bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preferred Speed and Cost of Transport: The Effect of Incline
Authors: Wickler Steven J. , Hoyt Donald F. , Cogger Edward A. , Hirschbein Misty H. 
Published: April 2021

ABSTRACT
Preferred speed is the behavioral tendency of animals to utilize a relatively narrow set of speeds near the middle of a much broader range that they are capable of using within a particular gait. Possible explanations for this behavior include minimizing musculoskeletal stresses and maximizing energetic economy. If preferred speed is determined by energetic economy (cost of transport, CT), then shifts in preferred speed should produce shifts in CT. To test this hypothesis, preferred speeds were measured in trotting horses on the level and on an incline. The preferred trotting speed decreased from 3.29±0.24 m s−1 on the level to 3.05±0.30 m s−1 (means ± S.D., N=6) on an 11.8 % incline. The rate of oxygen consumption was measured as a function of trotting speed on a treadmill and was a curvilinear function of speed in all horses under both conditions (level and 10 % incline). This curvilinear relationship resulted in a CT that was a U-shaped function of speed. The speed at which CT was minimal (i.e. at which trotting was most energetically economical) was very near the preferred speed on the level and decreased on the incline, again to a speed near the preferred speed on the incline.
Hair Cells, Hearing and Hopping: A Field Guide to Hair Cell Physiology in the Frog
Authors: Smotherman Michael S. , Narins Peter M. 
Published: April 2021

ABSTRACT
For more than four decades, hearing in frogs has been an important source of information for those interested in auditory neuroscience, neuroethology and the evolution of hearing. Individual features of the frog auditory system can be found represented in one or many of the other vertebrate classes, but collectively the frog inner ear represents a cornucopia of evolutionary experiments in acoustic signal processing. The mechano-sensitive hair cell, as the focal point of transduction, figures critically in the encoding of acoustic information in the afferent auditory nerve. In this review, we provide a short description of how auditory signals are encoded by the specialized anatomy and physiology of the frog inner ear and examine the role of hair cell physiology and its influence on the encoding of sound in the frog auditory nerve. We hope to demonstrate that acoustic signal processing in frogs may offer insights into the evolution and biology of hearing not only in amphibians but also in reptiles, birds and mammals, including man.
Three-Dimensional Kinematics and Wake Structure of the Pectoral Fins During Locomotion in Leopard Sharks Triakis Semifasciata
Authors: Wilga C. D. , Lauder G. V. 
Published: April 2021

ABSTRACT
The classical theory of locomotion in sharks proposes that shark pectoral fins are oriented to generate lift forces that balance the moment produced by the oscillating heterocercal tail. Accordingly, previous studies of shark locomotion have used fixed-wing aircraft as a model assuming that sharks have similar stability and control mechanisms. However, unlike airplanes, sharks are propelled by undulations of the body and tail and have considerable control of pectoral fin motion. In this paper, we use a new approach to examine the function of the pectoral fins of leopard sharks, Triakis semifasciata, during steady horizontal swimming at speeds of 0.5–2.0 l s−1, where l is total body length, and during vertical maneuvering (rising and sinking) in the water column. The planar orientation of the pectoral fin was measured using three-dimensional kinematics, while fluid flow in the wake of the pectoral fin and forces exerted on the water by the fin were quantified using digital particle image velocimetry (DPIV). Steady horizontal swimming in leopard sharks is characterized by continuous undulations of the body with a positive body tilt to the flow that decreases from a mean of 11 ° to 0.6 ° with increasing flow speeds from 0.5 to 2.0 l s−1. Three-dimensional analysis showed that, during steady horizontal locomotion, the pectoral fins are cambered, concave downwards, at a negative angle of attack that we predict to generate no significant lift.
Leopard shark pectoral fins are also oriented at a substantial negative dihedral angle that amplifies roll moments and hence promotes rapid changes in body position. Vortices shed from the trailing edge of the pectoral fin were detected only during vertical maneuvering. Starting vortices are produced when the posterior plane of the pectoral fin is actively flipped upwards or downwards to initiate rising or sinking, respectively, in the water column. The starting vortex produced by the pectoral fin induces a pitching moment that reorients the body relative to the flow. Body and pectoral fin surface angle are altered significantly when leopard sharks change vertical position in the water column. Thus, locomotion in leopard sharks is not analogous to flight in fixed-wing aircraft. Instead, a new force balance for swimming leopard sharks is proposed for steady swimming and maneuvering. Total force balance on the body is adjusted by altering the body angle during steady swimming as well as during vertical maneuvering, while the pectoral fins appear to be critical for initiating maneuvering behaviors, but not for lift production during steady horizontal locomotion.
Seasonal Changes in Buoyancy and Diving Behaviour of Adult Grey Seals
Authors: Beck Carrie A. , Bowen W. Don , Iverson Sara J. 
Published: April 2021

ABSTRACT
Phocid seals go through dramatic seasonal changes in body mass and composition as a result of the spatial and temporal separation of foraging, reproduction and moulting. These changes in body fat content and body mass result in seasonal changes in buoyancy, which in turn may influence diving behaviour. We examined the longitudinal changes in buoyancy and diving behaviour of 14 adult grey seals (Halichoerus grypus) during two periods that represent maximal contrast in body mass and composition. During both the post-moulting (PM) and pre-breeding (PB) periods, grey seals were negatively buoyant. However, buoyancy increased by 47.9 % between the PM and PB periods. Descent rate was significantly faster during the PM period (1.0±0.07 m s−1) than during the PB period (0.7±0.06 m s−1), suggesting that seals were aided by negative buoyancy during the downward portion of dives.
Ascent rate was also significantly faster during the PM period (0.8±0.06 m s−1) than during the PB period (0.6±0.05 m s−1), contradicting the prediction that more buoyant animals should ascend faster. The effects of drag could not account for this discrepancy. Dive depth and surface interval between dives did not differ significantly between the two periods. Similarly, the distribution of dive shapes used by individuals did not differ between the two periods. However, dive duration was significantly longer during the PB period than during the PM period (5.5±0.25 min compared with 4.4±0.24 min, respectively) as was time spent at the bottom of the dive (3.1±0.22 min compared with 2.5±0.15 min, respectively).
Partial Experience with the Arc of the Sun is Sufficient for all-Day Sun Compass Orientation in Homing Pigeons, Columba Livia
Authors: Budzynski Cheri A. , Dyer Fred C. , Bingman Verner P. 
Published: April 2021

ABSTRACT
The ability of animals to learn to use the sun for orientation has been explored in numerous species. In birds, there is conflicting evidence about the experience needed for sun compass orientation to develop. The prevailing hypothesis is that birds need entire daytime exposure to the arc of the sun to use the sun as an orientation cue. However, there is also some evidence indicating that, even with limited exposure to the arc of the sun, birds, like insects, can use the sun to orient at any time of day. We re-examine this issue in a study of compass orientation in a cue-controlled arena. Two groups of young homing pigeons received different exposure to the sun. The control group experienced the sun throughout the day; the experimental group experienced only the apparent descent of the sun. After 8 weeks of sun exposure, we trained both groups in the afternoon to find food in a specific compass direction in an outdoor arena that provided a view of the sun but not landmarks. We then tested the pigeons in the morning for their ability to use the morning sun as an orientation cue. The control group and the experimental group, which was exposed to the morning sun for the first time, succeeded in orienting in the training direction during test 1. The orientation of the experimental group was no different from that of the control group, although the experimental first trial directional response latencies were greater than the control latencies. Subsequently, we continued training both groups in the afternoon and then tested the pigeons during the morning under complete cloud cover. Both groups displayed random directional responses under cloud cover, indicating that the observed orientation was based on the visibility of the sun. The data indicate that pigeons with limited exposure to the arc of the sun can, like insects, use the sun for orientation at any time of day.
Exploring Dynamic Similarity in Human Running Using Simulated Reduced Gravity
Authors: Donelan J. Maxwell , Kram Rodger 
Published: April 2021

ABSTRACT
The Froude number (a ratio of inertial to gravitational forces) predicts the occurrence of dynamic similarity in legged animals over a wide range of sizes and velocities for both walking and running gaits at Earth gravity. This is puzzling because the Froude number ignores elastic forces that are crucial for understanding running gaits. We used simulated reduced gravity as a tool for exploring dynamic similarity in human running. We simulated reduced gravity by applying a nearly constant upward force to the torsos of our subjects while they ran on a treadmill. We found that at equal Froude numbers, achieved through different combinations of velocity and levels of gravity, our subjects did not run in a dynamically similar manner. Thus, the inertial and gravitational forces that comprise the Froude number were not sufficient to characterize running in reduced gravity. Further, two dimensionless numbers that incorporate elastic forces, the Groucho number and the vertical Strouhal number, also failed to predict dynamic similarity in reduced-gravity running. To better understand the separate effects of velocity and gravity, we also studied running mechanics at fixed absolute velocities under different levels of gravity. The effects of velocity and gravity on the requirements of dynamic similarity differed in both magnitude and direction, indicating that there are no two velocity and gravity combinations at which humans will prefer to run in a dynamically similar manner. A comparison of walking and running results demonstrated that reduced gravity had different effects on the mechanics of each gait. This suggests that a single unifying hypothesis for the effects of size, velocity and gravity on both walking and running gaits will not be successful.
Wolbachia Infection and Cytoplasmic Incompatibility in the Cricket Teleogryllus Taiwanemma
Authors: Kamoda Satoru , Masui Shinji , Ishikawa Hajime , Sasaki Tetsuhiko 
Published: April 2021

ABSTRACT
Wolbachia are cytoplasmically inherited bacteria found in many arthropods. They induce various reproductive alterations in their hosts, including cytoplasmic incompatibility, thelytokous parthenogenesis, feminization and male-killing. In this study, we examined Wolbachia infection and its effects on the host cricket Teleogryllus taiwanemma. In a phylogenetic study based on the wsp gene coding for a Wolbachia surface protein, the Wolbachia strain harboured by T. taiwanemma was clustered together with those harboured by Laodelphax striatellus, Tribolium confusum, Acraea encedon, Trichogramma deion and Adalia bipunctata. Crossing experiments using the Wolbachia-infected and uninfected strains of cricket showed that the infection is associated with the expression of unidirectional cytoplasmic incompatibility: the egg hatch rate in the incompatible cross between the infected males and uninfected females was 20.3 %. We also examined the distribution of Wolbachia within the host using polymerase chain reaction assays; they were detected in the antennae, heads, forewings, hindwings, testes, ovaries, Malpighian tubules, foot muscles and fat bodies. Quantitative polymerase chain reaction assays showed that the bacterial density was highest in the fat bodies, followed by the ovaries and testes. Wolbachia were not detected in the haemolymph or in mature spermatozoa. The spermatozoa of the infected male may be modified by the presence of Wolbachia during its development. To examine this possibility, we compared the profiles of sperm proteins between the infected and uninfected males using two-dimensional gel electrophoresis. However, no differences in the protein profiles were observed.
Estimation of Thermal Constants: The Importance of using Equilibrium Temperature Rather than Ambient Temperature Demonstrated with Hoverflies (Diptera, Syrphidae, Genus Eristalis)
Authors: Bressin S. , Willmer P. G. 
Published: April 2021

ABSTRACT
Water evaporation has a marked effect on the passive rates of body temperature change of eristaline hoverflies. It results in the equilibrium temperature of these flies being significantly lower than ambient temperature. Different values for the cooling and warming constants are therefore obtained depending on whether equilibrium or ambient temperature is used as the baseline. Hence, care must be taken when estimating these constants with all animals, especially those of moderate to high permeability. It is recommended that equilibrium temperature be used in such situations. Evaporative cooling is probably also responsible for cooling constants being higher than warming constants in this and other studies.
Locomotor Repertoire of The Larval Zebrafish: Swimming, Turning and Prey Capture
Authors: Budick Seth A. , O’Malley Donald M. 
Published: April 2021

ABSTRACT
Larval zebrafish (Brachydanio rerio) are a popular model system because of their genetic attributes, transparency and relative simplicity. They have approximately 200 neurons that project from the brainstem into the spinal cord. Many of these neurons can be individually identified and laser-ablated in intact larvae. This should facilitate cellular-level characterization of the descending control of larval behavior patterns. Towards this end, we attempt to describe the range of locomotor behavior patterns exhibited by zebrafish larvae. Using high-speed digital imaging, a variety of swimming and turning behaviors were analyzed in 6-to 9-day-old larval fish. Swimming episodes appeared to fall into two categories, with the point of maximal bending of the larva’s body occurring either near the mid-body (burst swims) or closer to the tail (slow swims). Burst swims also involved larger-amplitude bending, faster speeds and greater yaw than slow swims. Turning behaviors clearly fell into two distinct categories: fast, large-angle escape turns characteristic of escape responses, and much slower routine turns lacking the large counterbend that often accompanies escape turns. Prey-capture behaviors were also recorded. They were made up of simpler locomotor components that appeared to be similar to routine turns and slow swims. The different behaviors observed were analyzed with regard to possible underlying neural control systems. Our analysis suggests the existence of discrete sets of controlling neurons and helps to explain the need for the roughly 200 spinal-projecting nerve cells in the brainstem of the larval zebrafish.
Olfactory Learning in the Cricket Gryllus Bimaculatus
Authors: Matsumoto Yukihisa , Mizunami Makoto 
Published: April 2021

ABSTRACT
The olfactory learning capability of the cricket Gryllus bimaculatus was studied. Crickets were deprived of drinking water for 4 days and were individually trained to associate peppermint with water and vanilla with NaCl solution. Their odour preference was tested before and after training by allowing them to choose between peppermint or vanilla sources. The time spent visiting each source served as a measure of odour preference. Crickets exhibited an initial preference for vanilla over peppermint, but preference for the latter increased after only one training session. The olfactory memory formed by a single training session decayed with time but remained for at least 24 h. Memory formed by three training sessions was extremely robust, and did not decay significantly between 1 and 7 days after training. The preference formed was easily altered by reversal training in which vanilla was associated with water and peppermint with saline solution. This study shows that crickets have a highly developed olfactory learning capability characterized by fast acquisition, long retention and easy rewriting of memory.
Acoustic Identification of Twelve Species of Echolocating Bat By Discriminant Function Analysis and Artificial Neural Networks
Authors: Parsons Stuart , Jones Gareth 
Published: April 2021

ABSTRACT
We recorded echolocation calls from 14 sympatric species of bat in Britain. Once digitised, one temporal and four spectral features were measured from each call. The frequency–time course of each call was approximated by fitting eight mathematical functions, and the goodness of fit, represented by the mean-squared error, was calculated. Measurements were taken using an automated process that extracted a single call from background noise and measured all variables without intervention. Two species of Rhinolophus were easily identified from call duration and spectral measurements. For the remaining 12 species, discriminant function analysis and multilayer back-propagation perceptrons were used to classify calls to species level. Analyses were carried out with and without the inclusion of curve-fitting data to evaluate its usefulness in distinguishing among species. Discriminant function analysis achieved an overall correct classification rate of 79 % with curve-fitting data included, while an artificial neural network achieved 87 %. The removal of curve-fitting data improved the performance of the discriminant function analysis by 2 %, while the performance of a perceptron decreased by 2 %. However, an increase in correct identification rates when curve-fitting information was included was not found for all species. The use of a hierarchical classification system, whereby calls were first classified to genus level and then to species level, had little effect on correct classification rates by discriminant function analysis but did improve rates achieved by perceptrons. This is the first published study to use artificial neural networks to classify the echolocation calls of bats to species level. Our findings are discussed in terms of recent advances in recording and analysis technologies, and are related to factors causing convergence and divergence of echolocation call design in bats.
Action of Adenosine on Energetics, Protein Synthesis And K+ Homeostasis in Teleost Hepatocytes
Authors: Krumschnabel Gerhard , Biasi Christina , Wieser Wolfgang 
Published: April 2021

ABSTRACT
In a comparative study, we analysed the effects of adenosine on the energetics, protein synthesis and K+ homeostasis of hepatocytes from the anoxia-tolerant goldfish Carassius auratus and the anoxia-intolerant trout Oncorhynchus mykiss. The rate of oxygen consumption did not respond immediately to the addition of adenosine to the cells from either species, but showed a significant decrease in trout hepatocytes after 30 min. The anaerobic rate of lactate formation was not significantly affected by adenosine in goldfish hepatocytes, but was increased in trout cells. We also studied the effects of adenosine on the two most prominent ATP consumers in these cells, protein synthesis and Na+ /K+ -ATPase activity. Under aerobic conditions, adenosine inhibited protein synthesis of hepatocytes from goldfish by 51 % and of hepatocytes from trout by 32 %. During anoxia, the rate of protein synthesis decreased by approximately 50 % in goldfish hepatocytes and by 90 % in trout hepatocytes, and this decrease was not altered by the presence of adenosine. Adenosine inhibited normoxic Na+ /K+ -ATPase activity and K+ efflux by 20–35 % in the cells of both species. An investigation into the mechanism underlying the inhibition of protein synthesis by adenosine indicated that, in the goldfish cells, adenosine acts via a membrane receptor-mediated pathway, i.e. the effect of adenosine was abolished by applying the A1 receptor antagonist 8-phenyltheophylline. In the trout, however, the uptake of adenosine into hepatocytes seems to be required for an effect on protein synthesis. [Ca2+ ]i does not seem to be involved in the inhibition of protein synthesis by adenosine.
Circulatory Impairment Induced by Exercise in the Lizard Iguana Iguana
Authors: Farmer Colleen G. , Hicks James W. 
Published: April 2021

ABSTRACT
Mechanical integration of the cardiac, muscular and ventilatory pumps enables mammals to vary cardiac output over a wide range to match metabolic demands. We have found this integration lacking in a lizard (Iguana iguana) that differs from mammals because blood flow from the caudal body and ventilation are maximal after, rather than during, exercise. Because Iguana iguana are constrained from ventilation during intense locomotion, they appear to be unable to recruit the abdomen and thorax as a pump for venous return. This constraint on simultaneous running and costal breathing arises from their musculoskeletal design, which is similar to that of basal tetrapods, and so a constraint on venous return during exercise may be ancestral for tetrapods. We suggest that mechanical coupling of the pulmonary and cardiac pumps may have been important for the evolution of high-speed locomotor stamina in terrestrial vertebrates.
Temporal and Spatial Expression of the Cell-Cycle Regulator Cul-1 in Drosophila and Its Stimulation by Radiation-Induced Apoptosis
Authors: Filippov Valery , Filippova Maria , Sehnal Frantisek , Gill Sarjeet S. 
Published: April 2021

ABSTRACT
Cul-1 protein is part of the ubiquitin ligase complex that is conserved from yeast to humans. This complex specifically marks cell-cycle regulators for their subsequent destruction. Two null mutations of the cul-1 gene are known, in budding yeast and in nematodes. Although in both these organisms the cul-1 gene executes essentially the same function, the manifestation of its lack-of-function mutations differs considerably. In yeast the mutation causes arrest at the G1/S-phase transition, whereas in nematodes excessive cell divisions occur because mutant cells are unable to exit the mitotic cycle. We isolated cul-1 orthologues from two model organisms, Drosophila melanogaster and mouse. We show that the Drosophila full-length cul-1 gene restores the yeast mutant’s inability to pass through the G1/S-phase transition. We also characterize expression of this gene at the transcript and protein levels during Drosophila development and show that cul-1 gene is maternally supplied as a protein, but not as an RNA transcript. Zygotic transcription of the gene, however, resumes at early stages of embryogenesis. We also found an increase in cul-1 transcription in cultured cells treated with a lethal dose of γ-irradiation.