bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of Evisceration in the Holothurian Eupentacta Quinquesemita and Evidence for the Existence of an Endogenous Evisceration Factor
Authors: Byrne Maria 
Published: April 2021

ABSTRACT
The stimuli provoking evisceration of Eupentacta quinquesemita (Selenka) and autotomy of isolated pharyngeal retractor muscle (PRM) tendons were investigated. Tendon autotomy is a two-part response involving PRM contraction and breakdown of tendon connective tissue. An evisceration factor (EF) was detected in coelomic fluid expelled during evisceration. EF was isolated in tissue extracts and the haemal system and peritoneum were sources of EF activity. Autotomy and evisceration were induced by electrical stimulation, K+ and EF, and the effect of these agents was inhibited by anaesthetics. The acetylcholine antagonist tubocurarine chloride elicited evisceration, suggesting that evisceration may involve inhibition of cholinergic transmission. Evisceration and autotomy appear to be neurally controlled and the presence of an endogenous EF suggests neurosecretory or hormonal activity. Cells involved in evisceration may be located at a distance from the autotomy tissues and effect connective tissue breakdown through the medium of the coelomic fluid. Hypothetical sequences of events and possible roles for EF are presented.
Energetics of Hermit Crabs During Locomotion: the Cost of Carrying a Shell
Authors: Herreid Clyde F. , Full Robert J. 
Published: April 2021

ABSTRACT
Oxygen consumption was measured as hermit crabs (Coenobita compressus) walked at controlled velocities on a motor-driven treadmill inside a small respirometer. The crabs displayed an aerobic response to exercise with a rapid increase in reaching a steady state in about 5–6 min followed by a rapid recovery. The highest was four times the resting rate. was directly dependent on the velocity of travel (V) : . Metabolic rate was increased significantly in crabs with bilateral leg ablation.
The cost of shell carrying was evaluated by comparing of crabs with and without their protective snail shells at different velocities; the absolute difference was constant (0·7mlO2g−1 h−1), suggesting that the cost of shell support was constant per unit of time regardless of speed.
The cost of transport dropped dramatically with speed for crabs both with and without snail shells. Crabs carrying shells used twice as much O2 per gram per kilometre as did ‘nude’ crabs walking slowly at 0·02kmh−1, but the difference decreased to 1·3 times when velocity was increased 10-fold. Hermit crabs did not increase their proportionately with load: the loaded/unloaded ratio was consistently less than the mass loaded/unloaded ratio. This apparent increase in efficiency may be due to the fact that crabs carrying heavy shells alter their leg position and tend to drag their shell.
Crabs with and without shells have the same minimum cost of transport CM, so travel at the highest velocity is theoretically the most economical way to cover a given distance. Appropriately, crabs on the beach average a fast 0·23 km h−1 which produces a low cost of transport only 1·3 times higher than CM. The CM of six-legged hermit crabs is comparable to that of mammals, birds, crabs and insects of similar size and indicates that leg number does not affect fuel economy.
Human Homing: Still No Evidence Despite Geomagnetic Controls
Authors: Westby G. W. Max , Partridge Karen J. 
Published: April 2021

ABSTRACT
Baker’s highly influential and widely cited studies suggest that people are capable of non-visual navigational performance comparable to that of homing pigeons. Past failures to replicate this work have been attributed by Baker to geomagnetic influences. We report a series of experiments in which both temporal and spatial geomagnetic controls were introduced. We could still find no evidence for blindfold homeward orientation in humans.
Aspects of Sensory Integration in the Crayfish Swimmeret System
Authors: Heitler W. J. 
Published: April 2021

ABSTRACT
The chief sensory effects observed in response to movement and position of a single swimmeret are ipsilateral reflexes such that the amplitude of spontaneous rhythmic activity is augmented when the swimmeret is held protracted, and diminished when the swimmeret is held retracted. A major source of these reflexes appears to be the non-spiking stretch receptors (NSSRs) at the base of the swimmeret. Sinusoidally-varying current injected into a single NSSR produces a beat-frequency modulation of spontaneously-generated rhythm very similar to that produced by applying sinusoidal movement to the whole swimmeret. The spontaneous rhythm does not entrain to the applied movement. Spiking receptors responding to movement and cuticle distortion may be largely responsible for a dynamic component of the reflex, and also for inconsistently-observed arousal effects and changes in frequency of spontaneously-generated rhythms.
Fine Analysis of Predatory and Defensive Motor Events in Torpedo Marmorata (Pisces)
Authors: Belbenoit Pierre 
Published: April 2021

ABSTRACT
Predation and defence of Torpedo marmorata, elicited with biological., and inanimate stimuli, were studied in experimental conditions. Patterns of responses of neonates and adults are described, and chains of separate, coordinated motor acts are defined. Jumping predation, creeping predation, defence of the disc and defence of the tail are distinguished. Each predatory behaviour consists of stimulus reaction chains, whereas defensive types of behaviour involve single stimulus reactions. During jumping behaviour, tail strokes provoked by the initial response in the chain are displayed during the whole period of predation; these ‘delayed’ tail strokes provoke displacements of the prey, thus probing the substrate and furnishing biological cues. Large behavioural variations are reported, including incomplete chains of responses, repetition of responses, oriented responses, stimulus intensity/response magnitude relationships and missing of certain motor acts. Ontogenetic maturation of the behaviour patterns is observed in embryos and in immature neonates. Sets of electric organ discharges (EODs), which accompany the defensive responses and certain predatory responses, show a stereotyped pattern, characteristic for each EOD motor act. Variations found in the EOD pattern are often related to the effects of fatigue on the EOD rate. Electric shock provokes the immobilization of the prey, or the flight of the aggressor. Effective use of the EOD by neonates as a weapon against prey is reported. The possible neuronal basis of the sensorimotor organization which may account for the results is discussed.
Morphometry Of The Gills Of The Elasmobranch Scyliorhinus Stellaris In Relation To Body Size
Authors: Hughes George M. , Perry Steven F. , Piiper Johannes 
Published: April 2021

ABSTRACT
In order to study the dependence of the dimensions of the respiratory apparatus on body size and to provide a morphometric basis for the analysis of branchial gas exchange function, the gills of 12 specimens of Scyliorhinus stellaris L., weighing 0·58–2·62 kg, were examined morphometrically. The average values and the local variations of the structural parameters determining diffusive gas transfer properties of the gills were determined. Particular attention was paid to corrections for shrinkage effects in surface area measurements and to corrections for the Holmes and slant effects in measurements of paraffin sections.
The shape and size of secondary lamellae varied according to the sampling site on the filament, and filament length varied with its location on the gill arch. Also the water-blood distance varied, mainly because of frequent occurrence of thickenings at mid-height of the secondary lamellae.
The total gill surface area increased proportionally to (body mass)0·78, mainly because of an increase in surface area of individual lamellae rather than an increase in their number. Since the thickness of the secondary lamellae varied little with body mass, the observed increase in total filament length in proportion to body mass is attributed to an increase in interlamellar distance. The water-blood distance varied little with body mass.
The extent of shrinkage was found to be about 10% of filament length, but because of the compensating increase in secondary lamellar frequency this had no effect on gill area estimates, although it did affect the interlamellar dimensions. Shrinkage of individual secondary lamellae was extremely difficult to estimate, partly because of non-isometric shrinkage within the gill system. Underestimation of secondary lamellar area using paraffin sections could approach 30% mainly because of a reduction in the proportion of the pillar cell system exposed above the level of the gill filaments.
Aminergic and Peptidergic Neuromodulation in Crustacea
Authors: Beltz Barbara S. , Kravitz Edward A. 
Published: April 2021

ABSTRACT
Biogenic amines and peptides can act both as circulating neurohormones and as classical central and peripheral neurotransmitters. This article reviews some of the variety of roles played by amines and peptides in crustacean nervous systems. Cardiac, stomatogastric and postural systems are used to illustrate: (1) the functional versatility of amines and peptides; (2) the molecular basis of their actions; (3) the coexistence of amines and peptides with other bioactive compounds; and (4) the developmental expression of amine and peptide phenotypes. We will deal in detail with the postural neuromuscular system of the lobster, Homarus americanus. Physiological and pharmacological experiments have shown that the biogenic amines serotonin and octopamine are capable of regulating posture by direct neurohormonal actions on the muscles and by central actions that alter motoneuronal output. We have localized serotonin to identified neurones in the lobster ventral nerve cord and have shown further that the pentapeptide proctolin coexists with the amine in these cells. Such neurones provide a convenient system in which to study the functional interactions between peptide and amine cotransmitters. In addition, the serotonin and proctolin phenotypes of these cells are first expressed at widely different times in development. This presents the possibility of studying the regulation of these two transmitter phenotypes in a system that is readily amenable to experimental manipulation.
Ionic Channels and Hormone Release From Peptidergic Nerve Terminals
Authors: Lemos José R. , Nordmann Jean J. 
Published: April 2021

ABSTRACT
Although there is considerable evidence that depolarization of nerve cell terminals leads to the entry of Ca2+ and to the secretion of neurohormones and neurotransmitters, the details of how ionic currents control the release of neuroactive substances from nerve terminals are unknown. The small size of most nerve terminals has precluded direct analysis of membrane ionic currents and their influence on secretion. We now report that it is possible, using patch-clamp techniques, to study stimulus-secretion coupling in isolated peptidergic nerve terminals.
Sinus gland terminals from Cardisoma are easily isolated following collagenase treatment and appear morphologically and electrically very similar to nondissociated nerve endings. We have observed two types of single-channel currents not previously described. The first (‘f’) channel is activated by intracellular Na+ and the second (‘s’) by intracellular Ca2+. Both show little selectivity between Na+ and K+. In symmetrical K+, these cation channels have mean conductances of 69 and 213 pS, respectively. Furthermore, at least three types of Ca2+ channels can be reconstituted from nerve terminal membranes prepared from sinus glands. Nerve terminals can also be isolated from the rat neural lobe. These neuro-secretosomes release oxytocin and vasopressin, in response to membrane depolarization, only in the presence of external Ca2+. The depolarization of the nerve endings is associated with an increase in intracellular free Ca2+ concentration and this increase, measured using a fluorescent indicator, is abolished by Ca2+ channel blockers. Channels similar in their properties to the f and s channels also exist in rat neural lobe endings. Since these channels have not been found in other neurones or neuronal structures they may be unique to peptidergic nerve terminals.
The Physical Aspects of Fish Locomotion
Authors: Richardson E. G. 
Published: April 2021

ABSTRACT
The resistance of an inert fish moving in water is approximately the same as that of a wooden model similar in form and moving at the same velocity. When a lamina is made to vibrate in a current of air, it exerts a thrust in the direction in which the vibrations are travelling over the lamina; as long as the velocity of movement of the vibrations exceeds that of the external current of air, the resistance of the lamina is negative. Attention is drawn to the significance of the Katzmayr effect in respect to the locomotion of fish.
Production of Oestrogenic Substance by the Bird Testis
Authors: Callow R. K. , Parkes A. S. 
Published: April 2021

ABSTRACT
Oestrogenic substances are now known to be elaborated and excreted by the males of various species of mammals. The testes and urine of the stallion (Zondek, 1934), in particular, and the testes of the hog and bull (Courrier, 1934) contain notable amounts of oestrogenic compounds. In the case of the horse, the urine is relatively inactive in castrates (viz. geldings), so that it may be assumed that the testis is the origin of this oestrogenic material. Oestrone is isolated from stallion’s urine after mild chemical treatment, and it would appear that, whilst oestrone may not occur as such in the urine, the primary oestrogenic material in the stallion is a simple derivative of oestrone.
Water Permeability of Palaemon Longirostris and other Euryhaline Caridean Prawns
Authors: Campbell Peter J. , Jones M. B. 
Published: April 2021

ABSTRACT
Water permeability [based on the half-time of exchange of body water with the environment (T1/2)] of the upper estuarine prawn Palaemon longirostris was measured in a range of salinities at 4, 12 and 20°C. Prawns acclimated for 7 days were compared with prawns exposed to acute salinity changes. Acclimation to low salinity and low temperature caused a significant reduction in permeability. Transfer of prawns from 34 to 0.5 ‰ had no immediate effect on permeability; however, transfer from 0.5 to 34 ‰ caused an immediate significant rise in permeability. Heart rate of P. longirostris acclimated to 0.5 and 34 ‰ at 4, 12 and 20°C was unaffected by salinity, but was significantly reduced at low temperature.
The permeabilities of three other prawn species (Palaemonetes varians, Crangon crangon and Palaemon elegans), which have different horizontal distributions in estuaries and different salinity tolerance ranges, were also studied and compared with the values obtained for P. longirostris. P. varians and C. crangon showed significantly reduced permeabilities at low compared with high salinities; however, the permeability of P. elegans was unchanged at the two salinities used for this species (22 and 34 ‰). At each experimental salinity, permeabilities followed the sequence: P. longirostris&lt;P. varians&lt;C. crangon&lt;P. elegans. Results show that reduction of permeability is an important physiological adaptation to life in dilute saline regions and may be involved in separating species with overlapping salinity tolerance ranges.
Effect of Variation in Form on the Cost of Terrestrial Locomotion
Authors: Full Robert J. , Zuccarello Daniela A. , Tullis Alexa 
Published: April 2021

ABSTRACTThe mass-specific minimum cost of terrestrial locomotion (Cmin) decreases with an increase in body mass. This generalization spans nearly eight orders of magnitude in body mass and includes two phyla. The general relationship between metabolic cost and mass is striking. However, a significant amount of unexplained interspecific variation in Cmin exists at any given body mass. To determine how variation in morphology and physiology affects metabolic energy cost, we measured the oxygen consumption of three comparably sized insects running on a miniature treadmill; the American cockroach Periplaneta americana, the caterpillar hunting beetle Calosoma afline and the Australian field cricket Teleogryllus commodus. Steady-state oxygen consumption increased linearly with speed. Cmin was similar for crickets and cockroaches (8.0 and 8.5mlO2g−1km−1, respectively), but was substantially lower for beetles (4.6ml O2 g−1km−1). The predicted value of Cmin for all three insects was within the 95% confidence intervals of the Cminversus body mass function. However, the 95% confidence intervals extend approximately 2.5-fold above and 40 % below the regression line, making the variation at any given body mass nearly sixfold. Normalizing for the rate of muscle force production by determining the metabolic cost per stride failed to account for the interspecific variation in the cost of locomotion observed in the three insects. Ground contact costs (i.e. multiplied by leg contact time during a stride) in insects were similar to those measured in mammals (1.5–3.1 J kg−1) and were independent of speed, but did not explain the interspecific variation in the cost of locomotion. Muscles of the caterpillar hunting beetle may have a greater mechanical advantage than muscles of the Australian field cricket and American cockroach. Variation in musculo-skeletal arrangement, apart from variation in body mass, could translate into significant differences in the minimum cost of terrestrial locomotion.
Effects of prestretch at the onset of stimulation on mechanical work output of rat medial gastrocnemius muscle-tendon complex
Authors: Ettema G. J. , Huijing P. A. , van Ingen Schenau G. J. , de Haan A. 
Published: April 2021

ABSTRACT
Work output of rat gastrocnemius medialis (GM) muscle (N=5) was measured for stretch-shortening contractions, in which initiation of stretch occurred prior to the onset of activation, and for contractions with an isometric prephase. Duration of the active prephase (prestretch and pre-isometric) varied from 20 to 200 ms. Subsequent shortening (from optimum length+4 mm to optimum length-2 mm) lasted 150 ms. Stretch velocities of 5, 10 and 20mms−1 were used, and the shortening velocity was 40mms−1. The effects of several combinations of active stretch duration and active stretch amplitude were compared. Using forcecompliance characteristics, the work of the contractile element (CE), elastic energy storage and release of the undamped series elastic component (SEC) were distinguished. During shortening, an extra amount of work output was produced, induced by active stretch, of which the largest contribution (70–80%) was due to higher elastic energy release. Enhancement of the storage and utilization of elastic energy during the stretch-shortening cycle, caused by higher transition-point forces (i.e. force at onset of shortening), increased with active stretch amplitude and was associated with a net loss of work, probably due to cross-bridge detachment during active stretch. Net work over the stretch-shortening cycle remained positive for all prestretch contractions, indicating that when a muscle performs this type of contraction, it is able to contribute to work performance on body segments. It is concluded that, in stretch-shortening movements of rat GM muscle, maximal positive work output is incompatible with maximal net work output. Consequences for complex movements in vivo are discussed.
Activity of the hypaxial muscles during walking in the lizard Iguana iguana
Authors: Carrier D. 
Published: April 2021

ABSTRACT
The role that the hypaxial muscles play in locomotion has been largely ignored by biologists. In tetrapods, there are at least three possibilities. First, the hypaxial muscles might bend the trunk laterally to increase stride length. Second, they might stabilize the trunk against the horizontal, lateral and vertical components of the propulsive force. Alternatively, they might not be involved in locomotion. This study evaluated these three hypotheses by analyzing the activity of the hypaxial muscles of green iguanas (Iguana iguana). During walking, the rectus abdominis, obliquus externus superficialis and profundus, intercostales externi, and ventral portion of the intercostales interni on one side of the trunk acted synergistically with the lateral portion of the intercostales interni and obliquus internus on the other side of the trunk. This pattern supports the hypothesis that the hypaxial muscles act to stabilize the trunk during locomotion. Specifically, the longitudinally oriented rectus abdominis, obliquus externus profundus and ventral portion of the intercostales interni appear to stabilize the trunk against the horizontal and lateral components of the propulsive force, which tend to rotate the girdles in the horizontal plane. The obliquely oriented obliquus externus superficialis, intercostales externi, lateral portion of the intercostales interni and obliquus internus appear to stabilize the trunk against the vertical component, which induces long-axis torsion in the trunk. Thus, the demands of locomotion may provide a functional explanation for the basic organization of the hypaxial muscles of tetrapods.
Properties of potassium currents and their role in membrane excitability inDrosophilalarval muscle fibers
Authors: Singh S. , Wu C. F. 
Published: April 2021

ABSTRACTThe larval muscle fibers of Drosophila show four outward K+ currents in addition to the inward Ca2+ current in voltage-clamp recordings. The Shaker (Sh) and the slowpoke (slo) mutations, respectively, eliminate the voltage-activated fast K+ current (IA) and the Ca2+-activated fast K+ current (ICF)-Quinidine specifically blocks the voltage-activated delayed K+ current (IK) at micromolar concentrations. We used Sh, slo and quinidine to remove specifically one or more K+ currents, so as to study physiological properties of these currents not previously characterized, and to examine their role in membrane excitability. A linear relationship was observed between the peak ICF and the peak Ica at different membrane potentials. ICF inactivated considerably during a 140ms pulse to +20 mV. Recovery from inactivation was not complete for up to 2 s at the holding potential of −50 mV, which is much slower than the recovery of Ca2+ current from inactivation. In addition to IA and ICF, two delayed K+ currents are also observed in these fibers, the voltage-activated IK and the Ca2+-activated Ics-Near the end of a 500 ms depolarizing pulse, both IA and ICF are inactivated. Ca2+-free and 20 mmol 1−1 Ca2+ saline were used to examine the tail currents of the remaining IK and Ics-The tail currents of Ics were slower than those of IK and reversed between −30 and −50mV in different fibers. We further studied the dose-dependence of the blockade of IK by quinidine, which did not indicate a simple one-to-one binding mechanism. Current-clamp recordings from normal, Sh, slo and the double-mutant Sh;slo fibers suggested that ICF plays a stronger role than IA in repolarization of the larval muscle membrane. Elimination of ICF facilitates the occurrence of action potentials. Further elimination of IK prolonged the action potentials to several hundred milliseconds.