles should be optimal if ecological costs (predation risk and time devoted to thermoregulation) are minimized while physiological benefits (performance efficiency and energy gain) are maximized. However, depending on the exact shape of the cost and benefit curves, different thermoregulatory optima may exist, even between sympatric species. We studied thermoregulation in two coexisting colubrid snakes, the European whipsnake (Hierophis viridiflavus, Lacépède 1789) and the Aesculapian snake (Zamenis longissimus, Laurenti 1768) that diverge markedly in their exposure, but otherwise share major ecological and morphological traits. The exposed species (H. viridiflavus) selected higher body temperatures (~30°C) than the secretive species (Z. longissimus, ~25°C) both in a laboratory thermal gradient and in the field. Moreover, this difference in body temperature was maintained under thermophilic physiological states such as digestion and molting. Physiological and locomotory performances were optimized at higher temperatures in H. viridiflavus compared to Z. longissimus, as predicted by the thermal coadaptation hypothesis. Metabolic and energetic measurements indicated that energy requirements are at least twice higher in H. viridiflavus than in Z. longissimus. The contrasted sets of coadapted traits between H. viridiflavus and Z. longissimus appear to be adaptive correlates of their exposure strategies.
Simultaneous biologging of heart rate and acceleration, and their relationships with energy expenditure in free-swimming sockeye salmon (Oncorhynchus nerka)
Venue: Journal of Comparative Physiology B

Monitoring the physiological status and behaviour of free-swimming fishes remains a challenging task, although great promise stems from techniques such as biologging and biotelemetry. Here, implanted data loggers were used to simultaneously measure heart rate (fH), visceral temperature, and a derivation of acceleration in two groups of wild adult sockeye salmon (Oncorhynchus nerka) held at two different water speeds (slow and fast). Calibration experiments performed with individual fish in a swim tunnel respirometer generated strong relationships between acceleration, fH, tail beat frequency and energy expenditure over a wide range of swimming velocities. The regression equations were then used to estimate the overall energy expenditure of the groups of fish held at different water speeds. As expected, fish held at faster water speeds exhibited greater fH and acceleration, and correspondingly a higher estimated energy expenditure than fish held at slower water speeds. These estimates were consistent with gross somatic energy density of fish at death, as determined using proximate analyses of a dorsal tissue sample. Heart rate alone and in combination with acceleration, rather than acceleration alone, provided the most accurate proxies for energy expenditure in these studies. Even so, acceleration provided useful information on the behaviour of fish and may itself prove to be a valuable proxy for energy expenditure under different environmental conditions, using a different derivation of the acceleration data, and/or with further calibration experiments. These results strengthen the possibility that biologging or biotelemetry of fH and acceleration may be usefully applied to migrating sockeye salmon to monitor physiology and behaviour, and to estimate energy use in the natural environment.
Distress call-induced gene expression in the brain of the Indian short-nosed fruit bat, Cynopterus sphinx
Venue: Journal of Comparative Physiology A

Individuals in distress emit audible vocalizations to either warn or inform conspecifics. The Indian short-nosed fruit bat, Cynopterus sphinx, emits distress calls soon after becoming entangled in mist nets, which appear to attract conspecifics. Phase I of these distress calls is longer and louder, and includes a secondary peak, compared to phase II. Activity-dependent expression of egr-1 was examined in free-ranging C. sphinx following the emissions and responses to a distress call. We found that the level of expression of egr-1 was higher in bats that emitted a distress call, in adults that responded, and in pups than in silent bats. Up-regulated cDNA was amplified to identify the target gene (TOE1) of the protein Egr-1. The observed expression pattern Toe1 was similar to that of egr-1. These findings suggest that the neuronal activity related to recognition of a distress call and an auditory feedback mechanism induces the expression of Egr-1. Co-expression of egr-1 with Toe1 may play a role in initial triggering of the genetic mechanism that could be involved in the consolidation or stabilization of distress call memories.
The allometry of rodent intestines
Venue: Journal of Comparative Physiology B

This study examined the allometry of the small intestine, caecum, colon and large intestine of rodents (n = 51) using a phylogenetically informed approach. Strong phylogenetic signal was detected in the data for the caecum, colon and large intestine, but not for the small intestine. Most of the phylogenetic signal could be attributed to clade effects associated with herbivorous versus omnivorous rodents. The herbivorous rodents have longer caecums, colons and large intestines, but their small intestines, with the exception of the desert otomyine rodents, are no different to those of omnivorous rodents. Desert otomyine rodents have significantly shorter small intestines than all other rodents, reflecting a possible habitat effect and providing a partial explanation for the low basal metabolic rates of small desert mammals. However, the desert otomyines do not have shorter colons or large intestines, challenging claims for adaptation to water retention in arid environments. Data for the Arvicolidae revealed significantly larger caecums and colons, and hence longer large intestines, with no compensatory reduction in the length of the small intestine, which may explain how the smallest mammalian herbivores manage to meet the demands of a very high mass-specific metabolic rate. This study provides phylogenetically corrected allometries suitable for future prediction testing.
Gene expression survey of mitochondrial uncoupling proteins (UCP1/UCP3) in gilthead sea bream (Sparus aurata L.)
Venue: Journal of Comparative Physiology B

The aim of this work is to underline the biological significance of mitochondrial uncoupling proteins (UCPs) in ectothermic fish using the gilthead sea bream (Sparus aurata L.) as an experimental model. A contig of 1,990 bp in length was recognized as a UCP1 ortholog after initial searches in the gilthead sea bream AQUAFIRST database (http://www.sigenae.org/aquafirst). Additional searches were performed in skeletal muscle by RT-PCR, and the amplified PCR product was recognized as UCP3 after sequence completion by 5′- and 3′RACE. UCP1 expression was mostly detected in liver, whereas UCP3 transcripts were only found in skeletal and cardiac muscle fibres (white skeletal muscle > red skeletal muscle > heart). Specific gene regulation of UCP1 (liver) and UCP3 (white skeletal muscle) was addressed in physiological models of age, seasonal growth and energy-metabolic unbalances. Both the increase in energy demand (stress confinement) and the reduction in energy supply during adaptive cold response in winter down-regulated UCP1 expression. Conversely, transcript levels of UCP3 were higher with age, seasonal fattening and dietary deficiencies in essential fatty acids leading to the increase in fatty acid flux towards the muscle. This close association between UCP1 and UCP3 with the oxidative and metabolic tissue status is perhaps directly related to the ancestral protein UCP function, and allows the use of UCPs as lipotoxicity markers in ectothermic fish.
Segmental expression of claudin proteins correlates with tight junction barrier properties in rat intestine
Venue: Journal of Comparative Physiology B

In tubular epithelia, barrier function varies in a segment-specific way. The aim of this study was to correlate the presence of tight junction proteins and paracellular barrier properties along rat intestine. Tissue segments of duodenum, jejunum, ileum, and colon were stripped of submucosal cell layers and mounted in Ussing chambers for impedance spectroscopy to measure epithelial resistance (Repi). In parallel, expression of tight junction proteins was analysed by Western blots and immune fluorescence confocal microscopy. Colon showed highest Repi, followed by duodenum, jejunum, and ileum. In small intestine, common transepithelial resistance (Rtrans or TER) overestimated true Repi by ~60%. In colon, strongest expression of “tightening” claudins 1, 3, 4, 5, and 8 was detected. In accordance with Repi the most proximal of the small intestinal segments, duodenum exhibited highest expression of “tightening” claudins and lowest expression of claudins mediating permeability, namely claudin-2, -7, and -12, compared to jejunum and ileum. These results correspond to the specific role of the duodenum as the first segment facing the acidic gastric content.
Pollinating birds differ in spectral sensitivity
Venue: Journal of Comparative Physiology A

Pollinating animals and their angiosperm hosts often show strong co-adaptation in traits that increase the likelihood of a successful transfer of pollen and nutrient rewards. One such adaptation is the reported colour difference caused by unequal distribution of anthocyanidin pigments amongst plant species visited by hummingbirds and passerines. This phenomenon has been suggested to reflect possible differences in the colour vision of these pollinating birds. The presence of any such difference in colour vision would arguably affect the ecological and evolutionary interactions between flowers and their visitors, accentuating differences in floral displays and attractiveness of plants to the favoured avian pollinators. We have tested for differences in colour vision, as indicated by the amino acid present at certain key positions in the short-wavelength-sensitive type 1 (SWS1) visual pigment opsin, between the major groups of pollinating birds: the non-passerine Trochilidae (hummingbirds), the passerine Meliphagidae (honeyeaters) and Nectariniidae (sunbirds) plus five other Passerida passerine families. The results reveal gross spectral sensitivity differences between hummingbirds and honeyeaters, on the one hand, and the Passerida species, on the other.
Effects of capture stress on free-ranging, reproductively active male Weddell seals
Venue: Journal of Comparative Physiology A

Physiological stress responses to capture may be an indicator of welfare challenges induced by animal handling. Simultaneously, blood chemistry changes induced by stress responses may confound experimental design by interacting with the biological parameters being measured. Cortisol elevation is a common indicator of stress responses in mammals and reproductive condition can profoundly influence endocrine response. We measured changes in blood cortisol and testosterone induced by handling reproductively active male Weddell seals (Leptonychotes weddellii) early and late in the breeding season. Weddell seals have the highest resting cortisol levels of all mammals yet showed a clear, prolonged elevation in cortisol in response to capture. Responses were similar when first caught and when caught a second time, later in the breeding season. Baseline testosterone levels declined over the breeding season but were not altered by capture. Administering a light dose of diazepam significantly ameliorated the cortisol response of handled animals without affecting testosterone levels. This may be an effective way of reducing acute capture stress responses. Male breeding success in years males were handled was no different to the years they were not, despite the acute capture response, suggesting no long-term impact of handling on male reproductive output.
The transition in hemoglobin proton-binding characteristics within the basal actinopterygian fishes
Venue: Journal of Comparative Physiology B

Carbon dioxide (CO2) transport in the blood of fishes is aided by the proton-binding properties of hemoglobin (Hb) through either a high-intrinsic buffer value and small oxylabile proton binding (Haldane effect), or a low buffer value and large Haldane effect. Primitive species, such as elasmobranchs and sarcopterygians have been shown to rely on the former, while derived species, such as teleosts rely on the latter. Both strategies are effective in the transport of CO2 in the blood. However, there is a paucity of information on the nature of the transition between these two strategies that appears to occur within the intermediate group of fishes, the basal actinopterygians. The objective of the present study was to simultaneously assess the intrinsic Hb buffer values and Haldane effects of species within the basal actinopterygian lineage to characterize the transition in Hb-proton-binding strategy seen among the fishes. Expressed in order of most basal to most derived, the species investigated included American paddlefish (Polyodon spathula), white sturgeon (Acipenser transmontanus), spotted gar (Lepisosteus oculatus), alligator gar (Atractosteus spatula), bowfin (Amia calva), and mooneye (Hiodon tergisus). Hemolysates from these species were prepared and Hb titrations (under oxygenated and deoxygenated conditions) were performed in both the presence and absence of saturating levels of organic phosphates (GTP). The findings suggest that the nature of the Hb-proton-binding transition may have been punctuated rather than gradual, with the Hb buffer value decreasing and the Haldane effect increasing significantly in bowfin from fairly steady ancestral levels in the four more basal species. This change is coupled with the initial appearance of the choroid rete, as well as an increase in the magnitude and onset pH of the Root effect in bowfin, suggesting that the change in Hb-proton-binding strategy may be associated with the evolution of enhanced O2 delivery to the eye and an in vivo operational Root effect.
Effects of fresh and seawater ingestion on osmoregulation in Atlantic bottlenose dolphins (Tursiops truncatus)
Venue: Journal of Comparative Physiology B

Bottlenose dolphins (Tursiops truncatus) are marine mammals with body water needs challenged by little access to fresh water and constant exposure to salt water. Osmoregulation has been studied in marine mammals for a century. Research assessing the effects of ingested fresh water or seawater in dolphins, however, has been limited to few animals and sampling times. Nine 16- to 25-h studies were conducted on eight adult dolphins to assess the hourly impact of fresh water, seawater, and seawater with protein ingestion on plasma and urine osmolality, urine flow rate (ufr), urinary and plasma solute concentrations, and solute clearance rates. Fresh water ingestion increased ufr. Fresh water ingestion also decreased plasma and urine osmolality, sodium and chloride urine concentrations, and solute excretion rates. Seawater ingestion resulted in increased ufr, sodium, chloride, and potassium urine concentrations, sodium excretion rates, and urine osmolality. Seawater with protein ingestion was associated with increased ufr, plasma osmolality, sodium excretion, and sodium, chloride, potassium, and urea urine concentrations. In conclusion, bottlenose dolphins appear to maintain water and plasma solute balance after ingesting fresh water or seawater by altering urine osmolality and solute clearance. Ingestion of protein with seawater appears to further push osmoregulation limits and urine solute concentrations in dolphins.
Central regulation of the pharyngeal and upper esophageal reflexes during swallowing in the Japanese eel
Venue: Journal of Comparative Physiology A

We investigated the regulation of the pharyngeal and upper esophageal reflexes during swallowing in eel. By retrograde tracing from the muscles, the motoneurons of the upper esophageal sphincter (UES) were located caudally within the mid-region of the glossopharyngeal-vagal motor complex (mGVC). In contrast, the motoneurons innervating the pharyngeal wall were localized medially within mGVC. Sensory pharyngeal fibers in the vagal nerve terminated in the caudal region of the viscerosensory column (cVSC). Using the isolated brain, we recorded 51 spontaneously active neurons within mGVC. These neurons could be divided into rhythmically (n = 8) and continuously (n = 43) firing units. The rhythmically firing neurons seemed to be restricted medially, whereas the continuously firing neurons were found caudally within mGVC. The rhythmically firing neurons were activated by the stimulation of the cVSC. In contrast, the stimulation of the cVSC inhibited firing of most, but not all the continuously firing neurons. The inhibitory effect was blocked by prazosin in 17 out of 38 neurons. Yohimbine also blocked the cVSC-induced inhibition in five of prazosin-sensitive neurons. We suggest that the neurons in cVSC inhibit the continuously firing motoneurons to relax the UES and stimulate the rhythmically firing neurons to constrict the pharynx simultaneously.