bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feeding patterns ofChelus fimbriatus(Pleurodira:Chelidae)
Authors: Lemell Patrick , Lemell Christoph , Snelderwaard Peter , Gumpenberger Michaela , Wochesländer Robert , Weisgram Josef 
Published: April 2021

SUMMARYThe kinematics of feeding on fish have been studied in the aquatic feeding specialist Chelus fimbriatus, the fringed turtle, to provide a basic description of complete feeding cycles. Anatomical findings supplement the kinematic results. High-speed video (500 frames s-1) recordings and X-ray film (150 frames s-1) are used to analyse the kinematic variables characterizing head, hyoid, oesophageal and prey movements. The high velocities, especially of mouth opening, the forward thrust of the head and suction of the prey, are unique among turtles and comparable with those of aquatic salamanders and certain fishes (unidirectional feeders, in contrast to Chelus fimbriatus). The expandability of the pharynx and the anterior half of the oesophagus enables a specific type of unidirectional flow, at least during the early stages of the feeding cycle. This considerably improves the feeding performance compared with that of other aquatic turtles. The streamlined shape of the skull, the large hyoid apparatus, the highly reduced tongue and the extremely distensible oesophagus support the kinematics to a great extent, making C. fimbriatus a specialized suction feeder that can be regarded as one endpoint in the feeding evolution of aquatic reptiles.
Doppler-shift compensation behavior in horseshoe bats revisited: auditory feedback controls both a decrease and an increase in call frequency
Authors: Metzner Walter , Zhang Shuyi , Smotherman Michael 
Published: April 2021

SUMMARY
Among mammals, echolocation in bats illustrates the vital role of proper audio-vocal feedback control particularly well. Bats adjust the temporal,spectral and intensity parameters of their echolocation calls depending on the characteristics of the returning echo signal. The mechanism of audio-vocal integration in both mammals and birds is, however, still largely unknown. Here, we present behavioral evidence suggesting a novel audio-vocal control mechanism in echolocating horseshoe bats (Rhinolophus ferrumequinum). These bats compensate for even subtle frequency shifts in the echo caused by flight-induced Doppler effects by adjusting the frequency of their echolocation calls. Under natural conditions, when approaching background targets, the bats usually encounter only positive Doppler shifts. Hence, we commonly believed that, during this Doppler-shift compensation behavior,horseshoe bats use auditory feedback to compensate only for these increases in echo frequency (=positive shifts) by actively lowering their call frequency below the resting frequency (the call frequency emitted when not flying and not experiencing Doppler shifts). Re-investigation of the Doppler-shift compensation behavior, however, shows that decreasing echo frequencies(=negative shifts) are involved as well: auditory feedback from frequencies below the resting frequency, when presented at similar suprathreshold intensity levels as higher echo frequencies, cause the bat's call frequency to increase above the resting frequency. However, compensation for negative shifts is less complete than for positive shifts (22% versus 95%),probably because of biomechanical restrictions in the larynx of bats. Therefore, Doppler-shift compensation behavior involves a quite different neural substrate and audio-vocal control mechanism from those previously assumed. The behavioral results are no longer consistent with solely inhibitory feedback originating from frequencies above the resting frequency. Instead, we propose that auditory feedback follows an antagonistic push/pull principle, with inhibitory feedback lowering and excitatory feedback increasing call frequencies. While the behavioral significance of an active compensation for echo frequencies below RF remains unclear, these behavioral results are crucial for determining the neural implementation of audio-vocal feedback control in horseshoe bats and possibly in mammals in general.
Olfactory sensitivity for aliphatic alcohols in squirrel monkeys and pigtail macaques
Authors: Laska Matthias , Seibt Alexandra 
Published: April 2021

SUMMARYThe view that primates are microsmatic animals is based mainly on an interpretation of neuroanatomical features, whereas physiological evidence of a poorly developed sense of smell in this order of mammals is largely lacking. Using a conditioning paradigm, we therefore assessed the olfactory sensitivity of three squirrel monkeys (Saimiri sciureus) and of four pigtail macaques (Macaca nemestrina) for a homologous series of aliphatic alcohols (ethanol to 1-octanol) and isomeric forms of some of these substances. In the majority of cases, the animals of both species significantly discriminated concentrations below 1 part per million from the odourless solvent, and with 1-hexanol individual monkeys even demonstrated thresholds below 10 parts per billion. The results showed (i) that both primate species have a well-developed olfactory sensitivity for aliphatic alcohols, which for the majority of substances matches or even is better than that of species such as the rat, (ii) that both species generally show very similar olfactory detection thresholds for aliphatic alcohols, and (iii) that a significant negative correlation between perceptibility in terms of olfactory detection threshold and carbon chain length of both the aliphatic 1-and 2-alcohols exists in both species. These findings support the idea that across-species comparisons of neuroanatomical features are a poor predictor of olfactory performance and that general labels such as `microsmat' or`macrosmat', which are usually based on allometric comparisons of olfactory brain structures, are inadequate to describe the olfactory capabilities of a species. Further, our findings suggest that olfaction may play an important and hitherto underestimated role in the regulation of behaviour in the species tested.
Gills are needed for ionoregulation before they are needed for O2 uptake in developing zebrafish,Danio rerio
Authors: Rombough Peter 
Published: April 2021

SUMMARYA variation on the classic ablation method was used to determine whether O2 uptake or ionoregulation is the first to shift from the skin to the gills in developing zebrafish, Danio rerio. Zebrafish larvae,ranging in age from 3 to 21 days postfertilization, were prevented from ventilating their gills and forced to rely on cutaneous processes by exposing them to one of two anaesthetics (tricaine methanesulphonate or phenoxyethanol)or by embedding their gills in agar. They were then placed in solutions designed to compensate selectively for impaired O2 uptake (42%O2), impaired ionoregulatory capacity (50% physiological saline) or impairment of both functions (42% O2+50% physiological saline). Survival under these conditions was compared with that in normoxic (21%O2) fresh water. Neither hyperoxia nor 50% physiological saline had any significant effect on the survival of newly hatched larvae (3 days postfertilization), suggesting that at this stage cutaneous exchange was sufficient to satisfy both ionoregulatory and respiratory requirements. At 7 days postfertilization, the skin still appeared capable of satisfying the O2 requirements of larvae but not their ionoregulatory requirements. Physiological saline significantly improved survival at 7 days postfertilization; hyperoxia did not. At 14 days postfertilization, both hyperoxia and 50% saline significantly improved survival, indicating that at this stage gills were required for O2 uptake as well as for ionoregulation. At 21 days postfertilization, only hyperoxia significantly improved survival. By this stage, larvae apparently are so dependent on gills for O2 uptake that they suffocate before the effects of ionoregulatory impairment become apparent. Thus, it would appear that in zebrafish it is the ionoregulatory capacity of the skin not its ability to take up O2 that first becomes limiting. This raises the possibility that ionoregulatory pressures may play a more important role in gill development than is generally appreciated.
Salt and water regulation by the leatherback sea turtleDermochelys coriacea
Authors: Reina Richard D. , Jones T. Todd , Spotila James R. 
Published: April 2021

SUMMARYWe measured the salt and water balance of hatchling leatherback sea turtles, Dermochelys coriacea, during their first few days of life to investigate how they maintain homeostasis under the osmoregulatory challenge of a highly desiccating terrestrial environment and then a hyperosmotic marine environment. Hatchlings desiccated rapidly when denied access to sea water,with their hematocrit increasing significantly from 30.32±0.54 % to 38.51±1.35 % and plasma Na+ concentration increasing significantly from 138.2±3.3 to 166.2±11.2 mmoll-1 in 12 h. When hatchlings were subsequently put into sea water, hematocrit decreased and plasma Na+ concentration was unchanged but both were significantly elevated above pretreatment values. In other hatchlings kept in sea water for 48 h, body mass and plasma Na+ concentration increased significantly, but hematocrit did not increase. These data show that hatchlings were able to osmoregulate effectively and gain mass by drinking sea water. We stimulated hatchlings to secrete salt from the salt glands by injecting a salt load of 27 mmol kg-1. The time taken for secretion to begin in newly hatched turtles was longer than that in 4-day-old hatchlings, but the secretory response was identical at 4.15±0.40 and 4.13±0.59 mmol Na+ kg-1 h-1respectively. Adrenaline and methacholine were both potent inhibitors of salt gland secretion in a dose-dependent manner, although methacholine administered simultaneously with a subthreshold salt load elicited a transient secretory response. The results showed that hatchling leatherbacks are able to tolerate significant changes in internal composition and efficiently use their salt glands to establish internal ionic and water balance when in sea water.
Influence of cues from the anterior medial eyes of virtual prey onPortia fimbriata, an araneophagic jumping spider
Authors: Harland Duane P. , Jackson Robert R. 
Published: April 2021

SUMMARYPortia fimbriata from Queensland, Australia, is a jumping spider(Salticidae) that preys on other spiders, including other salticids. Cryptic stalking (palps retracted, walking very slowly and freezing when faced) is a prey-specific tactic deployed exclusively against salticid prey. Using vision alone, P. fimbriata discriminates salticid from non-salticid prey, with the prey salticid's large anterior median (AM) eyes providing critical cues. Here,using computer-rendered virtual three-dimensional lures, we clarify experimentally some of the specific optical cues from AM eyes that influence the behaviour of P. fimbriata. Control lures were based on Jacksonoides queenslandicus, the salticid upon which P. fimbriata most commonly preys in nature. Experimental lures were modified to isolate specific combinations of AM eye features. For presentation to P. fimbriata, lures were projected on a small screen positioned in front of a web-covered platform. Each individual P. fimbriata was tested once with a control lure and once with a lure on which some AM eye feature had been altered. P. fimbriata was affected by the presence-versus-absence of AM eyes, by the size and shape of these eyes and by AM eye position. Horizontal position on the face of a single AM eye had no discernible influence on whether P. fimbriata initiated cryptic stalking, but reduced how often P. fimbriata froze when faced by the prey. The implications of the findings are discussed in relation to perceptual processes underlying the predatory strategy of P. fimbriata.
A Ca2+-sensing receptor modulates shark rectal gland function
Authors: Fellner Susan K. , Parker Laurel 
Published: April 2021

SUMMARY
The elasmobranch Squalus acanthias controls plasma osmolality and extracellular fluid volume by secreting a hypertonic fluid from its rectal gland. Because we found a correlation between extracellular Ca2+concentration and changes in cytosolic Ca2+([Ca2+]i), we sought the possible presence of a calcium-sensing receptor in rectal gland artery and tubules. Cytosolic Ca2+ of both tissues responded to the addition of external Ca2+ (0.8-5.3 mmol l-1) in a linear fashion. Spermine,Gd3+ and Ni2+, known agonists of the calcium-sensing receptor, increased [Ca2+]i. To assess the participation of inositol triphosphate (IP3) generation, sarcoplasmic/endoplasmic reticulum (SR/ER) Ca2+ depletion, and activation of store-operated Ca2+ entry, we utilized thapsigargin and ryanodine to deplete Ca2+ SR/ER stores and the inhibitory reagents TMB-8 and 2-APB to block IP3 receptors. In each case, these agents inhibited the[Ca2+]i response to agonist stimulation by approximately 50 %. Blockade of L-channels with nifedipine had no significant effect. Increases in ionic strength are known to inhibit the calcium-sensing receptor. We postulate that the CaSR stimulates Ca2+-mediated constriction of the rectal gland artery and diminishes cyclic AMP-mediated salt secretion in rectal gland tubules during non-feeding conditions. When the shark ingests sea water and fish, an increase in blood and interstitial fluid ionic strength inhibits the activity of the calcium-sensing receptor, relaxing the rectal gland artery and permitting salt secretion by the rectal gland tubules.
Electrophysiological properties of the tongue epithelium of the toad Bufo marinus
Authors: Baker Timothy K. , Rios Karina , Hillyard Stanley D. 
Published: April 2021

SUMMARY
The dorsal lingual epithelium from the tongue of the toad Bufo marinus was mounted in an Ussing-type chamber, and the short-circuit current (Isc) was measured using a low-noise voltage clamp. With NaCl Ringer bathing the mucosal and serosal surfaces of the isolated tissue, an outwardly directed (mucosa-positive) Isc was measured that averaged -10.71±0.82 μA cm-2 (mean ± S.E.M., N=24) with a resistance of 615±152 Ω cm2 (mean ± S.E.M., N=10). Substitution of chloride with sulfate as the anion produced no significant change in Isc. Fluctuation analysis with either NaCl or Na2SO4 Ringer bathing both sides of the tissue revealed a spontaneous Lorentzian component, suggesting that the Isc was the result of K+ secretion through spontaneously fluctuating channels in the apical membrane of the epithelium. This hypothesis was supported by the reversible inhibition of Isc by Ba2+ added to the mucosal Ringer. Analysis of the kinetics of Ba2+ inhibition of Isc indicates that there might be more than one type of K+ channel carrying the Isc. This hypothesis was supported by power spectra obtained with a serosa-to-mucosa K+gradient, which could be fitted to two Lorentzian components. At present, the K+ secretory current cannot be localized to taste cells or other cells that might be associated with the secretion of saliva or mucus. Nonetheless, the resulting increase in [K+] in fluid bathing the mucosal surface of the tongue could presumably affect the sensitivity of the taste cells. These results contrast with those from the mammalian tongue, in which a mucosa-negative Isc results from amiloride-sensitive Na+ transport.
Visual navigation in desert ants Cataglyphis fortis: are snapshots coupled to a celestial system of reference?
Authors: Åkesson Susanne , Wehner Rüdiger 
Published: April 2021

SUMMARY
Central-place foraging insects such as desert ants of the genus Cataglyphis use both path integration and landmarks to navigate during foraging excursions. The use of landmark information and a celestial system of reference for nest location was investigated by training desert ants returning from an artificial feeder to find the nest at one of four alternative positions located asymmetrically inside a four-cylinder landmark array. The cylindrical landmarks were all of the same size and arranged in a square, with the nest located in the southeast corner. When released from the compass direction experienced during training (southeast), the ants searched most intensely at the fictive nest position. When instead released from any of the three alternative directions of approach (southwest, northwest or northeast), the same individuals instead searched at two of the four alternative positions by initiating their search at the position closest to the direction of approach when entering the landmark square and then returning to the position at which snapshot, current landmark image and celestial reference information were in register. The results show that, in the ants'visual snapshot memory, a memorized landmark scene can temporarily be decoupled from a memorized celestial system of reference.
Extreme resistance to desiccation and microclimate-related differences in cold-hardiness of gall wasps (Hymenoptera: Cynipidae) overwintering on roses in southern Canada
Authors: Williams Jason B. , Shorthouse Joseph D. , Lee Richard E. 
Published: April 2021

SUMMARYFour species of cynipid wasp of the genus Diplolepis that induce galls on roses (Rosa species) in southern Canada and two species of inquiline cynipid associated with these galls were studied for their cold-hardiness and resistance to water loss and for possible links between these adaptations. Mid-winter-acclimated supranivean D. spinosa and Periclistus pirata had lower supercooling points (-38 to -40°C)and higher hemolymph osmolalities (1760-1849 mosmol kg-1) than subnivean D. polita, D. gracilis, D. radicum and Periclistussp. (-31 to -32°C and 977-1464 mosmol kg-1, respectively). During a simulated transition from summer/fall to mid-winter conditions, the glycerol concentration of D. spinosa more than tripled, reaching a final value of 0.98 moll-1, while its supercooling point decreased by 13°C from the initial value of -27.4°C; however, glycerol concentration and supercooling point did not change for the subnivean species. The permeability of the cuticle of all species was extremely low (0.33-1.00μg h-1 cm-2 mmHg-1 at 5°C and 0 %relative humidity; 1 mmHg=0.133 kPa), even compared with that of desert species; however, there was no difference in cuticular permeability between supranivean and subnivean prepupae. Transition temperatures ranged between 32.3 and 34.6°C; below 30°C, temperature had little effect on rates of water loss for all species (Q10=1.13-1.87).
Kinematics of plaice,Pleuronectes platessa, and cod,Gadus morhua, swimming near the bottom
Authors: Webb Paul W. 
Published: April 2021

SUMMARYThe kinematics of plaice (Pleuronectes platessa, L=22.1 cm) and cod (Gadus morhua, L=25.0 cm, where L is total fish length)swimming at various speeds at the bottom and lifted to heights, h, of 10, 50 and 100 mm by a thin-wire grid were measured. For cod, tailbeat frequency, amplitude, body and fin span and propulsive wavelength were unaffected by h and varied with speed as described for fusiform pelagic species. In contrast, the kinematics of plaice was affected by h. Body and fin spans and propulsive wavelength were independent of swimming speed and h. Tailbeat amplitude was independent of swimming speed, but averaged 1.5 cm at h=0 and 2.5 cm at h≥10 mm. Plaice tailbeat frequency increased with swimming speed for fish at the bottom but was independent of swimming speed at h=10, 50 and 100 mm,averaging 4.6, 6.0 and 5.8 Hz respectively. Total mechanical power, P, produced by propulsive movements calculated from the bulk-momentum form of elongated slender-body theory was similar for cod and plaice swimming at the bottom but, at h≥10 mm, P for plaice was larger than that for cod. Plaice support their weight in water by swimming at a small tilt angle. The small changes in swimming kinematics with swimming speed are attributed to decreasing induced power costs to support the weight as speed increases. The contribution of the tail to power output increased monotonically with the tail gap/span ratio, z/B, for z/B=0.23 (h=0 mm) to z/B=1.1 (h=50 mm). The smaller tailbeat amplitude of the tail decreased both z/B and the power output for plaice swimming at the bottom. For the maximum body and fin span of plaice, the contribution to power output increased for local z/B values of 0.044 (h-0 mm) to 0.1 (h=10 mm) and declined somewhat at larger values of z/B. The smaller effect of the bottom on power output of the largespan anterior body sections may result from the resorption of much of the upstream wake at the re-entrant downstream tail.
Weakfish sonic muscle: influence of size, temperature and season
Authors: Connaughton M. A. , Fine M. L. , Taylor M. H. 
Published: April 2021

SUMMARYThe influence of temperature, size and season on the sounds produced by the sonic muscles of the weakfish Cynoscion regalis are categorized and used to formulate a hypothesis about the mechanism of sound generation by the sonic muscle and swimbladder. Sounds produced by male weakfish occur at the time and location of spawning and have been observed in courtship in captivity. Each call includes a series of 6-10 sound pulses, and each pulse expresses a damped, 2-3 cycle acoustic waveform generated by single simultaneous twitches of the bilateral sonic muscles. The sonic muscles triple in mass during the spawning season, and this hypertrophy is initiated by rising testosterone levels that trigger increases in myofibrillar and sarcoplasmic cross-sectional area of sonic muscle fibers. In response to increasing temperature, sound pressure level (SPL), dominant frequency and repetition rate increase, and pulse duration decreases. Likewise, SPL and pulse duration increase and dominant frequency decreases with fish size. Changes in acoustic parameters with fish size suggest the possibility that drumming sounds act as an `honest' signal of male fitness during courtship. These parameters also correlate with seasonally increasing sonic muscle mass. We hypothesize that sonic muscle twitch duration rather than the resonant frequency of the swimbladder determines dominant frequency. The brief (3.5 ms), rapidly decaying acoustic pulses reflect a low-Q, broadly tuned resonator, suggesting that dominant frequency is determined by the forced response of the swimbladder to sonic muscle contractions. The changing dominant frequency with temperature in fish of the same size further suggests that frequency is not determined by the natural frequency of the bladder because temperature is unlikely to affect resonance. Finally, dominant frequency correlates with pulse duration (reflecting muscle twitch duration),and the inverse of the period of the second cycle of acoustic energy approximates the recorded frequency. This paper demonstrates for the first time that the dominant frequency of a fish sound produced by a single muscle twitch is apparently determined by the velocity of the muscle twitch rather than the natural frequency of the swimbladder.