bluuebunny/crossref_metadata_2025 huggingface dataset:
Behaviour and Motor Output for an Insect Walking on a Slippery Surface:II. Backward Walking
Authors: Graham D. , Epstein S.
Published: April 2021

Coordination of the legs and the motor activity of four muscles in a middle leg were recorded in adult stick insects walking on a slippery glass surface. Backward walking was not achieved by a simple phase shift of levators and depressors. In all muscles examined, there was a considerable disturbance of motor activity during backward walking when compared with that found in forward walking. In backward walking, recovery was performed, in the middle leg, by strong fast unit activity in the retractor muscle and all muscles showed weak activity at inappropriate times. Fast motor output appeared to be superimposed on the forward walking motor pattern to produce the movements required for backward walking in this insect.
Further Studies of Crayfish Escape Behaviour:II. Giant Axon-Mediated Neural Activity in the Appendages
Authors: Cooke Ian R. C.
Published: April 2021

Stereotyped responses were evoked in a number of motoneurones in the appendages of semi-intact crayfish when the command neurones for escape behaviour were activated. The medial giant neurones mediated short latency responses in pereiopod common inhibitor, promotor and extensor motoneurones, several abdominal first root neurones and one uropod exopodite promotor motoneurone. The lateral giant neurones mediated short latency responses in the pereiopod common inhibitor neurones, the same abdominal first root neurones and one uropod protopodite promotor motoneurone. These responses can be correlated with stereotyped movements of the appendages which occur in the normal escape behaviour of crayfish.
Neurohormonal Modulation of theLimulusHeart: Amine Actions on Cardiac Ganglion Neurones
Authors: Augustine George J. , Fetterer Raymond H.
Published: April 2021

Octopamine (OCT), dopamine (DA), epinephrine (EPI) and norepine-phrine (NE) are endogenous excitors of the Limulus heart. The cellular sites of action of these amines were investigated by recording responses of neurones in the cardiac ganglion. There was an increase in spike frequency in pacemaker neurones, accompanied by a depolarization and an increase in the rate of repolarization of the ‘pacemaker potential’. DA also produced a transient decrease in pacemaker spike frequency which preceded its excitatory effect. All four amines produced slow, dose-dependent increases in the frequency of bursting activity in cardiac ganglion follower neurones. These increases were blocked by the antagonist phentolamine. DA and NE also produced transient decreases in burst rate which were blocked by the antagonist metergoline. Local application of DA on to pacemaker cells increased follower cell burst frequency, while similar applications on to follower cells did not affect burst frequency. This indicates that DA acts directly upon pacemaker neurones to increase cardiac ganglion burst activity. In addition to their pacemaker-mediated effects, the amines also had direct effects upon follower cells. These effects were examined after eliminating follower cell bursting activity with cobalt ions. OCT and, to a smaller extent, EPI, depolarized follower cells. DA and, occasionally, NE hyperpolarized follower cells. The hyperpolarizing DA response was due to a conductance increase and was blocked by metergoline and ergonovine.
Sperm Receptivity in Sea Urchin Oocytes and Eggs
Authors: Dale Brian
Published: April 2021

An electrophysiological method for studying the receptivity to spermatozoa of sea urchin eggs and oocytes is described. Pairs of adjacent oocytes and eggs, with intact jelly layers, were impaled and simultaneously exposed to a known concentration of spermatozoa. Two parameters were studied. The time from insemination to the first successful collision (as indicated by a step depolarization across the egg plasma membrane) and the total number of successful collisions. Sperm densities of 107ml-1 were used, which ensured almost immediate interaction between several thousand spermatozoa and each female gamete. In all cases, under control conditions, the oocyte was more receptive to spermatozoa than was the egg, giving rise to the first electrical event at about 5 s post-insemination, compared to about 13 s for the egg. In addition, whereas 10-15 spermatozoa usually entered the oocyte, only one entered the egg. The low receptivity of eggs appears to be independent of resting potential. Cytoplasmically immature eggs or mature eggs briefly exposed to nicotine, strychnine, choline or Tris tend to be polyspermic and have comparable receptivity to oocytes. The data suggest that there are a limited number of viable interaction sites on the oocyte surface and that during cytoplasmic maturation these sites are rendered less receptive. In the mature egg there may be one preferential sperm entry site. This hypothesis is consistent with the experimental data and would explain why sea urchin eggs are usually monospermic at high sperm densities.
Characterization of the Cold-Induced Contracture of the Anterior Byssal Retractor Muscle of Mytilus Edulis
Authors: Linehan Catherine M.
Published: April 2021

When the anterior byssal retractor muscle (ABRM) of Mytilus edulis was subjected to a sudden reduction in temperature during a contractionrelaxation cycle, a tension increment, the cold-induced contracture (CIC), was observed. The CIC could be obtained in a muscle stimulated by the application of acetylcholine (ACh), caffeine or high-K+ solutions, but could not be elicited from a muscle at rest or in ‘catch’. When the muscle was released from ‘catch’ by the application of 5-hydroxytryptamine (5-HT), a CIC could once again be produced. The CIC tension elicited after the application of ACh was shown to follow a log-dose relationship with respect to ACh concentration but no CIC was observed at an ACh concentration at which the initial tension was 10% or less of maximum. The CIC tension decreased with time after the application of ACh and appeared to be dependent on both the initial and final temperatures and on the size of the temperature drop. The significance of these results and possible explanations are considered.
Cost of Locomotion: Unsteady Medusan Swimming
Authors: Daniel Thomas L.
Published: April 2021

The influence of unsteady (time varying) motion on the energetics of swimming was investigated with measurements and theoretical estimates of the specific cost of locomotion for two species of hydrozoan medusae: Gonionemus vertens L. Agassiz and Stomotoca atra L. Agassiz. These species, both about 1 g, provide a broad range of swimming speeds for which locomotor energetics can be explored. The cost of locomotion (a dimensionless ratio defined as the rate of energy consumption divided by the product of an animal’s weight and speed) was estimated from the oxygen consumption rate of medusae tethered to a force platform. Swimming beat frequency, as monitored by the force platform, was correlated with velocity obtained from ciné-films of freely swimming medusae.

The specific cost of locomotion was 6-3 (dimensionless), nearly one order of magnitude greater than the extrapolated cost of locomotion for a vertebrate swimmer of equivalent body mass. The great magnitude of this cost is attributed to two aspects of the periodic pulsatile pattern of locomotion by these cnidarians: (1) the energy expenditure for periodic accelerations of the animal’s mass and some mass of fluid about it and (2) the energy dissipated in bell deformations and recovery strokes. Nearly 25% of the augmented cost is attributed to the energy required to overcome an unsteady flow force, that is the force required to accelerate fluid about the animal. Such a high cost of locomotion is apparently a general consequence of swimming with a discontinuous production of thrust.

The mechanics of discontinuous swimming are explored by measuring the hydrodynamic coefficients associated with unsteady flows (added-mass coefficients) for models of medusae. The results suggest that the effects of vortex formation and shedding may significantly increase the magnitude of the forces produced by or resisting unsteady animal locomotion.
On the Reactions of Isolated Parts ofParamecium Caudatum
Authors: Horton Frances M.
Published: April 2021

The mode of swimming and reactions to acid of parts of Paramecium have been compared with the behaviour of the intact animal. Hind ends are more sensitive to acid than fore ends, which in this respect do not differ from whole individuals. Pieces lacking oral cilia swim spirally like intact animals.
On the Sensitivity of the Chemoreceptors on the Antenna and Fore-Tarsus of the Honey-Bee, Apis Mellifica L
Authors: Marshall Joseph
Published: April 2021

The experiments to be described were undertaken as a preliminary study of the reactions of the contact chemoreceptors on the antenna and fore-tarsus of the honey-bee, Apis mellifica L., to various concentrations of sucrose solutions. Experiments were also carried out to estimate the effect of antennal amputation on chemotropic response.
The Energy Sources in Ontogenesis
Authors: Baldwin Ernest
Published: April 2021

By studying the respiratory quotients of developing embryos, valuable indications can be obtained as to the nature of the substances undergoing metabolic oxidation within them. Many different embryos have been made the subject of such studies, but probably only the most recent data can be wholly accepted. The values given by the earlier workers were for the most part calculated by dividing the amount of CO2 given off from a sample of the material by the amount of oxygen consumed under the same conditions. But such a method of calculation is liable to be entirely misleading, since the amount of CO2 given off from the material may be very different from the amount actually produced by metabolic oxidation. Thus, as Richardson (1929) writes: “Even when the apparatus is technically correct, errors of interpretation may arise. The quotient as measured may not reflect the concurrent oxidation. In this event, it is convenient to designate the observed quotient as the measured quotient, and the supposed quotient due to oxidation as the metabolic quotient.” It is clear that if CO2 be retained in the material under examination, e.g. on account of pH changes or the deposition of calcareous matter in the developing embryo, the measured quotient will be lower than the metabolic quotient, unless the amount of bound CO2 can be determined before and after the period during which the oxygen uptake is measured. These considerations would apply particularly to the snail eggs which formed the material for the present study ; here, as we shall see, large amounts of CO2 are required for shell formation, and consequently any quotients obtained by the earlier methods would have been grossly inaccurate and quite useless as the basis of any hypothesis as to the energy sources of the developmental processes. It is only of recent years, with the development of manometric technique, that it has been possible to make proper allowances for any retention of CO2, a fact which must be borne in mind in considering the earlier data.
The Nerve Net of the Actinozoa
Authors: Pantin C. F. A.
Published: April 2021

Certain features have been supposed to characterise the nerve net. Response is said to vary with the strength of stimulus: and while conduction may occasionally take place in an all or nothing manner, yet in general conduction is supposed to take place with a decrement. To investigate these points, the responses of Calliactis parasitica to mechanical and electrical stimuli have been investigated. Electrical excitation of the column of the anemone shows that a response results from a succession of stimuli and not from a single stimulus. The character of the response is independent of the strength of the individual stimuli. It depends solely upon the number of stimuli and upon the interval of time between them. All responses are highly developed facilitation phenomena. Each electrical stimulus induces a single excitation impulse in the nerve net. But a mechanical stimulus is followed by the discharge of a battery of impulses from the sense organs. These increase in number and frequency with the intensity of the mechanical stimulus. A response may therefore vary with the strength of a mechanical stimulus, but only in relation to the number and frequency of impulses discharged by the sense-organs. Stimulation of the intact column of the anemone shows complete conduction over its whole nerve net. Mechanical stimulation of the disc appears to show conduction with a decrement. Such a stimulus excites a battery of impulses. Each impulse is conducted without decrement, but it facilitates the entrance of succeeding impulses into adjoining sections of the disc nerve net. There is no decrement of excitation strength under any conditions in the nerve net. But there may be a numerical decrement as a battery of impulses spreads from a stimulus. The nerve net is physiologically similar to ordinary nerve. A method is described for determining the strength duration relationship for the threshold of electrical excitation of the nerve net. The relation is of the usual form with a chronaxie of about 2·4σ. The nerve net has well-defined relative and absolute refractory periods: the latter is about 40·65σ. The relation of facilitation to refractory period is considered. The whole nerve net of the column of the anemone acts as a conducting layer in its most simple form, directly transmitting excitation from the stimulus to the muscle. Facilitation takes place between the nerve net and its appropriate muscles. Conduction in the disc nerve net involves facilitation between parts of the nerve net in addition. The true characteristics of the nerve net are diffuse conduction and the extreme development of facilitation. Diffuse conduction may be total, as in the column, or restricted, as in the disc of Calliactis. Facilitation may be between the nerve net and the muscles, or between parts of the nerve net.
The Nerve Net of the Actinozoa
Authors: Pantin C. F. A.
Published: April 2021

Stimulation of the column of the anemone Calliatis parasitica elicits a graded series of responses. Each response is primarily due to the action of a single set of muscles. The means by which this effect is produced is physiologically simple. Part of the nerve net beneath the intact column behaves as a single conducting unit and the various muscles communicate with it. The muscles, however, are only activated through the facilitation of a series of impulses. Each muscle has its own appropriate frequency range, to which a facilitated response can be obtained. The range of frequencies is extraordinarily low, from 1 impulse in 1 sec. to 1 impulse in 10 sec. “Interneural” facilitation can be demonstrated between adjacent conducting units of the nerve net of the disc. From various points on the disc several stimuli may be required to establish a conducting path to the sphincter muscle. The apparent continuity of conduction throughout the column in the intact animal is due to specialised tracts running vertically up the mesenteries. These are joined by a conducting ring in the neighbourhood of the sphincter. In addition to this “through-conduction” system, there is a general nerve net within the column wall in which interneural facilitation is evident. The velocity of conduction in the general nerve net of the column has the slow rate of 10–20 cm. per sec. But for the sphincter-mesenteric system the rate is over 1 metre per sec. The relative development of both interneural facilitation and of conduction velocity within the nerve net give consistent pictures of its physiological organisation. These agree with its morphological organisation. Comparison with other species shows that the through-conduction system is a specialisation, developed in varying degrees in different species. It is most highly developed where protective reactions are most perfect, as in Calliactis. The importance of the “impulse group” propagated from a stimulated sense organ as the natural unit in behaviour of Calliactis is discussed.
The Temperature and Humidity Relations of the Cockroach
Authors: Gunn D. L.
Published: April 2021

Previous studies in this series (Gunn, 1933, 1934) have dealt with certain aspects of the physiology of the common black beetle, Blatta orientalis. The present paper is a comparison of that and two other exotic native species of cockroaches. The smallest of the three, Blatella germanica, is found in hotel kitchens, hospitals and public houses, and most rarely in private houses. Development from hatching to the last moult occupies 3 months at 23 ° C. (Zabinski, 1929). Blatta orientalis is very common in similar places and also in older houses of the poorer class. Its development occupies 1 year at 23° C. (Zabinski, 1929). Periplaneta americana, the largest species, seems to be found only in the tropical houses in Zoological and Botanical Gardens. The duration of its life cycle appears to be unknown. No reasons have hitherto been given for the existing distribution of these three species. In this paper some contributory reasons are put forward.

In the experiments here described, adult males only were used. P. americana was obtained from a dealer and the other species were caught locally. All animals were kept a few days before use, and were fed on carrot and water in an oven at 25° C.
The Response of the Lamprey to Injection of Anterior Lobe Pituitary Extract
Authors: Young J. Z. , Bellerby C. W.
Published: April 2021

There have been many investigations on the effect of administration of anterior lobe pituitary preparations on the metamorphosis and sexual development of Amphibia, but so far as can be ascertained no similar work has been done on lampreys. These animals live for several years buried in the mud as ammocoete larvae and eventually metamorphose abruptly, changing their shape and colour and acquiring eyes and a sucker. Various workers have attempted without success to produce this change by injection of iodine or thyroid extracts (Remy, 1922; Horton, 1934).
The Rate of Movement of Planaria Alpina
Authors: Beauchamp R. S. A.
Published: April 2021

Planaria alpina normally moves by gliding, that is to say the ventral surface secretes mucus over which the animal travels by means of waves created in the ventral musculature. These waves travel from behind forwards.
The Effect of Temperature on the Development of the Eggs and Larvae of the Cut-Throat Trout (Salmo Clarkii Clarkii Richardson)
Authors: Merriman Daniel
Published: April 2021

The eggs of the cut-throat trout (Salmo clarkii clarkii Richardson) were raised from fertilisation through hatching at constant temperatures of 11·3, 8·25 and 6·35° C. These temperatures are well within the limits of normal development of cut-throat trout. The temperature is not the limiting factor in determining the length of the hatching period, because there are a number of other factors that may cause eggs to hatch either prematurely early or abnormally late, and thus the use of the hatching period as a comparable stage of development for eggs raised at different temperatures may result in error. The average size of cut-throat trout embryos at the moment of hatching was smaller at the higher temperatures and larger at the lower temperatures. The maximum increment of growth in the cut-throat trout occurred about the 41st day at 8·25° C. and about the 28th day at 11·3° C. The percentage of dry weight of the cut-throat trout embryos showed a steady decrease from about 25 to 14 per cent., while that of the yolks showed an increase from about 46 to 55 per cent. Cut-throat trout embryos absorbed water from the yolk and also, at a faster rate, from the environment, both somewhat before and after hatching, so that the percentage of wet weight of the larvae was steadily increasing up to the time the experiment was completed.
Modification of Mammalian Sexual Cycles
Authors: Bissonnette Thomas Hume
Published: April 2021

Cases are given in which female ferrets, already coming into, or in, oestrus as the result of artificially increased lighting in winter and spring, underwent regression or were retarded in their activation by reduction of either intensity or duration of daily illumination. In some cases activation was resumed when light time or intensity was increased again. These results are taken to indicate that, in female ferrets, any inherent rhythm or cycle of sexual activity is modified either naturally or artificially by changes of the cycles of duration and intensity of the light to which they are exposed daily, and so made to correspond in phases with the seasons, or changed therefrom. The rising daily illumination in spring and the falling one in late summer and autumn probably accelerate and retard the sexual activity of the female ferret, or accelerate the onset of anoestrus in late summer and autumn. The data on modification of sexual cycles or activity in ferrets, so far obtained, are consistent with these conclusions.
The Origin and Fate of Urea in the Developing Hen’s Egg
Authors: Needham Joseph , Brachet Jean , Brown Robert K.
Published: April 2021

The urea formed by the chick embryo during its development is not derived from the ammonia of general protein catabolism, either directly or by way of the ornithine cycle. Nor is it derived from uric acid by a complex uricase similar to that of fishes and Amphibia (Stransky’s complex: uricase, allantoinase and allantoicase). The uricase discovered in the chick embryo by Przylecki probably breaks down uric acid only as far as allantoin. The urea of the chick embryo is entirely derived from an active arginine-arginase system present at all stages examined from the second day of incubation onward. The arginase of the embryo, quantitatively estimated, falls off very regularly as development proceeds, reaching a minimum about the 12th day. This negative heterogony is experimentally shown not to be due to the parallel diminution of activators such as glutathione and ascorbic acid, but must be regarded as a real diminution in the relative amount of the enzyme. It forms an important support for the view of Edlbacher, hitherto mainly based on observations of tumour tissues, that arginase is an enzyme associated with high growth rate and probably nuclein synthesis, as well as with the production of urea as a vehicle of waste nitrogen. Arginase is also contained in the yolk-sac, but in much smaller quantity than in the embryo. Here also the low activity is not due to the absence of activators. Experiments made to test the possibility that the urea, once formed, might, as would be the case on Wiener’s theory, participate in the formation of uric acid, took the form of injection of possible precursors into the egg on the 12th day of development and estimation of the uric acid in the egg on the 15th. In this way it is shown that urea cannot be converted into uric acid by the chick embryo. This conclusion is in agreement with much recent work on the adult bird. A preliminary test was also made of the possibility that biuret and sarcosine could be condensed to uric acid by the chick embryo. The results were negative.
Changes in the Thyroid Gland of Certain Mammals and Birds Following Hypophysectomy
Authors: Rowlands I. W.
Published: April 2021

The weight of the thyroid of the normal anoestrous ferret of both sexes is approximately half that of the oestrous ferret, but there is little histological difference. Hypophysectomy during oestrus or anoestrus decreases the weight of the thyroid of the ferret to a level slightly lower than that for the normal anoestrous ferret. In the hibernating hedgehog the thyroid becomes hypotrophie (Adler, 1920), and a similar condition is found in the hypophysectomised animal. No change in weight of the thyroid of the guinea-pig is noticed following hypophysectomy, but atrophy of the vesicular epithelium and distention of the vesicles with non-vacuolated colloid is regularly observed. Hypophysectomy in birds leads to similar atrophic changes in the thyroid.
Diurnal Changes in Structure and Function of the Compound Eye of Ligia Exotica (Crustacea, Isopoda)
Authors: Hariyama Takahiko , Meyer-Rochow V. Benno , Eguchi Eisuke
Published: April 2021

The ultrastructure of the retinula cells of Ligia exotica changes diurnally and in response to light/dark adaptation. At the low phase of electroretinogram (ERG) amplitude (at noon), the arrangement of microvilli is ordered and the rhabdom is of the open type. An irregular arrangement of microvilli appears at the high phase of ERG amplitude (at midnight), when the rhabdom is of the closed type. The pigment granules disperse at midnight and assemble at noon. A centrally positioned, spike-producing eccentric cell is present in each ommatidium.

Spectral response curves based on ERG measurements have two maxima, one to light of 383 nm wavelength, the other at around 520 nm. These two peaks represent the two classes of receptor cells identified by intracellular recordings. The ERG responses to light of 383 nm and 520 nm wavelengths display a diurnal rhythmicity, being high at night and low during the day. However, the responses to green light are more strongly affected than those to ultraviolet light. Consequently, the eye displays a relatively higher ultraviolet-sensitivity during the day, whereas at night sensitivity to green light is increased.

This behaviour, which persists in continuous darkness, suggests that an endogenous mechanism is involved in bringing about the observed diurnal morphological and physiological changes in the compound eye of Ligia exotica.
The Promotion of Catecholamine Release in Rainbow Trout, Salmo Gairdneri, By Acute Acidosis: Interactions Between Red Cell pH and Haemoglobin Oxygen-Carrying Capacity
Authors: Boutilier R. G. , Iwama G. K. , Randall D. J.
Published: April 2021

A fall in blood pH was generated either by infusion of HCl or by reducing gill ventilation and raising blood in rainbow trout, Salmo gairdneri Richardson. The acute acidosis resulting from HCl infusion caused an increase in plasma adrenaline and noradrenaline concentrations, the adrenaline increase being proportional to the decrease in blood pH. Fish subjected to a prolonged respiratory acidosis, caused by a reduction in gill ventilation, showed no increase in catecholamines 24 h after the change in gill ventilation. We suggest that catecholamine levels increase in response to a pH decrease, but if acidotic conditions are maintained, circulating catecholamines return to low levels.

There was a much smaller decrease in erythrocytic pH with a fall in plasma pH when catecholamine levels were high. This ameliorating effect of catecholamines on erythrocytic pH during a plasma acidosis maintains the oxygen-carrying capacity of the haemoglobin. If erythrocytic pH was decreased by increasing blood vitro, then there was a fall in haemoglobin oxygen-carrying capacity which was proportional to the reduction in pH.

We conclude that catecholamines are released into the blood in proportion to the fall in blood pH but if the pH is maintained the circulating catecholamines return to their initial low levels. The elevated catecholamine concentrations in blood safeguard against any impairment of haemoglobin oxygen-carrying capacity by maintaining erythrocytic pH in the face of a plasma acidosis.
Spontaneous and Elicited Bag Cell Discharges in Gonadectomized Aplysia
Authors: Ferguson Graham P. , Parsons David W. , Maat Andries Ter , Pinsker Harold M.
Published: April 2021

The neuroendocrine bag cells of the hermaphroditic marine gastropod, Aplysia, secrete peptide hormones that induce release of ripe eggs from the ovotestis. The egg string is subsequently deposited on the substrate by means of a complex sequence of rhythmic head and neck movements. Gonadectomy (removal of the ovotestis) was performed in two closely related species of Aplysia to prevent completely the synthesis, build-up and release of eggs. Chronically implanted electrodes were used either to monitor spontaneous bag cell discharges (A. brasiliana) or to selectively elicit bag cell discharges (A. californica) in gonadectomized and mock-operated animals. Gonadectomized animals showed the normal occurrence of spontaneous bag cell discharges in the complete absence of eggs, indicating that feedback from ripe eggs in the ovotestis is not necessary for normal activation of the bag cells. However, gonadectomized animals showed a significant decrease in specific head and neck movements following elicited bag cell discharges. This finding indicates that, once the bag cells fire and the eggs are released, input from the eggs is necessary for normal expression of the behaviour associated with egg deposition.
Oxygen Consumption During Hover-Feeding in Free-Ranging Anna Hummingbirds
Authors: Bartholomew George A. , Lighton John R. B.
Published: April 2021

Rates of oxygen consumption during hover-feeding of wild, unrestrained, adult male Anna hummingbirds (Calypte anna) were measured with an artificial outdoor feeder converted into a respirometer mask. A computer sampled changes in O2 concentration in air drawn through the mask, automatically detecting the presence of a hummingbird from a drop in the O2 concentration, and photoelectrically timing the duration over which the feeder functioned as a mask. Birds coming to the feeder were weighed on a trapeze perch suspended from a force transducer. Feeding bouts consisted of sallies which carried the head in and out of the feeding mask about once a second. The volume of O2 consumed per feeding sally was linearly related to the length of the sally. The energy cost of hover-feeding in five hummingbirds, mean mass 4·6 g, was 41·5 ± 6·3 ml O2g−1 h−1.
Cardiac Performance in Response to Loading Pressures and Perfusion With 5-Hydroxytryptamine in the Isolated Heart of Busycon Canaliculatum (Gastropoda, Prosobranchia)
Authors: Smith P. J. S. , Hill R. B.
Published: April 2021

In this study the effects of a molluscan neurotransmitter, 5-hydroxytryptamine (5-HT), were examined on the isolated and pumping heart of the gastropod mollusc Busycon canaliculatum. Unlike in previous studies, the response was measured in such a way as to equate it with cardiac output. In addition, the effects on the myogram form and the manner of perfusate ejection were also examined.

As would be expected from previous studies, 5-HT affects heart rate, showing a positive chronotropic response at a threshold of around 10−9moll−1. Stroke volume shows little evidence of being regulated by 5-HT concentration. This observation was unexpected as 5-HT is commonly reported to regulate the ‘force’ of contraction in a molluscan heart and, at constant perfusion conditions, this might have been expected to find expression as an increase in stroke volume. 5-HT does, however, have a very clear dose-dependent effect on the aortic pressure pulse amplitude and duration. Amplitude increases markedly (250%) over the concentrations used (10−10-10−6mol 1−1) with a threshold around 10−8moll−1. The effect on the duration has the same threshold but the opposite result, with a reduction to approximately 50% of the original value. The same amount of perfusate is therefore being ejected at a higher pressure and flow rate. It is suggested that this might have important implications for a soft-bodied animal with a hydrostatic skeleton.

The electrical activity of the heart was also examined and showed that 5-HT increased the amplitude of both the spike and plateau phase of the action potential. The duration of the latter was reduced. This is discussed with reference to other studies.
Bone Strain: A Determinant of Gait and Speed?
Authors: Biewener Andrew A. , Taylor C. Richard
Published: April 2021

Principal strains were recorded in vivo from the radial and tibial midshafts of three goats as they increased speed and changed gait. These data were compared with strain data measured for the radius and tibia of the dog (Rubin & Lanyon, 1982) and the horse (Biewener, Thomason & Lanyon, 1983b) in order to test the hypothesis that similar peak bone strains (stresses) occur at functionally equivalent points in the gaits of different species. Multiple recordings of in vivo strain along the caudal diaphyses of the radius and tibia of one goat were made to test the validity of this technique for measuring peak locomotor stress. Measured strains were extremely consistent over the animal’s full range of speed (coefficient of variation for the radius 0·05–0·08, and for the tibia 0·06–0·11). The data from the three gauges, which were spaced 15 mm apart, demonstrated that maximal strains act at the midshaft, substantiating the use of this technique to measure peak locomotor bone strains. Strain levels recorded at the trot-gallop transition and top galloping speeds of the goat were similar to the values reported for the dog and horse, despite large differences in absolute speed (goat, 4·3ms-1; dog, 6·9ms-1; horse, 7·5ms-1 at maximum gallop). The second moments of area of the tibia and radius (+ ulna) of the dog are 29 % and 113 % greater than for goats of equal size, explaining how similar strains are achieved in the dog at higher speeds than the goat. Furthermore, peak bone strains recorded at the fastest trotting speed were similar to those recorded at the fastest galloping speed for each species. Peak strains recorded for the goat at a maximum gallop correspond to stresses of +37·9 MPa (cranial) and —47·7 MPa (caudal) in the radius and +36·3 MPa (cranial) and —50·3 MPa (caudal) in the tibia, representing a safety factor to yield failure of three.
Regeneration of Fibre Types in Paired Asymmetric Closer Muscles of the Snapping Shrimp, Alpheus Heterochelis
Authors: Govind C. K. , Mearow K. M. , Wong A.
Published: April 2021

The fibre composition of the closer muscle in the paired asymmetric (snapper and pincer) chelipeds of the snapping shrimp, Alpheus heterochelis (Say), was determined in the pristine and in the regenerated conditions. In the pristine condition, the snapper muscle has exclusively slow fibres in both male and female shrimps. The pincer muscle has a central band of fast muscle sandwiched by slow muscle. This band of fast muscle is proportionately and significantly larger in the female than in the male (36% compared to 21%), thus demonstrating a subtle form of sexual asymmetry.

The chelipeds were induced to regenerate following their removal within 24 h of a moult. During the intervening intermoult, limb buds formed which, at the next moult, transformed into newly regenerated chelipeds. In these regenerated chelipeds the snapper muscle was usually entirely composed of slow fibres as in the pristine muscle. In a few animals, however, a scattering of fast fibres occurred in the central region; a condition reminiscent of the pincer muscle. The regenerated pincer muscle resembled its pristine counterpart in having a central band of fast fibres sandwiched by slow fibres. In male shrimps, the proportion of fast fibres in the regenerated muscle was similar to that in the pristine muscle. In females, however, the proportion of fast muscle was significantly smaller in the regenerated than in the pristine condition (21 % compared to 36 %). Since a closer muscle with a central band of fast fibres sandwiched by slow is found during regeneration in pincer and occasionally snapper chelipeds, such a pattern represents an early developmental stage which is being recapitulated during regeneration. There is no evidence in Alpheus heterochelis that the pincer muscle initially regenerates exclusively fast fibres as was reported for A. californiensis.
Detection of Infrasound By The Atlantic Cod
Authors: Sand Olav , Karlsen Hans E.
Published: April 2021

Below about 50 kHz the level of ambient noise in the sea increases continuously towards lower frequencies. In the infrasound range the spectral slope is particularly steep. This low-frequency noise may propagate long distances with little attenuation, causing a directional pattern of infrasound in the sea. Using a standing-wave acoustic tube, we have studied the sensitivity of cod to infrasound down to 0·1 Hz by means of the cardiac conditioning technique. The threshold values, measured as particle acceleration, showed a steady decline towards lower frequencies below 10 Hz, reaching a value close to 10−5 ms−2 at 0·1 Hz. The spectrum level at 0·1 Hz in the sea ranges between 120 and 180 dB (re 1 μPa), with corresponding particle accelerations from less than 10−6 to more than 10−4ms−2. The sensitivity of cod is thus sufficient to detect the highest levels of ambient infrasound, and we put forward the hypothesis that fish may utilize information about the infrasound pattern in the sea for orientation during migration, probably in addition to an array of other sensory inputs.
Haemolymph Acid-Base, Electrolyte and Gas Status During Sustained Voluntary Activity in the Land Hermit Crab (Coenobita Compressus)
Authors: Wheatly Michèle G. , Mcmahon Brian R. , Burggren Warren W. , Pinder Alan W.
Published: April 2021

After 3 h (50 m) of voluntary walking, the haemolymph pH of the land hermit crab Coenobita compressus (H. Milne Edwards) decreased by 0·4units. This was accompanied by increases in CO2 tension bicarbonate (HCO3- + CO32-) and lactate concentrations. The hypercapnic acidosis was partially compensated by metabolic bicarbonate accumulation and an H+ deficit developed. Unloaded crabs accumulated less of a proton load than crabs transporting mollusc shells. During activity, oxygenation of the haemocyanin (HCy) accounted for the release of 0·3 mmol CO21-1, via the Haldane effect, which was seven times more than in settled crabs. Control acid-base balance was re-established within 1 h of recovery. At this time, acidic equivalents were excreted at a mean flux rate of 5 mequivkg-1 h-1 into a source of external water. [Na+] and the ratio of [Na+] : [Cl-] increased during exercise.

Coenobita haemolymph had a high O2-carrying capacity . HCy oxygen-binding characteristics were typical of other decapods (ϕ = -0·44), yet no lactate sensitivity was apparent. Settled in vivo values of O2 tension and content were located around the half-saturation tension (P50) of the dissociation curve. During exercise, increased and an unopposed Bohr shift decreased the O2-binding affinity, thereby reducing postbranchial saturation. Quantitatively, however, compensations in cardiac output were more instrumental in increasing the O2 delivery to respiring tissues. During recovery, haemolymph remained high and the venous reserve doubled.
Correlations Between Body Angles and Substrate Curvature in the Parasitoid Wasp Trichogramma Minutum: A Possible Mechanism of Host Radius Measurement
Authors: Schmidt J. M. , Smith J. J. B.
Published: April 2021

The parasitoid wasps of the genus Trichogramma use the surface curvature of their insect egg hosts to set an upper limit to the number of progeny allocated to the host, as well as the duration of their host examination. In addition, host recognition and host acceptance are in part mediated by surface curvature. In this paper, the relationships between the positions of body parts of the wasp and surface curvature are examined in order to determine a possible mechanism for curvature detection by ‘the wasp.

Wasps of different sizes were photographed in profile while examining glass bead models of different diameters. The positions of selected body parts were analysed using a digitizer and microcomputer. The height of the wasp above the model surface did not change with surface curvature. Furthermore, the angle of the head relative to the thorax was also constant over the range of models used. Only the scapal-head angle and flagellar-head angle changed significantly with surface curvature.

A curvature detecting mechanism is proposed in which the wasp uses the scapal-head angle to measure the curvature of the surface. The body of the wasp is maintained at a preferred height and angle to the substrate, serving as a fixed platform from which curvature measurements are made. Additional features of this mechanism, as well as its correlation with morphological and behavioural findings, are discussed.
Myocardial Intracellular pH in A Perfused Rainbow Trout Heart During Extracellular Acidosis in the Presence and Absence of Adrenaline
Authors: Farrell A. P. , Milligan C. L.
Published: April 2021

Myocardial intracellular pH was measured in a perfused rainbow trout, Salmo gairdneri, with DMO (5,5-dimethyl-2,4-oxazolidinedione), to test the hypothesis that catecholamines promote active regulation of myocardial pH in order to protect contractility during a respiratory acidosis comparable to that observed after exercise. Under control conditions (extracellular pH= 8·0; ), myocardial pH was 7·53 ± 0·01 (N=5). Acidosis (extracellular pH = 7·45; ) reduced contractility, mechanical efficiency and intracellular pH (7·25 + 0·04), but did not affect myocardial O2 consumption. The addition of 0·5 μmoll-1 adrenaline during extracellular acidosis prevented the loss of contractility, restored mechanical efficiency, but did not change intracellular pH significantly. Thus, adrenaline enabled cardiac contractility to recover, without intracellular pH regulation, possibly by modulation of sarcolemmal calcium changes. The absence of a myocardial acidosis after exercise in vivo is discussed with respect to possible intracellular pH regulation via lactate uptake and metabolism.
Inhibition of A Chloride Pump By Acetazolamide In The Intestine of Aplysia Californica
Authors: Gerencser George A.
Published: April 2021

The isolated intestine of Aplysia californica, bathed in a substrate-free NaCl seawater bathing medium, generates a spontaneous transepithelial potential difference such that the serosal surface is negative relative to the mucosal surface (Gerencser, 1978b). The short-circuit current (Isc) is accounted for by active absorptive mechanisms for both Na+ and Cl−, the Cl− transport mechanism being more vigorous than that for Na+ (Gerencser, 1978a). However, Cl− transport appeared to be independent of Na+ transport, for the Isc measured in an Na+-free seawater bathing medium was shown to be identical to a net active absorptive flux of Cl− (Gerencser, 1984a). It was hypothesized that active Cl− absorption in Aplysia enterocytes was mediated by a primary active transport process, because it had been demonstrated that the intracellular Cl− electrochemical potential was less than that measured in the extracellular medium (Gerencser & White, 1980), even in the absence of extracellular Na+ (Gerencser, 1983). Lending strength to this hypothesis, Gerencser & Lee (1983, 1985a) demonstrated the existence of a CU-stimulated ATPase activity in Aplysia enterocyte plasma membranes, suggesting a cause-and-effect relationship between ATPase activity and Cl− transport. The ATPase activity stimulated by Cl− was strongly inhibited by acetazolamide. In addition, Gerencser (1984b) and Gerencser & Lee (1985b) have demonstrated an ATP-dependent Cl− uptake in Aplysia inside-out enterocyte plasma membrane vesicles (EPMV). Therefore, the present study was undertaken to assess the effect of acetazolamide on the ATP-driven Cl− uptake mechanism in EPMV..

Seahares (Aplysia californica) were obtained from Marinus Inc. (Westchester, CA) and were maintained at 25 °C in circulating filtered seawater. Adult Aplysia (600-1000 g) were used in these experiments. The plasma membrane vesicles were prepared from Aplysia intestinal enterocytes by homogenization and differential and discontinuous sucrose density-gradient centrifugation techniques as described previously (Gerencser & Lee, 1985a). Vesicle transport experiments were also performed as previously described (Gerencser & Lee, 1985b).
Effects of Ionic Environment on Viscosity of Catch Connective Tissue in Holothurian Body Wall
Authors: Hayashi Yutaka , Motokawa Tatsuo
Published: April 2021

The effects of cations (H+, Na+, K+, Ca2+, Mg2+) on the mechanical properties of the catch connective tissue in the dermis of a sea cucumber, Holothuria leucospilota Brandt, were studied. The manipulation of the ionic environment caused rapid (apparent in minutes) and reversible viscosity change. Artificial sea water (ASW) with a high concentration of Ca2+ (50 mmol 1−’) increased the normal viscosity 9 times; Ca2+-free ASW decreased it to one-tenth. Ca2+ was the only ion which caused a viscosity change whose range was as large as the range of the viscosity distribution of the dermis in ASW. Manipulation of the concentration of other ions caused an increase in viscosity. An increase of more than five-fold was observed in the following solutions: ASW with acidic (pH 4) or basic (pH 9, 10) pH ; Na+-free ASW whose Na+ was replaced by either sucrose or choline; ASW with high (100mmoll−1) concentration of K+; ASW with low (0 mmol 1−1) or high (250 mmol 1−1) concentrations of Mg2+. The dermis contracted in distilled water, although this tissue contained no muscle cells.
Salt and Water Balance In the Spider, Porrhothele Antipodiana (Mygalomorpha: Dipluridae): Effects of Feeding Upon Hydrated Animals
Authors: Butt A. G. , Taylor H. H.
Published: April 2021

The spider, Porrhothele antipodiana, starved and provided with water, produced urine via the anal excretory system (Malpighian tubules, midgut diverticula and stercoral pocket) at a mean rate of about 2·5-μlg-1 day-1 and with a mean Na+/K+ ratio of about 1·0. Salts ingested from the prey were eliminated by two mechanisms. A K+-rich (Na+/K+ about 0·2) anal diuresis lasted about 3 days following a single meal and was maintained at more than 30μg-1 day-1 during feeding ad libitum. The second mechanism, interpreted as coxal secretion, functioned only during feeding itself and delivered Na+ into the prey at a constant rate of about 3 %h-1 of total body Na+. This progressively raised the Na+/K+ ratio of the prey debris from 0·47 to 0·96 and, because of re-ingestion, recycled more Na+ than was originally present in the prey.

Feeding was associated with large net increases in dry weight and ions, particularly K+, which were mainly stored in the diverticular tissue (midgut diverticula and Malpighian tubules embedded in adipose tissue). The stercoral fluid (final urine) was slightly hyposmotic to the haemolymph in starved and fed spiders. Only about half of its osmolarity was accounted for by Na+, K+ and Cl-. The volume of water gained from the meal was about equal to that lost in diuresis, and P. antipodiana drinks to maintain water balance because of relatively high transpirational and other losses. The primary function of the diuresis is probably elimination of ions from the meal, and not volume regulation.
Localization and release of FMRFamide-like immunoreactivity in the cerebral neuroendocrine system of Manduca sexta
Authors: Carroll L. S. , Carrow G. M. , Calabrese R. L.
Published: April 2021

The distribution of FMRFamide-like immunoreactivity (FLI) in the cerebral neuroendocrine system of the moth, Manduca sexta, is described and evidence is provided for calcium-dependent release of FLI from the neurohaemal organs.

FLI was detected by indirect immunofluorescence in approximately 25 bilaterally symmetrical pairs of somata in the pupal protocerebrum. In addition, FLI was observed in neurites in the brain, as well as in axons of the nervi corporis cardiaci and nervi corporis allati, and in terminals in the neurohaemal corpora cardiaca (CC) and corpora allata (CA). All immunocytochemical staining was blocked by preabsorption of the anti-FMRFamide antiserum with synthetic FMRFamide. We localized FLI to identified protocerebral neurosecretory cells (NSCs) by combining intracellular injection of Lucifer Yellow and indirect immunofluorescence. Among the NSCs in each hemisphere, FLI was observed in both group Ila (lateral) cells, in most group lib (lateral) cells, and in two cells of group lb (medial). FLI was extracted from the brain and neurohaemal organs and measured using radioimmunoassay (RIA). Calcium-dependent release of FLI was evoked from isolated CC-CA by high potassium depolarization in vitro and was quantified by RIA of the bathing medium.

These results suggest that FLI may have a neurohormonal or neurotransmitter function in Manduca.