nils-herrmann/clean_scirepeval huggingface dataset:
Acute temperature effects on metabolic rate, ventilation, diffusive water exchange, osmoregulation, and acid–base status in the Pacific hagfish (Eptatretus stoutii)
Venue: Journal of Comparative Physiology B

The Pacific hagfish (Eptatretus stoutii) is a representative of the most basal extant craniates, and is a marine osmoconformer with an extremely low metabolic rate (MO2 = 475 µmol O2/kg/h at 12 °C). We investigated potential physiological trade-offs associated with compensatory changes in gill ventilation and perfusion when 12 °C-acclimated hagfish were acutely exposed to 7 °C or 17 °C, as reflected in diffusive unidirectional water flux ($${J_{{{\text{H}}_2}{\text{O}}}}$$JH2O, measured with tritiated water: 3H2O), net ammonia flux (Jamm), and plasma ion and acid–base status. $${J_{{{\text{H}}_2}{\text{O}}}}$$JH2O was high (~ 1.4 L/kg/h at 12 °C) in comparison to marine teleosts and elasmobranchs. MO2 increased linearly with temperature (R2 = 0.991), and was more sensitive (Q10 = 3.22) in the 12–7 °C range than either Jamm (1.86) or $${J_{{{\text{H}}_2}{\text{O}}}}$$JH2O (1.35), but the pattern reversed from 12 to 17 °C (Q10s: MO2 = 2.77, Jamm = 2.88, $${J_{{{\text{H}}_2}{\text{O}}}}$$JH2O = 4.01). Heart rate, ventilatory index (a proxy for total ventilation), and coughing frequency also increased but with different patterns. At 17 °C, plasma [Ca2+] and [Mg2+] decreased, although osmolality increased, associated with elevations in plasma [Na+] and [Cl−]. Blood pH and PCO2 were unaffected by acute temperature changes while [HCO3−] increased. Hyperoxia (PO2 > 300 Torr) attenuated the increase in $${J_{{{\text{H}}_2}{\text{O}}}}$$JH2O at 17 °C, did not affect Jamm, and had diverse effects on plasma ion and acid–base status. Our results suggest a clear osmorespiratory compromise occurring for the diffusive water fluxes as a result of acute temperature changes in this osmoconformer.
Alteration in branchial NKA and NKCC ion-transporter expression and ionocyte distribution in adult hilsa during up-river migration
Venue: Journal of Comparative Physiology B

Hilsa (Tenualosa ilisha) is a clupeid that migrates from the off-shore area through the freshwater river for spawning. The purpose of this study was to investigate the involvement of branchial Na+/K+-ATPase (NKA) and Na+/K+/2Cl− cotransporter (NKCC) in maintaining ionic homeostasis in hilsa while moving across the salt barriers. Hilsa, migrating through marine and brackish waters, did not show any significant decline in NKA activity, plasma osmolality, and plasma ionic concentration. In contrast, all the parameters declined significantly, after the fish reached in freshwater zone of the river. Immunoblotting with NKA α antibody recognized two bands in gill homogenates. The intensity of the higher molecular NKA band decreased, while the other band subsequently increased accompanying the movement of hilsa from marine water (MW) to freshwater. Nevertheless, total NKA expression in marine water did not change prior to freshwater entry. NKCC expression was down-regulated in gill, parallel with NKA activity, as the fish approached to the freshwater stretch of river. The NKA α-1 and NKCC1 protein abundance decreased in freshwater individuals by 40% and 31%, respectively, compared to MW. NKA and NKCC1 were explicitly localized to branchial ionocytes and immunoreactive signal appeared throughout the cytoplasm except for the nucleus and the most apical region indicates a basolateral/tubular distribution. Immunoreactive ionocytes were distributed on the filaments and lamellae; lamellar ionocytes were more in number irrespective of habitat salinity. The decrease in salinity caused a slight reduction in ionocyte number, but not in size and the underlying distribution pattern did not alter. The overall results support previously proposed models that both the ion transporters are involved in maintaining ionic homeostasis and lamellar ionocytes may have the function in hypo-osmoregulation in migrating hilsa, unlike other anadromous teleosts.
Thermal physiological performance of two freshwater turtles acclimated to different temperatures
Venue: Journal of Comparative Physiology B

The thermal physiological performance of invasive species may play a crucial role in determining their invasion success. In this study, we acclimated two cohorts of hatchlings of freshwater turtles (native Mauremys reevesii and invasive Trachemys scripta elegans) from low and high-latitude collection sites, respectively, to different thermal conditions (20 and 30 °C) for 4 weeks, and then compared their thermal tolerance and locomotor performance. T. scripta elegans hatchlings could swim faster (but righted themselves more slowly), and tolerate a higher temperature and wider temperature range than M. reevesii hatchlings. Similarly, T. scripta elegans hatchlings had a greater maximal performance (Pmax) value for swimming speed (but a lower Pmax value for righting time) than M. reevesii hatchlings. Temperature acclimation had a significant impact on the thermal tolerance and locomotor ability of turtles, but the acclimation effect did not differ between the two species. T. scripta elegans hatchlings seemed to have a greater thermal plasticity than M. reevesii hatchlings. High-latitude individuals showed a greater low-temperature tolerance, but lower locomotor ability (longer righting time) than low-latitude ones. However, the thermal plasticity did not differ between latitudinal cohorts. Our results indicated that T. scripta elegans performed better than M. reevesii, which might contribute to its range expansion and invasive success.
Behavioural and physiological responses to low- and high-intensity locomotion in Chinese shrimp Fenneropenaeus chinensis
Venue: Journal of Comparative Physiology A

We explored stroke behaviour, energy sources, and their related metabolic enzymes during multi-intensity swimming and tail-flipping at low- and high-intensity modes in Chinese shrimp Fenneropenaeus chinensis. In swimming, shrimp were encouraged to swim at velocities of 3, 6, 9 cm s−1 for 200 min (low-intensity), and at 12, 15, 18 cm s−1 until fatigue (high-intensity). In tail-flipping, shrimp were encouraged to tail-flip by tapping cephalothorax at frequencies of 0.020, 0.040, 0.063 Hz (one tap every 50, 25, 16 s) for 5 min (low-intensity), and at 0.083, 0,100, 0.125 Hz (one tap every 12, 10, 8 s) until no response (high-intensity). Results showed that shrimp increased stroke rates of pleopods and uropods to elevate swimming and tail-flipping ability. For low-intensity locomotion, glycogen was burned in aerobic pathway due to low pleopods beat frequency in swimming; however, glycogen was anaerobically burned due to high uropods beat amplitude in tail-flipping. Anaerobic metabolism occurred in high-intensity locomotion in either swimming or tail-flipping. Critical contents of muscle lactate causing locomotion fatigue might be around threefold of rest condition. Shrimp reduced locomotive time to avoid glycogen exhaustion and lactate accumulation during high-intensity locomotion. These findings highlight our understanding of physiological mechanisms of locomotion activities in shrimp.
Honey bee workers generate low-frequency vibrations that are reliable indicators of their activity level
Venue: Journal of Comparative Physiology A

In social insects, the tuning of activity levels among different worker task groups, which constitutes a fundamental basis of colony organization, relies on the exchange of reliable information on the activity level of individuals. The underlying stimuli, however, have remained largely unexplored so far. In the present study, we describe low-frequency thoracic vibrations generated by honey bee workers (Apis mellifera) within the colony, whose velocity amplitudes and main frequency components significantly increased with the level of an individual’s activity. The characteristics of these vibrations segregated three main activity level-groups: foragers, active hive bees, and inactive hive bees. Nectar foragers, moreover, modulated their low-frequency vibrations during trophallactic food unloading to nestmates according to the quality of the collected food. Owing to their clear association with the activity level of an individual and their potential perceptibility during direct contacts, these low-frequency thoracic vibrations are candidate stimuli for providing unambiguous local information on the motivational status of honey bee workers.
Emergence of a complex movement pattern in an unfamiliar food place by foraging ants
Venue: Journal of Comparative Physiology A

Although visual cues are essential for navigation in ants, few studies address movement dynamics in ants when they search and forage after finding food in an unfamiliar environment. Here I introduced Japanese wood ants to an unfamiliar food location by capturing individuals leaving their nest. The food was located at the centre of a straight, narrow, open-top channel. Next, I determined the segment lengths of the foraging paths of the ants between consecutive U-turns. I found that individuals travelled along characteristic and complex paths if they detected a visual landmark. This movement property was not detectable when individuals foraged in the channel without any visual landmarks. These results reveal the movement dynamics of ants when they encounter food in a novel place.
A reinterpretation of “Homing pigeons’ flight over and under low stratus” based on atmospheric propagation modeling of infrasonic navigational cues
Venue: Journal of Comparative Physiology A

Pigeons flying above temperature inversion and related low-stratus layers appear to lack important navigational cues, and a reinterpretation of Wagner’s 1978 study suggests that these cues are low-frequency acoustic signals (infrasound). Wagner released homing pigeons above opaque stratus over the Swiss Plateau to determine whether they could locate their loft beneath it. Birds above the clouds appeared lost, while those that descended beneath them returned home directly. Atmospheric propagation modeling of infrasonic waves virtually transmitted from the loft area shows that these signals would have been ducted beneath the inversion layer, and would not have reached the release sites above it. The absence of homeward infrasonic cues above temperature inversions could explain the disorientation of Wagner’s birds, especially if such signals are the predominant cues used by pigeons to home. The possible generation of infrasonic navigational signals in the loft area and recent queries concerning the infrasound navigational “map” hypothesis are also discussed.
Expression of glucose transporters and morphometry in the intestine of Japanese quails after hatch
Venue: Journal of Comparative Physiology B

The intestinal physiology and mechanisms involved in nutrient transport are not well established in quails (Coturnix coturnix japonica). The present study assessed the growth performance, morphological development, duodenal density and the expression of Sglt1 and Glut2 of female Japanese quails from 1 to 49 days of age. The three small intestine segments were sampled weekly from 1 to 49 days of age to evaluate villus height, crypt depth and villus: crypt ratio, and goblet cell counts. Scanning electronic microscopy was used to determine duodenal villus density, and real-time polymerase chain reaction (qPCR) was used to study the sodium/glucose cotransporter-1 Sglt1 and glucose transporter Glut2 in the jejunum. Villus height and crypt depth in the duodenum, jejunum and ileum increased with age until 42 and 49 days of age (P < 0.001), and regression analysis evidenced a quadratic effect (P < 0.0001), indicating increasing values to a maximum and then a decrease afterwards. Goblet cell counts increased (P < 0.001) in duodenum, jejunum and ileum from 1 to 42 days, decreasing at 49 days, which was also corroborated by the regression analysis. Villus density in the duodenum was greater in the first week, decreased with age and increased again at 42 days, probably due to the proximity with egg production onset. The expression of Sglt1 and Glut2 mRNA in the jejunum varied with age. In conclusion, the intestinal mucosa of female Japanese quail developed morphologically until 42days and functionally until earlier ages, indicating an adaptation to the exogenous diet during the first weeks of life.
Changes in responsiveness to allatostatin treatment accompany shifts in stress reactivity in young worker honey bees
Venue: Journal of Comparative Physiology A

Exposing honey bees to isopentylacetate (IPA) can cause stress-related changes in learning performance. In bees of foraging age, IPA’s effects on learning are mimicked by C-type allatostatins (AstCC, AstCCC) injected into the brain. Here we ask whether allatostatins induce a similar response in young (6-day-old) bees and if so, whether their effects on learning performance are modulated by queen mandibular pheromone (QMP). We found that young bees exposed to IPA responded less to the conditioned stimulus during training than controls (Type 1-like stress response). AstCC treatment induced a similar response, but only in bees maintained without QMP. Bees exposed to QMP responded to AstCC with increased odour responsiveness and odour generalisation in the 1-h memory test (Type 2-like response). Type 2-like responses could be induced also by the A-type allatostatin, AstA. However, in bees exposed to QMP, AstA-induced odour generalisation was absent. Effects of AstCCC treatment in young bees were weak, indicating that responsiveness to this peptide changes with age. Our findings are consistent with the hypothesis that honey bee allatostatins play a role in stress reactivity, but suggest in addition that allatostatin signalling is age dependent and susceptible to modulation by pheromone released by the queen bee.
Overwintering adaptations and extreme freeze tolerance in a subarctic population of the wood frog, Rana sylvatica
Venue: Journal of Comparative Physiology B

The terrestrially hibernating wood frog (Rana sylvatica) is well-known for its iconic freeze tolerance, an overwintering adaptation that has received considerable investigation over the past 35 years. Virtually, all of this research has concerned frogs indigenous to the temperate regions of its broad range within North America. However, recent investigations have shown that frogs of subarctic populations are extremely cold hardy, being capable of surviving freezing for longer periods and at much lower temperatures as compared to conspecifics from temperate regions. Their exceptional freeze tolerance is partly supported by an enhanced cryoprotectant system that uses very high levels of urea and glucose to limit ice formation, regulate metabolism, and protect macromolecules and cellular structures from freezing/thawing stresses. In the weeks before they begin hibernating, northern frogs undertake radical physiological transitions, such as depletion of fat stores and catabolism of muscle protein, that prime the cryoprotectant system by accruing urea and stockpiling glycogen from which glucose is mobilized during freezing. Concentrations of cryoprotectants ultimately achieved in Alaskan frogs when freezing occurs vary among tissues but generally are higher than those of frogs inhabiting milder climates. This review summarizes the molecular, biochemical, and physiological adaptations permitting this northern phenotype to survive the long and harsh winters of the region.
Auditory sensitivity exhibits sexual dimorphism and seasonal plasticity in music frogs
Venue: Journal of Comparative Physiology A

Seasonal changes in the structure and function of the vertebrate brain have been described in many species, particularly in seasonal breeders. However, it remains unclear whether sexual dimorphism varies between breeding seasons for specific brain regions. Auditory event-related potential (ERP) changes were evaluated in the Emei music frog (Babina daunchina) to assess sexual dimorphism and seasonal variations in auditory sensitivity. An acoustic playback experiment using an oddball paradigm design was conducted, in which two conspecific call types were used as deviant stimuli with synthesized white noise as standard stimulus. ERP components were analyzed for the telencephalon and mesencephalon of both sexes in the non-reproductive and reproductive states. Results show that auditory sensitivity is modulated by reproductive status, implying that seasonal plasticity is involved in auditory perception. Moreover, the amplitude of the N1 ERP component (mean amplitudes during the interval occurring 30–130 ms after stimulus onset) is higher in females for the telencephalon and higher in males for the mesencephalon, regardless of reproductive status and acoustic stimulus type. These results show that auditory ERP responses for specific brain regions exhibit sexual dimorphism in the absence of exogenous sexual stimulation during both the two reproductive states in the music frog.
Does silvering or 11-ketotestosterone affect osmoregulatory ability in the New Zealand short-finned eel (Anguilla australis)?
Venue: Journal of Comparative Physiology A

Silvering has been associated with advancing osmoregulatory ability. Given the demonstrated role of 11-ketotestosterone (11KT) in mediating many of the silvering-related changes, we investigated the role of 11KT in driving this advanced osmoregulatory ability in the New Zealand short-finned eel (Anguilla australis). Yellow (non-migratory) eels with or without 11KT implants and blank-implanted silver (migratory) eels, either held in freshwater or subjected to seawater challenge, were sampled to determine serum [Na+] and [Cl−], pituitary prolactin mRNA levels, gill Na+/K+-ATPase activity and gill mRNA levels for Na+/K+-ATPase-α1 subunit and for Na+/K+/2Cl− co-transporter-1α-subunit. Developmental stage and 11KT treatment advanced the eels’ osmoregulatory ability. Thus, serum [Na+] and [Cl−] were affected by developmental stage and 11KT treatment upon seawater challenge. However, seawater challenge, not 11KT treatment or developmental stage, produced the strongest and the most consistent effects on A. australis osmoregulatory processes, inducing significant effects in all the relevant parameters we measured. In light of our results and in view of the eel’s marine ancestry, we contend that A. australis, or freshwater eels in general, are highly tolerant and able to adapt quickly to changing salinities even at the yellow stage, which may preclude a critical need for an advanced osmoregulatory ability at silvering.
Seafinding revisited: how hatchling marine turtles respond to natural lighting at a nesting beach
Venue: Journal of Comparative Physiology A

Hatchling marine turtles emerge at night from underground nests on oceanic beaches and then use visual cues to crawl from the nest site to the sea (“seafinding”). However, the light wavelengths (λ’s) used to accomplish this orientation have not been thoroughly documented, nor do we understand why some λ’s are favored over others. We measured nocturnal radiance on the horizon at 20 nm intervals between 340 and 600 nm at two nesting beach sites and then, under laboratory conditions, determined the lowest intensities of those λ’s that induced green turtle and loggerhead hatchlings to crawl toward each light source (a low positive “phototaxis threshold”). Both species were similarly sensitive and were attracted to all λ’s. Radiance measures at all λ’s were greater toward the seaward horizon than toward the landward horizon, providing an important orientation cue regardless of variation in lunar illumination. Previous studies document that both species detect λ’s longer than those that are most attractive. We hypothesize that seafinding is a specialized response mediated by cones that are sensitive to the shorter λ’s (to minimize the effects of dark noise) but such as rods, are especially sensitive to low levels of nocturnal illumination.
Ontogenetic changes in cutaneous and branchial ionocytes and morphology in yellowfin tuna (Thunnus albacares) larvae
Venue: Journal of Comparative Physiology B

The development of osmoregulatory and gas exchange organs was studied in larval yellowfin tuna (Thunnus albacares) from 2 to 25 days post-hatching (2.9–24.5 mm standard length, SL). Cutaneous and branchial ionocytes were identified using Na+/K+-ATPase immunostaining and scanning electron microscopy. Cutaneous ionocyte abundance significantly increased with SL, but a reduction in ionocyte size and density resulted in a significant decrease in relative ionocyte area. Cutaneous ionocytes in preflexion larvae had a wide apical opening with extended microvilli; however, microvilli retracted into an apical pit from flexion onward. Lamellae in the gill and pseudobranch were first detected ~ 3.3 mm SL. Ionocytes were always present on the gill arch, first appeared in the filaments and lamellae of the pseudobranch at 3.4 mm SL, and later in gill filaments at 4.2 mm SL, but were never observed in the gill lamellae. Unlike the cutaneous ionocytes, gill and pseudobranch ionocytes had a wide apical opening with extended microvilli throughout larval development. The interlamellar fusion, a specialized gill structure binding the lamellae of ram-ventilating fish, began forming by ~ 24.5 mm SL and contained ionocytes, a localization never before reported. Ionocytes were retained on the lamellar fusions and also found on the filament fusions of larger sub-adult yellowfin tuna; however, sub-adult gill ionocytes had apical pits. These results indicate a shift in gas exchange and NaCl secretion from the skin to branchial organs around the flexion stage, and reveal novel aspects of ionocyte localization and morphology in ram-ventilating fishes.
Enhancement of habituation during escape swimming in starved crayfish
Venue: Journal of Comparative Physiology A

Feeding is important to supply the immediate energy needs of animals and starved animals must expend energy in attempting to acquire foods irrespective of the danger of predation risk. Crayfish escape from attack of predators by tailflipping and in response to rostral stimuli crayfish show backward escape swimming following an initial rapid flexion of the abdomen. Since the tailflip is an energetically costly behaviour, the occurrence of a tailflip diminishes if a stimulus is repeatedly applied through habituation. In this study, we have compared the process of this habituation between fed and starved crayfish. We found that in starved animals habituation was enhanced compared to fed animals. The presence of food in the experimental tanks further enhanced habituation of starved animals. Starved crayfish thus showed trade-offs between energy saving and predation risk.
Magnetoreception: activation of avian cryptochrome 1a in various light conditions
Venue: Journal of Comparative Physiology A

The avian magnetic inclination compass is based on radical pair processes, with cryptochrome (Cry) assumed to form the crucial radical pairs; it requires short-wavelength light from UV to green. Under high-intensity narrow-band lights and when yellow light is added, the magnetic compass is disrupted: migratory birds no longer prefer their migratory direction, but show other orientation responses. The candidate receptor molecule Cry1a is located in the shortwavelength-sensitive SWS1 cone photoreceptors in the retina. The present analysis of avian retinae after the respective illuminations showed that no activated Cry1a was present under 565 nm green light of medium and high intensity, and hardly any under high intensity 502 nm turquoise, whereas we found activated Cry1a at all three tested intensities of 373 nm UV and 424 nm blue light. Activated Cry1a also was found when 590 nm yellow light was added to low-intensity light of the four colors; yet these light combinations result in impaired magnetic orientation. This indicates that the disruption of the magnetic compass does not occur at the receptor level in the retina, but at higher processing stages, where the unnatural, almost monochromatic or bichromatic illumination causes yet unknown responses that interfere with the inclination compass.