bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinematics, Muscular Activity and Propulsion in Gopher Snakes
Authors: Moon Brad R. , Gans Carl 
Published: April 2021

ABSTRACT
Previous studies have addressed the physical principles and muscular activity patterns underlying terrestrial lateral undulation in snakes, but not the mechanism by which muscular activity produces curvature and propulsion. In this study, we used synchronized electromyography and videography to examine the muscular basis and propulsive mechanism of terrestrial lateral undulation in gopher snakes Pituophis melanoleucus affinis. Specifically, we used patch electrodes to record from the semispinalis, longissimus dorsi and iliocostalis muscles in snakes pushing against one or more pegs. Axial bends propagate posteriorly along the body and contact the pegs at or immediately posterior to an inflection of curvature, which then reverses anterior to the peg. The vertebral column bends broadly around a peg, whereas the body wall bends sharply and asymmetrically around the anterior surface of the peg. The epaxial muscles are always active contralateral to the point of contact with a peg; they are activated slightly before or at the point of maximal convexity and deactivated variably between the inflection point and the point of maximal concavity. This pattern is consistent with muscular shortening and the production of axial bends, although variability in the pattern indicates that other muscles may affect the mechanics of the epaxial muscles. The kinematic and motor patterns in snakes crawling against experimentally increased drag indicated that forces are produced largely by muscles that are active in the axial bend around each peg, rather than by distant muscles from which the forces might be transmitted by connective tissues. At each point of force exertion, the propulsive mechanism of terrestrial lateral undulation may be modeled as a type of cam-follower, in which continuous bending of the trunk around the peg produces translation of the snake.
Mechanical Properties of the Tadpole Tail Fin
Authors: Doherty Penny A. , Wassersug Richard J. , Lee J. Michael 
Published: April 2021

ABSTRACT
The tadpole tail fin is a simple double layer of skin overlying loose connective tissue. Collagen fibres in the fin are oriented at approximately ±45 ° from the long axis of the tail.
Three tests were conducted on samples of the dorsal tail fin from 6–10 Rana catesbeiana tadpoles to establish the fin’s viscoelastic properties under (1) large-deformation cyclic loading at 1 and 3 Hz, (2) small-deformation forced vibration at 1 and 3 Hz, and (3) stress relaxation under a 0.1 s loading time. The fin was very fragile, failing easily under tensile loads less than 7 g. It was also strikingly viscoelastic, as demonstrated by 72±1 % hysteresis loss (at 3 Hz), 16±3 % stress remaining after 100 s of stress relaxation and a phase angle of 18±1 ° in forced vibration. As a consequence of its viscoelastic properties, the fin was three times stiffer in small than in large deformation. This may account for the ability of the fin to stay upright during normal undulatory swimming, despite the absence of any skeletal support.
Tadpoles in nature are often found with damaged tails. We suggest that the unusually viscoelastic and fragile nature of the fin helps tadpoles escape the grasp of predators. Because the fin deforms viscoelastically and tears easily, tadpoles can escape predators and survive otherwise lethal attacks with only minor lacerations to the fin. Recent studies have shown that certain tadpoles develop taller fins in the presence of predators. This developmental plasticity is consistent with the tail fin acting as a protective but expendable ‘wrap’ around the core muscle tissue.
Resistance Reflex That Maintains Upright Head Posture in the Flesh Fly Neobellieria Bullata (Sarcophagidae)
Authors: Gilbert Cole , Bauer Eric 
Published: April 2021

ABSTRACT
In flesh flies Neobellieria bullata, we investigated a resistance reflex that maintains upright head posture around the roll axis relative to the thorax. The gain of the reflex depends upon the fly’s behavioral state: moving flies immediately correct 90 % of the amplitude of experimentally imposed roll perturbations, returning the head almost to the fully upright position; motionless flies allow perturbations to persist for minutes before correcting only 70 % of perturbation amplitude.
To investigate the role of various neural pathways, we examined the control of head posture after sectioning relevant propriosensory or motor nerves. Excision of the prosternal chordotonal organ causes no decrements in the control of head posture. Unilateral deafferentation of a cervical propriosensory organ, the prosternal organ, induces roll towards the cut side. Unilateral section of the frontal nerve, a mixed motor nerve that supplies the neck depressors and levators, leads to unilateral deficits in correcting perturbations towards the contralateral side. After bilateral propriosensory or frontal motor nerve section, approximately 40 % of perturbation amplitude is still corrected. To determine the contributions of the passive elastic properties of the neck skeleto-muscular system, flies were tested under reversible nitrogen anesthesia. They immediately corrected 40 % of perturbation amplitude. Taken together, the results demonstrate that passive elasticity plus active prosternal nerve afference to contralateral depressors innervated by the frontal nerve in combination constitute a sufficient and necessary reflex loop to control head roll posture.
Specific Behavioural Responses Triggered by Identified Mechanosensory Receptor Cells in the Apical Field of the Giant Rotifer Asplanchna Sieboldi
Authors: Joanidopoulos Konstantin D. , Marwan Wolfgang 
Published: April 2021

ABSTRACT
The giant rotifer Asplanchna sieboldi swims by the propulsive effect of thousands of cilia arrayed in clusters around the apical field, which has several mechanosensory structures (sensilla) located at defined positions. Males and females differ in both their patterns of behaviour and their sensory receptor equipment. Unstimulated males swim straight with occasional spontaneous changes in direction until they hit an obstacle with their apical field. Depending on the direction and the strength of the mechanical interference, the animals show different behavioural responses. To analyse the effect of excitation of the apical mechanosensitive sensilla on these responses, males were held on microcapillaries, and the sensitivity of individual sensilla was assayed using micromanipulator-mediated mechanical stimulation. Stimulation of each of the four different types of sensillum triggered a specific and well-defined initial behavioural response. Individual animals behaved identically with respect to the receptor specificity of the responses. The behaviour of free-swimming males upon contact with obstacles or females is discussed on the basis of these results.
Comparative Kinematics and Hydrodynamics of Odontocete Cetaceans: Morphological and Ecological Correlates With Swimming Performance
Authors: Fish Frank E. 
Published: April 2021

ABSTRACT
Propulsive morphology and swimming performance were compared for the odontocete cetaceans Delphinapterus leucas, Orcinus orca, Pseudorca crassidens and Tursiops truncatus. Morphological differences were apparent among the whales. The general body contour and low-aspect-ratio caudal flukes of D. leucas indicated that this species was a low-performance swimmer compared with the other species. Propulsive motions were video-taped as animals swam steadily in large pools. Video tapes were analyzed digitally using a computerized motion-analysis system. Animals swam at relative velocities ranging from 0.4 to 2.4 body lengths s−1. The stroke amplitude of the flukes decreased linearly with velocity for D. leucas, but amplitude remained constant for the other species. Tail-beat frequencies were directly related to relative swimming velocity, whereas the pitch angle of the flukes was inversely related to relative swimming velocity. Unsteady lifting-wing theory was used with regression equations based on kinematics to calculate thrust power output, drag coefficients and propulsive efficiency. Compared with other species, O. orca generated the largest thrust power (36.3 kW) and had the lowest drag coefficient (0.0026), whereas T. truncatus displayed the largest mass-specific thrust power (23.7 W kg−1) and P. crassidens had the highest efficiency (0.9). D. leucas did not swim as rapidly as the other species and had a comparatively higher minimum drag coefficient (0.01), lower mass-specific thrust power (5.2 W kg−1) and lower maximum efficiency (0.84). Minimum drag coefficients were associated with high swimming speeds, and maximum efficiencies corresponded with velocities in the range of typical cruising speeds. The results indicate that the kinematics of the propulsive flukes and hydrodynamics are associated with the swimming behaviors and morphological designs exhibited by the whales in this study, although additional factors will influence morphology.
Vasoactivity of Adenosine in the Trout (Oncorhynchus Mykiss) Coronary System: Involvement of Nitric Oxide and Interaction with Noradrenaline
Authors: Mustafa Tariq , Agnisola Claudio 
Published: April 2021

ABSTRACT
A vasoconstrictory response to adenosine has been reported in coronary rings from fish. Since the reactivity of the large coronary arteries and the microcirculation may differ, the present study was undertaken to determine the role of adenosine in the intact coronary system of trout under constant pressure or flow using an isolated and non-working heart preparation. The involvement of nitric oxide (NO) and the interaction with noradrenaline were also studied. At 10−9 to 10−8 mol l−1, adenosine caused a vasoconstrictory response, whereas between 10−7 and 10−5 mol l−1 the response was predominantly vasodilative. Theophylline abolished both these responses to adenosine. The vasodilation induced by adenosine (at 10−5 mol l−1) was significantly reduced when the preparation was perfused under constant-flow than rather under constant-pressure conditions. The nitric oxide synthase inhibitor Nω-nitro-L-arginine (L-NA, 10−4 mol l−1) partially reduced the vasodilation induced by adenosine (at 10−5 mol l−1) under constant-pressure but not under constant-flow conditions. Perfusion of the intact coronary system with L-arginine or with adenosine significantly increased the rate of nitrite (NO2−) release, while perfusion with L-NA or theophylline reduced NO2− release. Chemical denudation of the coronary endothelium by CHAPS resulted in the loss of both the L-arginine- and adenosine-mediated vasodilation and the L-arginine-induced increase in the rate of NO2− release. Adenosine (10−5 mol l−1) offset and overrode the vasoconstriction induced by 10−7 mol l−1 noradrenaline. L-NA inhibited only the adenosine-induced vasodilation but not the ability to offset noradrenaline vasoconstriction, excluding the involvement of NO in the interaction between adenosine and noradrenaline.
Does Blood Acid–Base Status Modulate Catecholamine Secretion in the Rainbow Trout (Oncorhynchus Mykiss)?
Authors: Julio Alejandra E. , Montpetit Colin J. , Perry Steve F. 
Published: April 2021

Summary
The direct and modulating effects of acidosis on catecholamine secretion in rainbow trout (Oncorhynchus mykiss) were assessed in vivo using cannulated fish and in situ using a perfused cardinal vein preparation. In situ, acidosis (a reduction in perfusate pH from 7.9 to 7.4) did not elicit catecholamine release or modulate the secretion of catecholamines evoked by the non-specific cholinergic receptor agonist carbachol (3×10−7 to 10−5 mol kg−1) or the muscarinic receptor agonist pilocarpine (10−7 mol kg−1). Acidosis, however, significantly increased the secretion rates of noradrenaline and adrenaline in response to nicotine (10−8 to 10−7 mol kg−1). In vivo, intra-arterial injections of nicotine (300–600 nmol kg−1) into normocapnic or moderately hypercapnic fish (water or 0.67 kPa) caused a dose-dependent elevation of circulating catecholamine levels. At the highest dose of nicotine, the rise in plasma catecholamine levels was significantly enhanced in the hypercapnic fish.
Acute hypoxia in vivo caused an abrupt release of catecholamines when arterial haemoglobin O2-saturation was reduced to approximately 55–60 %; this catecholamine release threshold during hypoxia was unaltered in hypercapnic fish. However, the hypoxia-induced catecholamine release was significantly greater in hypercapnic fish than in normocapnic fish.
The results of this study suggest that blood acid–base status, while not influencing catecholamine secretion directly or influencing the blood O2 content threshold for catecholamine release during hypoxia, may modulate the secretory process specifically in response to nicotinic receptor stimulation of chromaffin cells.
An Analysis of Synthetic Processing of Odor Mixtures in the Honeybee (Apis Mellifera)
Authors: Chandra Sathees , Smith Brian H. 
Published: April 2021

ABSTRACT
Both sensory transduction and central processing of odor mixtures can give rise to several different kinds of interaction, which can influence how well individual components are perceived and processed. In particular, odor mixtures are believed to give rise to ‘configural’ or ‘synthetic’ properties that are not characteristic of the components. However, the exact nature of these effects, particularly with regard to their expression in behavior, remains to be examined in detail. Here we use feature-negative and transwitching conditioning paradigms to show that honeybees can use configural cues in odor processing. However, the nature of these configural cues is not similar to that predicted by some models of conditioning. We propose that configural models may be capable of accounting for a substantial portion of odor mixture processing.
A Respirometric Analysis of Fuel Use During Aerobic Swimming at Different Temperatures in Rainbow Trout (Oncorhynchus Mykiss)
Authors: Kieffer James D. , Alsop Derek , Wood Chris M. 
Published: April 2021

ABSTRACT
Instantaneous fuel usage at 5 °C or 15 °C was assessed by measurement of rates of O2 consumption , CO2 excretion and nitrogenous waste excretion (Ṁnitrogen =ammonia-N + urea-N) in juvenile rainbow trout (Oncorhynchus mykiss) at rest and during swimming at 45 % and 75 % of aerobic capacity (Ucrit). After 2 weeks of training at approximately 1 body length s−1 (BL s−1), critical swimming speeds (approximately 3.0 BL s−1) and whole-body energy stores (total protein, lipids and carbohydrates) were identical in fish acclimated to 5 °C or 15 °C. and increased with swimming speed at both temperatures and were higher at 15 °C than at 5 °C at all speeds, but the overall Q10 values (1.23–1.48) were low in these long-term (6 weeks) acclimated fish. The respiratory quotient (, approximately 0.85) was independent of both temperature and swimming speed. In contrast to and , the rate of ammonia excretion was independent of swimming speed, but more strongly influenced by temperature (Q10 1.4–2.8). Urea excretion accounted for 15–20 % of Ṁnitrogen, was unaffected by swimming speed and showed a tendency (P&lt;0.07) to be positively influenced by temperature at one speed only (45 % Ucrit). Nitrogen quotients (NQ) were generally higher in warm-acclimated fish, remaining independent of swimming speed at 15 °C (0.08), but decreased from about 0.08 at rest to 0.04 during swimming at 5 °C. Instantaneous aerobic fuel use calculations based on standard respirometric theory showed that both acclimation temperature and swimming speed markedly influenced the relative and absolute use of carbohydrates, lipids and proteins by trout. At rest, cold-acclimated trout used similar proportions of carbohydrates and lipids and only 27 % protein. During swimming, protein use decreased to 15 % at both speeds while the relative contributions of both lipid and carbohydrate increased (to more than 40 %). On an absolute basis, carbohydrate was the most important fuel for fish swimming at 5 °C. In contrast, resting fish acclimated to 15 °C utilized 55 % lipid, 30 % protein and only 15 % carbohydrate. However, as swimming speed increased, the relative contribution of carbohydrate increased to 25 %, while the protein contribution remained unchanged at approximately 30 %, and lipid use decreased slightly (to 45 %). On an absolute basis, lipid remained the most important fuel in fish swimming at 15 °C. These results support the concept that lipids are a major fuel of aerobic exercise in fish, but demonstrate that the contribution of protein oxidation is much smaller than commonly believed, while that of carbohydrate oxidation is much larger, especially at higher swimming speeds and colder temperature.
Dynamic gearing in running dogs
Authors: Carrier David R. , Gregersen Colin S. , Silverton Natalie A. 
Published: April 2021

ABSTRACT
Dynamic gearing is a mechanism that has been suggested to enhance the performance of skeletal muscles by maintaining them at the shortening velocities that maximize their power or efficiency. We investigated this hypothesis in three domestic dogs during trotting and galloping. We used ground force recordings and kinematic analysis to calculate the changes in gear ratio that occur during the production of the external work of locomotion. We also monitored length changes of the vastus lateralis muscle, an extensor muscle of the knee, using sonomicrometry in four additional dogs to determine the nature and rate of active shortening of this muscle. During both trotting and galloping, the gear ratios of the extensor muscles of the elbow, wrist and ankle joints were relatively constant early in limb support, but decreased rapidly during the second half of support. The gear ratio at the hip exerted an extensor moment initially, but decreased throughout limb support and became negative midway through support. This pattern of decreasing gear ratio during the second half of support indicates that dynamic gearing does not maximize muscle power or efficiency at the elbow, wrist, hip and ankle joints. In contrast, the extensor muscles of the shoulder and knee joints exhibited an increase in gear ratio during limb support. In two dogs, the vastus lateralis muscle shortened at a relatively constant rate of 3.7–4 lengths s−1 during intermediate-speed galloping. This pattern of increasing gear ratio and constant velocity of muscle shortening at the knee joint is consistent with the hypothesis of dynamic gearing. Given the amount of work done at the knee and shoulder joints of running dogs, dynamic gearing may contribute to the economy of constant-speed running and may be important to integrated limb function.
Fiber capillarization and ultrastructure of pigeon pectoralis muscle after cold acclimation
Authors: Mathieu-Costello O. , Agey P. J. , Quintana E. S. , Rousey K. , Wu L. , Bernstein M. H. 
Published: April 2021

ABSTRACT
We investigated the effect of 2 months of exposure to cold conditions (0–5 °C) on capillarization and on fiber size, distribution and ultrastructure in the pectoralis muscle of nine pigeons (Columbia livia; mean body mass 700±31 g) and compared the results with measurements from four control birds (mean mass 715±42 g) kept at normal ambient temperature (22–23 °C) for the same period. Superficial and deep portions of the muscles, taken from the central area of the right or left pectoralis major muscle, were perfusion-fixed in situ, processed for electron microscopy and analyzed by morphometry. Aerobic fibers represented the vast majority of fibers (93±1 %, mean ± S.E.M.) in all samples. After cold-acclimation, fiber sectional area was reduced and capillary density increased proportionally. There was no change in the degree of orientation (anisotropy) of capillaries, capillary-to-fiber ratio or fiber type distribution compared with controls. The volume density of mitochondria and lipid droplets in aerobic fibers and capillary diameter increased in response to cold, while the linear relationship between capillary length per fiber volume and fiber mitochondrial volume density remained unchanged. Capillary surface area, intrafiber lipid deposition and fiber mitochondrial volume density were all correlated in cold-acclimated pigeons. The results indicate a close match between the aerobic capacity of the highly aerobic fibers of the pectoralis muscle and their vascularization to meet the increased energetic demand of shivering.
Effect of a magnetic pulse on the orientation of silvereyes, zosterops l. lateralis, during spring migration
Authors: Wiltschko Wolfgang , Munro Ursula , Ford Hugh , Wiltschko Roswitha 
Published: April 2021

ABSTRACT
The orientation behaviour of Australian silvereyes, Zosterops l. lateralis, was tested during their spring migration, when they head southward to their Tasmanian breeding grounds. With only the local geomagnetic field as a cue, the birds significantly preferred their normal southerly migratory direction. Treatment with a short, strong magnetic pulse designed to alter the magnetization of single-domain magnetite led to a significant deflection towards the east for the next 4 days. This was followed by a period of non-oriented behaviour. From day 10 onwards, the birds returned to their original southerly headings. Together with previous findings, these data suggest that the navigational ‘map’ of these birds includes magnetic parameters and that a magnetite-based receptor provides them with information about their position. The transient nature of the effect is not easily explained on the basis of single-domain magnetite.
Looking all Around: Honeybees use Different Cues in Different Eye Regions
Authors: Lehrer Miriam 
Published: April 2021

ABSTRACT
Based on results of early as well as recent behavioural studies, the present review compares the performance of different eye regions in exploiting information on shape, colour and motion, relevant to the honeybee’s foraging task. The comparisons reveal similarities, as well as differences, among the performances of various eye regions, depending on the visual parameter involved in the task under consideration. The outcome of the comparisons is discussed in the light of anatomical and optical regional specializations found in the bee’s peripheral visual pathway, as well as in the light of the foraging bee’s natural habits. It is concluded that the functional differences found among different eye regions are based on neural mechanisms subserving the bee’s natural needs, rather than on peripheral specializations.