bluuebunny/crossref_metadata_2025_split huggingface dataset:
Behavioural Thermoregulation of Chum Salmon During Homing Migration in Coastal Waters
Authors: Tanaka Hideji , Takagi Yasuaki , Naito Yasuhiko 
Published: April 2021

ABSTRACT
Homing Pacific salmon are suggested to utilise directional cues in shallow water while migrating in coastal waters. Since salmonids are typical cold-water fish, they may have to cope with warm surface water while gathering directional information. We studied behavioural thermoregulation of 31 free-ranging chum salmon Oncorhynchus keta using micro data loggers off the Sanriku coast from early October to December. The surface water temperature was approximately 20 °C in early October and decreased to approximately 12 °C in December. The seasonal change of water temperature transformed the behaviour of salmon markedly from deep diving to shallow swimming. In October, salmon frequently dived to depths exceeding 100 m. Duration of deep dives tended to be prolonged as the thermal difference between sea surface and bottom water increased. The results indicated that salmon sought the coolest thermal refuge that they could exploit by vertical movement. Thermal refuge could be a way for salmon to minimise metabolic energy cost; however, salmon repeatedly returned to the surface water column. We found a positive correlation between surface swimming of salmon and the presence of cool covering water, which could contain river waters. This suggests that salmon tend to be risk-prone when subjected to a high concentration of directional cues. Salmon in December spent most of their time in shallow water. These findings suggest that salmon adjusted their behavioural strategy with the hydrographic structure of the sea in order to achieve a balance between acquiring directional cues and behavioural thermoregulation.
Vocal Tract Function in Birdsong Production: Experimental Manipulation of Beak Movements
Authors: Hoese William J. , Podos Jeffrey , Boetticher Nicholas C. , Nowicki Stephen 
Published: April 2021

ABSTRACT
Kinematic analyses have demonstrated that the extent to which a songbird’s beak is open when singing correlates with the acoustic frequencies of the sounds produced, suggesting that beak movements function to modulate the acoustic properties of the vocal tract during song production. If motions of the beak are necessary for normal song production, then disrupting the ability of a bird to perform these movements should alter the acoustic properties of its song. We tested this prediction by comparing songs produced normally by white-throated sparrows and swamp sparrows with songs produced when the beak was temporarily immobilized. We also observed how temporarily loading the beak of canaries with extra mass affected vocal tract movements and song production. Disruption of vocal tract movements resulted in the predicted frequency-dependent amplitude changes in the songs of both white-throated sparrows and swamp sparrows. Canaries with mass added to their beak sang with their beak open more widely than normal and produced notes with greater harmonic content than those without weights. Both manipulations resulted in acoustic changes consistent with a model in which beak motions affect vocal tract resonances, thus supporting the hypothesis that dynamic vocal tract motions and post-production modulation of sound are necessary features of normal song production.
Responses Of Young Xenopus LaeviS TAdpoles To Light Dimming: Possible Roles For The Pineal Eye
Authors: Jamieson D. , Roberts Alan 
Published: April 2021

ABSTRACT
When the light is dimmed, the pineal eye of hatchling Xenopus laevis tadpoles excites the central pattern generator for swimming, but the behavioural significance of pineal excitation is unclear. We show that tadpoles spend 99 % of their time hanging from the surface meniscus or solid objects using mucus secreted by a cement gland on the head. Attachment inhibits swimming, but unattached tadpoles swim spontaneously. Provided that their pineal eye is intact, they attach closer to the water surface in the dark than in the light and attach preferentially to the underside of floating objects that cast shadows. Dimming causes tadpoles swimming horizontally to turn upwards and is very effective in initiating upward swimming in unattached tadpoles. Similar pineal-dependent responses during swimming are present up to stage 44. Pinealectomy blocks responses to dimming at all stages. Recordings from immobilised tadpoles reveal that light dimming induces faster fictive swimming and that pineal activity is increased for up to 20 min during sustained light dimming. We suggest that the increase in pineal discharge during dimming increases the probability of upward swimming and, in this way, increases the probability of tadpoles attaching to objects higher in the water column that cast shadows.
Simple Mechanisms Organise Orientation of Escape Swimming in Embryos and Hatchling Tadpoles of Xenopus Laevis
Authors: Roberts Alan , Hill N. A. , Hicks Robin 
Published: April 2021

ABSTRACT
Many amphibian tadpoles hatch and swim before their inner ears and sense of spatial orientation differentiate. We describe upward and downward swimming responses in hatchling Xenopus laevis tadpoles from stages 32 to 37/38 in which the body rotates about its longitudinal axis.
Tadpoles are heavier than water and, if touched while lying on the substratum, they reliably swim upwards, often in a tight spiral. This response has been observed using stroboscopic photography and high-speed video recordings. The sense of the spiral is not fixed for individual tadpoles. In ‘more horizontal swimming’ (i.e. in directions within ±30 ° of the horizontal), the tadpoles usually swim belly-down, but this position is not a prerequisite for subsequent upward spiral swimming.
Newly hatched tadpoles spend 99 % of their time hanging tail-down from mucus secreted by a cement gland on the head. When suspended in mid-water by a mucus strand, tadpoles from stage 31 to 37/38 tend to swim spirally down when touched on the head and up when touched on the tail. The three-dimensional swimming paths of stage 33/34 tadpoles were plotted using simultaneous video images recorded from the side and from above. Tadpoles spiralled for 70 % of the swimming time, and the probability of spiralling increased to 1 as swim path angles became more vertical.
Tadpoles were neutrally buoyant in Percoll/water mixtures at 1.05 g cm−3, in which anaesthetised tadpoles floated belly-down and head-up at 30 °. In water, their centre of mass was ventral to the muscles in the yolk mass.
A simple mathematical model suggests that the orientation of tadpoles during swimming is governed by the action of two torques, one of which raises the head (i.e. increases the pitch) and the other rotates (rolls) the body. Consequently, tadpoles (i) swim belly-down when the body is approximately horizontal because the body is ballasted by dense yolk, and (ii) swim spirally at more vertical orientations when the ballasting no longer stabilises orientation.
Measurements in tethered tadpoles show that dorsal body flexion, which could produce a dorsal pitch torque, is present during swimming and increases with tailbeat frequency.
We discuss how much of the tadpole’s behaviour can be explained by our mathematical model and suggest that, at this stage of development, oriented swimming responses may depend on simple touch reflexes, the organisation of the muscles and physical features of the body, rather than on vestibular reflexes.
Allometric Scaling Relationships of Jumping Performance in the Striped Marsh Frog Limnodynastes Peronii
Authors: Wilson Robbie S. , Franklin Craig E. , James Rob S. 
Published: April 2021

ABSTRACT
We constructed a force platform to investigate the scaling relationships of the detailed dynamics of jumping performance in striped marsh frogs (Limnodynastes peronii). Data were used to test between two alternative models that describe the scaling of anuran jumping performance; Hill’s model, which predicts mass-independence of jump distance, and Marsh’s model, which predicts that jump distance increases as M0.2, where M is body mass. From the force platform, scaling relationships were calculated for maximum jumping force (Fmax), acceleration, take-off velocity (Umax), mass-specific jumping power (Pmax), total jumping distance (DJ) and total contact time for 75 L. peronii weighing between 2.9 and 38.4 g. Fmax was positively correlated with body mass and was described by the equation Fmax=0.16M0.61, while Pmax decreased significantly with body mass and was described by the equation Pmax=347M−0.46. Both DJ and Umax were mass-independent over the post-metamorph size range, and thus more closely resembled Hill’s model for the scaling of locomotion. We also examined the scaling relationships of jumping performance in metamorph L. peronii by recording the maximum jump distance of 39 animals weighing between 0.19 and 0.58 g. In contrast to the post-metamorphic L. peronii, DJ and Umax were highly dependent on body mass in metamorphs and were described by the equations DJ=38M0.53 and Umax=1.82M0.23, respectively. Neither model for the scaling of anuran jumping performance resembled data from metamorph L. peronii. Although the hindlimbs of post-metamorphic L. peronii scaled geometrically (body mass exponent approximately 0.33), the hindlimbs of metamorphs showed greater proportional increases with body mass (mass exponents of 0.41–0.42).
Catarrhine Photopigments are Optimized for Detecting Targets Against a Foliage Background
Authors: Sumner Petroc , Mollon J. D. 
Published: April 2021

ABSTRACT
The colour vision of many primates is trichromatic, whereas that of all other mammals is thought to be dichromatic or monochromatic. Moreover, the triplets of cone pigments in different catarrhines (Old World apes and monkeys) are strikingly similar in their spectral positions. We ask whether the selective advantage of trichromacy lies in an enhanced ability to find edible leaves or fruit. Further, we ask whether any factor in these two search tasks has constrained the particular set of cone spectral sensitivities observed in all catarrhines. We measured the spectral properties of the natural environments of six primate species in Uganda: Pan troglodytes, Cercopithecus mitis, Cercopithecus ascanius, Lophocebus albigena, Colobus guereza and Colobus badius. We concentrated on the fruit and leaves in their diets and the leaves of the trees that make up the background against which these diet items must be found. We plotted these measured stimuli in colour spaces appropriate for each primate species, and found that both frugivory and folivory are facilitated by the extra dimension of colour vision found in catarrhines but lacking in most other mammals. Furthermore, by treating the task of searching for food as a signal-detection task, we show that, of all possible combinations of cone sensitivities, the spectral positions of the actual primate pigments are optimal for finding fruit or young leaves against the background of mature leaves. This is because the variance of the chromaticities of the mature leaves is minimised in one channel of the primate’s colour vision, so allowing anything that is not a mature leaf to stand out.
Slow Muscle Function of Pacific Bonito (Sarda Chiliensis) During Steady Swimming
Authors: Ellerby D. J. , Altringham J. D. , Williams T. , Block B. A. 
Published: April 2021

ABSTRACT
The Pacific bonito, Sarda chiliensis, is anatomically intermediate between mackerel and tuna. The specialisations exhibited by tuna are present in the bonito, but to a lesser degree. Slow-twitch muscle strain and activity patterns were determined during steady swimming (tailbeat frequency 1.2–3.2 Hz) at four locations on the body of Sarda chiliensis using sonomicrometry and electromyography. Both strain and the phase of electromygraphic activity were independent of tailbeat frequency. The strain of superficial slow-twitch muscle increased from ±3.1 % l0 at 0.35FL to ±5.8 % l0 at 0.65FL, where l0 is muscle resting length and FL is the body length from snout to tail fork. Between 0.35 and 0.65FL, there was a negative phase shift of 16 ° in the onset of electromygraphic activity in superficial slow-twitch muscle relative to the strain cycle. Muscle activity patterns are comparable with those of tuna. At 0.58FL, the onset of activity in deep slow-twitch muscle was approximately synchronous with the onset of activity in superficial muscle in the same myotome at 0.65FL. The distribution of slow-twitch muscle along the body of Sarda chiliensis and four additional fish species, Anguilla anguilla, Oncorhynchus mykiss, Scomber scombrus and Thunnus albacares, was also measured. Slow-twitch muscle appears to become more concentrated at approximately 0.5FL as swimming kinematics become more thunniform.
Effects of Catecholamines and Purines on Luminescence in the Brittlestar Amphipholis Squamata (Echinodermata)
Authors: Bremaeker N. De , Baguet F. , Mallefet J. 
Published: April 2021

ABSTRACT
The effects of catecholamines (dopamine, adrenaline, noradrenaline and its derivatives), 5-hydroxytryptamine and purines (adenosine, ATP and their derivatives) on the acetylcholine-induced luminescence of isolated arms and dissociated photocytes of the luminescent ophiuroid Amphipholis squamata were tested. The results showed that catecholamines and 5-hydroxytryptamine (10−5 to 10−3 mol l−1) had a strong dose-dependent inhibitory effect on acetylcholine-induced luminescence. In contrast, purines (10−4 and 10−3 mol l−1) triggered luminescence in the absence of acetylcholine and/or potentiated acetylcholine-induced luminescence. The results with specific purinergic agonists and antagonists indicated the involvement of P1- and P2-like purinoceptors in the control of luminescence.
Our study suggests that, in addition to the previously described cholinergic system in Amphipholis squamata, there may be a purinergic system, acting in synergy with acetylcholine, and an inhibitory neuromodulatory catecholaminergic system, all associated with the control of luminescence.
Blood Pressure Control in a Larval Amphibian, Xenopus Laevis
Authors: Warburton Stephen J. , Fritsche Regina 
Published: April 2021

ABSTRACT
The regulation of arterial pressure in early vertebrate embryos and larvae with non-innervated hearts is poorly understood. We used nanoliter intravascular injections in anaesthetized Xenopus laevis larvae (stage 49–51) to assess their ability to maintain arterial pressure in the face of a volume load. Injections of saline and hetastarch (a volume expander) were made into the ventricle. Arterial pressure, end-diastolic ventricular volume, end-systolic ventricular volume and heart rate were measured. Injection of 800 nl caused a rapid rise in arterial pressure and stroke volume. There were no changes in heart rate, indicating the absence of an arterial baroreflex. Blood pressure in saline-injected animals recovered quickly (within 5 min), whereas hetastarch injections caused hypertension to be maintained for much longer, for over 40 min in the most extreme case. We surmise that Starling forces at the capillary play an important role in pressure regulation but are not adequate to explain the entire response. Finally, there was ample evidence for a Frank–Starling relationship in the ventricle.
The Mechanistic Basis of Aerobic Performance Variation in Red Junglefowl
Authors: Hammond Kimberly A. , Chappell Mark A. , Cardullo Richard A. , Lin Ruei-Shiuan , Johnsen Torgeir S. 
Published: April 2021

ABSTRACT
We examined aerobic performance, organ and muscle mass and enzymatic activity in red junglefowl (Gallus gallus). We tested three models of performance limitation (central limits, peripheral limits, symmorphosis) and explored relationships between basal metabolic rate (BMR), aerobic capacity and social rank. Males had a lower BMR, a higher and a greater aerobic scope than females. Females possessed larger peritoneal and reproductive organs, while males had larger hearts, lungs and leg muscles. In females, BMR was correlated with spleen mass and was correlated with hematocrit and large intestine mass. Male BMR was correlated with intestinal tract and lung mass, and was correlated with heart and pectoralis mass. Male citrate synthase activity averaged 57 % higher than that of females and was correlated with (this correlation was not significant in females). Female social status was not correlated with any variable, but male dominance was associated with higher aerobic scope, larger heart and lungs, smaller peritoneal organs and greater leg citrate synthase activity. We conclude that aerobic capacity is controlled by system-wide limitations (symmorphosis) in males, while in females it is controlled by central organs.
In neither sex is elevated aerobic capacity associated with increased maintenance costs
Effect of Temperature On pH and Electrolyte Concentration in Air-Breathing Ectotherms
Authors: Stinner J. N. , Hartzler L. K. 
Published: April 2021

ABSTRACT
The aim of this study was to determine the effects of temperature upon pH, protein charge and acid–base-relevant ion exchange in air-breathing ectotherms. Plasma and skeletal muscles in cane toads (Bufo marinus) and bullfrogs (Rana catesbeiana) were examined at 30, 20 and 10 °C. In addition, skeletal muscle ion concentrations were examined in black racer snakes (Coluber constrictor) at 30 and 10 °C. Cooling the amphibians produced a reduction in most of the plasma ion concentrations (Na+, K+, Ca2+, Cl−, SO42−) and in protein concentration because of increased hydration. Between 30 and 10 °C, total plasma osmolality fell by 14 % in the toads and by 5 % in the frogs. Plasma protein charge, calculated using the principle of electroneutrality, was unaffected by temperature, except possibly for the toads at 10 °C. The in vivo skeletal muscle ΔpHi/ΔT ratio, where pHi is intracellular pH and T is temperature, between 30 and 20 °C averaged −0.014 °C−1 in the toads and −0.019 °C−1 in the frogs. Between 20 and 10 °C, there was no change in pHi in the toads and a −0.005 °C−1 change in the frogs. The in vitro skeletal muscle ΔpHi/ΔT averaged −0.011 °C−1 in both toads and frogs. In all three species, skeletal muscle inulin space declined with cooling. Intracellular ion concentrations were calculated by subtracting extracellular fluid ion concentrations from whole-muscle ion concentrations. In general, temperature had a large effect upon intracellular ion concentrations (Na+, K+, Cl−) and intracellular CO2 levels. The relevance of the changes in intracellular ion concentration to skeletal muscle acid–base status and protein charge and the possible mechanisms producing the adjustments in intracellular ion concentration are discussed. It is concluded that ion-exchange mechanisms make an important contribution to adjusting pH with changes in temperature.
Lipid Compositional Correlates of Temperature-Adaptive Interspecific Differences in Membrane Physical Structure
Authors: Logue James A. , De Vries Art L. , Fodor Elfrieda , Cossins Andrew R. 
Published: April 2021

ABSTRACT
Teleost species from cold environments possess more disordered brain synaptic membranes than species from warm habitats, thereby providing equivalent physical structures at their respective habitat temperatures. We have related this adaptive interspecific biophysical response to the fatty acid composition of brain membranes from 17 teleost species obtained from Antarctic, temperate and semi-tropical waters, as well as from rat and turkey as representative homeotherms. Cold-adaptive increases in membrane disorder (determined by fluorescence anisotropy with diphenylhexatriene as probe) were correlated with large and linear increases in the proportion of unsaturated fatty acids, from 35 to 60 % in phosphatidylcholine (PtdCho) and from 55 to 85 % in phosphatidylethanolamine (PtdEth). For PtdCho, the cold-adaptive increase in unsaturation was associated almost entirely with increased proportions (from 7 to 40 %) of polyunsaturated fatty acids (PUFAs), with mono-unsaturates (MUFAs) providing an approximately constant proportion in all species. Exactly opposite effects were evident for phosphatidylethanolamine (PtdEth). Thus, the compositional adaptation for PtdCho occurred largely by exchange of polyunsaturated and mono-unsaturated fatty acid in the sn-2 position, whilst for PtdEth it involved exchanges between saturates and mono-unsaturates at the sn-1 position. This difference may be related to the different molecular shapes of the two phosphoglycerides and the need to maintain the balance between bilayer-stabilising and -destabilising tendencies. This comparative study provides a more comprehensive view of the compositional adjustments that accompany and perhaps account for temperature-adaptive interspecific differences in membrane physical structure.
The Visually Controlled Prey-Capture Behaviour of the European Mantispid Mantispa Styriaca
Authors: Kral Karl , Vernik Martin , Devetak Dušan 
Published: April 2021

ABSTRACT
Mantispids (Mantispa styriaca) are predatory insects; on bright sunny days, they wait in ambush for insect prey. The prey is captured as soon as it is within reach by means of lightning-speed strikes with the powerful forelegs. The strikes can take less than 60 ms. The mantispid accomplishes this almost as effectively as the larger praying mantis, which occupies a similar habitat, even though the praying mantis has apposition eyes with a high-resolution fovea, whereas the mantispid has unspecialized optical superposition eyes. Mantispa styriaca reacts to an item of prey when the latter covers a critical visual angle. The detection of prey immediately triggers adjustment reactions in the mantispid, which attempts to position the prey item in the visual field of both eyes and in the capture zone. Irrespective of the size of the prey, the capture reaction of the mantispid is always triggered if the distance to the prey falls below a certain critical value. As indicated by the analysis of individual video frames, immediately before an aimed strike, the item of prey is always positioned exactly in the centre of the binocular field of vision in the extended midsagittal plane of the mantispid’s head. The strike may be triggered by the ommatidia of the left and right eyes, the lines of sight of which converge precisely on this region. The principal conclusion to be drawn is that the prey-capture behaviour of the mantispid appears to be based on a triangulation mechanism.
The Development of Fatigue Quality in High- and Low-Stressed Tendons of Sheep (Ovis Aries)
Authors: Pike Anna V. L. , Ker Robert F. , Alexander R. Mcneill 
Published: April 2021

ABSTRACT
The time taken to rupture in cyclic fatigue tests, to a stress of 45 MPa, was used to compare the fatigue quality of tendons from sheep of varying ages. Muscle and tendon cross-sectional areas were used to calculate the stress-in-life of each tendon. For any given age, high-stressed plantaris tendons were of a higher fatigue quality than low-stressed extensor tendons. Both fatigue quality and stress-in-life increased with age for each tendon type. High-stressed tendons are subjected to large increases in stress-in-life during growth, and fatigue quality increased significantly with this stress. This relationship was not seen, however, in low-stressed tendons, which are not subjected to a comparable range of stresses over time. It is possible that cells modify tendon fatigue quality in response to tendon loading history. Whilst Young’s modulus was seen to increase with age, no difference was detected between high- and low-stressed tendons.