bluuebunny/crossref_metadata_2025_split huggingface dataset:
‘Paradoxical Driving’ of Walking Activity in Locusts
Authors: Moorhouse J. E. , Fosbrooke I. H. M. , Kennedy J. S. 
Published: April 2021

ABSTRACTGregarious fifth-instar larvae of Locusta migratoria migratorioides were placed singly on a counterbalanced, recording treadmill providing precise measurements of (i) walking bout length, (ii) non-walking bout length, (iii) walking speed and (iv) distance walked, over periods of hours.Under constant conditions in light the walking activity was often inter-rupted but gradually built up to a high intensity which was then sustained for 1−2 h before finally declining; there were orderly relations between the measured behavioural components. In continuous darkness walking activity was less interrupted but less intense and quickly declined; there were less orderly relations between the components.Under alternating 10 min periods of light and darkness the relations between the behavioural components were again more orderly in the light than the dark. However, walking activity was sharply depressed in these short light periods but was promptly resumed in each subsequent dark period and grew stronger as the fight–dark alternation continued.These diverse and at first sight paradoxical results are all consistent with the principle of post-inhibitory rebound (‘antagonistic induction’). This type of behavioural after-effect, acting on different time scales, is exemplified by the surge of walking observed in the dark on the release of the experimentally applied inhibition of walking by light, as well as by the build-up and sustained walking in continuous light (‘paradoxical driving’).
Patterns of Water and Solute Regulation in the Muscle Fibres of Osmoconforming Marine Decapod Crustaceans
Authors: Freel Robert W. 
Published: April 2021

ABSTRACT
The patterns of myoplasmic water and solute regulation were examined in several species of marine decapod crustaceans acclimated to various salinities. Three osmoconformers (Callianassa californiensis, Cancer anten-narius, Emerita analoga) and one weak osmoregulator (Pachygrapsus crassipes) were studied. Although haemolymph water and solute activities varied with adaptational salinity in these species, regulation of cell water content was apparent in all but 25 % s.w. acclimated Pachygrapsus. Cell water regulation was correlated with the regulation of ninhydrin-positive solutes. An estimate of the extent of the regulation was achieved by comparing the observed cell hydration changes to that predicted for an ideal osmometer and to that of a perfect volume regulator. It was concluded that the extent of cell volume regulation was variable and incomplete, particularly in dilute salinities. Net losses of myoplasmic sodium, chloride, and ninhydrin-positive nitrogen were observed in animals acclimated to dilute sea water, while net gains of these solutes were noted in crabs acclimated to concentrated sea water. In contrast, the amounts of cell potassium and calcium plus magnesium were relatively constant fractions of the cell dry weight at any salinity. A simple mechanism, based upon Donnan considerations, is sufficient to account for the constancy of myoplasmic potassium and the variability of cell chloride with changing extracellular osmolarity.
Transmembrane Activity Gradients of K and Cl in the Muscle Fibres of Osmoconforming Marine Decapod Crustaceans
Authors: Freel Robert W. 
Published: April 2021

ABSTRACT
The resting membrane potentials (Em) and the transmembrane activity gradients for K and Cl were measured in the muscle fibres of osmoconforming (Callianassa and Cancer) and weakly osmoregulating (Pachygrapsus) marine crustaceans acclimated to various osmotic conditions. The muscle membranes of sea water acclimated crabs behave as good K electrodes. However, a slight contribution of Na to the resting potential was demonstrated in all species. The ratio PNa/PK, was about 0·1 Equilibrium potentials (measured with ion-selective microelectrodes) for Cl were equal to Em, while EK was always more negative than Em as a result of the slight Na contribution. Acclimation to dilute or concentrated sea water had little effect on the K electrode properties or Na permeabilities of these fibres. The muscle fibres were depolarized in crabs acclimated to concentrated sea water and were hyperpolarized in crabs adapted to dilute sea water. These changes resulted solely from alterations in (aK)i/(aK)O which were in turn brought about by changes in cellular and haemolymph hydration. Since the Na contribution to Em was so small in all conditions, it was concluded that the distributions of K and Cl are best considered in terms of Donnan equilibria, and that the cellular K and Cl adjustments observed during salinity adaptation reflect the passive re-establishment of new equilibrium distributions for these ions.
Ventilation in An Aquatic and A Terrestrial Chelonian Reptile
Authors: Glass Imogens , Burggren Warren W. , Johansen Kjell 
Published: April 2021

ABSTRACT
Periods of breath-holding are interrupted by episodes of continuous breathing in the aquatic turtle Pelomedusa subrufa, whereas single breaths and short periods of breath-holding alternate in the terrestrial tortoise Testudo pardalis. This implies that partial pressures of O2 and CO2 in expired air are stable in Testudo in contrast to cyclic fluctuations in Pelo-medusa. In spite of this, air convection requirements (, ml BTPS/ml STPD) are not significantly different for the two species (25·4 in Testudo, 27·3 in Pelomedusa), and differences in weight-specific ventilation between the species can only be ascribed to a difference in mean body weight. The end-tidal in Pelomedusa (mean 15·2 mmHg) is lower than in Testudo (mean 24·7 mmHg), which reflects aquatic CO2 elimination in Pelomedusa. In Testudo, the time course of ventilation correlates with the time course of increase of end-tidal during CO2 breathing, but no simple relationship is evident between ventilation and blood in Pelomedusa. In both species tidal volume as well as respiratory frequency increase approximately in proportion to the end-tidal , although the response to 6% CO2 breathing could be less than expected from extrapolation of the responses to 2 and 4% CO2. Both species also increase ventilation during hypoxia, but hyperoxia depresses ventilation.
Giant Nerve Fibre Activity in Intact, Freely Moving Earthworms
Authors: Drewes C. D. , Landa K. B. , McFall J. L. 
Published: April 2021

ABSTRACT
An approach is described for recording and characterizing giant nerve fibre activity in intact, freely moving earthworms. Medial giant fibre (MGF) spikes were conducted in an anterior-posterior direction at a mean rate of 32·2 m/s; lateral giant fibre (LGF) spikes were conducted in a posterior-anterior direction at a mean rate of 12·6 m/s. Rates of giant fibre spike conduction and maximal frequencies of firing (up to 500/s) in intact animals were higher than values previously reported in isolated preparations. MGF spikes were followed 1:1 by presumed giant motor axon spikes and facilitating muscle potentials. Single MGF or LGF spikes evoked by applying tactile stimulation were not accompanied by longitudinal contraction, but a series of two or more MGF spikes or three or more LGF spikes were accompanied by such contractions. MGF and LGF spikes occurred infrequently during locomotory movements in the absence of any experimenter-applied stimulation, suggesting that sensory inputs associated with normal locomotion over an irregular substrate are sufficient to excite giant fibres.
The Permeability of the Skin of the Aquatic Anuran Xenopus Laevis (Pipidae)
Authors: Yorio T. , Bentley P. J. 
Published: April 2021

ABSTRACT
The undirectional transcutaneous fluxes of Na, Cl, water and urea were measured, in vitro, in the pipoid anuran Xenopus laevis. An active uptake (outside to inside) of Na was observed but Cl movements appeared to be passive. The effluxes of Na and Cl were low compared to those measured in other species of amphibians. The active Na transport was less than that of more terrestrial species and, although it could be stimulated by vasotocin, aldosterone was ineffective. The permeability of the skin to water was also low and although it was increased in the presence of vasotocin the magnitude of the response was much less than seen in more terrestrial anurans. The skin was permeable to urea but the movement of this solute was not remarkable when compared to that in other amphibians. These properties of the skin are discussed in relation to the animal’s aquatic manner of life.
Propagation of Action Potentials Through Electrotonic Junctions in the Salivary Glands of the Pulmonate Mollusc, Helisoma Trivolvis
Authors: Kater S. B. , Rued J. R. , Murphy A. D. 
Published: April 2021

ABSTRACT
The secretory cells of the salivary glands of the snail, Helisoma trivolvis, exhibit regenerative, overshooting action potentials whose amplitude may exceed 100 mV. The salivary glands consist of paired, tubular, epithelial structures with acinar outpocketings. The secretory cells display extensive electrical coupling which allows action potentials to propagate along the glandular epithelium.
Salivary glands from nine genera of gastropod molluscs were examined. The genera comprised one opisthobranch, one prosobranch, two terrestrial pulmonate slugs, one terrestrial pulmonate snail, and four aquatic pulmonate snails. Action potentials were recorded from all of the examined glands, suggesting that the production of action potentials in salivary glands is a general phenomenon among gastropods.
Some Responses of the Electric Ray (Torpedo Marmorata) to Low Ambient Oxygen Tensions
Authors: Hughes G. M. , Johnston I. A. 
Published: April 2021

ABSTRACT
Blood samples were taken during prolonged hypoxia experiments in which the inspired water oxygen tension was less than 10 mmHg. The oxygen tension of the post-branchial blood was about 5 mmHg and its pH shows a significant lowering from normoxic levels. The decrease in blood pH is correlated with increases in levels of lactate and pyruvate. The lactate/pyruvate ratio increases during hypoxia. An increase in blood succinate was also found, and strongly suggests the accumulation of multiple anaerobic end-products within the tissues. Recovery to normoxic levels of succinate takes place almost immediately following the restart of ventilation whereas the decrease in lactate concentration is slower. It is concluded that these adaptations may be related to the habitat of the fish at low tide in pools where the may fall very markedly.
The Distribution of Blood Flow in the Gills of fish: Application of A New Technique to Rainbow Trout (Salmo Gairdneri)
Authors: Booth John H. 
Published: April 2021

ABSTRACT
Injecting vitally stained blood cells into the ventral aorta of unrestrained cannulated fish, and rapid freezing in liquid nitrogen, provided a method of investigating blood flow patterns in the gills. Rainbow trout in air-saturated water perfused an average of 58% of the secondary lamellae of the gills. Perfusion of the filamental central compartment was insignificant indicating that the effects of any non-respiratory shunting would be unimportant. If the functional surface area of the gills is variable, it seems likely that this would be accomplished through lamellar recruitment. There was no evidence that pillar cell contraction affected lamellar perfusion. There was preferential perfusion of lamellae near the base of the filaments, and of filaments near the dorsal end of the gill arches.
Respiratory and Circulatory Changes in the Lobster (Homarus Vulgaris) During Long Term Exposure to Moderate Hypoxia
Authors: Butler P. J. , Taylor E. W. , McMahon B. R. 
Published: April 2021

ABSTRACT
Within a few hours of the lobsters being placed in the experimental chamber in normoxic water (, 130−135 mmHg), their heart rate, oxygen uptake and ventilation volume were relatively high. The scaphog-nathites were simultaneously active on both sides (bilateral ventilation) for 50% of the time, active on one side only (unilateral ventilation) for 32% of the time and simultaneously inactive (respiratory pause) for 18% of the time. Percentage extraction of O2 (% Ext.) was relatively low. 48 h after having been set up, heart rate, and had decreased significantly, % Ext. had increased and bilateral ventilation occupied 25% of the time. Heart rate was low and the beat irregular. Upon subsequent exposure to hypoxia (, 50−55 mmHg), fell, there was initial hyperventilation, bilateral ventilation for 89 % of the time, heart beat was more regular but did not change significantly. An initial increase in pHa caused the O2 affinity of the Hcy to rise. After 72 h exposure to hypoxia and pHa had declined, but was still higher than at the end of the period of normoxia. Blood lactate, and % Ext. were not significantly different from the values recorded after 48 h in normoxic water. Upon return to normoxic water, and the time the animals spent ventilating both branchial chambers fell, but increased. It is concluded that for settled lobsters, could be maintained during moderate hypoxia by increasing , maintaining a regular heart beat, and at least initially by increasing the O2 affinity of the Hcy.
Distributions of Nerve and Muscle Fibre Types in Locust Jumping Muscle
Authors: Hoyle Graham 
Published: April 2021

ABSTRACT
Muscle fibres of the locust extensor tibiae (jumping muscle) were examined by interference microscopy and by electron microscopy. The electrical responses of single fibres and the mechanical responses of bundles or selected regions to the nerve fibres were examined. Four axons innervate the muscle: fast (FETi), slow (SETi), common inhibitor (CI) and dorsal unpaired median (DUMETi). Their distributions were examined by combined electrophysiological tracing and EM sectioning.
The mean diameter of muscle fibres in different regions varies from 40 to 140 μm and is related to the local leg thickness rather than muscle fibre type. The fine structure of a fibre is related to its innervation. Fibres innervated by FETi but not SETi are of fast type ultrastructurally. Fibres innervated by SETi but not by FETi are of slow type ultrastructurally. Fibres innervated by both axons are generally intermediate between the extremes though more nearly of fast type than slow. Distal slow muscle fibres have much slower relaxation rates than do proximal ones. The most proximal bundles are of mixed muscle fibre type. There is an abrupt transition from a mixed population to homogeneous fast type, in the muscle units immediately distal to the most proximal bundles. This transition is associated with the presence of DUMETi terminals on some of the fibres distal to the transition point. There are no SETi endings on these same fibres. Fibres innervated by both SETi and FETi are scattered throughout the leg, but are commonest in the dorsal bundles. The percentage of these increases progressively passing distally. The most distal muscle fibres are innervated by SETi but not by FETi.
It is concluded that different regions of the muscle will play different roles functionally since they are differentially sensitive to the pattern of SETi discharge.
Intersegmental Reflex Coordination by A Single Joint Receptor Organ (Cb) in Rock Lobster Walking Legs
Authors: Clarac F. , Vedel J. P. , Bush B. M. H. 
Published: April 2021

ABSTRACT
In the decapod Crustacea, Palinurus vulgaris and Jasus lalandii, the reflex influences of one particular proprioceptor organ, the coxo-basal chordotonal organ (CB), on all the muscles operating the proximal and distal joints of the same leg, have been analysed. The distal end of CB was clamped in fine forceps mounted on a servo-controlled stretcher, and CB length changes of 2 mm were applied. Motor unit activity of the different muscles was recorded as electromyograms (EMGs).
Two types of proprioceptive reflex evoked by CB length changes have been investigated: (a) resistance reflexes of the two levator and two depressor muscles of the same leg segment, the coxopodite, i.e. ‘intrasegmental reflexes’, (b) ‘intersegmental reflexes’ induced in the muscles operating the proximal (T-C) joint of the same leg, and in all eight muscles of the limb segments distal to CB. Both levator muscles respond reflexly to imposed CB stretch (which normally occurs with limb ‘depression’), while both depressors respond during CB shortening (or passive ‘elevation’ of the leg). Intersegmentally, CB stretch reflexly activates the M-C extensor muscle, and sometimes facilitates the T-C remotor and C-P bender muscles. Shortening of the single CB organ of a leg excites one or two tonic motor units of the T-C promotor and M-C flexor muscles, and also facilitates the remotor, I-M reductor, and the single stretcher-opener excitatory motoneurone. Some of these muscles, particularly the M-C flexor and extensor muscles, are also influenced intersegmentally by the resting length of CB, usually but not invariably in the same direction as for the corresponding dynamic reflexes.
The role of the CB chordotonal organ is discussed, with particular consideration of its intersegmental reflex influence on the posture of the entire leg, and on the more complex motor behaviour of locomotion, where it may be specially significant in coordination of the limb in lateral walking. A complex picture of both tonic and dynamic, intra- and intersegmental reflex regulation of the positions and movements of the limb segments, thus emerges.
Intersegmental Reflex Actions from A Joint Sensory Organ (Cb) to A Muscle Receptor (Mco) In Decapod Crustacean Limbs
Authors: Bush B. M. H. , Vedel J. P. , Clarac F. 
Published: April 2021

ABSTRACT
In the walking legs of decapod crustaceans, intersegmental reflex actions originate from various joint proprioceptors. The activity of the ‘accessory flexor’ (AF) muscle, which with the myochordotonal organ (MCO) constitutes a muscle proprioceptor for the mero-carpopodite (M-C) joint, is modulated by the sensory discharge of a joint receptor (CB chordotonal organ) for the more proximal, coxo-basal (C-B) joint. Selective mechanical stimulation of the CB organ also reflexly modifies the motor activities of the main M-C flexor and extensor muscles (recorded as EMGs).
Dynamic CB stretch (as would occur during a dorso-ventral C-B movement - i.e. ‘depression’ of the limb) stimulates motor discharge to the M-C extensor muscle, while dynamic release of CB (as during a ventrodorsal C-B movement - or leg ‘elevation ‘) excites the accessory flexor as well as the main flexor muscle. Successive M-C muscle responses to repetitive sinusoidal changes of CB length differ quantitatively according to the direction (stretch or release) of the first CB movement, in some cases increasing but more commonly ‘adapting’ with repetition. Reflex discharge frequencies of the extensor, flexor and accessory flexor motoneurones increase with velocity of CB movement. Eye illumination, and spontaneous or other sources of increased central excitability, generally increase the CB reflex drive to the flexor and accessory flexor muscles and, in parallel, decrease the reflex action on the extensor muscle.
The results are discussed in terms of the role of proprioceptive reflexes in intersegmental co-ordination of the leg joints. In particular the significance of the reflex regulation of the myochordotonal receptors, and thereby the gain of the M-C resistance reflexes, is considered in the light of the observed ‘co-activation’ of main flexor and receptor muscle motoneurones.
Heat Transfer in Dragonflies: ‘Fliers’ and ‘Perchers’
Authors: Heinrich Bernd , Casey Timothy M. 
Published: April 2021

ABSTRACT
Both ‘perchers’ (Libellula saturata) and ‘fliers’ (Anax junius and Aeshna multicolor) remained active in the field in sunshine at air temperatures from at least 24 °C to 36 °C. The percher basked at low air temperatures and regulated exogenous heat input by postural adjustments. It markedly reduced flight activity at high air temperatures but flew nearly continuously at intermediate temperatures. In direct sunlight, the abdomen of L. saturata heated faster than the thorax, but this percher exhibited little or no capacity to transfer heat between abdomen and thorax. In contrast, the fliers gave no evidence of behavioural thermoregulation, but both showed impressive capacities for heat transfer from thorax to abdomen. When heated exogenously on the thorax the temperature of the entire abdomen of both fliers increased uniformly, but with endogenous heat production during pre-flight warm-up there was only a slight temperature increase near the anterior portion of the abdomen. Removal of abdominal air sacs or immobilizing the abdomen with wax to prevent all abdominal pumping did not significantly alter the capacity to transfer heat from thorax to abdomen. Ligation of the heart anywhere along the length of the abdomen abolished heat transfer. Given sufficient exogenous heat input, fliers that can regulate their thoracic temperature by transferring the excess heat to the abdomen died in about 2 min due to overheating when the heart was occluded. Under our experimental conditions the fliers appeared to thermoregulate exclusively via a control of blood circulation.
Sources of Variation in the Output of Locust Spiracular Motoneurones Receiving Common Synaptic Driving
Authors: Burrows Malcolm 
Published: April 2021

ABSTRACT
The closer muscles of the left and the right spiracles of a thoracic segment are both innervated by two motoneurones, which spike in a variety of patterns during expiration. This paper seeks to explain the origin of these patterns. No direct coupling between the two motoneurones is revealed. In an isolated thoracic ganglion both motoneurones spike at different frequencies with no tendency for their spikes to become synchronized. The two closer motoneurones in one segment receive common, patterned depolarizing synaptic potentials during expiration caused by interneurones relaying information from the metathoracic ganglion. The closer motoneurones of all the thoracic segments receive the same pattern of synaptic potentials from these interneurones. Despite this, the spiracles of one segment may remain shut while those on other segments continue to open and close rhythmically. The interplay between common synaptic driving, the threshold of the motoneurones for spike initiation, and the tendency for a motoneurone to spike at a particular frequency even in the absence of interneuronal driving, explains the various patterns of spikes during expiration. Common synaptic driving imposes the same basic pattern of commands on all the motoneurones, but the individual motoneurones determine the final pattern of motor spikes. To be effective in producing a patterned output, an input pattern must operate within narrow limits on either side of the threshold of the motoneurone. If the depolarization is too large, a high frequency of unpatterned spikes will result; if too small, then either there will be no output or a low frequency of spikes will result whose patterning will be affected by other inputs.