bluuebunny/crossref_metadata_2025 huggingface dataset:
Motor Unit Distribution of the Dorsal Longitudinal Flight Muscles In Locusts
Authors: Neville A. C.
Published: April 2021

The peripheral pathways of the ‘fast’ motor fibres to the locust dorsal longitudinal flight muscles are described at the single unit level, from electrophysiological and histological studies. This is summarized in a diagram on Pl. 1. Both pterothoracic dorsal longitudinal muscles consist of five anatomically distinct motor units, arranged in layers from dorsal to ventral. Each of the four more ventral units of both muscles receives a motor axon from the segment in front via the recurrent nerve, whereas the uppermost motor unit is innervated in each case from the segment containing the muscle. The motor units are nearly equal both in size and capability for work. Each of the five ‘fast’ motor axons innervates one topographically distinct bundle of muscle fibres. There is no overlap between muscle motor units. Even within a single muscle, motor units are capable of vibrating at independent frequencies. This indicates that the coupling of units which occurs during flight is neither structurally nor functionally rigid. With respect to peripheral features, the motor units within each dorsal longitudinal muscle are designed for fast response which improves the synchronization when the relevant neurons fire simultaneously (large motor axons, 15–25 μ in average diameter with high propagation velocity, 8 m./sec. at flight temperature). It is suggested that a tonic motor output, containing at least three units, which was recorded from mesothoracic nerve IBa, travels to the small lateral dorsal muscles.
Electrical Responses from Dually Innervated Tactile Receptors on the Thorax of the Crayfish
Authors: Mellon Deforest
Published: April 2021

Electrophysiological recordings have been obtained from tactile receptors which occur in shallow pits on the crayfish carapace. Controlled mechanical stimulation has established that each receptor is innervated by a pair of sensory neurons. One of these neurons responds when the receptor is moved anteriorly, and the partner cell responds to displacement in the opposite direction. The receptors are sensitive to motion of the fluid medium in which they are immersed, and they may provide the animal with a means for determining the speed and direction of water currents. Vital staining procedures have confirmed the presence of two bipolar sensory cells associated with each receptor. An abrupt increase in the diameter of the sensory axons occurs several hundred microns proximal to the cell bodies of the neurons, and it is suggested that this is the locus of spike initiation.
Movement of the Flagella of Polytoma Uvella
Authors: Brokaw C. J.
Published: April 2021

Dark-field photographic records of the wave patterns of moving flagella have been made using multiple-flash exposures at flash rates of up to 50 per sec. Patterns obtained from ATP-reactivated isolated flagella show reduced amplitude of bending, but are otherwise similar to those obtained from flagella under normal conditions. The co-ordination required to produce propagated waves of active bending appears to be preserved after isolation and reactivation. Addition of methyl cellulose to the medium to increase the viscosity reduces the frequency of beat much more than the amplitude. This behaviour can be partially explained by an analysis of the equations for sinusoidal wave movement of flagella which shows that maximum efficiency of forward swimming will be obtained if the amplitude of beat is maintained greater than times the wavelength, and variations in available power or viscosity are compensated by changes in beat frequency. Wave patterns at low frequencies in low ATP concentrations are unlike those obtained when the frequency is reduced by increased viscosity. The effect of ATP concentration on beat frequency is not explained by an effect on the power available for beating or by an effect on the ‘internal viscosity’ of the flagella.
A Stretch Reflex Controlling Wingbeat Frequency in Grasshoppers
Authors: Wilson Donald Melvin , Gettrup Erik
Published: April 2021

The stretch receptors of the wing hinge of the locust Schistocerca fire once or twice at the top of the wingstroke during normal flight. Removal of the four stretch receptors results in a decrease of the wingstroke frequency to about one-half normal. Interference with the normal timing of the stretch-receptor input (mechanically or by electrical stimulation) does not affect the normal wingstroke frequency. With respect to this sensory source the centrally generated motor output pattern is independent of input phase. The results are discussed briefly in relation to the question of central v. peripheral control of locomotion.
Free Flight of Aphids in the Laboratory
Authors: Kennedy J. S. , Booth C. O.
Published: April 2021

The working principles, design and operation of an apparatus for keeping aphids in free flight are described. It consists of a large black-walled chamber with a battery of lights above a central opening in the roof and a fan blowing air down past them into the chamber. The aphid flies up toward the lights and is held at a small, fixed distance from them by adjusting the downward air speed to balance the aphid’s rate of climb, which can thus be recorded continuously. The uninterrupted first flight of virginoparous Aphis fabae in this chamber comprises a brief erratic opening phase, a long ‘cruising’ phase during which the rate of climb declines, and a final brief erratic phase when it falls to zero and the aphid flies away from the lights. Contact with a non-host surface will then restore the previous behaviour and a number of flights, similar but of decreasing duration, ensue until exhaustion at hr. During one flight and over a series of flights there are changes in the aphid’s responsiveness to the main lights and to light reflected from the chamber walls or from small objects such as leaves presented in the chamber. There appears to be an optimal (‘preferred’) light intensity for the positive phototaxis, which starts high but declines as the photokinesis (locomotor excitation, measured by the rate of climb) declines, until near exhaustion when the phototaxis becomes negative even to the lowest intensities.
Osmotic Regulation in the Brackish Water Teleost, Blennius Pholis
Authors: House C. R.
Published: April 2021

The sodium effluxes between the blood and the medium have been studied in Blennius pholis in 10, 40 and 100% s.w. and in transfer from 40 to 100% s.w. under equilibrium conditions with the isotope 24Na. In addition the sodium influxes have been studied in 40 and 100% s.w. in a similar manner. The total flux in 100% s.w. has been found to be 100 mm. Na/1. blood/hr., and in 40 and 10% s.w. it has been found to be 20 mm. Na/1. blood/hr. The results are interpreted as showing that the presence or absence of exchange diffusion does not alter the estimation of the active sodium efflux across the gills in 100% s.w. The efflux experiments showed that the animal had a rapid adaptive ability to osmo-regulate upon transference from 40 to 100% s.w. The electric potential differences between the blood and external medium have been measured in animals adapted to 10, 40, 100 and 150% s.w. and the blood serum concentrations of sodium and chloride ions have been measured in these media. The mean potential differences ± standard deviation in 10, 40, 100 and 150% S.w. have been found to be – 3 ± 4·5 mV., +23 + 4 mV., +23 + 3 mV. and + 29·5 ± 5 mV. respectively (external medium taken as reference). The results are interpreted as showing that there is active outward excretion of chloride ions in animals adapted to 150, 100 and 40 % s.w. and active inward absorption of chloride ions in 10% s.w. and of sodium ions in animals adapted to 40 and 10% s.w. The drinking rate in 100 % s.w. has been calculated to be 27 mm. Na/kg. fish/hr. or 6 % body weight/hr.
A Method for Chronically Implanting Stimulating Electrodes into the Brains of Locusts, and Some Results of Stimulation
Authors: Fraser Rowell C. H.
Published: April 2021

Methods are described for implanting permanent stainless-steel electrodes into the brains of locusts, for stimulating the brain under near-normal conditions, and for localizing the electrode subsequently. Threshold currents measured under these conditions are lower than those required in acute preparations, or if the animal is restrained. The results of stimulation are described for four common aspects of behaviour. These are antennal movement, locomotion, feeding and sexual behaviour. The effect of stimulation on antennal and locomotory movements largely confirms previous work on crickets. Feeding and foraging behaviour, which is a very common result, is shown to be almost completely determined by peripheral stimuli at the time of brain stimulation. The role of the latter is permissive or disinhibitory rather than causal or excitatory. Integrated sexual behaviour is occasionally inhibited, but never elicited, by stimulation. This contrasts with observations on crickets, and its implications are discussed.
The Swimming Speeds of Plaice Larvae
Authors: Ryland J. S.
Published: April 2021

The swimming speeds attained by hatchery-reared plaice larvae have been determined by measurements made (a) in still water, and (b) against a current flowing through a long glass tube. In still water contact stimuli were used to initiate swimming. No optomotor response was found, and it was not possible to use the ‘fish-wheel’ of Bainbridge (1958). Larvae in the experimental tube stemmed the current for brief periods only, their position then being near the periphery of the upper quadrant. The speeds were found to show a linear relationship to larval length multiplied by the height of the post-anal musculature. Observations in still water show that these values correspond to those of steady swimming: they are not maximum speeds. Speeds ranged from about 1·5 cm./sec. when newly hatched to 9 cm./sec. in late larvae. Darting velocities of up to 15 cm./sec. were recorded with half-grown (stage III) larvae. In such larvae cruising speeds were about three fish-lengths (3L) per second, and the maxima about 10L/sec. The design of gear for collecting fish larvae at sea is discussed. Only a high-speed tow-net, towed at about ten times the velocity attainable by the largest larvae and giving almost no warning of its approach, can be considered to collect a quantitatively balanced sample.
The Development of Phototaxis in the Frog (Rana Temporaria)
Authors: Muntz W. R. A.
Published: April 2021

Many experiments have shown that when a frog is disturbed it escapes towards the light, and that blue light is more effective than any other colour in guiding this response (see Pearse, 1910, for a review). A previously reported experiment (Muntz, 1962 b) has shown that the greater effectiveness of blue light is not simply due to the animals’ possessing a greater sensitivity to light in this part of the spectrum, but involves colour vision; the animals will respond preferentially to blue irrespective of the intensity or saturation of the stimulating lights. They will, for example, choose a blue illuminated window in preference to a window illuminated by an additive mixture of the same blue light together with a green light, in spite of the fact that the latter window contains as much blue as the former, as well as the green.
Comparative Physiology of the Vertebrate Autonomic Nervous System. I. Innervation of the Urinary Bladder of the Toad (Bufo Marinus)
Authors: Burnstock G. , O’shea Judith , Wood Margaret
Published: April 2021

The anatomy, physiology and pharmacology of the innervation of the bladder of the toad (Bufo marinus) have been studied. Motor fibres only have been demonstrated to innervate the toad bladder. These fibres travel mainly in the 9th spinal nerve, but may also be present in the 10th, 7th and occasionally in the 8th spinal nerves. Usually, all these fibres reach the bladder via the pelvic nerves. The response of the bladder to nerve stimulation was qualitatively the same whichever nerve was stimulated and whatever parameters of stimulating pulse were applied. The optimal frequency at 20° C. was about 20 pulses/sec. ACh causes contraction of the toad bladder. Adrenaline and noradrenaline usually cause relaxation, but dopamine and low concentrations of noradrenaline can cause weak excitation. The bladder is insensitive to both histamine and 5-HT. Atropine reduced the response of the bladder to pelvic nerve stimulation by up to 50%. Eserine did not potentiate the nerve-mediated response, but nor did it potentiate the direct action of ACh. All the adrenergic blocking agents used reduced or completely blocked the nerve-mediated response, but the response to applied ACh is also reduced under these conditions. All the ganglionic blocking agents tested reduced the nerve-mediated response. However, only mecamylamine markedly reduced the response without affecting the action of applied ACh. It was concluded that a division into sympathetic and parasympathetic innervation of the toad bladder was not justified, and that the nerve fibres which innervate this organ are probably all of one type, regardless of their origin, with at least 50 % of the pelvic nerve fibres being pre-ganglionic. The pharmacological evidence presented favours the view that these nerves are cholinergic rather than adrenergic. The evolutionary implications of these results have been discussed.
The Relation of Oxygen Consumption to Substrate Particle Size in Two Burrowing Mayflies
Authors: Eriksen Clyde H.
Published: April 2021

This study is concerned with the relation of oxygen consumption to substrate particle size in the morphologically similar burrowing mayflies Ephemera simulans and Hexagenia limbata. Nymphs, 16 –24 mm in length, were placed at 13·0 ° C. for 24 hr. before experimentation. Oxygen consumption experiments employed the standard ‘oxygen consumed in a closed bottle’ technique and a modification. The standard technique was referred to as the ‘blank-bottle’ method, while the modification was called the ‘substrate-bottle’ method (washed substrate fractions were placed in the bottle). The relationship between substrate particle size and oxygen consumption was indicated by a bimodal curve. The oxygen consumption fell, rose and fell once more as the particle size decreased from ϕ – 4 to ϕ + 5. Substrate selection experiments with E. simulans nymphs revealed an inverse relationship between selection for particle size and oxygen consumption. The burrowing front legs of the nymphs seem to be modified for a given substrate (coarse for E. simulans ; fine for H. limbata) and, the less favourable the substrate, the more work that must be done to gain admittance or to burrow further. The particle size in which the nymphs showed the least oxygen consumption was considered to be an ‘optimal substrate’ (ϕ – 1 for E. simulans and probably silt for H. limbata).
Properties of Interneurones in the Abdominal Nerve Cord of A Dragonfly Nymph
Authors: Fielden Ann
Published: April 2021

Responses of single interneurones in the abdominal connectives of the dragonfly nymph following electrical stimulation of the segmental nerves were investigated. Excitation and inhibition were seen in fibres with a resting discharge. Repetitive trains of impulses, varying between units and with the source of the afferent volley, were common. Changes in the intensity and frequency of stimulation affected the pattern of the repetitive responses. An increase in the intensity of the volley shortened the latency and increased the length of the train, while an increase in rate reduced the number of impulses. Most interneurones responded to stimulation of more than one afferent pathway. Multisegmental fibres and multiple connexions of fibres were common. These responses are compared with those of spinal interneurones and discussed in relation to their function in the animal.
Analysis of the Haemolymph of Arion Ater L. (Gastropoda: Pulmonata)
Authors: Roach D. K.
Published: April 2021

Methods are described for the collection of slug haemolymph and its analysis for cations, anions, total electrolytes, protein, Δ and pH. Of the cations measured, potassium and calcium show the greatest variation, being two to three times as variable as sodium, the most constant. About 20 % of the blood calcium exists in a bound form. Of the anions measured, chloride is the most concentrated and least variable. Sulphate and alkalinity are about equally variable, three times the chloride fluctuation. The phosphate concentration is very low. The variation of total electrolytes is only half that of the total solutes, as measured by Δ, while protein is very variable. The pH is remarkably alkaline but varies only within narrow limits. Formulae are given for two physiological salines, capable of maintaining both muscular and ciliary activity.
The Control of Meal Size in the Blood Sucking Bug,Rhodnius Prolixus
Authors: Bennet-Clark H. C.
Published: April 2021

The object of this investigation was to examine the mode of operation of the pharyngeal pump of Rhodnius and its possible role in determining rate of feeding and maximum size of meal. The rate of pulsation of the pump remains constant throughout the meal, falling only in the last few seconds. The pump is filled by muscular withdrawal of the piston and empties by elastic return of the piston. The properties of the pump, which is very small, were studied on a working model. The model displayed marked ‘click’ properties, the force behind the emptying stroke increasing as the stroke progressed ; thus the emptying stroke, once initiated, was always completed. The pressure volume relations of the isolated abdomen were explored as a function of time. It is concluded that the pump is stopped at a critical abdominal pressure of 2·5 cm. Hg., which prevents the initiation of the emptying stroke, that the rate of feeding is mainly limited by the rate of filling of the pump and that the size of the meal taken depends upon the ease with which the cuticle can be stretched. Confirmatory evidence is adduced and discussed.
Studies On Crop Function in the Cockroach (Periplaneta AmericanaL.)
Authors: Davey K. G. , Treherne J. E.
Published: April 2021

The nervous pathway involved in the control of crop-emptying has been worked out by the method of nerve section. This pathway involves nerve 5 from the pharynx to the frontal ganglion, the recurrent nerve, the oesophageal nerve and ganglion, the ingluvial nerve and ganglion Function is not abolished by nerve section between the brain and the frontal ganglion. The sensory end of the pathway is in the pharynx where there is a sense organ which, it is suggested, is an osmoreceptor. A preliminary account of its structure is given.
Spectral Sensitivity of the Herring, Clupea Harengus L
Authors: Blaxter J. H. S.
Published: April 2021

Herring (Clupea harengus) require light for feeding and avoiding nets. The threshold light intensity for these behaviour patterns and also for phototaxis, using different colours of tight, was measured and used to obtain spectral sensitivity curves. The maximum sensitivity of dark-adapted herring lay between 510 and 520 mμ. The threshold light intensity, using white light, varied from 3·6 × 10−2 to 2·9 × 10−4 photopic lux, depending on the behaviour being studied. A parallel experiment on a dark-adapted human subject gave a maximum sensitivity at 500 mμ and a threshold light intensity, using white tight, of 3·4 ×10−7 photopic lux. Pigment extracted from dark-adapted eyes of herring had a maximum absorption at 500 mμ. Suggestions are made for measurement of underwater light intensity in studies on fish behaviour.
The Passage of Spermatozoa Through and Into the Zona Pellucida of the Rabbit Egg
Authors: Dickmann Z.
Published: April 2021

To obtain information about the sperm pathway through the zona pellucida of the rabbit egg, ordinary and phase contrast microscopy were used to study (1) zonae through which spermatozoa had passed, and (2) spermatozoa within zonae.

The observations revealed that the spermatozoon makes a narrow slit in the zona as it passes through it. Such slits have a characteristic shape—’ the penetration curve ‘. It is concluded that to pass through the zona, the spermatozoon must follow the penetration curve.

Most of the spermatozoa observed within the thickness of the zona apparently started on the curved course and then stopped. They may have stopped within the zona because they were deficient in a substance which normally acts in conditioning the zona to allow spermatozoa to pass through it.

Hair-like structures protrude from the front ends of sperm heads into the zona. No definite conclusion has been reached as to whether they are slits in the zona or solid structures ; however, the pictorial evidence favours the interpretation that they are filaments protruding from the sperm heads.
Relative Refractoriness and Patterned Discharge of Locust Flight Motor Neurons
Authors: Wilson Donald M.
Published: April 2021

The threshold recovery after impulse propagation in locust peripheral motor axons to flight muscles is described. The refractoriness is large enough to have functional significance for at least 10 msec, and may be detected after 50-100 msec. The refractoriness to successive impulses accumulates. Ganglionic and axonal preparations demonstrate frequency division, apparently due to the refractoriness of the motor neuron. Accumulating refractoriness gives rise to non-integral division. Behaviour of the locust preparations is compared to that of an electronic model. Antidromic stimulation during flight shows that refractory oscillation may regulate the interval between the closer spaced pairs of impulses in the motor units during flight, but that the wingbeat cycle must have another cause.
Frog Fast Muscle: I. Mechanical Power Output in Isotonic Twitches
Authors: Pennycuick C. J.
Published: April 2021

The paper is primarily concerned with predicting the response of the muscle (frog ilio-fibularis fast fibres) to a given stimulus under given conditions of load. The predictive value of theories based on ‘active state ‘is considered in this context. A method is described for measuring the speed of shortening at frequent intervals during an isotonic twitch. A family of speed vs. tension curves is drawn up, each curve representing a particular time after the stimulus. These are translated into power vs. tension curves. The rate of fall of mechanical power output increases linearly with time after the stimulus, but is independent of tension. At the beginning of the twitch, mechanical power output increases slightly with temperature, but later in the twitch the trend is reversed, as rate of fall of power also increases with temperature. The high extensibility, characteristic of resting muscle, reappears suddenly at the end of an isotonic twitch, causing a ‘break’ in the speed record. This occurs earlier at low than at high tensions. The basis of predicting an isometric twitch from isotonic data, based on certain assumptions which have been made by previous authors, is explained. The tension peak in an isometric twitch is reached sooner than would be predicted on these assumptions.
Functional Design of the Tracheal System of Flying Insects as Compared with the Avian Lung
Authors: Weis-Fogh Torkel
Published: April 2021

A process as demanding in power as that of flapping flight influences most physiological systems very greatly and above all the respiratory system. In the thorax of adult winged insects, it has become so intricate and integrated by fusion and extension that it is difficult to describe in comparative or in functional terms. In fact, because of lack of knowledge about the functional morphology little is known about the supply of oxygen to the wing muscles and the exchange of respiratory gases between the thorax and the ambient air.
Response of Fast Muscle Fibres to Series of Impulses
Authors: Pennycuick C. J.
Published: April 2021

The peak power at the beginning of an isotonic twitch is increased if it is initiated while a previous twitch is still in progress ; the effect is cumulative over the first few twitches of a series. The time taken to drop from peak power to zero power is not affected. The power cycle in an isometric tetanus is considered and a possible method of predicting isometric tension, as a function of stimulus rate, from isotonic measurements, is explained. The steady component of tension is found to vary approximately with the logarithm of the stimulus rate in various fast muscles of the frog and dogfish. The problem of incorporating the results of the present and previous papers in an empirical muscle model is reconsidered.
Gill Ventilation and the Role of Reversed Respiratory Currents in Carcinus Maenas (L.)
Authors: Arudpragasam K. D. , Naylor E.
Published: April 2021

A method is described for obtaining continuous records of the direction of flow of the respiratory current of Carcinus by recording changes of pressure in the gill chamber. Frequent and rhythmic reversals of the normally forward-flowing respiratory current appear to irrigate the upper surfaces of the posterior gills and do not serve primarily to clean the gills. The rate of reversal of this respiratory current increases spontaneously at times of high tide. It decreases under conditions of carbon-dioxide accumulation and increases under conditions of oxygen depletion in the absence of excess carbon dioxide. The pattern of gill ventilation varies according to whether crabs are totally in water, partially buried in sand, or in very shallow water.
Factors Altering Spiracle Control in Adult Dragonflies: Water Balance
Authors: Miller P. L.
Published: April 2021

Dragonflies caught in the wild display a marked variation in the degree of control exercised over their spiracles. In the laboratory desiccation produces tighter control and hydration looser control of spiracle 2: that is, in a partially desiccated insect the thresholds of the spiracular responses to carbon dioxide and to oxygen lack are raised. In desiccated insects the frequency of motor impulses to the spiracles is higher than in hydrated individuals. These effects can be reproduced by perfusion with physiological salines of various strengths. The reaction does not depend on the osmotic pressure of the solution but on the concentration of one or more of its constituents. The isolated mesothoracic ganglion is able to mediate this reaction.
Factors Altering Spiracle Control in Adult Dragonflies: Hypoxia and Temperature
Authors: Miller P. L.
Published: April 2021

The steady output of impulses in the two motor axons to spiracle 2 of mature individuals of the large African gomphid dragonfly, Ictinogomphus ferox Rambur, is reduced in frequency with hypoxia and abolished in about 2 % oxygen. After perfusion of the insect with hypertonic saline the threshold of this response is raised, whereas, following perfusion with hypotonic solutions, it is lowered. Teneral dragonflies give only a weak response to hypoxia—comparable to that of the mature insect perfused with hypertonic saline. This may help to conserve water before feeding commences. Little change in the frequency of motor impulses follows gassing with carbon dioxide mixtures in air up to 20% ; this is in contrast to the reactions reported in some other insects. A raised temperature causes an increased frequency and the Q10 for the reaction is 2·7 (15-25° C.). Above 30-35° C. the frequency declines rapidly. A rise in the threshold of the hypoxic response does not accompany the increased frequency brought about by a raised temperature. A similai; increase in frequency occurs when either the head or the thorax alone is heated. Pterothoracic temperatures of about 30-35° C. are probably maintained in this species while perching in the sun. In this temperature range it is able to take off instantly when potential prey is sighted. High pterothoracic temperatures are considered in relation to spiracle control.
‘Sliffer’s Patches’ and the Thermal Sense in Acrididae (Orthoptera)
Authors: Makings P.
Published: April 2021

The term ‘Slifer’s patches’ is applied in this paper to the series of specialized areas of cuticle which Slifer named ‘antennal crescents’ and ‘fenestrae’. None of the existing evidence supports her suggestion that these patches have a thermoreceptive function. Behaviour changes caused by damaging them can be reproduced by damaging other parts of the cuticle. The antennal-lowering response is not dependent upon stimulation of the patch situated near the antennal base. Destruction of all of the patches does not reduce the ability of locusts to orientate to, and assume the basking posture under the influence of, a lamp ; nor does it reduce their ability to respond similarly to a heat source in darkness and with a cooled floor on which the locusts move. It does not change the leaning response produced by heat stimulation of decapitated locusts. The antennal scape and articular membrane are more effective in producing an antennal-lowering response when stimulated by a hot probe than are the antennal patches or adjacent areas. The median response-time for kicking of the hind legs in response to the local application of a hot probe to the abdomen is shorter when the probe is applied to a part of the normal cuticle than when it is applied to a patch. The antenna, including the flagellum, is sensitive to heat. Stimulation of the distal part of the flagellum by means of a hot wire produced an avoiding response when the wire temperature rose above 40°C. If one antenna is removed locusts in arena tests show a marked tendency to turn the intact side of the body away from a lamp, or a heat source in darkness. Locusts with both antennae removed show a reduced tendency to akinesis under the influence of a heat source in darkness. The detection by locusts of heat stimulation at intensities above the nociceptive threshold may depend on a sensory system which is at least partly distinct from that involved at lower intensities.
Nervous Control of Chromatophores in Teleost Fishes
Authors: Pye J. D.
Published: April 2021

Observations of earlier workers on the chromatic responses to local heating or cooling of the skin of Phoxinus have been confirmed. They have also been found to hold true for anaesthetized fish, in which finer control and observation are possible. The results of a series of nerve-section experiments are held to exclude any possibility that the responses of the intact fish are mediated by a nervous reflex from thermoreceptors in the skin. The responses of melanophores following section of the chromatic motor tracts, or when isolated from the body, are considered to be independent cellular responses. Normal responses in the intact fish show clear temperature thresholds and are completely dependent upon continuation of the respiratory rhythm. Possible physiological mechanisms for mediating these non-adaptive responses are discussed and a new hypothesis is put forward.
Central Control of an Insect Segmental Reflex: I. Inhibition by Different Parts of the Central Nervous System
Authors: Fraser Rowell C. H.
Published: April 2021

An earlier paper (Rowell, 1961a) described a reflex cleaning or grooming movement by the front leg in Schistocerca gregaria; it is evoked by stimulation of the sensilla of the prothoracic sternum. In the unrestrained animal this response can only rarely be seen, but under experimental conditions it can be obtained reliably if the connectives uniting the prothoracic ganglion to the rest of the C.N.S. are cut, provided that the tarsi of the front legs are not allowed to contact anything. Under all other conditions the reflex is partially or completely inhibited.
Co-Ordinating Systems and Behaviour in Hydra
Authors: Passano L. M. , Mccullough C. B.
Published: April 2021

A technique of recording electrical activity from an intact, essentially normal specimen of Hydra is described. The existence of regularly recurring co-ordinated longitudinal contractions of the ectodermal muscles is confirmed and re-emphasized. Such contractions are found to consist of a patterned series of individual co-ordinated contractions, each preceded by a single large, compound potential. The overall contraction, consisting of a variable number between 5 and 12 or more contractions depending on species, is thus called a contraction burst. These contraction-burst potentials originate endogenously ; they are considered to be the most important effector activity in Hydra. Contraction-burst potentials originate in the hypostome and are conducted throughout the column at approximately 15 cm./sec. Contraction-burst patterns have been studied quantitatively in two species, showing interspecific differences between both regular contraction bursts and those associated with locomotion. Certain extrinsic and intrinsic variables affect contraction-burst frequency. Day-light, and nutritional state, both modify this rate, with the former giving rise to a circadian activity cycle under natural conditions. Single electric shocks usually cause a single co-ordinated muscle contraction. Such stimuli can markedly reduce endogenous contraction-burst activity. Sudden illumination interrupts contraction bursts temporarily, even halting those in progress. Blue light is most effective. This stimulus has been used as a tool to investigate the properties of the pacemaker systems concerned with contraction bursts. The nature and properties of these pacemakers is discussed.
Electrophysiological Investigations of the Heart of Squilla Mantis
Authors: Brown Hilary F.
Published: April 2021

There was a seasonal variation in the strength of the effect which extracts of the pericardial organs of Squilla mantis exert on the animal’s heart. The extract was most effective in the spring and summer. An investigation was made of the way in which the pericardial organ extract acts at a cellular level to increase the amplitude and frequency of the heart beat. The extract did not affect the rate of impulse firing within the ganglionic nerve trunk burst. It increased the ratio of the number of impulses per burst : burst interval. It initiated burst firing in complete g.n.t.’s which had become quiescent, and in those which had previously given only one impulse in response to an applied stimulus. The junction potentials recorded intracellularly from Squilla heart muscle increased in height on adding pericardial extract. Some of this increase resulted from facilitation of the junction potentials at the increased heart rate, but 10–20% of the increase was rate-independent. These results suggest that the extract acts at a minimum of two primary sites within the heart.
The Evaporation of Water From Helix Aspersa
Authors: Machin John
Published: April 2021

Observations of intact specimens of Helix aspersa together with experiments with isolated skin preparations are described. Under normal atmospheric conditions increases in haemocoelic pressure, probably due to general muscular activity, are sufficient to maintain the superficial mucous coating of the skin. Under conditions of rapid water loss more intense muscular undulations serve to spread mucus which collects in the grooves to more exposed areas of the skin. The water content, the rate of water loss in dry air, the equilibrium in saturated air and depression of freezing point of isolated mucus samples have been measured. The vapour pressure of mucus has been shown to be within 0-4% of that of distilled water under the same conditions. The significance of the above findings is discussed in relation to evaporative water loss and water uptake of an intact snail.
The Evaporation of Water From Helix Aspersa
Authors: Machin John
Published: April 2021

The construction and use of a wind-tunnel apparatus is described in which measurements of evaporation under controlled conditions of temperature, humidity and air flow can be made. Two mathematical formulae, applicable to evaporation in relatively low wind speeds, are described. It is suggested that a promising approach to evaporation from moist-skinned animals is provided by the application of Leighly’s formula: where the rate of evaporation (E) is expressed in terms of the vapour pressure at the evaporating surface (p0) and in the ambient air (pd), the wind speed (ν) and the length of the evaporating surface parallel to the wind (x). The constant, K, is calculated independently and the terms n and c are left for empirical determination. Values of n and c for different types of evaporating surface are given together with the method used in their calculation. Those relating to flat evaporators and to the snail, Helix aspersa, are shown to differ significantly. In general n increases and c decreases as the amount of air disturbance caused by the snail increases. The fact that n for flat surfaces is in good agreement with previously established theory is taken as evidence that Leighly’s formula may be validly applied. The combined determination of n and c is introduced as a convenient assessment of a complex form in terms of air flow and evaporation.
Stretch Receptor Organs in Squilla Mantis Latr. (Crustacea: Stomatopoda)
Authors: Pilgrim R. L. C.
Published: April 2021

Structures which have been described as muscle receptor organs were found to respond to experimentally applied stretch. The presence of both slowly-adapting and fast-adapting receptors was determined in those organs where two sensory cells and two receptor muscles have been described, i.e. in the abdomen and posterior four thoracic segments. In the fourth thoracic segment, with two cells on a single receptor muscle, one organ is slowly-adapting and the other fast-adapting, with properties not distinguishable from those where separate receptor muscles are present. In the third thoracic segment, with a single cell and receptor muscle, the organ is slowly-adapting. In the second thoracic segment a slowly-adapting cell was discovered. It is without a receptor muscle or accessory innervation and resembles an N-cell of the Decapoda. The reactions of the abdominal organs to acetylcholine and to y-amino butyric acid are qualitatively similar to those in Decapoda. The series of stretch-sensitive organs in Squilla and in Decapoda are compared. The evidence supports the hypothesis that there was, in the trunk of the primitive Malacostraca, a segmentally arranged series of slowly-adapting and fast-adapting receptor organs, that anatomical simplification of the anterior organs has occurred progressively with the development of the carapace and that N-cells are derived from the slowly-adapting type.
Co-Ordination of Successive Activities in An Aphid. Depression of Settling After Flight
Authors: Kennedy J. S. , Booth C. O.
Published: April 2021

Flight has a cumulative ‘priming’ effect (excitatory after-effect) on the settling responses of an aphid landing on a surface, even when the flight has been interrupted by one or more previous landings. But when the bouts of flying between landings were kept brief (1 min.) there was also an opposite, depressing or inhibitory aftereffect on settling which reduced and in certain conditions regularly outweighed the priming effect. Which of the two after-effects predominated depended on the kind of surface landed on each time, on the strength of the settling responses at previous landings and on the total time the aphid had been flying. The depressing effect as measured on a standard host leaf was negligible when the flight had been interrupted by landings on a card, where the settling responses were weakest and soonest inhibited by flight again, greater after landings on a no host leaf and greatest after landings on the host leaf, itself where settling responses were strongest. When two successive landings were both made on the same surface, a depression of settling at the second landing was more likely after a strong previous settling response than after a weak one; it was also more likely when the two landings were made on a non-host than when they were made on a host. Flight and settling are nervous antagonists and the terms ‘antagonistic induction’ and ‘antagonistic depression’ are applied, respectively, to the excitatory and the inhibitory after-effects of flight on settling. These are components in the co-ordination of flight and settling as successive activities and do not necessarily describe the sequences observed.
Studies on the Mode of Action of the Diapause Hormone in the Silkworm, Bombyx Mori L
Authors: Hasegawa Kinsaku
Published: April 2021

The susceptibility of ‘non-diapause’ pupae to diapause hormone, the sexual difference in production of diapause hormone in the suboesophageal ganglion (SG), the changes in diapause hormone content of the SG during larval-pupal-adult development, and the hormone production in polyvoltine race, were studied by injecting diapause hormone extracts into pupae expected to produce non-diapause eggs. The susceptibility of ‘non-diapause’ pupae of a bivoltine race (Daizo) was very low, or the hormone injected was almost inactivated. The susceptibility of ‘nondiapause’ race to diapause hormone is different in different races. As for sexual differences in content of diapause hormone in moth heads, males are superior to females, which was further substantiated by injecting extracts from the SG of both sexes. From the activity of diapause hormone extracts derived from larval, pupal and adult SG, the hormone production in SG is raised during the late pupal stage, especially in males. It is also observed that larval SG produces the hormone, and the hormone production in the SG of male moths after mating becomes weak. Male moth heads of ‘non-diapause’ worms (polyvoltine race), as well as of ‘diapause ‘worms, contain diapause hormone ; though activity is less than in ‘diapause ‘worms, which reflects the occurrence of diapause eggs caused by SG-transplantation. It is highly probable that the bioassay by injecting diapause hormone extracts reveals the activity of the SG in the silkworm. The activity of the SG in the polyvoltine race has been discussed from the standpoint of diapause determination in the silkworm.
The Distribution and Exchange of Inorganic Ions in the Central Nervous System of the Stick Insect Carausius Morosus
Authors: Treherne J. E.
Published: April 2021

The distribution and exchange of inorganic ions between the central and the haemolymph has been studied in the stick insect, Carausius morosus, by flame photometry and radioactive tracers. The exchanges of labelled ions show rapid and slow components which correspond to extracellular and intracellular compartments within the central nervous system. The uptake of sodium from the haemolymph and its concentration in the extracellular fluid is reduced in the presence of metabolic inhibitors. The distribution between haemolymph and extracellular fluid of calcium and magnesium, and also of sodium in poisoned preparations, conforms to a Donnan equilibrium. The distribution of potassium, even in poisoned preparations, does not conform and it is suggested that the activity of this ion may be lower than in free solution. The concentration of magnesium is appreciably greater in the extracellular than in the intracellular compartment. The possible role of magnesium in nervous transmission in this insect is discussed.
Micropuncture Studies of the Concentrations of Sodium, Potassium and Inulin in the Crayfish Antennal Gland
Authors: Riegel J. A.
Published: April 2021

The concentrations of sodium, potassium and inulin in the blood and urine have been measured at various sites in the antennal gland of Orconectes limosus and Austropotamobius pallipes pallipes. The sodium concentration in all parts of the antennal gland is less than the sodium concentration in the blood. Only in the bladder is the sodium concentration significantly different from the sodium concentration in the other parts. The potassium concentration in all parts of the antennal gland, except the bladder, is greater than the potassium concentration in the blood. The potassium concentration within the bladder is much less than that in the blood. The U/B ratio for inulin exceeds one in all parts of the antennal gland. These results are discussed in relation to the function of various parts of the antennal gland and to the manner in which urine is formed by the crayfish antennal gland.
Sodium Balance in the Freshwater Prawn, Palaemonetes Antennarius
Authors: Parry Gwyneth , Potts W. T. W.
Published: April 2021

The sodium content of the freshwater prawn Palaemonetes antennarius and the rates of influx and efflux of sodium in fresh water and a variety of other media are described. The greater part of the influxes in all media is due to active uptake. The relationship between active uptake and the external and internal concentrations is described and it is concluded that the animal is living close to its viable limits of dilution. The greater part of the efllux in fresh water is due to loss in the urine.
On The Initiation of Spermatophore Formation in the African Migratory Locust, Locusta Migratoria Migratorioides Reiche and Fairmaire
Authors: Gregory G. E.
Published: April 2021

The behaviour of the male culminating in spermatophore formation is divisible into four phases: approach; mounting; copulation; and spermatophore formation. All appear to be controlled and co-ordinated solely through the nervous system. The initiation of sexual behaviour requires the brain and one or more of the receptor-bearing head structures (antennae, palpi and eyes) to be functional. Approach and mounting behaviour involves the receptors, nervous system and effectors of the head and thorax only. Copulation is controlled through the ganglia of the abdomen but for its initiation these ganglia have to be in nervous communication with a centre anterior to them. Also both cerci must be functional. Spermatophore formation is initiated, and its early stages are controlled, by an anterior centre which has its effect through the last abdominal ganglion. The later stages of formation, appear to be controlled by the last abdominal ganglion alone. The presence of the female is essential for the initiation and early stages of spermatophore formation, but her role during the later stages of the process appears to be a completely passive one.
The Fate of Thorium Dioxide Injected Into the Pedal Sinus of Bullia (Gastropoda: Prosobranchiata)
Authors: Brown A. C. , Brown Rosalind J.
Published: April 2021

The removal and ultimate disposal of foreign particles injected into the haemolymph of the sandy-beach snail, Bullia, has been studied by using the radio-opaque dye Thorotrast. Particles are removed by phagocytic haemocytes which migrate by various routes to the outside of the body. The main pathway is through the heart wall into the pericardial cavity and via the renopericardial canal into the lumen of the kidney, from which the cells escape into the mantle cavity. The injection of foreign particles stimulates a marked increase in the haemocyte population and also in the mitotic index. The final discussion integrates the available evidence and a comparison is made between Bullia and other molluscs. The origin of the macrophages is discussed.
Joint Receptors in the Antennule of Panulirus Argus Latreille
Authors: Wyse Gordon A. , Maynard Donald M.
Published: April 2021

A single elastic strand organ, presumably a chordotonal proprioceptor, occurs at each of the three distal joints of the antennule in Panulirus argus. These organs are essentially identical with those described at the joints of the pareiopods. Movement at the second and third joints is along one dorso-ventral axis. Unidirectional movement and position receptors responding to flexion and extension occur at both joints. Movement at the first joint is biaxial, either dorso-ventral or medio-lateral. Many unidirectional movement and position receptors are non-specific to axis, and respond to flexion along both axes or to extension along both axes. In addition, some completely specific position and movement receptors occur that respond to extension or to flexion only along one axis. No bi-directional axis-specific receptors were found. Accessory strands act in conjunction with the main elastic strand during joint movement to produce differential stretch according to direction or axis of movement. It is suggested that such differential mechanical distortion is responsible for the part receptor specificity observed.