bluuebunny/crossref_metadata_2025 huggingface dataset:
Activity in the Locust Nerve Cord in Response to Wing-Nerve Stimulation
Authors: Gettrup Erik
Published: April 2021

Nerve cord activity in response to repetitive stimulation of wing nerves 1C1 and 1D was investigated in preparations of locusts. Firings of single central units occurred at latencies defined with an accuracy of few milliseconds. Various recordings of latencies show that it is not possible to exclude ganglionic synapses within the pathways considered. Records from the connectives anterior to the mesothoracic ganglion or from the abdominal connectives show an increase in activity during repetitive stimulation. When recorded between prothoracic and mesothoracic ganglia a response was found in ipsilateral as well as contralateral connectives. The ipsilateral and contralateral responses were delayed differently with respect to the stimulus. When nerve 1C1 of metathorax was activated the ipsilateral delay amounted to 7 msec., s.d. 2 msec., whereas the contralateral delay was found to be 8 msec., s.d. 3·4 msec. Ipsi- and contralateral latencies during stimulation of 1D of the metathorax were 5 msec., s.d. 1·4 msec.
A Quantitative Analysis of Ciliary Movement by Means of High-Speed Microcinematography
Authors: Baba Shoji A. , Hiramoto Yukio
Published: April 2021

An optical arrangement for high-speed microcinematography has been designed so as to record ciliary movement, and the movements of single large abfrontal cilia of Mytilus gill have been photographed at 400–500 frames/sec. with brief exposures of 1/20,000 sec. A quantitative description of the movement of the cilium is presented in terms of the changes of the curvature at various regions of the ciliary shaft and of the change of the basal angle. The principle of the description mentioned above is also applied to the movement of the cilium in media of high viscosities, and some parameters of the movement (duration, amplitude of the basal angle, maximum curvature and propagation velocity of the bending wave) are presented. The resistance experienced by the cilium during its beating has been evaluated under some hydrodynamic assumptions, and the flow induced by the cilium and the bending moment of the ciliary shaft due to the viscous resistance have been calculated over a single beat. The change of the degree of bending of the ciliary shaft (curvature) takes place in advance of the change of the bending moment at the same region in the distal as well as in the proximal regions of the ciliary shaft. This fact indicates that active processes are involved in bending and unbending of the ciliary shaft during its beat.
Urea and Osmoregulation in the Diamondback Terrapin Malaclemys Centrata Centrata (Latreille)*
Authors: Gilles-Baillien M.
Published: April 2021

The blood of the diamondback terrapin going from fresh water to 50% sea water shows an increase in its osmotic pressure which is mainly due to an increase in Na and Cl concentrations. The blood of terrapins living in sea water compared with the blood of terrapins living in 50 % sea water shows a higher osmotic pressure which is the result solely of a higher urea concentration; Na and Cl concentrations are no longer affected in this second stage of adaptation. Urine of 50% sea-water terrapins and of sea-water terrapins is generally isosmotic to the blood while the urine of fresh-water terrapins is usually hypo-osmotic. The bladder appears to play an essential part in reducing water loss in the seawater terrapins but is not implicated in the salt balance. When each animal is considered individually, the urea concentration in the urine is always higher than in the serum, suggesting that the high urea concentration in the blood of terrapins adapted to sea water is due to an urea accumulation in the bladder.
Hypo-Osmotic Urine in Nereis Diversicolor
Authors: Smith Ralph I.
Published: April 2021

Although Beadle as early as 1937 suggested that the urine of Nereis diversicolor O. F. Müller might be of lower concentration than the body fluids when this worm is hyperregulating in low salinities, there has been no direct measurement of urine concentration to support this reasonable idea. Jørgensen & Dales (1957) studied osmotic water uptake and loss in N. diversicolor and calculated that this animal reduces its permeability to water by over 60% when in fresh water. On the assumption that chloride permeability was comparably reduced, they calculated that the observed rate of chloride exchange and the level of chloride concentration in the coelomic fluid were compatible with the production of a small volume of urine isotonic in chloride to the body fluid. However, Potts & Parry (1964) in reviewing this matter regarded the evidence of Jørgensen & Dales for reduced permeability to water as not well founded and, without presenting new data but by making the assumption that no changes in permeability occurred, drew up a balance-sheet for chloride exchanges which led them to postulate a reduction of chloride loss in low salinities by production of an hypotonic urine. Although there is no incompatibility between reduction of chloride loss by reduction of permeability to water (and hence urine volume) and by resorption of chloride from a consequently hypotonic urine, the fact that different authors can postulate these as alternative mechanisms on the basis of the same data makes it evident that measurements of urine concentration and volume would be useful in further attempts at analysis of the regulation of chloride and water in N. diversicolor. In a preceding paper (Smith, 1970a) there has been shown a correlation between chloride loss and weight loss compatible with the production of hypotonic urine by this species at low salinities, but this evidence is not conclusive. It has further been shown (Smith, 1970b) that N. diversicolor reduces its apparent permeability to water (as D2O) in low salinities, which seems to confirm the view of Jørgensen & Dales (1957), but the urine volumes calculated were such as to make it probable that chloride resorption and production of a urine hypotonic in chloride to the body fluid can also take place.
Sodium Regulation in the Freshwater Mollusc Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)
Authors: Greenaway Peter
Published: April 2021

Sodium regulation in normal, sodium-depleted and blood-depleted snails has been investigated. Limnaea stagnalis has a sodium uptake mechanism with a high affinity for sodium ions, near maximum influx occurring in external sodium concentrations of 1·5–2 mM-Na/1 and half maximum influx at 0·25 mM-Na/1. L. stagnalis can maintain sodium balance in media containing 0·025 mM-Na/1. Adaptation to this concentration is achieved mainly by an increased rate of sodium uptake and a fall of 37% in blood sodium concentration, but also by a reduction of the sodium loss rate and a decrease in blood volume. A loss of 23% of total body sodium is necessary to stimulate increased sodium uptake. This loss causes near maximal stimulation of the sodium uptake mechanism. An experimentally induced reduction of blood volume in L. stagnalis increases sodium uptake to three times the normal level. About 40% of sodium influx from artificial tap water containing 0·35 mM-Na/1 into normal snails is due to an exchange component. Similar exchange components of sodium influx were also observed in sodium-depleted and blood-depleted snails in the same external sodium concentration.
The Central Course of the Hair Afferents and the Pattern of Contralateral Activation in the Central Nervous System of the Scorpion, Heterometrus Fulvipes
Authors: Sanjeeva-Reddy P. , Rao Kandula Pampapathi
Published: April 2021

As in the crustaceans and insects, so in the scorpion the primary afferent fibres constitute a considerable proportion of the axons in the central connectives. The possibility of a sensory neurone sending collaterals, while passing through a ganglion, which activate a contralateral interneurone has been conclusively demonstrated. This type of activation differs from the pattern of contralateral activation so far demonstrated in the insects and crustaceans. In the latter groups, the available evidence indicates the activation of contralateral interneurones by the terminal branches of the sensory axons, but not by the collaterals. It has been emphasized that in the scorpion, but not in insects and crustaceans, the tactile input from a single hair is adequate to trigger the central responses, which in itself is an advantage in analysing the integrative processes and functional connexions between neurones.
The Role of 5-Hydroxytryptamine and Cyclic Amp in the Control of Fluid Secretion by Isolated Salivary Glands
Authors: Berridge M. J.
Published: April 2021

Isolated salivary glands of Calliphora have been used as a system on which to study the mode of action of a hormone. Cyclic AMP, which is thought to mediate the action of many different hormones, can stimulate fluid secretion equally as well as 5-HT. Methyl xanthines, which inhibit the hydrolysis of intracellular cyclic AMP by phosphodiesterase, can stimulate secretion and prolong recovery time after removal of 5-HT. Methyl xanthines can sensitize salivary glands to both 5-HT and cyclic AMP. Butyryl derivatives of cyclic AMP can stimulate secretion, but their effect is slower and lasts longer. Certain amino acids and malate support fluid secretion more effectively than trehalose or glucose. It is concluded that cyclic AMP plays an important role in the ability of 5-HT to control fluid secretion by salivary glands.
Modifications in the Automatic Diver Balance Technique
Authors: Bergfors T. , Mild K. H. , Løvtrup S.
Published: April 2021

The automatic electromagnetic diver balance, described by Larsson & Løvtrup (1966), is based on the principle that a diver with density less than the surrounding medium is prevented from rising to the surface by an electromagnetic force acting on a small piece of iron placed in the diver. Since it was first introduced, the balance has displayed certain imperfections which have hampered experimental progress. The primary causes of these disturbances have been traced to temperature oscillations in the flotation medium, to details in the electronic design and to the magnetic materials used in the core and in the diver. In the course of the work to remedy these sources of trouble our understanding of the theory of the method has greatly improved and as a consequence we have been able to devise other innovations which enhance the precision of the method. This report presents in brief outline the theory and the various modifications introduced.
Ionic Content of Haemolymph in the Cockroach, Periplaneta Americana
Authors: Pichon Y.
Published: April 2021

The haemolymph of the American cockroach, Periplaneta americana, has been analysed for Na+, K+ and Ca2+ ions in different experimental conditions. The ionic content of the haemolymph is maintained constant after the first larval instar. It is characterized by a rather high K+ level and a particularly large variability which could be related either to the nature of the diet (lettuce) or to numerous alterations of the blood and tissues in relation to the moulting cycle. The regulation of this ionic content when the animal is given different diets is particularly effective. Starvation results in a decrease in the mean ionic concentration in the blood, this decrease following a pronounced increase of the Na+ and K+ levels when starvation is associated with dehydration. The blood K+ level can be raised artificially with high K+ diets (lettuce leaves or high K+ saline) but is then very variable. These results are discussed in terms of absorption, excretion and storage mechanisms. The analysis of blood samples collected successively from the dorsal thorax of different individuals shows that, when the animals are fed normally, the ionic composition varies widely, showing that in these conditions the haemolymph is not homogenous. Serial measurements of blood ions in different regions of the animal show unequal distribution of Na+, Ka+ and Ca2+. This result is discussed in view of the very special circulatory system of insects when compared with that of vertebrates. The overall picture of insect blood which can be drawn from these experiments is that the complexity of the regulatory system together with the fact that the circulatory system is open and lacunous allows relatively wide variations in the ionic concentration to occur on both sides of a genetically fixed mean. This particular feature must be taken into account when one considers the physiological role of blood ions in mechanisms such as excitation, conduction or muscular contraction.
The Visual Mechanisms of Tenebrio Molitor: Some Aspects of the Spectral Response
Authors: Yinon U.
Published: April 2021

The spectral responses of a ‘stored product’ insect, Tenebrio molitor, have been studied electrophysiologically. Although primarily inhabiting a darkened environment the insect possesses a visual mechanism which could enable it to discriminate various wavelengths. The visible range for T. molitor lies between <350 and 700 mμ; and the efficiency and sensitivity curves both have maxima between 520 and 550 mµ. Latency and amplitude also indicate maximum response in this same region of the spectrum. Under normal conditions of dark adaptation the screening pigment does not affect the spectral sensitivity. Miniature threshold potentials concealed in the normal background noise were detected by the use of the computer of average transients. The two principal components of the ERG, as well as minor components which were occasionally detected, were similarly related to wavelength. This seems to imply that the various ERG components originate in receptors of one single type.
Effects of Sub-Lethal High Temperature On an Insect, Rhodnius Prolixus (Stål.)
Authors: Okasha A. Y. K.
Published: April 2021

The reproductive activity in both sexes is completely inhibited during the exposure of adults to 34°C immediately after feeding. The changes that take place in the reproductive system in males and females during exposure parallel those brought about by starvation or allatectomy. Females exposed for 6 days to 34°C immediately after feeding, then decapitated and placed at 28°C, fail to form eggs, while those left with the head intact form mature eggs. The course of oxygen consumption of normal males and females is compared with that of insects placed immediately after feeding at 34°C and their respiration measured at the same temperature. It seems that the corpus allatum is not active at high temperature, or if active its hormone is ineffective. It is suggested that it is the synthesis of specific adult proteins which is interfered with by high temperature, hence the inhibition of the reproductive activity.
Chloride Regulation at Low Salinities by Nereis Diversicolor (Annelida, Polychaeta)
Authors: Smith Ralph I.
Published: April 2021

The ability of the common brackish water polychaete worm Nereis diversicolor O. F. Müller to regulate osmotically and ionically has been well established (Schlieper, 1929; Beadle, 1937; Smith, 1955; Hohendorf, 1963; Oglesby, 1970; and others). Jørgensen & Dales (1957) demonstrated an uptake of chloride against the concentration gradient at low salinities, with a maximum rate of exchange under steady-state conditions at external chloride concentrations of 65–120 mM/I, and a drop in uptake rate to about one-third of that maximum in fresh water (Cl = 1·4mM/l). Fretter (1955) demonstrated a comparable uptake of sodium against the concentration gradient in this species, but without the maximum shown in the chloride exchanges.
Aspects of the Physiology of Terrestrial Life in Amphibious Fishes: II. The Chilean Clingfish, Sicyases Sanguineus
Authors: Gordon Malcolm S. , Fischer Siegmund , Tarifeño S. Eduardo
Published: April 2021

A study has been made of major aspects of the physiological adaptations for terrestrial life possessed by the amphibious clingfish, Sicyases sanguineus, on the coast of central Chile. These fish can survive for more than 112 days out of water, if not exposed to severe dehydration or thermal stresses. Rates of evaporative water loss while out of water are low. Upper lethal temperatures are also low, reflecting the uniformly cool water temperatures of their environment. In nature the fish rarely leave areas in which they are frequently washed over by waves. These fish demonstrate an unusual combination of metabolic and cardiovascular adjustments to emersion. Metabolic rates (oxygen consumption) of small (1–5 g weight) fish are higher out of water than in water. Larger fish show a pattern of intermittent oxygen uptake when out of water. Heart rates respond to emersion (and associated cessation of breathing movements) in the pattern of the diving syndrome. Lactic acid concentrations in the blood gradually increase above control levels during the first few hours of emersion, then remain constant at about × 3 control level. There is no indication of peripheral vascular shutdown during emersion. Emersion produces a marked shift towards ureotelism in waste nitrogen production. There appears to be no systemic accumulation of ammonia during emersion. The generality of the results, and also their physiological significance, are discussed.
The Control of Water Loss in Desert Tenebrionid Beetles
Authors: Ahearn Gregory A.
Published: April 2021

Total water loss in tenebrionid beetles was composed of transpiratory losses from the cuticle and spiracles, water associated with defaecation, and water from the release of defensive quinone droplets or oral fluids. Freshly killed specimens of E. armata, C. muricata and C. verrucosa had higher transpiration rates over long and short exposures than did living animals of the same species. These results may reflect the cessation of active water retention by cuticular and spiracular regulation in dead animals. Cuticular transpiration, although low in absolute rate, was a greater source of water loss than respiratory transpiration in E. armata, C. muricata and C. verrucosa at temperatures from 25 to 42·5°C and at 0% R.H., suggesting that spiracular control of water loss was of considerable importance in maintaining water balance. A marked increase in respiratory transpiration over previous low rates was observed at 40°C for E. armata and at 42·5°C for C. muricata and C. verrucosa, and indicated a temperature-induced breakdown in spiracular water regulation due to increased respiratory activities. In contrast, cuticular transpiration maintained a linear rate of increase over the temperature range investigated. A direct relationship existed between oxygen consumption and estimated respiratory transpiration for E. armata from 25 to 40°C and at 0% R.H. Evidence for the presence of discontinous respiration and unidirectional tracheal air flow in E. armata was presented. Cuticular transition temperatures were measured for E. armata (40°C), C. muricata (47·5°C), and C. verrucosa (50°C) with results showing that the autumn species (E. armata) possessed a lower cuticular breakdown point than either of the two summer species. Much of the success of tenebrionid beetles in desert habitats is due to the development of highly impermeable cuticles and well regulated spiracular control mechanisms for reducing the loss of body water.
Temperature Dependence of the Neural Control of the Moth Flight System
Authors: Hanegan James L. , Heath James Edward
Published: April 2021

The transition from the warm-up motor pattern to the flight motor pattern in the saturnid moth H. cecropia, is described. The transition from warm-up to flight was found to be dependent on the temperature of the thoracic ganglia. A model to account for the two different motor output patterns and the transition of the warm-up pattern to the flight pattern is proposed.
Active Transport of Caesium by the Isolated and Short-Circuited Midgut of Hyalophora Cecropia
Authors: Zerahn Karl
Published: April 2021

The short-circuited midgut from the larvae of Hyalophora cecropia can actively transport potassium and rubidium from blood side to lumen. In this paper it is demonstrated that caesium also can be actively transported. Transport of potassium does not interfere with the metabolism of the midgut; nor does transport of caesium. Potassium and rubidium compete for the transport mechanism in a one-to-one ratio but competition between potassium and caesium is more complicated. At high caesium:potassium ratios the active transport taking place is transport of caesium; when the ratio is 2 there is more transport of potassium than of caseium; when the ratio is i there is no transport of caesium.
Geotaxis in Motile Micro-Organisms
Authors: Roberts A. M.
Published: April 2021

It is suggested that the principal cause of geotaxis in many motile micro-organisms is a gravity-induced hydrodynamic torque, the size of which depends upon the shape of the organism. The nature of the torque has been investigated using small scale models. An expression for the distribution of organisms in long, vertical columns has been derived. The distribution of Paramecium in long, vertical columns has been determined, and it has been shown that the strength of the hydrodynamic interaction is sufficient to account for the negative geotaxis usually exhibited by this organism. The induction of positive geotaxis in certain circumstances has been considered. The survival value of negative geotaxis for free-swimming organisms in search of food may explain the characteristic shape of many protozoa.
Components of A Response Programme Involving Inhibitory and Excitatory Reflexes in the Surf Clam
Authors: Mellon DeForest , Prior David J.
Published: April 2021

Electrical records from ganglion cells in the central nervous system and from intact muscle groups controlling siphon retraction and shell-valve adduction have revealed qualitative similarities in the response characteristics of two neurone-effector systems following stimulation of tactile afferents. Simultaneous electrical records from neurones and muscle indicate that Type I ganglion cells are motoneurones to the fast portion of the posterior adductor muscle. The waveform and polarity of the post-synaptic responses of Type 1 cells depend critically upon the intensity of stimulation over intact sensory pathways. High-intensity input transiently excites the fast portion of the adductor; low-intensity input inhibits the adductor motoneurones. The input organization of Type I neurones therefore permits discrimination of stimulus magnitude and thus controls the characteristics of the response programme."
The Study of Evaporation from Small Surfaces by the Direct Measurement of Water Vapour Pressure Gradients
Authors: Machin John
Published: April 2021

The construction, maintenance and calibration of a sensitive instrument capable of making numerous vapour-pressure measurements within humidity gradients by the dew-point method is described. Coefficients of diffusion of water vapour in air, calculated from observed vapour-pressure gradients and measured rates of evaporation agree with theoretical and other experimental values in still air. Apparent coefficients in wind speeds between 10 and 100 cm/s were significantly lower than those in still air. This finding, together with the performance of the dew-point probe, is discussed in relation to its possible use in the study of evaporation from animals and plants."
The Metabolic Cost of Swimming in Ducks
Authors: Prange Henry D. , Schmidt-Nielsen Knut
Published: April 2021

The metabolic cost of swimming was studied in mallard ducks (Anas platy-rhynchos) which had been trained to swim steadily in a variable-speed water channel. At speeds of from 0·35 to 0·50 m/sec the oxygen consumption remained relatively constant at approximately 2·2 times the resting level. At speeds of 0·55 m/sec and higher the oxygen consumption increased rapidly and reached 4·1 times resting at the maximum sustainable speed of 0·70 m/sec.. The maximum sustainable swimming speed of the ducks coincided with the limit predicted from hydrodynamic considerations of the water resistance of a displacement-hulled ship of the same hull length as a duck (0·33 m). The cost of transport (metabolic rate/speed) reached a minimum of 5·77 kcal/ kg km at a swimming speed of 0·50 m/sec. Ducks swimming freely on a pond were observed to swim at the speed calculated in experimental trials to give minimum cost of transport. Drag measurements made with model ducks indicated a maximum overall efficiency (power output/power input) for the swimming ducks of about 5%. Ships typically have maximum efficiencies of 20–30%. Because of the difficulty in delimiting the cost of swimming activity alone from the other bodily functions of the duck, overall efficiency may present an incorrect description of the swimming performance of the duck relative to that of a ship. An hydrodynamic parameter such as speed/length ratio whereby a duck excels conventional ships may present a more appropriate comparison.
Single-Session Learning by Octopuses
Authors: Wells M. J. , Young J. Z.
Published: April 2021

In order to study the mechanisms of learning it is desirable to evolve techniques for evaluating long-lasting changes brought about by single events in the lives of animals. Techniques for the study of ‘one-trial learning’ are well known for vertebrates, but tend to involve learning not to perform some act that is followed by punishment. One-trial learning opens up the possibility of investigating the effects of electroconvulsive shock, spreading depression, anaesthetics, drugs and so on on the establishment of long lasting records in the central nervous systems.
Optomotor Responses and Nystagmus in Intact, Blinded and Statocystless Cuttlefish (Sepia Officinalis L.)
Authors: Messenger J. B.
Published: April 2021

Evidence is reviewed confirming that the eyes of Sepia move under the influence of gravity, angular acceleration and visual receptors. Visual nystagmus and optomotor responses are described in free-swimming Sepia; these survive bilateral destruction of the statocysts, though they are abolished by blinding. Post-rotatory nystagmus is shown by intact animals in a plain background; in bilaterally blinded animals there are post-rotatory movements of the head. These responses disappear if the statocysts are removed. The post-rotatory nystagmus of intact animals is almost completely suppressed by visual cues. Other effects of blinding and statocyst removal are described.
Effects of Catecholamines On the Neuromuscular Junction of the Somatic Muscle of the EarthwormPheretima Communissima
Authors: Ito Y. , Kuriyama H. , Tashiro N.
Published: April 2021

Effects of catecholamines and adrenergic blocking agents on the neuromuscular junction of the somatic muscle of the earthworm, Pheretima communissima were studied by the microelectrode technique. Effects of catecholamines and their blocking agents on the post-junction membrane could be summarized as follows: (a) Adrenaline and isoprenaline (10−8–10−5 g/ml) hyperpolarized the membrane in proportion to the applied concentration. However, noradrenaline (10−8–10−5 g/ml) had no effect on the membrane potential, (b) Changes of the membrane resistance which appeared on treatment with catecholamines were in parallel with the changes of the membrane potential, (c) In the presence of excess calcium ions and in sodium-free (tris) solution, adrenaline and isoprenaline had no effect on the membrane potential or on the input resistance of the membrane. An increase of potassium ions and reduction of chloride ions had no relation to the actions of adrenaline and isoprenaline on the post-junctional muscle membrane, (d) Propranolol competitively inhibited the action of isoprenaline on the post-junctional muscle membrane but phentolamine had no effect on this action. Effects of catecholamines and their blockers on the m.e.j.p. and m.i.j.p. were observed, (a) After treatment with picrotoxin, the m.e.j.p. could be recorded in sodium-free solution. The frequency of the m.e.j.p. was increased by noradrenaline and adrenaline but not by isoprenaline. In normal Ringer’s solution isoprenaline slightly increased the frequency of m.e.j.p. but this appeared to be due to the effect of isoprenaline on the post-junctional membrane, (b) Phentolamine increased the mean amplitude of the m.e.j.p. but had no effect on the frequency of the m.e.j.p. After treatments with phentolamine effects of noradrenaline were inhibited, (c) After pre-treatment with d-tubocurarine, noradrenaline and adrenaline increased the frequency of the m.i.j.p. but only adrenaline increased the mean amplitude. Isoprenaline had no effect on the frequency but increased the mean amplitude of the m.i.j.p. From the above results it is concluded that the α-response to catecholamines increased the release of chemical transmitter from the nerve terminals; the β-response increased the membrane potential and the input resistance of the post-junctional muscle membrane. Both α-and β-responses to the catecholamines facilitated the transmission mechanism of the earthworm somatic muscle.
Function of the Supernumerary Sense Cells and the Relationship Between Modality of Adequate Stimulus and Innervation Pattern of the Scorpion Hair Sensillum
Authors: Sanjeeva-Reddy P.
Published: April 2021

Mechanical stimulation of a single hair results in the discharge of four or five sense cells thereby refuting the classical generalization that mononeural innervation is characteristic of the mechanoreceptive hairs. By electrophysiological methods three functional units can be recognized: the ‘L’, ‘I’ and ‘S’ units. The ‘L’ unit conveys information about the duration and velocity of the dynamic phase; its discharge is phasic. The ‘I’ unit conveys information about the duration of the static phase and about the displacement of the hair; its discharge is tonic and the duration of discharge increases with extent of displacement. The ‘S’ unit is highly sensitive but responds only during the initial phase of displacement; if the hair is already extensively displaced the ‘S’ unit does not respond to further movement. These findings indicate that all the functional units may be meaningfully concerned in encoding the parameters of a mechanical stimulus. The widespread occurrence of multiple innervation of receptors, and its functional significance, is discussed; and a thorough re-investigation of stimulus—response relationships in the mechanoreceptive hairs of arthropods is advocated.
Oxygen Uptake and Transport by the Rainbow Trout During Exposure to Carbon Monoxide
Authors: Holeton George F.
Published: April 2021

Rainbow trout, brown trout and pike were exposed to 5% carbon monoxide which was sufficient to combine with over 90% of their haemoglobin. Trout tested at 10 and 15°C did not survive exposures to carbon monoxide longer than 30 min, but those tested at 5°C survived exposures of up to 3 h. Even at 5°C the trout were weakened and unable to stay upright. The respiratory responses of trout exposed to 5% carbon monoxide at 5°C for 30 min were examined in detail. The trout responded to carbon monoxide with an increase in the flow of blood and water past the gills. As a result the mean partial pressure gradient of oxygen from water to blood across the gill membrane was increased. In spite of these changes oxygen uptake fell by 40%. An increase was observed in heart rate and blood pressure in both the ventral and dorsal aorta of CO-exposed fish. There was a drop in the oxygen diffusing capacity or transfer factor of the gills of CO-exposed trout. Although the fish were rendered anoxic there was no bradycardia, suggesting that this reflex response depends upon either environmental or arterial PO2 and not upon arterial oxygen content. The observed responses to carbon monoxide may be a result of either anoxia, anoxaemia, reduced pH, or a combination of these factors
The Control of Sodium Uptake by the Larva of the Mosquito Aedes Aegypti (L.)
Authors: Stobbart R. H.
Published: April 2021

The time-course of the fluxes causing net sodium uptake through the anal papillae, and the control of this uptake, have been studied in fed sodium-deficient fourth-instar larvae of the mosquito Aëdes aegypti in 2 mM/1 NaCl. Influx, outflux and uptake rate all decline exponentially with time, suggesting that effective negative feedback operates continually upon the transporting system. Uptake is impaired or eventually stopped when certain tissues are destroyed, or ligatured or clamped out of the circulation. The effect is not explicable in terms of impaired circulation of haemolymph through the papillae, and is taken to indicate that a hormone is involved in sodium uptake. Interruption of the nerve cord suggests that an abdominal monitoring centre conveys information forwards along the nerve cord to a control centre in the thoracic ganglia to inhibit or increase hormone production. The hormone is apparently produced by the thoracic ganglia and the retro-cerebral complex (corpora allata and homologues of the prothoracic glands combined). Evidence that a second hormone, produced in the head, is also involved in sodium uptake is at present inconclusive. A possible mechanism of hormone action is suggested and discussed in relation to what is known of the functioning of the ionic carriers in the anal papillae.
The Central Nervous Control of Colour Change in the Minnow (Phoxinus Phoxinus L.)
Authors: Gentle Michael J.
Published: April 2021

A series of ablations were carried out in the optic tectum of the minnow, Phoxinus phoxinus, in order to investigate its importance in colour change. The presence of the anterior or posterior tectum alone one on or both sides caused persistent pallor in normal fish. The presence of the anterior tectum on one side and the posterior on the other enabled the fish to adapt chromatically to its background. Small bilateral removals from the dorsal part of the optic tectum did not effect colour change. Larger removals from the dorsal tectum reduced the extent of change and still larger removals caused the fish to pale on all backgrounds.
Sun Navigation in Homing Pigeons—Attempts to Shift Sun Coordinates
Authors: Walcott Charles , Michener Martin C.
Published: April 2021

Small time errors in the biological clocks of pigeons appear to have no effect on their navigation. An error of 2 h seems to shift the pigeons’ orientation as predicted by a suncompass hypothesis, but 6 h shifts gave initial orientation that was too scattered to analyse. Alteration of the apparent sun altitude with mirrors at the loft was without effect on navigation. The administration of 30% D2O in the pigeon’s drinking water combined with a random light schedule and holding at a westerly point had no effect on the pigeon’s homing. We conclude that the pigeon’s navigation is probably not based on either the sun or on accurate sense of time at the home loft.
Acoustic Location of Prey by Barn Owls (Tyto Alba)
Authors: Payne Roger S.
Published: April 2021

Barn owls (Tyto alba) can locate prey in total darkness using only the sense of hearing, with an error of less than 1° in both the vertical and horizontal planes. Differences between the behaviour of barn owls flying at prey in complete darkness (analysed from films taken under infra-red illumination) and their behaviour in the light are correlated with the problems they must face in acoustic orientation. Experiments with owls trained to strike a concealed loudspeaker show that they depend on frequencies of sound above 5 kHz. Measurements of sound pressure in the region of the owl’s eardrum, made with a probe-tube microphone while moving a loudspeaker around the owl’s head, reveal that for frequencies above 8-5 kHz the ear is highly directional. At such frequencies, regions of high sensitivity (tightly isolated by peripheral regions of low sensitivity) are directed along different paths for the two ears. These regions of good sensitivity are correlated with the asymmetry of the barn owl’s external ears. Movements of a flap of skin in front of the ear opening changes the overall directional sensitivity patterns by redirecting the regions of maximum sensitivity. A theory is presented to explain how a barn owl might locate the position of a sound source by moving its head until the intensity of all frequencies comprising a complex sound is brought to a maximum in both ears (aided perhaps by differences in inter-aural time delay that are enhanced by intensity disparities).
Directional Change in A Flying Beetle
Authors: Burton Alexander J.
Published: April 2021

Rhinoceros beetles of the genus Oryctes turn in flight by a differential change in the stroke angle, or amplitude, of the wings of the two sides. This method of turning has been briefly described (Burton, 1964) and what follows is a fuller account of the turning mechanisms in these beetles.
Rhythmic Activity in the Insect Nervous System
Authors: Miller P. L.
Published: April 2021

Spiracle 1 of Sphodromantis lineola possesses a moveable valve equipped with two closer muscles which act as synergists, receive identical innervation but act on different regions of the valve. The two muscles are controlled by two motor axons which produce simultaneous small EPSPs in the two muscles of the left and right spiracles. Valve activity can be facultatively coupled to the abdominal ventilatory rhythm. Three patterns of coupling have been recognized. Ventilation-coupled activity includes burst formation. Similar repetitive bursts can be produced in the spiracle nerves of an isolated segment by treatment with CO2 and by mechanical stimulation.
The Role of the Lateral-Line Efferent System in Xenopus Laevis
Authors: Russell I. J.
Published: April 2021

Efferent impulses have been recorded from branches of lateral-line nerves. The functional significance of the efferent innervation and its action on afferent impulse activity has been examined. Neither mechanical stimulation of the lateral-line receptors nor electrical stimulation of afferent nerves excites lateral-line efferent activity. Trains of efferent impulses accompany all active movements for their duration. In immobilized animals a close correlation exists between impulses in lateral-line efferent nerve fibres and motor impulses in ‘large’ nerves innervating ‘twitch’ muscles, but not with impulses in nerves innervating ‘slow’ muscles. A close similarity also exists between impulse activity in different lateral-line efferent fibres. Whereas electrical stimulation of ascending tracts in the spinal cord fails to excite lateral-line efferent fibres, stimulation of the spinal cord in the region of descending reticular motor axons causes efferent impulses to follow each pulse after brief, constant, latencies. It is suggested that the efferent neurones may be innervated by axon collaterals from reticular cells. Electrical stimulation of efferent fibres innervating a lateral-line receptor produces transitory inhibition of impulse activity in the afferent nerve fibres. The inhibition has a long variable latency (11-30 ms) and persists for 40-60 ms. Upon cessation of inhibition, caused by a train of efferent impulses, afferent impulses reappear at an accelerated frequency (after-discharge), and quickly return to resting frequency. A role of the lateral-line efferent neurones during active movement is discussed.
A Preparation of Aplysia Fasciata for Intrasomatic Recording and Stimulation of Single Neurones During Locomotor Movements
Authors: Weevers R. De G.
Published: April 2021

Methods are described for suspending and clamping Aplysia fasciata so as to permit intrasomatic recording from neurones of the head ganglia during locomotor and other behavioural activities. Sensory responses of neurones in the pedal ganglion are classified into four main types, all being distinct from those of pleural ganglion cells. The pedal ganglion may well contain ‘motor cells’ for the greater part of the somatic musculature. Preliminary results suggest that the pleural LGC may be involved in promoting a change from swimming to creeping behaviour.
Observations of the Effects of Changes in Hydrostatic Pressure and Illumination On the Behaviour of Some Planktonic Crustaceans
Authors: Lincoln R. J.
Published: April 2021

Daphnia magna responds vigorously to a large increase in hydrostatic pressure when in total darkness, but this response is very much depressed in the presence of light. The weak response of Daphnia in light is apparent over a wide range of intensity. The effect of pressure on Daphnia appears to be largely kinetic and does not involve a specific orientation of the swimming activity. The overt threshold for Daphnia and Calanus under laboratory conditions are in the region of 3.5 bar (50 p.s.i.) and 0.7 bar (10 p.s.i.) respectively. The barosensitivity is not abolished by repetitive compression and decompression. Observations made of the behaviour of Calanus indicate that the pressure response is not inhibited by light as it is in Daphnia. Calanus which have been maintained at high ambient pressure for several hours remain sensitive to small increments of pressure. The response appears similar to that obtained at the level of atmospheric pressure.
Behavioural Physiology of the Colonial Hydroid Obelia
Authors: Morin James G. , Cooke Ian M.
Published: April 2021

Spontaneous electrical potentials from Obelia geniculata hydranths were recorded using fine-tipped suction electrodes. The primary behavioural responses of the hydranths were observed and correlated with specific electrical potentials: the contraction potential (KP) associated with hydranth withdrawal, the mouth-opening potential (MOP) associated with mouth opening, and the tentacle contraction potential (TKP) associated with oral flexion of individual tentacles. KPs occurred in rhythmic bursts while the TKP and MOP responses were infrequent and non-rhythmic. Two other species, O. longissima and Gonothyraea loveni, were shown to produce the same three types of potentials with corresponding behavioural responses. .The MOP activity may occasionally drive the KP responses within a hydranth, but the coupling is very loose. None of the other possible interactions within a hydranth was observed. .No interaction of any of the potentials between adjacent hydranths was found in the absence of external stimuli. .It seems likely that the KPs in Obelia are homologous with the contraction potential (CP) in Hydra and the hydranth potential (HP) in Tubularia. MOP and TKP activity do not show apparent homologies with potentials of the other hydroids Hydra, Tubularia and Cordylophora.
The Visual Mechanisms of Tenebrio Molitor: Changes in the Electroretinogram as Function of the Stimulus Duration
Authors: Yinon U.
Published: April 2021

The ERG complex of the compound eye of the yellow mealworm bettle Tenebrio molitor (L.) separates into two components with stimulus durations of longer than 100 ms. These are the ‘on’ and the ‘off’ effects. Above stimulus durations of 1 s the positive potential following the ‘on’ is faster and the positive ‘off’ is followed by a small negative one. The latent period of the ‘on’ is independent of the stimulus duration while for stimulus durations of longer than 300 ms the ‘off’ latency is coupled with the end of the stimulus. If measured after the extinction of the stimulus the ‘off’ latency is affected by the stimulus duration. The ‘on’ and ‘off’ amplitudes behave similarly for various stimulus durations. Both originate in the receptor cells. The Bunsen-Roscoe Law of photochemistry holds for stimulus durations of 10-40 ms. For a given intensity, the amplitudes diminished for durations longer than 300 ms.
The Effect of Light Regimes On the Circadian Rhythm of Flight Activity in the Mosquito Aedes Taeniorhynchus*
Authors: Nayar J. K. , Sauerman D. M.
Published: April 2021

The flight activity patterns of groups and individuals of sugar-fed A. taeniorhynchus females have been studied under different light regimes, by recording of flight sound as an indicator of flight activity. In an LD 12:12 regime, flight activity occurs both at light-off and light-on, forming a bimodal ‘alternans’ pattern. This basic pattern of flight activity persists with a periodicity of 23.5 h under continuous DD, but under continuous LL is masked over by irregular excessive outbursts of activity. The flight activity rhythm originates for the first time in the adult stage, and it is not carried over from rhythms of developmental stages. Flight activity rhythms can be entrained to a new light regime within 24 –36 h which is rather fast. An early light-off does not reset the phase of the rhythm, but a delayed light-off does. The flight activity rhythm can be entrained to 24 h light regimes other than LD 12:12. But a single stimulus of less than 12 h is not effective in initiating the bimodal circadian rhythm. Frequency demultiplication within certain limits can entrain the flight activity rhythm to 24 h. This flight activity rhythm of A. taeniorhynchus is compared with the activity rhythms of Aopheles gambiae and Culex pipiens pallens. It is concluded that the basic bimodal alternans pattern of flight activity is a persistent property of the circadian oscillating system, which suggests that other activity rhythms involving flight are dependent on the same rhythm.
A Quantitative Study of the Ionic Basis of Extraneuronal Potential Changes in the Central Nervous System of the Cockroach (Periplaneta Americana L.)
Authors: Pichon Y. , Moreton R B. , Treherne J. E.
Published: April 2021

Measurements have been made of the extraneuronal potential changes produced by replacement of sodium ions with other organic and inorganic cations in the solution bathing isolated abdominal connectives. On the basis of the observed extraneuronal potential changes it is possible to arrange monovalent cations in the following sequence of effectiveness: It is concluded that the ionic dependence of the extraneuronal potentials is similar to that of a theoretical model system consisting of a perineurial diffusion barrier in series with a long, narrow channel representing the system of intercellular clefts connecting the inwardly facing surface of the perineurium with the extraaxonal fluid. On the basis of this model the effect of high external concentrations of, for example, potassium ions would be to depolarize the outwardly facing perineurial cell membranes. The considerable departure of the observed potentials from the values predicted by the Nernst equation can be accounted for in terms of the short-circuiting effect, due to the finite ionic permeability of the tight junctions between perineurial cells. Qualitative predictions can also be made concerning the rates of movement of potassium and sodium ions in the extracellular system.
Innervation of the Abdominal Intersegmental Muscles in the Grasshopper
Authors: Tyrer N. M.
Published: April 2021

Extracellular records from the motor neurones to the median internal dorsal muscles (abdominal intersegmental) of Melanoplus differentialis have been made simultaneously with intracellular records from the muscle fibres. Four types of PSP have been recorded intracellularly: type 1, a large PSP with a regenerative response and a small overshoot; type 2, a PSP of between 5 and 15 mV; type 3, a PSP of between 1 and 5 mV; type 4, a hyperpolarizing PSP of up to 5 mV. Although there is variation in the size of the spikes recorded en passant, the four types of PSP can generally be correlated with large, medium, small and very small spikes. Evidence is presented to demonstrate that there are two motor units for each type of PSP in the dorsal intersegmental muscles. Each muscle appears to have a mixture of muscle fibres of each unit. This is consistent with the anatomical finding of eight motor neurones supplying the muscles.