bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Kinematics of Swallowing In The Buccal Mass of Aplysia Californica
Authors: Drushel Richard F. , Neustadter David M. , Shallenberger Lori Lyn , Crago Patrick E. , Chiel Hillel J. 
Published: April 2021

ABSTRACT
Changes in the positions, shapes and movements of the feeding apparatus (buccal mass) of the marine mollusc Aplysia californica were studied in intact, transilluminated juveniles. The buccal mass assumes characteristic shapes as its internal structure, the radula/odontophore, moves anteriorly (protracts) or posteriorly (retracts). These shapes are especially distinctive when the radula/odontophore has protracted forwards fully, is close to its resting or neutral position, or has retracted backwards fully. We refer to the shapes that occur at full protraction, transition and full retraction as shape 1 (spherical), shape 2 (ovoid) and shape 3 (Γ-shaped), respectively. We introduce this shape nomenclature in order to avoid confusion with the existing terms protraction and retraction, which we reserve exclusively to describe the direction of movement of the radula/odontophore.
The observed shape changes do not agree with those predicted on the basis of in vitro observations of a feeding head preparation, but are similar to shapes observed in vitro in the snail Lymnaea stagnalis. The buccal mass also rotates approximately 10 ° dorsally during retraction, pivoting on the attachment to the mouth, before the subsequent protraction and return of the buccal mass to the transition shape. This rotation may be due to activation of the extrinsic muscles of the buccal mass.
Plots of the buccal mass shape parameters eccentricity versus ellipticity create a two-dimensional shape space, which accurately quantifies the subtle transitions of shape between the different phases of the feeding cycle. Quantitative differences are observed between pure swallows and swallows with tearing behavior, but the qualitative shapes are similar. Hysteresis in the shape space plots of most swallows provides evidence for the hypothesis that protraction and retraction each have distinct ‘active’ and ‘return’ phases.
The observed kinematic pattern imposes constraints on the internal structures of the buccal mass and may be used to infer the shape and positions of the radula and odontophore.
Sprawling Locomotion in the Lizard Sceloporus Clarkii: Quantitative Kinematics of a Walking Trot
Authors: Reilly Stephen M. , Delancey Michael J. 
Published: April 2021

ABSTRACT
Although the hindlimb is widely considered to provide the propulsive force in lizard locomotion, no study to date has investigated the kinematic patterns of the lizard hindlimb during running for more than one stride for a single individual. The quantitative kinematics of the hindlimb, pelvis and backbone are described here for two individuals of the lizard Sceloporus clarkii using a fast walking trot on a treadmill moving at a constant speed of 0.833 m s−1. Pelvic rotation, femoral retraction, knee flexion and posterior movement of the foot all begin before the foot hits the substratum and, thus, there is a terminal portion of the swing phase during which the limb is retracting. Pelvic rotation (to the opposite side), femoral protraction and knee flexion all begin before the foot leaves the substratum. The foot, however, continues to move posteriorly into the early swing phase. Thus, limb retraction and protraction movements do not directly correlate with footfall phases. Axial bending involves a rough standing wave with two nodes, one centered on each limb girdle. In Sceloporus clarkii, the foot clearly remains lateral to the knee and, thus, has a more sprawling posture than that of any other vertebrate studied to date. Therefore, the generalization that the ‘lacertilian’ foot passes under the knee joint is no longer supported. The kinematics of sprawling locomotion in Sceloporus clarkii are compared and contrasted with the general understanding of lizard locomotion based on qualitative work to date. Comparisons with other tetrapods reveal a fundamental functional dichotomy in hindlimb retraction mechanics in salamanders and mammals versus lizards that may be related to a key morphological difference in the saurian caudifemoralis muscle.
Effect of Reduced Gravity on The Preferred Walk–Run Transition Speed
Authors: Kram Rodger , Domingo Antoinette , Ferriss Daniel P. 
Published: April 2021

ABSTRACT
We investigated the effect of reduced gravity on the human walk–run gait transition speed and interpreted the results using an inverted-pendulum mechanical model. We simulated reduced gravity using an apparatus that applied a nearly constant upward force at the center of mass, and the subjects walked and ran on a motorized treadmill. In the inverted pendulum model for walking, gravity provides the centripetal force needed to keep the pendulum in contact with the ground. The ratio of the centripetal and gravitational forces (mv2/L)/(mg) reduces to the dimensionless Froude number (v2/gL). Applying this model to a walking human, m is body mass, v is forward velocity, L is leg length and g is gravity. In normal gravity, humans and other bipeds with different leg lengths all choose to switch from a walk to a run at different absolute speeds but at approximately the same Froude number (0.5). We found that, at lower levels of gravity, the walk–run transition occurred at progressively slower absolute speeds but at approximately the same Froude number. This supports the hypothesis that the walk–run transition is triggered by the dynamics of an inverted-pendulum system.
The Anaerobic Endproduct Lactate Has a Behavioural and Metabolic Signalling Function in the Shore Crab Carcinus Maenas
Authors: Wachter Bart De , Sartoris Franz-Jozef , Pörtner Hans-Otto 
Published: April 2021

ABSTRACT
This study presents the first evidence that, in invertebrates, the anaerobic endproduct lactate has an alarm signal function and induces metabolic and behavioural responses as in the anuran Bufo marinus. In support of this function, behavioural hypothermia was demonstrated in the shore crab Carcinus maenas. The animals moved to a cooler environment when exposed to hypoxic conditions. A decrease in preferred temperature of the same magnitude was also found when normoxic animals were injected with an iso-osmotic lactate solution resulting in a haemolymph concentration of approximately 12 mmol l−1. Under normoxic and moderately hypoxic conditions , injection of this lactate solution also caused a significant increase in the rate of oxygen consumption (100 and 50 % respectively). The increase in the rate of oxygen consumption was smaller and delayed, but lasted longer, under hypoxic conditions compared with normoxic conditions. Low but significant correlations between levels of lactate and levels of adrenaline, octopamine and tryptophan suggest the involvement of biogenic amines in the mediation of the signal.
Pulsatile Urea Excretion in the Toadfish (Opsanus Beta) is Due to A Pulsatile Excretion Mechanism, not a Pulsatile Production Mechanism
Authors: Wood Chris M. , Hopkins Todd E. , Walsh Patrick J. 
Published: April 2021

ABSTRACT
When subjected to a crowding/confinement protocol in the laboratory, toadfish become facultatively ureotelic, excreting approximately 90 % of their nitrogenous waste as urea-nitrogen (urea-N). The great majority of this excretion occurs via large, irregular pulses from the head region which occur on average once per day, with a duration of 3 h or less. Pulses measured chemically by the appearance of urea-N in the external water were identical to those measured by assaying [14C]urea appearance in the water from the blood plasma. Individual toadfish maintained plasma urea concentrations over widely differing ranges (6600–39 890 μmol-N l−1). However, independent of absolute levels, both [14C]urea and total urea were distributed at ratios close to unity between the blood plasma and the water compartments of liver and white muscle. At times of pulsatile excretion, plasma urea concentration fell sharply. These decreases, distributed throughout the tissues of the whole body, closely matched the sizes of the measured excretion pulses. Between pulses, plasma urea concentration increased steadily at a much slower rate; the rate of rise, when distributed throughout the tissues of the whole body, corresponded to the time-averaged excretion rate over the whole day. Infusion of a typical pulse amount of urea immediately after the end of a natural pulse event raised plasma urea concentration slightly above the pre-pulse level, but did not induce another pulse event. Plasma cortisol levels declined by approximately 60 % over the 4 h period prior to a natural pulse event and then rose quickly again once the pulse had occurred. These results indicate that urea pulses are due to activation of an excretion mechanism that rapidly clears urea from the blood plasma, thereby lowering stores throughout the whole body. Metabolic production of urea is continuous and is not responsible for pulsatile excretion. The pulse event is not triggered by a specific plasma urea threshold, but may involve the hypothalamo–interrenal axis.
Maintenance of Motor Pattern Phase Relationships in the Ventilatory System of the Crab
Authors: Dicaprio R. A. , Jordan G. , Hampton T. 
Published: April 2021

ABSTRACT
The central pattern generator responsible for the gill ventilation rhythm in the shore crab Carcinus maenas can produce a functional motor pattern over a large (eightfold) range of cycle frequencies. One way to continue to generate a functional motor pattern over such a large frequency range would be to maintain the relative timing (phase) of the motor pattern as cycle frequency changes. This hypothesis was tested by measuring the phase of eight events in the motor pattern from extracellular recordings at different rhythm frequencies. The motor pattern was found to maintain relatively constant phase relationships among the various motor bursts in this rhythm over a large (sevenfold) range of cycle frequencies, although two phase-maintaining subgroups could be distinguished. Underlying this phase maintenance is a corresponding change in the time delay between events in the motor pattern ranging from 470 to 1800 ms over a sevenfold (300–2100 ms) change in cycle period. Intracellular recordings from ventilatory neurons indicate that there is very little change in the membrane potential oscillation in the motor neurons with changes in cycle frequency. However, recordings from nonspiking interneurons in the ventilatory central pattern generator reveal that the rate of change of the membrane potential oscillation of these neurons varies in proportion to changes in cycle frequency. The strict biomechanical requirements for efficient pumping by the gill bailer, and the fact that work is performed in all phases of the motor pattern, may require that this motor pattern maintain phase at all rhythm frequencies.
Cardiovascular Functions in Two Macruran Decapod Crustaceans (Procambarus Clarkii and Homarus Americanus) During Periods of Inactivity, Tail Flexion and Cardiorespiratory Pauses
Authors: Reiber Carl L. , Mcmahon Brian R. , Burggren Warren W. 
Published: April 2021

ABSTRACT
Arterial hemolymph flow was measured in restrained crayfish (Procambarus clarkii) and lobsters (Homarus americanus). Implanted pulsed Doppler flow transducers were used to measure arterial flows in the anterior aorta, posterior aorta, sternal artery, lateral artery, ventral thoracic artery and ventral abdominal artery, allowing determination of flow simultaneously in several arteries over a period of 4 days. Calculated Doppler hemolymph flow showed a strong correlation (P&lt;0.05) with ‘pumped’ hemolymph flow as determined by in situ calibration.
Arterial flow patterns remained constant during quiet conditions. In crayfish, cardiac output was 7.5±1.1 ml min−1 (252 ml kg−1 min−1), of which the anterior aorta received 1.3±0.15 ml min−1 (20.1±4.0 %), the posterior aorta received 0.8±0.1 ml min−1 (12.3±2.7 %) and the sternal artery received 5.2±1.4 ml min−1 (67.5±37.0 %). Mean heart frequency at rest was 125.6±5.2 beats min−1 and stroke volume was 0.06±0.01 ml beat−1 (1.98 ml kg−1 beat−1). In lobsters, cardiac output was 60.8±4.4 ml min−1 (93.6±6.8 ml kg−1 min−1), with the anterior aorta receiving 7.8±0.8 ml min−1 (12.8±2.7 %), the lateral arteries receiving 0.6±0.2 ml min−1 (1.0±0.5 %), the posterior aorta receiving 12.6±1.0 ml min−1 (20.7±3.3 %) and the sternal artery receiving 38.9±4.1 ml min−1 (64.0±13.4 %). Flows in the branches of the sternal artery were 0.3±0.05 ml min−1 (0.5±2 %) in the ventral abdominal artery and 4.0±0.1 ml min−1 (6.5±0.3 %) in the ventral thoracic artery. Lobster heart rate was 82.5±2.9 beats min−1 and stroke volume was 0.7±0.05 ml beat−1.
Periods of constant hemolymph flow were interrupted by tail flexions (abdominal flexion) and, in lobsters, periods of cardiac/respiratory pause. Tail movement increased flow (peak height and minimum flow values) in both crayfish and lobsters, although the general wave form of hemolymph flow and pressure did not change. In lobsters, periodic respiratory pauses were observed during which all arteries received hemolymph, despite the low heart rate.
Quantitative Modelling of the Effects of Selected Intracellular Metabolites on pH in Fish White Muscle
Authors: Arthur Peter G. , West Timothy G. , Hochachka Peter W. 
Published: April 2021

ABSTRACT
A model is presented that provides guidelines to the identification of key experimental variables influencing proton balance and intracellular pH in vertebrate white muscle. We have drawn on data from the literature on rainbow trout (Oncorhynchus mykiss) in an attempt to quantify the influence of metabolic, ionic and transport components of proton generation and proton consumption after exercise. Only minor changes in proton balance and in calculated intracellular pH were caused by considering changes in the concentration of bicarbonate or including the acid–base characteristics of purine nucleotides. Intracellular pH, as estimated by the model, was more acidic at some time points in recovery compared with in vivo measurements, and this would appear to result mainly from inaccuracies in quantifying the phosphate component of proton buffering. Nevertheless, the model was able to simulate the typical pattern of muscle acidosis and recovery observed for trout, including the transient post-exercise acidification and the slow recovery rate. As with previous pHi models, comparison of model estimates with experimental observations is essential in this approach in order to identify whether all of the relevant metabolic processes have been considered for accurate quantification of proton balance within the white muscle compartment.
Feeding Kinematics of Juvenile Swellsharks, Cephaloscyllium Ventriosum
Authors: Ferry-Graham Lara A. 
Published: April 2021

ABSTRACT
To investigate how feeding behaviors change with prey size, high-speed video recording was used to examine the kinematics of prey capture and transport in 1-year-old swellsharks Cephaloscyllium ventriosum (Scyliorhinidae: Carchariniformes) feeding on two differently sized prey items. Prey capture in these sharks generally consisted of an initially ram-dominated capture bite, one or more manipulation bites, a holding phase during which the food was held in the teeth of the shark, and then suction-dominated prey transport. During initial capture and transport, most of the water taken in is forced back out of the mouth anteriorly rather than continuing posteriorly out through the gill openings. Dye experiments in which dye-perfused prey items were ingested by the sharks confirm this observation; distinct jets of colored water were video-taped as they were ejected from the mouth. Very late in prey transport, a bolus of water is ejected through the gill slits; however, by this time, the majority of water appears already to have exited the buccal cavity through the mouth. Such patterns were observed for sharks feeding on both small and large prey items. Although a basic pattern of prey capture and transport was regularly repeated among strikes, kinematic patterns during prey capture and transport were variable both within and among individuals, indicating that prey acquisition is not tightly controlled. However, the amount of variability was similar among prey sizes. In addition, there were no detectable changes in behavior due to prey item size. Ram-suction index values confirmed that similar capture modes were being utilized for both prey sizes.
Honeybee Vision: Analysis of Orientation and Colour in the Lateral, Dorsal and Ventral Fields of View
Authors: Giger A. D. , Srinivasan M. V. 
Published: April 2021

ABSTRACT
The ability of honeybees (Apis mellifera) to learn and recognise peripherally presented patterns was investigated by training bees in a Y-maze which presented patterns on the side walls, the ceiling or the floor. We found that pattern orientation is learnt and recognised in the lateral and frontal visual field, but not in the dorsal or ventral fields. Colour information, in contrast, is used in the lateral and frontal as well as the ventral visual field, but not in the dorsal field. If pattern orientation is different on opposite sides of the visual field during training, both patterns are learned, but each on its own is sufficient for the bees to recognise the learnt stimulus. However, unilaterally learnt pattern information, be it orientation or colour, cannot be accessed when the test pattern is viewed on the other side. That is, interocular transfer of such information does not occur.
Processing of Artificial Visual Feedback in the Walking Fruit Fly Drosophila Melanogaster
Authors: Strauss Roland , Schuster Stefan , Götz Karl Georg 
Published: April 2021

ABSTRACT
A computerized 360 ° panorama allowed us to suppress most of the locomotion-induced visual feedback of a freely walking fly without neutralizing its mechanosensory system (‘virtual open-loop’ conditions). This novel paradigm achieves control over the fly’s visual input by continuously evaluating its actual position and orientation.
In experiments with natural visual feedback (closed-loop conditions), the optomotor turning induced by horizontal pattern motion in freely walking Drosophila melanogaster increased with the contrast and brightness of the stimulus. Conspicuously striped patterns were followed with variable speed but often without significant overall slippage.
Using standard open-loop conditions in stationarily walking flies and virtual open-loop or closed-loop conditions in freely walking flies, we compared horizontal turning induced by either horizontal or vertical motion of appropriately oriented rhombic figures. We found (i) that horizontal displacements and the horizontal-motion illusion induced by vertical displacements of the oblique edges of the rhombic figures elicited equivalent open-loop turning responses; (ii) that locomotion-induced visual feedback from the vertical edges of the rhombic figures in a stationary horizontal position diminished the closed-loop turning elicited by vertical displacements to only one-fifth of the response to horizontal displacements; and (iii) that virtual open-loop responses of mobile flies and open-loop responses of immobilized flies were equivalent in spite of delays of up to 0.1 s in the generation of the virtual stimulus.
Horizontal compensatory turning upon vertical displacements of oblique edges is quantitatively consistent with the direction-selective summation of signals from an array of elementary motion detectors for the horizontal stimulus components within their narrow receptive fields. A compensation of the aperture-induced ambiguity can be excluded under these conditions. However, locomotion-induced visual feedback greatly diminished the horizontal-motion illusion in a freely walking fly. The illusion was used to assay the quality of open-loop simulation in the new paradigm.
Octopamine Modulates the Responses and Presynaptic Inhibition of Proprioceptive Sensory Neurones in the Locust Schistocerca Gregaria
Authors: Matheson Thomas 
Published: April 2021

ABSTRACT
A multineuronal proprioceptor, the femoral chordotonal organ (feCO), monitors the position and movements of the tibia of an insect leg. Superfusing the locust metathoracic feCO with the neuromodulator octopamine, or the octopamine agonist synephrine, affects the position (tonic) component of the organ’s response, but not the movement (phasic) component. Both octopamine and synephrine act with the same threshold (10−6 mol l−1).
Individual sensory neurones that respond tonically at flexed tibial angles show increased tonic spike activity following application of octopamine, but those that respond at extended angles do not. Tonic spiking of phaso-tonic flexion-sensitive neurones is enhanced but their phasic spiking is unaffected.
Bath application of octopamine to the feCO increases the tonic component of presynaptic inhibition recorded in the sensory terminals, but not the phasic component. This inhibition should at least partially counteract the increased sensory spiking and reduce its effect on postsynaptic targets such as motor neurones. Furthermore, some phasic sensory neurones whose spiking is not affected by octopamine nevertheless show enhanced tonic synaptic inputs.
The chordotonal organ is not known to be under direct efferent control, but its output is modified by octopamine acting on its sensory neurones to alter their responsiveness to mechanical stimuli and by presynaptic inhibition acting on their central branches. The effects of this neuromodulator acting peripherally on sensory neurones are therefore further complicated by indirect interactions between the sensory neurones within the central nervous system. Increases of sensory neurone spiking caused by neuromodulators may not necessarily lead to parallel increases in the responses of postsynaptic target neurones.
Cholinergic Activation of Stridulatory Behaviour in the Grasshopper Omocestus Viridulus (L.)
Authors: Heinrich Ralf , Hedwig Berthold , Elsner Norbert 
Published: April 2021

ABSTRACT
When acetylcholine (ACh) and its agonists are injected into neuropile regions of the protocerebrum and the suboesophageal ganglion of male and female grasshoppers of the species Omocestus viridulus (L.), they elicit stridulation in a pattern no different from that of natural song. Stridulation can even be evoked in mated females which normally do not sing. By choosing suitable ACh agonists, nicotinic and muscarinic ACh receptors can be activated selectively. Activation of nicotinic ACh receptors produces individual song sequences with rapid onset; the stridulation induced by activation of the muscarinic ACh receptors begins after a longer latency, increases slowly in intensity and is maintained for many minutes. The sites within the cephalic ganglia where song can be initiated pharmacologically coincide with regions in which descending stridulatory command neurones arborize.