bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neural regulation of the heart muscle in an isopod crustacean: acceleration and peripheral inhibition
Authors: Delaleu J. C. , Holley A. 
Published: April 2021

ABSTRACT
In the neurogenic heart of the isopod crustacean Porcellio dilatatus, repetitive electrical stimulation of the cardiac nerves elicited either cardioacceleratory or cardio-inhibitory effects depending on the stimulation parameters. Acceleratory effects were accompanied by a decrease of membrane potential and by changes in the contour of the spontaneous electrical responses: increase in the speed of the rising phase and enhancement of the plateau phase. Inhibitory stimulation acted on rhythmicity and/or contour of spontaneous responses. At stimulation pulse frequencies beyond 25/s a hyperpolarization appeared after the cessation of the inhibitory train. Inhibitory stimulation elicited IJPs in the myocardium. Their reversal potential was found to be close to the value of the resting membrane potential. During inhibitory stimulation, the membrane resistance of the heart muscle was frequently decreased. The effects of changing the external chloride content, and of adding GABA and picrotoxin support the hypothesis that the inhibitory impulses increased the myocardium permeability to Cl−. On the basis of these findings it is assumed that cardio-inhibitory fibres act on both cardiac ganglion and myocardium. Comparisons are established between the wood-louse’s heart and the skeletal or heart muscle of some arthropods. The functional significance of peripheral inhibition is further discussed in relation to the nature of the spontaneous electrical responses and to contraction.
Analysis of burst activity of the buccal ganglion of Aplysia depilans
Authors: Rose R. M. 
Published: April 2021

ABSTRACT
Certain nonlinear properties of molluscan neurones suggest that network activity could be described in relation to nonlinear relaxation oscillators. A specific example is fitted by the Van der Pol equation with an exponentially decaying damping coefficient, and changes in the associated energy and sensitivity are considered. More precise details of the interaction pattern are determined by analysis of a single cycle of burst activity, and it is shown that there are two states of activity, depending on the balance of presumed inhibitory components. Previous results are discussed in relation to an overall decaying oscillation. Changes in subcomponents of a cycle are described for decaying sequences and the constancy of synaptic interaction is demonstrated. The results are briefly discussed in relation to catastrophe theory and learning.
Morphometric study of trout gills: a light-microscopic method suitable for the evaluation of pollutant action
Authors: Hughes G. M. , Perry S. F. 
Published: April 2021

ABSTRACT
Methods are described for the morphometric estimation of parameters of the gill system of trout which are relevant to its function in gas exchange. The methods have been used with 1 μm sections viewed under the light microscope. In particular the diffusion distances between water and blood are measured, which together with determinations of gill area, provide figures for the morphometrically estimated diffusing capacity. The methods have been used to compare the diffusing capacity of gills from control fish and those treated in polluted waters. The concept of relative diffusing capacity (Drol) is introduced which enables comparisons to be made without the need to determine the absolute diffusing capacity. Quantitative estimation of changes in relative volumes and surface areas of components of the secondary lamellae were determined, and employed to explain the possible anatomical causes of changes in Drol. It is suggested that these methods can be of value in the comparison of the gills of fish treated in different waters.
Branchial ion uptake in arctic grayling: resting values and effects of acid-base disturbance
Authors: Cameron J. N. 
Published: April 2021

ABSTRACT
Techniques for the measurement of unidirectional flux rates in fish which require no anaesthesia or surgery are described. Resting values for Cl− uptake at 10 and 17 °C were 8·03 ± 1·11 and 13·52±0·95μ-equiv. 200 g−1 h−1 (±S.E.), respectively; and for Na+ the rates were 15·49±0·40 and 26·30±0·36, respectively. Hypercapnic acidosis caused an increase in Na+ uptake, presumably through Na+/H+ (or ) exchange. It is suggested that this is a com-pensation mechanism leading to the increase in blood buffering observed in response to hypercapnia. Alkalosis was observed following acute temperature increase and was accompanied by an increase in the rate of exchange and also by an increase in Na+/H+ exchange. The role of these branchial ion exchange mechanisms in overall acid-base regulation is discussed.
Flow Visualization with Stereo Shadowgraphs of Stratified Fluid
Authors: Mccutchen C. W. 
Published: April 2021

ABSTRACT
Water stratified thermally or with dissolved material has a refractive index that varies with height. The stratification has no obvious visual effect until the fluid is disturbed, for example by a fish, but then it marks the creature’s wake with a jump in refractive index that is visible in shadowgraphic projection. Two shadowgraphs in stereo display the wake in three dimensions. For a permanent record, or for analysing events too quick for the eye to follow, movies can be taken of the shadowgraphs.
The Effect of Size on the Fast-Start Performance of Rainbow Trout Salmo Gairdneri, and A Consideration of Piscivorous Predator-Prey Interactions
Authors: Webb P. W. 
Published: April 2021

ABSTRACT
The fast-start (acceleration) performance of seven groups of rainbow trout from 9·6 to 38·7 cm total length was measured in response to d.c. electric shock stimuli. Two fast-start kinematic patterns, L-and S-start were observed. In L-starts the body was bent into an L or U shape and a recoil turn normally accompanied acceleration. Free manoeuvre was not possible in L-starts without loss of speed. In S-starts the body was bent into an S-shape and fish accelerated without a recoil turn. The frequency of S-starts increased with size from o for the smallest fish to 60–65 % for the largest fish. Acceleration turns were common. The radius of smallest turn for both fast-start patterns was proportional to length (L) with an overall radius of 0·17 L.
The duration of the primary acceleration stages increased with size from 0·07 s for the group of smallest fish to 0·10 s for the group of largest fish. Acceleration rates were independent of size. The overall mean maximum rate was 3438 cm/s2 and the average value to the end of the primary acceleration movements was 1562 cm/s2. The distance covered and velocity attained after a given time for fish accelerating from rest were independent of size.
The results are discussed in the context of interactions between a predator and prey fish following initial approach by the predator. It is concluded that the outcome of an interaction is likely to depend on reaction times of interacting fish responding to manoeuvres initiated by the predator or prey. The prey reaction time results in the performance of the predator exceeding that of the prey at any instant. The predator reaction time and predator error in responses to unpredictable prey manoeuvre are required for prey escape. It is predicted that a predator should strike the prey within 0·1 s if the fish are initially 5–15 cm apart as reported in the literature for predator-prey interactions. These distances would be increased for non-optimal prey escape behaviour and when the prey body was more compressed or depressed than the predator.
Respiration of the Amphibious Fishes Periophthalmus Cantonensis and Boleophthalmus Chinensis in Water and On Land
Authors: Tamura S. O. , Morii H. , Yuzuriha M. 
Published: April 2021

ABSTRACT
The routine oxygen consumption by Periophthalmus cantonensis and Boleophthalmus chinensis in water increased geometrically, whereas that in air increased logarithmically with temperature. At temperatures of more than 20 °C the oxygen uptake of both species was greater in water than in air. When the fishes were able freely to select either an aquatic or terrestrial habitat, the total oxygen consumption of Periophthalmus and Boleophthalmus was 236 and 110 ml/kg.h at 20 °C respectively; 66% (Periophthalmus’) and 70 % (Boleophthalmus) of the total uptake was from water, and 34 and 30 % of the total uptake was from air at 20 ± 1 °C. Oxygen uptake of fish limited to aquatic or terrestrial life was less than when they could freely select their habitat ; for Periophthalmus, uptake was reduced to 83 % when confined in water and to 50 % in air, and for Boleophthalmus, to 65 % in water and to 43 % in air. The proportion of oxygen uptake by the gill in water was 52% for Periophthalmus and 59 % for Boleophthalmus’, in air the corresponding figures were 27 and 52 %. The proportions of oxygen uptake via the skin in water was 48% for Periophthalmus and 36% for Boleophthalmus; in air the corresponding figures were 76 and 43 %. It is concluded that, on land, Periophthalmus relies mainly on its skin and Boleophthalmus relies mainly on its gills.
Hypersensitivity in the Anterior Median Eye of A Jumping Spider
Authors: Yamashita Shigeki , Tateda Hideki 
Published: April 2021

ABSTRACT
Changes in sensitivity of the photoreceptor cells of the anterior median eye of the jumping spider Menemerus confusus Boes, et Str. have been studied by recording electroretinograms (ERGs) and receptor potentials. The amplitudes of the responses (ERGs and receptor potentials) increase during repetitive stimulation, with a maximum increase at 3−5 s intervals. The sensitivity of the photoreceptor cell is greater for about 60 s following illumination (maximum magnitude at 3−5 s) than it is during complete dark adaptation. This phenomenon, which we call ‘hypersensitivity’, is lost within one day following surgery in physiological saline. Upon loss of hypersensitivity, the sensitivity decrease during light adaptation is greater than for the normal eye and the small increase of sensitivity following the onset of illumination observed for the normal eye is lost.
The Role of Environmental Calcium in Freshwater Survival of the Marine Teleost, Lagodon Rhomboides
Authors: Carrier Jeffrey C. , Evans David H. 
Published: April 2021

ABSTRACT
The marine teleost fish, Lagodon rhomboides, can only tolerate fresh water (5 mm Na) if Ca is also present (10 mm). Transfer to Ca-free fresh water is followed by a substantial increase in radioactive Na efflux with little or no change in the transepithelial potential. Addition of the chelating agent EDTA (2 mm) further increases Na efflux. Fish left in Ca-free fresh water for 2·5 h die with a total body Na less than 50 % of that found in animals acclimated to Ca-supplemented fresh water. Rates of Na uptake were measured on either sea-water-acclimated or Ca-supplemented fresh water-acclimated fish transferred to various low Na media. In both cases Na uptake has a high Km, is saturable, inhibited by external NH4, H and amiloride, and is not related to changes in the transepithelial potential. It is suggested that L. rhomboides is dependent upon external Ca to decrease diffusional Na loss in low salinities so that a relatively inefficient Na uptake can balance diffusional and urinary Na loss.
The Effects of Osmotic Stress on the Electrical Properties of the Axons of A Marine Osmoconformer (Maia Squinado. Brachyura: Crustacea)
Authors: Pichon Y. , Treherne J. E. 
Published: April 2021

ABSTRACT
In contrast to the depolarization observed in hyperosmotic media, exposure of peripheral nerve to hyposmotic conditions induced pronounced axonal hyperpolarization. It is suggested that this hyperpolarization resulted from increased potassium and chloride permeabilities which could assist axonal volume regulation in hyposmotic conditions. The hyperpolarization was readily reversible, but the spike-generating mechanism suffered irreversible damage at hyposmotic concentrations below 665 m-osmoles. It is suggested that this axonal damage contributes to the lethal effects of hyposmotic stress in this crustacean osmoconformer and, possibly, in some euryhaline osmoregulators.
Rhythmic Swimming Activity in Neurones of the Isolated Nerve Cord of the Leech
Authors: Kristan William B. , Calabrese Ronald L. 
Published: April 2021

ABSTRACT
Repeating bursts of motor neurone impulses have been recorded from the nerves of completely isolated nerve cords of the medicinal leech. The salient features of this burst rhythm are similar to those obtained in the semi-intact preparation during swimming. Hence the basic swimming rhythm is generated by a central oscillator. Quantitative comparisons between the impulse patterns obtained from the isolated nerve cord and those obtained from a semi-intact preparation show that the variation in both dorsal to ventral motor neurone phasing and burst duration with swim cycle period differ in these two preparations. The increase of intersegmental delay with period, which is a prominent feature of swimming behaviour of the intact animal, is not seen in either the semi-intact or isolated cord preparations. In the semi-intact preparation, stretching the body wall or depolarizing an inhibitory motor neurone changes the burst duration of excitatory motor neurones in the same segment. In the isolated nerve cord, these manipulations also change the period of the swim cycle in the entire cord. These comparisons suggest that sensory input stabilizes the centrally generated swimming rhythm, determines the phasing of the bursts of impulses from dorsal and ventral motor neurones, and matches the intersegmental delay to the cycle period so as to maintain a constant body shape at all rates of swimming.
Altered Calcium Conductance in Pawns, Behavioural Mutants of Paramecium Aurelia
Authors: Schein Stanley J. , Bennett M. V. L. , Katz George M. 
Published: April 2021

ABSTRACT
Pawns are behavioural mutants (in one of three genes) of Paramecium aurelia that have lost, to varying degrees, the reversal response which is thought to depend on the calcium influx during excitation. This report shows that all of the single and double mutants have reduced active inward (calcium) current, the reduction correlating with the degree of behavioural deficit. All of the mutants display normal resting potential, input impedance and delayed rectification. Mutants in genes pwA and pwC show normal anomalous rectification, but pwB mutants do not show anomalous rectification until the membrane is hyperpolarized further. We suggest that the pwA gene plays a role in depolarization sensitivity (the ‘gate’) and the pwB gene a role affecting either the wall of the channel itself or the total number of channels.
Calcium Channel Stability Measured by Gradual Loss of Excitability in Pawn Mutants of Paramecium Aurelia
Authors: Schein Stanley J. 
Published: April 2021

ABSTRACT
Mutants of Paramecium aurelia that are unable to reverse swimming direction are called pawns. They lack the inward ionic (calcium) current required for the upstroke of the electrically excitable membrane response. By following the progressive loss of reversal response and excitability in cells that are suddenly changed from a heterozygous (wild-type) state to a homozygous mutant state, an estimate of the stability and mean lifetime of the calcium channel has been obtained. During rapid growth, channel dilution due to division occurred, but no channel decay was observed. Under conditions of slow growth, decay could also be observed; channel lifetime was found to be from 5 to 8 days.
Electrical potentials from the eye and optic nerve of Strombus: effects of electrical stimulation of the optic nerve
Authors: Gillary Howard L. 
Published: April 2021

ABSTRACT
Photic stimulation of the mature eye of Strombus can evoke in the optic nerve ‘on’ activity in numerous small afferent fibres and repetitive ‘off’ bursts of afferent impulses in a smaller number of larger fibres. Synchronous invasion of the eye by electrically evoked impulses in small optic nerve fibres (apparently the ‘on’ afferents, antidromically activated) can evoke a burst of impulses in the larger ‘off’ fibres which propagate away from the eye. Invasion of the eye via one branch of optic nerve can evoke an answering burst in another branch. Such electrically evoked bursts are similar to light-evoked ‘off’ bursts with respect to their impulse composition, their ability to be inhibited by illumination of the eye, and their susceptibility to MgCl2 anaesthesia. Invasion of the eye by a train of repetitive electrically evoked impulses in the absence of photic stimulation can give rise to repetitive ‘off’ bursts as well as concomitant oscillatory potentials in the eye which are similar to those normally evoked by the cessation of a photic stimulus. The electrically evoked ‘off’ bursts appear to be caused by an excitatory rebound following the cessation of inhibitory synaptic input from photoreceptors which can be antidromically activated by electrical stimulation of the optic nerve. The experimental results suggest that the rhythmic discharge of the ‘off’ fibres evoked by the cessation of a photic stimulus is mediated by the abrupt decrease of inhibitory synaptic input from the receptors.
Egg Diapause in Ephippiger Cruciger (Orthoptera: Tettigoniidae): II. The Intensity and Elimination of the Final Egg Diapause
Authors: Dean R. L. , Hartley J. C. 
Published: April 2021

ABSTRACT
Unlike the initial diapause in Ephippiger cruciger, the late embryonic diapause occurs in every egg in natural environmental conditions. It is eliminated by one relatively prolonged period of cooling and the proportion of eggs completing diapause development increases with increased cooling time. Diapause is most effectively eliminated through the range of 4–12 °C over a period of 3–4 months. The optimal hatching temperature is lower than the optimal pre-diapause developmental temperature. There is evidence to show that although diapause development and post-diapause development can both proceed at some temperatures, a period of more intense cooling accelerates the processes. The intensity of diapause is not affected by the duration of exposure to high temperature prior to cooling. A comparison between the initial diapause and the second diapause is presented which suggests that the two types of diapause are alternative solutions to the same environmental problem.
Egg Diapause in Ephippiger Cruciger (Orthoptera: Tettigoniidae): III. Abnormal Development Through the Final Egg Diapause
Authors: Dean R. L. , Hartley J. C. 
Published: April 2021

ABSTRACT
Normally the egg of Ephippiger cruciger is subject to diapause when the embryo is almost fully developed. Most eggs die or develop erratically and slowly when chilled for some time at earlier non-diapausing stages. However, after 2 or 3 months’ cooling at a stage just before catatrepsis a few eggs developed more rapidly than usual and hatched without intervention of a diapause, at a temperature that is normally too high to allow diapause development to proceed. A possible mechanism, involving the neurosecretory system, for this diapause pattern is suggested.
A circadian rhythm in the locomotor behaviour of the giant garden slug Limax maximus
Authors: Sokolove P. G. , Beiswanger C. M. , Prior D. J. , Gelperin A. 
Published: April 2021

ABSTRACT
The locomotor activity of the garden slug Limax maximus was examined for components of circadian rhythmicity. Behavioural (running wheel) studies clearly demonstrated that the activity satisfies the principal criteria of circadian rhythmicity. In constant darkness at a constant temperature, the locomotor activity freeran with a period of about 24 h (range 23·6–24·6 h). The rhythm was also expressed in constant light with a period for individual slugs that tended to be shorter in LL than in DD. The period of the rhythm was temperature compensated (11·5–21·5 °C) with a Q10 approximately equal to 1·00. The locomotor rhythm could be entrained to 24 h LD cycles such that the circadian activity peak occurred during the dark. The phase angle between the onset of activity and lights-off was not fixed, but was a function of the photoperiod of the entraining light cycle.
The Uptake of Cadmium Into the Haemolymph of the Shore Crab Carcinus Maenas: The Relationship With Copper and Other Divalent Cations
Authors: Wright D. A. 
Published: April 2021

ABSTRACT
When Carcinus was exposed to 20 μ-mol 1-1 cadmium, the haemolymph cadmium level was initially dependent upon the salinity of the external medium. After 14 days the mean haemolymph cadmium level in 50% s.w. animals was nearly twice that of 100% s.w. animals. This trend was not sustained, however, and the situation was complicated by occasional inconsistent values.
In both in vivo and in vitro conditions nearly all the haemolymph cadmium becomes bound to haemolymph protein within a few days. The relationship between haemolymph cadmium, copper and protein concentration has been investigated. Although the latter are highly correlated with each other, cadmium formed a significant positive relationship with haemolymph copper (r = 0·523) and protein (r = 0·533) only after 3−4 weeks uptaike. Exposure to 20 μ-mol 1-1 cadmium has no obvious effects on haemolymph protein and copper concentrations, which are clearly dependent on feeding status. Mortalities among experimental animals were often preceded by a rise in haemolymph cadmium concentration. This is usually seen before there are any obvious signs of tissue breakdown.
Urine cadmium loss is probably unimportant as a pathway for the elimination of this metal. Urine cadmium concentrations often exceeded serum cadmium levels indicating that cadmium may sometimes be eliminated in bound form.
Body Weight and the Haematology of the American Plaice Hippoglossoides Platessoides
Authors: Smith John Clegg 
Published: April 2021

ABSTRACT
The relationship between haematological variables and body weight (W) is studied in the American plaice. Haematocrit, haemoglobin concentration, and cell volume and numbers are directly correlated with W, indicating that small fish have low blood oxygen solubility in spite of a high weight specific oxygen consumption . Examination of analytical models of the branchial apparatus suggests that, in small fish, is lowered to minimize blood viscosity and that a high is maintained by increasing the arteriovenous oxygen partial pressure difference. Mean cell haemoglobin content is positively correlated while mean cell surface area per unit haemoglobin tends to be negatively correlated with W. Mean erythrocyte residence time in the secondary lamellae is shown analytically to increase with W, possibly accounting for these relationships.
The Locust Jump
Authors: Heitler W. J. 
Published: April 2021

ABSTRACT
The flexor and extensor tibiae muscles of the mesothoracic leg have a constant lever ratio of about 2:1 throughout joint rotation. The mesothoracic tibiae can only flex to 25° about the femora, while the metathoracic tibiae, because of their specialized geometry, can flex almost parallel to the femora. Full metatibial flexion increases the mechanical advantage of the flexor muscle relative to the extensor at full flexion, and increases the vertical component of the thrust produced by tibial extension in a jump. A region in the dorsal proximal cuticle of the metatibia is stiff when stretched but buckles when compressed. The tibia is thus rigid under extensor stress, but bends under flexor stress. Metatibial bending can enable the proximal region of the tibia to become fully flexed even if the distal region is prevented from flexing fully, and may reduce the inertial shock to the femur when the tibia reaches full extension in a kick.