bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experience-dependent modification of ultrasound auditory processing in a cricket escape response
Authors: Engel Jeff E. , Hoy Ronald R. 
Published: April 2021

ABSTRACT
The ultrasound acoustic startle response (ASR) of crickets (Teleogryllus oceanicus) is a defense against echolocating bats. The ASR to a test pulse can be habituated by a train of ultrasound prepulses. We found that this conditioning paradigm modified both the gain and the lateral direction of the startle response. Habituation reduced the slope of the intensity/response relationship but did not alter stimulus threshold, so habituation extended the dynamic range of the ASR to higher stimulus intensities. Prepulses from the side (90 ° or 270 ° azimuth) had a priming effect upon the lateral direction of the ASR, increasing the likelihood that test pulses from the front (between −22 ° and +22 °) would evoke responses towards the same side as prepulse-induced responses. The plasticity revealed by these experiments could alter the efficacy of the ASR as an escape response and might indicate experience-dependent modification of auditory perception.
We also examined stimulus control of habituation by prepulse intensity or direction. Only suprathreshold prepulses induced habituation. Prepulses from one side habituated the responses to test pulses from either the ipsilateral or contralateral side, but habituation was strongest for the prepulse-ipsilateral side. We suggest that habituation of the ASR occurs in the brain, after the point in the pathway where the threshold is mediated, and that directional priming results from a second process of plasticity distinct from that underlying habituation. These inferences bring us a step closer to identifying the neural substrates of plasticity in the ASR pathway.
Modelling the locomotor energetics of extinct hominids
Authors: Kramer Patricia Ann 
Published: April 2021

ABSTRACT
Bipedality is the defining characteristic of Hominidae and, as such, an understanding of the adaptive significance and functional implications of bipedality is imperative to any study of human evolution. Hominid bipedality is, presumably, a solution to some problem for the early hominids, one that has much to do with energy expenditure. Until recently, however, little attention could be focused on the quantifiable energetic aspects of bipedality as a unique locomotor form within Primates because of the inability to measure empirically the energy expenditure of non-modern hominids. A recently published method provides a way of circumventing the empirical measurement dilemma by calculating energy expenditure directly from anatomical variables and movement profiles. Although the origins of bipedality remain clouded, two discernible forms of locomotor anatomy are present in the hominid fossil record: the australopithecine and modern configurations. The australopithecine form is best represented by AL 288-1, a partial skeleton of Australopithecus afarensis, and is characterized as having short legs and a wide pelvis. The modern form is represented by modern humans and has long legs and a narrow pelvis. Human walking is optimized to take advantage of the changing levels of potential and kinetic energy that occur as the body and limbs move through the stride cycle. Although this optimization minimizes energy expenditure, some energy is required to maintain motion. I quantify this energy by developing a dynamic model that uses kinematic equations to determine energy expenditure.
By representing both configurations with such a model, I can compare their rates of energy expenditure. I find that the australopithecine configuration uses less energy than that of a modern human. Despite arguments presented in the anthropological literature, the shortness of the legs of AL 288-1 provides no evidence that she was burdened with a compromised or transitional locomotor anatomy. Instead, she may well have been an effective biped at walking speeds, not despite her short legs, but rather because of them.
Physiological responses of king penguins during simulated diving to 136 m depth
Authors: Ponganis P. J. , Kooyman G. L. , Van Dam R. , LeMaho Y. 
Published: April 2021

ABSTRACT
To evaluate blood N2 uptake and the role of the respiratory volume (air sacs/lungs) as a N2 and O2 reservoir in deep-diving penguins, diving respiratory volume (VDR), heart rate (fH), venous , blood volume (Vb) and hemoglobin (Hb) concentration were measured in king penguins (Aptenodytes patagonicus) during forced submersions and compressions equivalent to depths up to 136 m. VDR was 69±18 ml kg−1 (mean ± S.D.) in 62 submersions ranging from 4.4 atmospheres absolute (ATA; 1 ATA=101 kPa) (34 m) to 14.6 ATA (136 m). Submersion fH averaged 30±7 beats min−1 (N=18), approximately 20 % of pre- and post-submersion values. Venous values during and after submersions as deep as 11.2 ATA (102 m) were all less than 2.8 atmospheres N2 (283 kPa) above ambient pressure, a previously measured threshold for symptomatic bubble formation. Mean Vb was 83±8 ml kg−1 (N=6); [Hb] was 17.6±0.7 g dl−1 (N=7). On a mass-specific basis, mean VDR, and therefore total available N2, is 41 % of that in shallow-diving penguin species. Total body O2 stores, calculated from measured VDR, Vb, [Hb], muscle mass and myoglobin concentration, are 45 ml kg−1, with 23 % in the respiratory system. This small respiratory fraction in comparison with that in shallow-diving penguins suggests a lesser reliance on the respiratory oxygen store for extended breath-holding and also a reduced uptake of nitrogen at depth.
Directional acoustic radiation in the strut display of male sage grouse Centrocercus urophasianus
Authors: Dantzker Marc S. , Deane Grant B. , Bradbury Jack W. 
Published: April 2021

ABSTRACT
We present evidence that the acoustic component of the strut display of male sage grouse Centrocercus urophasianus is highly directional and that the nature of this directionality is unique among measured vertebrates. Where vertebrate acoustic signals have been found to be directional, they are most intense anteriorly and are bilaterally symmetrical. Our results show that sage grouse acoustic radiation (beam) patterns are often asymmetric about the birds’ anterior–posterior axis. The beam pattern of the ‘whistle’ note is actually strikingly bilobate with a deep null directly in front of the displaying bird. While the sage grouse display serves to attract potential mates, male sage grouse rarely face females head on when they call. The results of this study suggest that males may reach females with a high-intensity signal despite their preference for an oblique display posture relative to those females. We characterized these patterns using a novel technique that allowed us to map acoustic radiation patterns of unrestrained animals calling in the wild. Using an eight-microphone array, our technique integrates acoustic localization with synchronous pressure-field measurements while controlling for small-scale environmental variation in sound propagation.
Evolutionary and acclimation-induced variation in the heat-shock responses of congeneric marine snails (genus Tegula) from different thermal habitats: implications for limits of thermotolerance and biogeography
Authors: Tomanek Lars , Somero George N. 
Published: April 2021

ABSTRACT
Heat stress sufficient to cause cellular damage triggers the heat-shock response, the enhanced expression of a group of molecular chaperones called heat-shock proteins (hsps). We compared the heat-shock responses of four species of marine snails of the genus Tegula that occupy thermal niches differing in absolute temperature and range of temperature. We examined the effects of short-term heat stress and thermal acclimation on the synthesis of hsps of size classes 90, 77, 70 and 38 kDa by measuring incorporation of 35S-labeled methionine and cysteine into newly synthesized proteins in gill tissue. Temperatures at which enhanced synthesis of hsps first occurred (Ton), temperatures of maximal induction of hsp synthesis (Tpeak) and temperatures at which hsp synthesis was heat-inactivated (Toff) were lowest in two low-intertidal to subtidal species from the temperate zone, T. brunnea and T. montereyi, intermediate in a mid-to low-intertidal species of the temperate zone, T. funebralis, and highest in a subtropical intertidal species from the Gulf of California, T. rugosa. Synthesis of hsps and other classes of protein by T. brunnea and T. montereyi was heat-inactivated at temperatures commonly encountered by T. funebralis during low tides on warm days. In turn, protein synthesis by T. funebralis was blocked at the upper temperatures of the habitat of T. rugosa. Acclimation of snails to 13 °C, 18 °C and 23 °C shifted Ton and Tpeak for certain hsps, but did not affect Toff. The heat-shock responses of field-acclimatized snails were generally reduced in comparison with those of laboratory-acclimated snails. Overall, despite the occurrence of acclimatory plasticity in their heat-shock responses, genetically fixed differences in Ton, Tpeak and Toff appear to exist that reflect the separate evolutionary histories of these species and may play important roles in setting their thermal tolerance limits and, thereby, their biogeographic distribution patterns.
Inhibiting ventilatory evaporation produces an adaptive increase in cutaneous evaporation in mourning doves Zenaida macroura
Authors: Hoffman Ty C. M. , Walsberg Glenn E. 
Published: April 2021

ABSTRACT
We tested the hypothesis that birds can rapidly change the conductance of water vapor at the skin surface in response to a changing need for evaporative heat loss. Mourning doves (Zenaida macroura) were placed in a two-compartment chamber separating the head from the rest of the body. The rate of cutaneous evaporation was measured in response to dry ventilatory inflow at three ambient temperatures and in response to vapor-saturated ventilatory inflow at two ambient temperatures. At 35 °C, cutaneous evaporation increased by 72 % when evaporative water loss from the mouth was prevented, but no increase was observed at 45 °C. For both dry and vapor-saturated treatments, cutaneous evaporation increased significantly with increased ambient temperature. Changes in skin temperature made only a minor contribution to any observed increase in cutaneous evaporation. This indicates that Z. macroura can effect rapid adjustment of evaporative conductance at the skin in response to acute change in thermoregulatory demand.
Sources of magnetic sensory input to identified neurons active during crawling in the marine mollusc Tritonia diomedea
Authors: Popescu I. R. , Willows A. O. D. 
Published: April 2021

ABSTRACT
Although the nudibranch mollusc Tritonia diomedea orients to the geomagnetic field, the anatomical site and the mechanism of the geomagnetic transducer are not known. Previous work on semi-intact preparations of Tritonia diomedea in which the brain is intact and nerve connections to the periphery are maintained showed that identifiable pedal ganglion neurons Pd5 fired an increased number of action potentials when the horizontal component of the ambient magnetic field was rotated. This response disappeared when all nerves emerging from the brain were cut, suggesting a peripheral locus for the geomagnetic transducer.
In the present work, we recorded intracellularly from Pd5 in preparations in which all peripheral nerves were cut except those containing the axons of neurons Pd5 (pedal nerves 2 and 3). These uncut, mixed, sensory-motor trunks innervate the locomotory epithelium of the foot upon which the animal crawls. In this further-reduced preparation, Pd5 again responded to magnetic field rotations with action potentials. To determine the direction of this action potential transmission in response to magnetic field rotations, we analyzed extracellular recordings from nerves containing the Pd5 axons and found that action potentials elicited in Pd5 by magnetic stimuli originate centrally and are transmitted peripherally.
In addition, we have explored the behavioral function of Pd5 neurons by simultaneously recording intracellular electrical activity and crawling rate of the semi-intact animal. A significant correlation was found between crawling rate and Pd5 action potential rate. We also found that action potentials in dorsal swim interneurons depolarized both Pd5 and the established locomotion motoneuron Pd21.
The biomechanics of fast-starts during ontogeny in the common carp cyprinus carpio
Authors: Wakeling James M. , Kemp Kirsty M. , Johnston Ian A. 
Published: April 2021

ABSTRACT
Common carp Cyprinus carpio L. were reared a constant temperature of 20 °C from the larval (7 mm total length) to the juvenile (80 mm) stage. Body morphology and white muscle mass distribution were measured. Fast-start escape responses were recorded using high-speed cinematography from which the velocities, accelerations and hydrodynamic power requirements were estimated. All three measures of fast-start performance increased during development. White muscle contraction regimes were calculated from changes in body shape during the fast-starts and used to predict the muscle force and power production for all longitudinal positions along the body. Scaling arguments predicted that increases in body length would constrain the fish to bend less rapidly because the cross-sectional muscle area, and hence force production, does not increase at the same rate as the inertial mass that resists bending. As predicted, the increases in body length resulted in decreases in muscle shortening velocity, and this coincided with increases in both the force and power produced by the muscles. The hydrodynamic efficiency, which relates the mechanical power produced by the muscles to the inertial power requirements in the direction of travel, showed no significant change during ontogeny. The increasing hydrodynamic power requirements were thus met by increases in the power available from the muscles. The majority of the increases in fast-start swimming performance during ontogeny can be explained by size-dependent increases in muscle power output. For all sizes, there was a decrease in muscle-mass-specific power output and an increase in muscle stress in a posterior direction along the body due to systematic variations in fibre strain. These changing strain regimes result in the central muscle bulk producing the majority of the power requirements during the fast-start, and this power is transmitted to the tail region of the fish and ultimately to the water via muscle in the caudal myotomes.
The sites of respiratory gas exchange in the planktonic crustacean daphnia magna: an in vivo study employing blood haemoglobin as an internal oxygen probe
Authors: Pirow R. , Wollinger F. , Paul R. J. 
Published: April 2021

ABSTRACT
Recent studies on Daphnia magna have revealed that the feeding current is important for uptake of oxygen from the ambient medium. Respiratory gas exchange should therefore mainly occur within the filtering chamber, whose boundaries are formed by the trunk and the extended carapace shell valves. The precise site of gas exchange in the genus Daphnia is, however, a matter of conjecture. We have developed a method of imaging the haemoglobin oxygen-saturation in the circulatory system of transparent animals, which provides an opportunity to localize oxygen uptake from the environment and oxygen release to the tissues. Experiments were carried out at 20 °C on 2.8–3.0 mm long parthenogenetic females maintained in hypoxic culturing conditions, which had resulted in an increased haemoglobin content in the haemolymph. In lateral views of D. magna, the highest values of haemoglobin oxygen-saturation occurred near the posterior margin of the carapace and, surprisingly, in the rostral part of the head. The ambient oxygen partial pressures at which haemoglobin was half-oxygenated were 15 mmHg (2.0 kPa) for the posterior carapace region and 6 mmHg (0.8 kPa) for the rostrum. Although not all parts of the circulatory system could be analyzed using this technique, the data obtained from the accessible regions suggest that the inner wall of the carapace is a major site of respiratory gas exchange. Taking the circulatory pattern and the flow pattern of the medium in the filtering chamber into consideration, it becomes clear that the haemolymph, after passing from the limbs to the carapace lacuna, becomes oxygenated while flowing through the ventral part of the double-walled carapace in a posterior direction. The laterally flattened rostral region, where sensory and central nervous system structures are located, seems to have direct diffusive access to ambient oxygen, which could be especially advantageous during severe hypoxia when the convective transport systems fail to supply enough oxygen to that region.
Morphological basis of kinematic diversity in feeding sunfishes
Authors: Wainwright Peter C. , Shaw Samantha S. 
Published: April 2021

ABSTRACT
The effects of differences among species in the scaling of lower jaw levers on the scaling of prey-capture kinematics are explored in three species of centrarchid fishes. We consider the jaw opening and closing lever systems and calculate the consequences of differences in the scaling of the in-levers for the scaling of the time taken to open the mouth (To) and the time taken to close the mouth (Tc) during prey capture. Predictions of To and Tc, based on differences in the scaling of jaw in-levers, are compared with the observed scaling of To and Tc in three centrarchid fishes. Video recordings (200 and 400 images s−1) were made of prey capture in largemouth bass Micropterus salmoides (33–206 mm standard length, SL), spotted sunfish Lepomis punctatus (24–145 mm SL) and bluegill sunfish Lepomis macrochirus (24–220 mm SL), and the fastest values of To and Tc were taken from the fastest recorded feeding event for each fish. The scaling exponents of To and Tc regressed on fish SL for largemouth bass were 0.592 and 0.572, respectively. Exponents observed for sunfishes were not significantly different from predicted values, based on scaling exponents in largemouth bass and interspecific differences in jaw lever proportions. Two conclusions are emphasized. First, between 25 and 220 mm SL, the time taken to open and close the mouth during the strike increases with body size in all three species, suggesting a general pattern for this family. Second, evolutionary changes in jaw lever mechanics are a major determinant of the diversity of prey-capture kinematics in this sample of centrarchid fishes.
Shear stress experienced by echinoderm eggs in the oviduct during spawning: potential role in the evolution of egg properties
Authors: Thomas Florence I. M. , Bolton Toby F. 
Published: April 2021

ABSTRACT
Shear stresses experienced by eggs in the oviduct of the echinoid Arbacia punctulata during spawning were calculated using engineering equations that describe laminar flow through pipes. Shear stresses in the oviduct ranged from 0 to 58.7 Pa. Two properties of eggs were identified that have the potential either to minimize the shear stress in the oviduct or to reduce the damage experienced by eggs exposed to high shear stress. These properties are the viscosity of the eggs and the presence of extracellular layers on eggs of A. punctulata. The viscosity of eggs decreases with increasing shear rates, which reduces the magnitude of shear stress experienced in the oviduct, while the extracellular layers mitigate the effect of shear stress on the eggs. Eggs with intact extracellular layers were damaged less frequently than were those with the extracellular layers removed. The results of this research indicate that physical stresses may be important selective factors in the evolution of gamete properties.
Reactive oxygen intermediate production by oyster hemocytes exposed to hypoxia
Authors: Boyd John N. , Burnett Louis E. 
Published: April 2021

ABSTRACT
Oysters are frequently exposed to severely hypoxic conditions, especially during summer months. During the summer, there are also large numbers of disease-related oyster mortalities. This research was conducted to determine whether exposure to environmental hypoxia reduces the ability of oyster hemocytes to produce reactive oxygen intermediates (ROIs), an important part of their defense system. Oysters of the species Crassostrea virginica were held in normoxic (, pH 7.8–8.0) and hypoxic conditions (, pH 7.1–7.4). In vivo hemolymph variables (and pH) were measured after both 1 hour and 2 days in each treatment to determine the appropriate environment for subsequent hemocyte experiments. Production of reactive oxygen intermediates by hemocytes was measured using luminol-enhanced chemiluminescence (CL). During CL tests, hemocytes were held under the following conditions: air (, pH 7.6), in vivo hemolymph conditions of normoxic oysters (, pH 7.6), and in vivo hemolymph conditions of hypoxic oysters (, pH 7.1). Production of ROIs under hypoxic conditions was 33 % of that under normoxia. This decrease was the result of specific and independent effects of lower oxygen levels and decreased pH. It was not due to any direct effect of CO2.
Ferromagnetic material in the eastern red-spotted newt notophthalmus viridescens
Authors: Brassart J. , Kirschvink J. L. , Phillips J. B. , Borland S. C. 
Published: April 2021

ABSTRACT
Behavioral results obtained from the eastern red-spotted newt (Notophthalmus viridescens) led to the suggestion of a hybrid homing system involving inputs from both a light-dependent and a non-light-dependent mechanism. To evaluate the possible role of a receptor based on biogenic magnetite in this animal, we performed magnetometry experiments on a set of newts previously used in behavioral assays. The natural remanent magnetization (NRM) carried by these newts was strong enough to be measured easily using a direct-current-biased superconducting quantum interference device functioning as a moment magnetometer. Isothermal remanent magnetizations were two orders of magnitude higher than the NRM, suggesting that ferromagnetic material consistent with magnetite is present in the body of the newt. The NRM has no preferential orientation among the animals when analyzed relative to their body axis, and the demagnetization data show that, overall, the magnetic material grains are not aligned parallel to each other within each newt. Although the precise localization of the particles was not possible, the data indicate that magnetite is not clustered in a limited area. A quantity of single-domain magnetic material is present which would be adequate for use in either a magnetic intensity or direction receptor. Our data, when combined with the functional properties of homing, suggest a link between this behavioral response and the presence of ferromagnetic material, raising the possibility that magnetite is involved at least in the map component of homing of the eastern red-spotted newt.
Target organ specificity of major neuropeptide stimulants in locust excretory systems
Authors: Coast G. M. , Meredith J. , Phillips J. E. 
Published: April 2021

ABSTRACT
The major stimulant of ileal fluid reabsorption in Locusta migratoria and Schistocerca gregaria corpora cardiaca, ion-transport peptide (ITP), had no stimulatory action on fluid secretion by isolated Malpighian tubules of S. gregaria, nor did it have a synergistic or antagonistic effect in combination with locustakinin (Lom-K) or Locusta-diuretic hormone (Locusta-DH). Stimulants of locust Malpighian tubules (Lom-K and Locusta-DH) had no action on either active transport of Cl− (measured as short-circuit current, Isc) or the rate of fluid reabsorption across S. gregaria ilea and recta in vitro. Thus, hormonal control of these major organs of the excretory system appears to be clearly separated.
Lom-K and Locusta-DH acted synergistically to stimulate secretion by S. gregaria Malpighian tubules, and the diuretic response was more rapid than the response of the ileum and rectum to hindgut stimulants. Taken together, these data suggest that, in the initial phase of post-prandial diuresis, urine flow will exceed fluid uptake in the hindgut, thereby allowing excess water to be eliminated.