bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytoplasmic pH recovery in acid-loaded haemocytes of squid (Sepioteuthis lessoniana)
Authors: Heming T. A. , Vanoye C. G. , Brown S. E. , Bidani A.
Published: April 2021

Cytoplasmic pH (pHi) of haemocytes of bigfin reef squid (Sepioteuthis lesso-niana Lesson) was determined with the fluorescent probe, 2′,7′-biscarboxyethyl-5,6-carboxyfluorescein (BCECF). The pHi of haemocytes suspended in nominally HCO3−-free medium (extracellular pH 7.4) averaged (±S.E.) 7.32±0.02. Intracellular pH was independent of external Na+ concentration and varied only slightly with changes in extracellular pH (pHe) (ΔpHi/ΔpHe=0.16 over the pHe range 6.8–7.8). Addition of weak acids (sodium propionate, potassium acetate) to haemocyte suspensions resulted in a rapid decrease in pHi. Haemocyte pHi then recovered with an average half-time of 3–4 min. Recovery of pHi was independent of external Na+ concentration and insensitive to amiloride, but was abolished by N-ethylmaleimide (NEM). These results argue against the involvement of plasma membrane Na+/H+ exchange or other Na+-dependent transport mechanisms in the pHi recovery of acid-loaded haemocytes. The results suggest that there is an NEM-sensitive proton extrusion mechanism in the plasma membrane of squid haemocytes.
Modelling Muscle Power Output in a Swimming Fish
Authors: Altringham John D. , Johnston Ian A.
Published: April 2021

Intact, electrically excitable fibre bundles were isolated from the fast and slow myotomal muscle of the bullrout (Myoxocephalus scorpius L.). Power output was measured under conditions simulating their activity in a fish swimming at different speeds. Preparations were subjected to sinusoidal length changes of ±5% of resting length, and stimulated briefly during each cycle. The number and timing of stimuli were adjusted at each cycle frequency to maximise power output. Maximum power was produced at 5–7 Hz for fast fibres (25–35 W kg−1) and 2 Hz for slow fibres (5–8 Wkg−1). Under these conditions, pre-stretch of active muscle provides an important mechanism for storing potential energy for release during the shortening part of the cycle.
Backbone Mechanics of the Blue Marlin Makaira Nigricans (Pisces, Istiophoridae)
Authors: Hebrank John H. , Hebrank Mary R. , Long John H. , Block Barbara A. , Wainwright Stephen A.
Published: April 2021

Over most of its length, the backbone of the blue marlin, like that of all other istiophorids, contains enlarged and flattened neural and hemal spines and zygapophyses, all of which span the intervertebral joints. These plates of bone restrict dorso-ventral bending of the backbone but their arrangement permits a high degree of lateral flexion. The spines and zygapophyses also appear to be important in stabilizing the relatively large intervertebral joints against axial compression and lateral shearing during bending. Although bone is an elastic material, these overlapping structures are not arranged so as to contribute to elastic recoil of the backbone during normal swimming movements.
An Identified Set of Local Nonspiking Interneurones which Control the Activity of Abdominal Postural Motoneurones in Crayfish
Authors: Toga Tetsuo , Takahata Masakazu , Hisada Mituhiko
Published: April 2021

Several interneurones have been reported to be involved in the control of activity of abdominal postural motoneurones in crayfish (Miall and Larimer, 1982a; Larimer and Jellies, 1983). These interneurones are mostly interganglionic, except for two (each encountered only once) which are local (Jellies and Larimer, 1985). The two local interneurones were found to be nonspiking, as reported in a variety of motor control systems of arthropods (Siegler, 1985). In the abdominal posture system, however, it is still unknown to what extent this type of neurone participates in the control of motoneurone activity. In this study, we repeatedly encountered and identified a set of local nonspiking interneurones which could control the postural motoneurone activity in the same fashion in different preparations.
Discontinuous Turning Reaction during Escape in Soldier Crabs
Authors: Nalbach Hans-Ortwin
Published: April 2021

In many animals, the approach of an object is perceived visually and elicits an escape reaction (Dill, 1974). The escape is often aimed directly away from the threat. In some cases, however, the animal heads towards a nearby refuge, or another preferred place. Blue crabs, for instance, escape from the shore into deeper water (Woodbury, 1986). When ghost crabs are threatened while foraging far away from their burrow, they may change their heading erratically during escape in response to the visually perceived movement of the approaching object (Vannini, 1980). Soldier crabs (Mictyris longicarpus Latreille) face a similar problem because they live on estuarine mud flats and have no permanent burrows. They may react to an approaching person at a distance of 29–33 m, i.e. when the person has a vertical angular size of 2.2–3.2° at the eye of the crab. This illustrates the high vertical visual acuity across the acute zone of the ‘flat-world type crab’ Mictyris (Zeil et al. 1986). Usually, they can avoid being caught by ‘screwing’ themselves into the substratum with astonishing speed (Cameron, 1966). On hard substrata, however, they have to escape. Unlike ghost crabs (Burrows and Hoyle, 1973), soldier crabs are slow, with a maximum velocity of about 10 cm s−1. This may be a consequence of their habit - atypical of brachyurans - of walking exclusively forwards (Sleinis and Silvey, 1980). During escape, soldier crabs walk on a straight path away from the approaching object and usually change their direction only in response to changes of the approach direction of the threatening object. I observed that when one walks around a soldier crab on a circular path at some distance, it still walks along straight paths and changes direction by making abrupt turns from time to time.
Recovery of Chloride Uptake in Sea Wateradapted Rainbow Trout (Salmo Gairdneri) after Transfer to Fresh Water
Authors: Battram John C. , Eddy F. B.
Published: April 2021

The ability of rainbow trout (Salmo gairdneri Richardson) to acclimate to sea water or partially diluted sea water has been studied many times (Houston, 1959; Parry, 1960; Eddy and Bath, 1979; Prunet and Boeuf, 1985). However, the reverse transition from sea water (SW) to fresh water (FW) has been less well studied. The transition from a hyperosmotic medium to a hypo-osmotic medium reverses the burden on the osmoregulatory organs, i.e. the gills and the kidney. SW teleost fish normally show net salt (NaCl) efflux, whereas FW fish need to acquire salt from the medium. Recent work on salmon (Salmo salar) transferred from SW to FW (Talbot and Potts, 1989; Talbot et al. 1989; Potts et al. 1989) has described the changes in sodium balance, osmoregulation and renal function in adult and juvenile fish. Potts et al. (1985) showed that salmon are capable of taking up sodium immediately on transfer to FW. Chloride uptake via the gills of FW fish is of equal importance to sodium uptake, and the two ions are thought to be transported independently (Maetz and Garcia-Romeu, 1964). This paper examines the changes in chloride transport that occur during the transition from SW to FW.
Directional variant and invariant hearing thresholds in the rainbow trout (Salmo Gairdneri)
Authors: Schellart Nico A. M. , Buwalda Rob J. A.
Published: April 2021

The gas-filled bladder, the fish middle-ear analogue, transforms sound pressure (p) into pulsations, which generate displacement waves with body-fixed orientation that stimulate the nearby labyrinths. Moreover, in addition to this indirect stimulation, the otolith organs are stimulated directly by the particle motion vector (v) in line with the source. For pure tones the vector sum of both stimulations results in elliptical displacement orbits, which are nearly identical for left and right ears. We hypothesize that these orbits are centrally analysed, either by breakdown into the original, direct and indirect components, the segregation hypothesis, or by analysis of their characteristic form and orientation, the orbit hypothesis. This provides fish with spatial hearing. Analysing the orbit form and orientation would constitute an essentially monaural mechanism of directional hearing that should show strong and characteristic azimuthal anisotropies. To investigate these anisotropies we have studied the rainbow trout Salmo gairdneri psychophysically with respect to directional-detection and directional-masking paradigms involving heart rate conditioning. We employed superpositioning of standing waves in a large tank for total control of a probe signal and a narrow-band noise masker.

With a sinusoidal p and v probe and a p and v (omnidirectional) noise masker, or with a pure v probe and a (‘uni’directional) p noise masker, trout proved to be equally sensitive to all directions. Only when the indirect stimulation was mimicked by a v stimulus, were we able to demonstrate anisotropy. This indicates that trout indeed use the orbit lengths in the detection and masking tasks. The results can be explained if binaural convergence plays a role, under the assumption that left and right orbits differ appreciably. This might be the case if the divergence in orientation between the indirect stimulations reaching the right and left labyrinths were much larger than would be expected from the geometrical relationships between the two labyrinths and the swimbladder.
Control of optomotor responses by descending deviation detector neurones in intact flying locusts
Authors: Hensler K. , Rowell C. H. F.
Published: April 2021

Neural control of optomotor responses in Locusta migratoria was studied using a newly developed preparation of intact, tethered, flying locusts. The preparation could perform normal flight behaviour and head movements while neurones in the neck connectives were recorded and stimulated intracellularly.

Course deviations simulated by an artificial horizon caused optomotor reactions, e.g. steering by the wings (monitored as steering reactions in M97 and M127, first basalar muscles of fore- and hindwings, respectively) and compensatory head movements. Intracellular recordings were made from two identified descending deviation detector neurones, PI(2)5 and DNC. Both neurones coded direction specifically for course deviations. Electrical activation of either neurone in tethered flight at frequencies of up to 230 Hz elicited steering in M97 and M127 and head rolling with latencies of less than 20 ms. These reactions were of the same quality and strength as compensatory head rolling and steering in M97 and M127 following horizon rolling of about 40°. This demonstrates directly a role of PI(2)5 and DNC in course control.
Scaling of atp-supplying enzymes, myofibrillar proteins and buffering capacity in fish muscle: Relationship to locomotory habit
Authors: Somero G. N. , Childress J. J.
Published: April 2021

Pelagic fishes with an ability to swim in strong bursts have previously been shown to have large size-dependent increases (positive allometric scaling exponents) in the activities of glycolytic enzymes in white skeletal muscle. This scaling of glycolytic activity has been hypothesized to provide the anaerobic power supporting the size-independence of relative burst swimming speeds (body lengths s−1) in these fishes. This paper presents tests of several predictions of this hypothesis, using different-sized individuals of two pelagic teleosts, the kelp bass (Paralabrax clathratus) and the freshwater rainbow trout (Salmo gairdneri), and a flatfish, the Dover sole (Microstomus pacificus). In the two pelagic species, an increase in body size was accompanied by an increase in activities in white muscle (i.u. g wet mass of muscle−1) of lactate dehydrogenase (LDH), an indicator of potential for anaerobic glycolysis, and creatine phosphokinase (CPK), an enzyme that helps maintain stable ATP concentration during muscular activity. Activities of citrate synthase (CS), an indicator of the potential for aerobic metabolism, decreased with size. In the flatfish, activities of all enzymes in white muscle decreased with body size, a trend proposed to reflect lack of adaptive value of strong burst swimming ability in this benthic fish. Activities of LDH and CS were size-independent in brain of flatfish, indicating that the scaling patterns observed in the muscle of this species were related to muscle function, not to common, organism-wide changes with size. In white muscle of P. clathratus, total protein and soluble protein concentrations and buffering capacity increased with body size in parallel, but myofibrillar protein was size-independent. These results suggest that the capacity for anaerobically powered work and the maximal potential to generate force scale only modestly in relation to total body mass and therefore do not appear to be functionally related to the pattern of glycolytic scaling. Thus, these data support the hypothesis that the functional role of the strongly positive scaling of glycolytic enzymes in the white muscle of pelagic fish is to provide increased power during burst swimming in larger-sized fishes.
A vibration-sensitive descending statocyst interneurone in the crayfish Procambarus Clarkii
Authors: Nakagawa H. , Hisada M.
Published: April 2021

An interneurone specifically sensitive to substratum vibration was identified in the crayfish circumoesophageal connective. The interneurone, called B1 in this paper, received excitatory input from the statocysts on both sides. Electrical stimulation of the statocyst nerve elicited several spikes in the interneurone with latencies that depended on which side was stimulated. B1 responded phasically to artificial bending of the statocyst sensory hairs. The response was similar to that of the phasic-type receptor in the statocyst. The morphology of B1 was studied by an intracellular staining technique using nickel chloride and subsequent silver intensification. The interneurone projects its neurite arborization to the dorsal part of the deutocerebrum and parolfactory lobe on both sides, where the statocyst primary afferents also project. The overlapping of central projections, together with the properties of the response of B1; suggests that the interneurone receives excitatory input from the phasic-type receptors and transmits information about phasic body movement, but not static positional information, to the posterior ganglia. Branches of B1 also project to the antennal and tegumentary lobes ipsilateral to the axon. B1 may receive additional mechanosensory information from the cuticular sensory hairs on the antennae and the cephalic body surface.
The Effect Of Iodoacetate On The Electrical Potential And On The Oxygen Uptake Of Frog Skin
Authors: Francis W. L. , Gatty O.
Published: April 2021

The relationship between the maintenance of the electrical potential difference across frog skin and the oxygen consumption of the skin has been investigated by Mansfield (1910), Lund (1925, 1926, 1928), Lund & Moorman (1931), Francis & Pumphrey (1933), Francis (1933, 1934), Taylor (1935), Boell & Taylor (1933), and Ponder & Macleod (1937). These workers investigated the effects of varying temperatures and varying concentrations of cyanide, oxygen, sulphide, carbon monoxide, butyl alcohol, amyl alcohol, and of various carbamates. The objective of the present work has been to use the somewhat more specific respiratory inhibitor iodoacetate to trace further the oxidative biochemistry of frog skin in so far as it is concerned with the maintenance of the electrical potential difference and to be able to cover all statements made by adequate tests of statistical significance and thereby to eliminate troubles arising from the variability of the skins.
Experimental Studies On The Sexual Cycle Of The South African Clawed Toad (Xenopus Laevis). II
Authors: Bellerby C. W.
Published: April 2021

When maintained at an optimum nutritional level both sexes of the South African clawed toad (Xenopus laevis) grow at a normal rate in the complete absence of light, or after removal of the eyes. No detectable atrophic changes take place in the ovaries and testes of eyeless animals after 18 months or in the gonads of male and female toads kept in absolute darkness for 7 months. No evidence is provided by the experiments to show that light is essential for the maintenance of reproductive activity in X. laevis or that seasonal variation in light intensity or wave-length plays any part in the control of the sexual cycle under natural conditions.
The Functioning of the Giant Nerve Fibres of the Squid1
Authors: Young J. Z.
Published: April 2021

Stimulation of single giant nerve fibres in the stellar nerves of the squid (Loligo pealii) shows them to be motor axons which produce contraction of the circular fibres of the mantle muscles. When a stellar nerve is stimulated with condenser discharges a maximal response is obtained at threshold voltage. No increase of response is obtained by further increase in the strength of stimulation except for an occasional slight increase at about ten times threshold voltage probably due to repetitive firing. It therefore appears that the stimulus produces a single impulse in the giant fibre, and that this is capable of exciting contraction in all the muscle fibres which it reaches. This confirms the conclusion reached on histological grounds that in spite of their syncytial nature each of the giant nerve fibres is a single functional unit. Since there are about ten giant fibres on each side the mantle is divided into 20 neuromotor units, each nerve fibre innervating an enormous number of muscle fibres. The existence of these units can also very readily be demonstrated by the fact that threshold electrical stimulation at any point within the territory innervated by each single giant fibre sets up a contraction of the muscle fibres of all parts of the territory with which the stimulated area is in connexion through the nerve. Stimulation of the smaller fibres in a stellar nerve after destruction of the giant fibre also causes contraction of the circular muscles of the mantle. The amount of this contraction increases progressively with increased voltage, presumably on account of the stimulation of more and more nerve fibres. The maximum tension developed in this way is always very much less than that produced by stimulation of the giant fibres. The mantle is therefore provided with a double mechanism of expiratory contraction, maximal contractions being produced by single impulses in the giant fibres and graded contractions by those in the smaller fibres of the nerve. Presumably the former contractions are those involved in rapid movement, the latter in respiration. There are also radial muscles, running through the thickness of the mantle, whose contractions effect the inspiration by making the cavity larger.
The Effect of Testis Hormone on the Preservation of Sperm Life in the Vas Deferens of the Fowl
Authors: Munro S. S.
Published: April 2021

As a result of the suggestion by Crew (1922), verified by Fukui (1923 a, b, c) and also independently by Moore and his associates (Moore, 1924 a, b; Moore & Chase, 1923; Moore & Oslund, 1924), the scrotum is now known to act essentially as a thermoregulator, the duty of which is to maintain a physiologically optimum temperature for testis function. Moore & Quick (1924) have shown that the temperature of the scrotum in various laboratory rodents is from 1 to 7° C. below peritoneal temperatures; and Fukui, and Moore and his collaborators, as quoted above, have shown conclusively that the mammalian testes do, in fact, require to be maintained at temperatures lower than those of the body in order to carry to completion their function of germ cell differentiation. If the temperature of the scrotum is experimentally raised to that of the body, the germinal epithelium shows rapid, and eventually complete, degeneration and the resulting atrophic testes consist of connective and interstitial tissue with very little but Sertoli cells discernible within the tubules. The sensitivity of germinal tissue to heat is extended to the mature spermatozoon since Heller (1929) found that sperm in the scrotal epididymis will live for 65 days, whereas this period is reduced to 14 days when the epididymis is elevated into the abdomen. Further, the very short life of mammalian sperm in the reproductive tract of the female, usually a matter of hours (for review see Hartmann, 1932), is presumably due also to the destructive action of heat.
On Galvanotropism and Oscillotaxis in Fish
Authors: Harreveld A. Van
Published: April 2021

A spinal fish bends with the concave side towards the anode in a D.C. field of transverse direction. This reaction, which lasts as long as the current passes, is shown to be a reflex (galvanotropic reflex). Other manifestations of this reflex have been found. In a field of dorso-ventral direction the animal is bent in the sagittal plane towards the anode. The unrest of body and tail in an ascending field in the longitudinal direction of the fish may be caused partly by the same reflex. The same reflex has also been found in some of the fin muscles. The structures (sensory end-organs) stimulated during the galvanotropic reflex are situated in the muscles (or tendons).

Galvanotropism has been demonstrated in fish in which the labyrinths and the lateral-line organs have been eliminated by the transection of their nerves.

The mechanism of galvanotropism is discussed and this phenomenon is found to be based on the galvanotropic reflex and the ability of the animal to swim.

A fish placed at 45° to the current lines in an A.C. field shows a curving of the body and tail. This is explained by the wedge shape of the fish body and tail, by which the two sides of the animal have a different angle with the current lines, and thus are differently stimulated. The mechanism of oscillotaxis is discussed in relation to this reaction.
The Respiration of Nematodes of the Alimentary Tract
Authors: Davey D. G.
Published: April 2021

Because of their peculiar habitat, tacitly assumed to have an oxygen content small enough to be negligible, the metazoan parasites living in the alimentary canal of various animals have long been the subjects of respiratory studies. The work of the earlier investigators reached its culmination in Weinland’s animal fermentation theory, put forward to explain the anaerobic existence of Ascaris lumbricoides and A. megalocephala. The fundamentals of the theory are embodied in the well-known equation
The Effect of Carbon Monoxide on the Oxygen Consumption of Drosophila Melanogaster Pupae
Authors: Wolsky Alexander
Published: April 2021

The aim of these investigations is a study of the effect of carbon monoxide on developmental processes in Drosophila. Such a study involves, of course, a determination of the carbon-monoxide action in a quantitative manner, and for this purpose it seemed to be most suitable to undertake a study of the oxygen uptake in different pupal stages, first under normal conditions and then in various mixtures of oxygen and carbon monoxide.
The Regulation of Osmotic Pressure and Chloride Concentration in the Haemolymph of Mosquito Larvae
Authors: Wigglesworth V. B.
Published: April 2021

In an earlier paper (Wigglesworth, 1933b) it was shown that the cuticle of the mosquito larva Aedes aegypti (= argenteus) is permeable to water only at the anal papillae, and that water is taken in continuously by these organs and excreted by the Malpighian tubules; observations which were confirmed by Pagast (1936). But a more important function of the anal papillae has recently been made clear by Koch (1938), who has shown that in larvae of Chironomus and Culex they absorb chloride ions. They are able to take up chloride from very dilute solutions (0·001 M) and behave in this respect like the skin of frogs and other fresh-water animals as demonstrated by Krogh (1937).
The Control of Photo-Pigmentary Responses in Eyeless Catfish
Authors: Wykes Ursula
Published: April 2021

In common with certain other teleosts and lacertilians, eyeless Amiurus nebulosus and Fundulus heteroclitus show a pigmentary response to changes in intensity of illumination. The melanophores contract in the darkness and expand in bright light. The control of this photic response was investigated in Amiurus. The contraction in darkness was not obtained in areas denervated by section of spinal nerves nor in the posterior part of the body after section of the cord. The response is therefore under the control of nervous reflexes passing through the brain. A similar melanophore contraction can be obtained by electrical stimulation of the cord at extremely low frequencies. The response remained in pinealectomized animals. Photoreceptors may possibly be located in the skin or the wall of the diencephalon may be sensitive to light. After hypophysectomy the response continues but the degree of melanophore expansion in bright light is diminished. The expanding hormone of the pituitary is therefore important in that it augments a melanophore response which is under nervous control.
The Oxygen Affinity of Haemoglobin in Splenectomized Bullfrogs
Authors: Mccutcheon F. H.
Published: April 2021

Evidence obtained from previous studies suggests that one of the factors which influence the affinity of amphibian haemoglobin for oxygen is the locus of erythrocyte formation (Barcroft, 1934; Hall, 1934). It has been shown for the developing bullfrog (McCutcheon, 1936), and also for different species of the class Amphibia (McCutcheon & Hall, 1937), that the oxygen dissociation curve shifts from left to right depending upon the extent to which the specimen is aquatic, semiaquatic, or terrestrial.
Studies in Reptilian Colour Changes
Authors: Kleinholz L. H.
Published: April 2021

Anolis becomes dark brown on a light-absorbing background and bright green on a light-dispersing background, the changes being accomplished by a dispersion or concentration of pigment within melanophores. Blinded lizards lose the ability to respond to changes in backgrounds, but become brown when in light and green when kept in darkness. Hypophysectomy results in permanent pallor. The brown colour can be temporarily elicited in such lizards by injection of appropriate extracts of the pituitary gland. Denervated regions of skin undergo normal colour changes. Electrical stimulation of hypophysectomized lizards evokes a mottled pattern. Mottling is under hormonal and not under nervous regulation.
Studies in Reptilian Colour Changes
Authors: Kleinholz L. H.
Published: April 2021

Melanophore contraction is not effected through a direct nervous agency, nor are the adrenal glands normally necessary to mediate the light state. The concentrated state of melanophore pigment is ordinarily due to the disappearance of the melanophore-dispersing hormone from the circulation. The rapid onset of pallor which follows electrical stimulation may be due to a vasoconstrictor effect. Intact skin in hypophysectomized lizards does not respond directly to light, but isolated skin darkens slightly in bright sunlight and becomes bright green again in diffuse light. Isolated skin responds to hormones, becoming generally dark in solutions of pituitary extract and showing the mottling reaction in solutions of adrenalin.
The Dynamics of Quadrupedal Walking
Authors: Manter John T.
Published: April 2021

The cat was used as a representative quadruped for a study of the action of the locomotor apparatus in walking. In the analysis the body was considered as being made up of eleven parts behaving in such a fashion that they could be considered as rigid bodies. The weight of each part was determined, the position of its centre of gravity and also its moment of inertia. Moving pictures were taken of the cat walking over a specially constructed platform which recorded the pressure exerted by each foot during the stride. The photographs recorded the position of the various parts of the body at successive instants. These records were analysed in terms of displacement, velocity and acceleration of the centre of gravity of the body as a whole, and also of its parts.

A comparison of vertical forces acting on single limbs of the cat during the walk shows that the reactions are greater on the forelimbs. This is not only due to the location of the centre of gravity nearer the forelimbs, but also is the result of a thrust produced at the forelimb which is largely responsible for an upward acceleration of the centre of mass of the body. Horizontal forces produced at the forefeet also tend to be greater than those at the hind. When horizontal impulse over the whole step is considered, it is shown that the forelimbs produce more retarding action, while the hindlimbs contribute more forwarding impulse to the body. The arrangement of steps is such that horizontal reactions on fore- and hindlimbs are antagonistic, thus damping fluctuations in horizontal acceleration and velocity of the centre of gravity with a probable saving in energy expenditure.

The kinetic energy of the body, derived from the data of the mass and velocity of separate parts, maintains an average level but undergoes cyclical changes during the stride. A possible transfer into gravitational potential energy can account for only a part of these kinetic energy changes which are thought to involve muscle action.

An analysis of the relationship between muscle forces about the joints and forces of reaction which co-operate to produce the recorded movement of an individual segment of the limbs allows the calculation of the resultant muscle torque acting on that segment. This provided actual measurements for the total muscle torque about each of the joints of the limbs at any instant. Correlation of these torques with the action of definite muscle groups indicates roughly the manner in which these muscles function in quadrupedal walking.
The Temperature and Humidity Relations of the Cockroach
Authors: Gunn D. L. , Cosway C. A.
Published: April 2021

In a diffusion gradient of humidity at uniform temperature, some cockroaches (Blatta orientalis, L.) show a tendency to spend more time in the drier region. Other individuals appear to be indifferent to the stimulus of air humidity. On desiccation, there is a tendency for cockroaches to become hygro-positive. In a temperature gradient, those individuals which react to humidity have a slightly but significantly higher preferred temperature in somewhat moist air than they have in dry air. It seems, then, that the observed preferred temperature represents a kind of balance between a pure temperature reaction and a humidity reaction. The change in humidity reaction resulting from desiccation is qualitatively satisfactory to explain the fall in preferred temperature which occurs at the same time.
Bite-to-bite variation of muscular activity in cats
Authors: Gans Carl , Gorniak Gerard C. , Morgan William K.
Published: April 2021

Changes in electromyographic (EMG) activity between successive bites in the jaw-closing muscles of cats are described for the reduction of food with different textures. Plots of these data suggest, and statistics confirm, that one cannot predict the magnitude of EMG activity from one bite to the next, but that predicting the direction of change in EMG activity (i.e. increases or decreases) may be possible, given the relative magnitude of a bite. The patterns observed also show that the degree of variability between masticatory cycles differs among the jaw-closing muscles and with food texture. These patterns of muscle activity are related to the neural control of jaw movements.
Nonspiking Pathways in a Joint-control Loop of the Stick InsectCarausius Morosus
Authors: Büschges Ansgar
Published: April 2021

In the stick insect Carausius morosus (Phasmida) intracellular recordings were made from local nonspiking interneurones involved in the reflex activation of the extensor motoneurones of the femur-tibia joint during ramp-like stimulation of the transducer of this joint, the femoral chordotonal organ (ChO). The nonspiking interneurones in the femur-tibia control loop were characterized by their inputs from the ChO, their output properties onto the extensor motoneurones and their morphology. Eight different morphological and physiological types of nonspiking interneurones are described that are involved in the femur-tibia control loop. The results show that velocity signals from the ChO are the most important movement parameter processed by the nonspiking interneurones. Altering the membrane potential of these interneurones had marked effects on the reflex activation in the extensor motoneurones as the interneurones were able to increase or decrease the response of the participating motoneurones. The processing of information by the nonspiking pathways showed another remarkable aspect: nonspiking interneurones were found to process sensory information from the ChO onto extensor motoneurones in a way that seems not always to support the generation of the visible resistance reflexes in the extensor tibiae motoneurones in response to imposed flexion and extension movements of the joint. The present investigation demonstrated interneuronal pathways in the joint-control loop that show ‘assisting’ characteristics.
Blood Respiratory Properties and the Effect of Swimming on Blood Gas Transport in the Leopard Shark Triakis Semifasciata
Authors: Lai N. Chin , Graham Jeffrey B. , Burnett Louis
Published: April 2021

Changes in vascular pressures, blood respiratory properties and blood gas transport induced by swimming were investigated in the leopard shark Triakis semifasciata (Girard). In resting sharks, the mean ventral and dorsal aortic pressures (systolic/diastolic) were 6.8/5.6 kPa and 4.5/3.9 kPa, respectively, and only the former were increased significantly during swimming. Swimming also caused a significant decline in venous , (1.6 to 0.9kPa), O2 content (0.9 to 0.4 mmol l−1) and percentage O2 saturation (, 39 to 18%) but the arterial variables were not affected. A significant decline in venous pH and an increase in venous also occurred during swimming but lactate concentration did not increase during or after swimming. An in vivo dissociation curve compiled from blood and data for sharks in the resting, swimming and post-swimming recovery phases shows a mean P50 of 2.04 kPa, as determined by Hill transformation. The pH-bicarbonate plot for this fish shows a weak blood buffer capacity of 9.3 mmol I−1 pH unit−1 and during swimming the average blood pH and bicarbonate concentration follow the buffer line which was not compensated in recovery. Neither oxygenated nor deoxygenated blood pH values were affected by CO2 equilibration, suggesting the absence of a Haldane effect. Thus, at the expense of respiratory acidosis, Triakis can aerobically sustain long (up to 60 min) and moderately intense (0.45 Ls−1, where L is body length) periods of swimming by increasing cardiac output and tapping its venous reserve.
Ionic Basis of Membrane Potential and of Acetylcholine-Induced Currents in the Cell Body of the Cockroach Fast Coxal Depressor Motor Neurone
Authors: David Jonathan A. , Sattelle David B.
Published: April 2021

The ionic basis of the resting potential and of the response to acetylcholine (ACh) has been investigated in the cell body membrane of the fast coxal depressor motor neurone in the metathoracic ganglion of the cockroach Periplaneta americana. By means of ion-sensitive microelectrodes, intracellular concentrations of three ion species were estimated (mmol l−1): [K+]i; 144±3; [Na+]j, 9±1; [Cl ],, 7±1. The resting potential of continuously superfused cells was –75.6±1.9mV at 22°C. A change in resting potential of 42.0±2.5mV accompanied a decade change in [K+]o. Experiments with (10−4mol l−1) ouabain, Na+ injection, low temperature (10°C) and non-superfused cells indicated the presence of an electrogenic sodium pump.

Under current-clamp, the cell body membrane was depolarized by sequentially applied, ionophoretic pulses (500ms duration) of ACh. Under voltage-clamp, such doses of ACh resulted in an inward current which was abolished in low-Na+ saline. Ion-sensitive electrodes revealed an increase in [Na+]i but no change in [Cl”]i in response to externally applied ACh. The ACh-induced current-voltage relationship was shifted in a negative direction by low-K+ saline. The ACh-induced inward current was usually followed by a delayed outward current which reversed at EK. Low-K+ saline had the same effect on this outward component as depolarizing the membrane. This suggests that the outward current component is carried by K+.

The ACh-induced inward current and the delayed outward current were potentiated either when [Ca2+]i was lowered by injecting the calcium chelator BAPTA or by exposure of the cell to low-Ca2+ saline. High-Ca2+ saline reduced the inward component of the response and produced a negative shift in the ACh-induced current-voltage relationship. The amplitude of the delayed outward current was enhanced initially and then depressed when the cell was exposed to high-Ca2+ saline.

The ACh-induced current in this neuronal cell body appears to be carried by Na+, K+ and, to a lesser extent, Ca2+. It is suggested that the delayed outward component is due to a combination of (i) Ca2+ entering the cell and activating a K+ conductance and (ii) Na+ entering the cell and stimulating the Na+/K+ pump. Ca2+ appears to regulate the permeability of the ACh-receptor-operated ion channel. Reducing the level of intracellular or extracellular Ca2+ increases the ACh-induced current. Possible mechanisms are discussed.
Salinity-induced Changes in Branchial Na+/K+-ATPase Activity and Transepithelial Potential Difference in the Brine ShrimpArtemia Sauna
Authors: Holliday Charles W. , Roye David B. , Roer Robert D.
Published: April 2021

Silver staining of the adult brine shrimp, Artemia salina, revealed that only the metepipodites of the phyllopodia were significantly permeable to chloride and/or silver ions. The metepipodites stained in a reticulated pattern, possibly indicating areas in the cuticle over cells specialized for chloride secretion. Crude homogenates of metepipodites had very high Na+/K+-ATPase enzyme specific activity (ESA) which increased in proportion to the salinity of the external medium and, thus, in proportion to the need for outward salt transport in these strongly hypo-osmoregulating animals. Metepipodite ESA as a percentage of whole-body ESA increased from 7·6% in 50% sea water (SW) to 25·0% in 400% SW. Gut and maxillary gland also had high Na+/K+-ATPase ESAs, implicating these organs in osmoregulatory processes as well. The time courses of increases in phyllopodial and gut ESAs in brine shrimps transferred from 100% SW to 400% SW are consistent with the induction of new Na+/K+-ATPase; 4–7 days was required for significant increases to occur. Haemolymph ion analyses and transepithelial potential differences, measured in brine shrimp acclimated in all the SW media, indicate that chloride is actively transported out of the brine shrimp while sodium is very close to electrochemical equilibrium across the body wall. Thus, the metepipodites of the brine shrimp appear to possess cells with many functional similarities to the teleost branchial chloride cells.
The effect of appendage and scale loss on instar duration in adult firebrats,Thermobia domestica(Thysanura)
Authors: Buck C. , Edwards J. S.
Published: April 2021

The loss of appendages immediately following a moult shortens the subsequent intermoult interval in adult Thermobia domestica. The loss of increasing numbers of appendages accelerates the ensuing moult incrementally. Leg amputation at sites distal to the trochanter-femoral autotomy plane has comparable effects in accelerating the moult. Functional legs regenerated at the first moult following amputation are at least 80% of normal length, while abdominal cerci are regenerated at a slower pace, attaining about 20% of normal length at the first post-operative moult. Scale loss also causes an acceleration of the following moult. It is proposed that changes in diffuse sensory input, rather than specific proprioceptive feedback, mediate the acceleration of the moult cycle.
The relationship between body mass and rate of rewarming from hibernation and daily torpor in mammals
Authors: Geiser F. , Baudinette R. V.
Published: April 2021

Rewarming rate from torpor and body mass were inversely related in. 86 mammals ranging in body mass between 2 and 8500 g. Most of the mammalian taxa investigated showed a similar change of rewarming rate with body mass. Only the insectivores showed a more pronounced increase in rewarming with a decrease in body mass than did the other taxa. The rates of rewarming of marsupials were similar to those of placentals. At low air temperature (Ta), the rate of rewarming of marsupials was not related to body mass, although a strong relationship between the two variables was observed in the same species at high Ta. The slopes relating rewarming rates and body mass of the mammalian groups and taxa analysed here were similar to those obtained earlier for mass-specific basal metabolic rate (BMR) and body mass in mammals, suggesting that the rate of rewarming and BMR are physiologically linked.
Patch-clamp Study of the Properties of the Sodium Current in Cockroach Single Isolated Adult Aminergic Neurones
Authors: Lapied Bruno , Malécot Claire O. , Pelhate Marcel
Published: April 2021

The properties of the fast Na+ inward current of the aminergic neurosecretory dorsal unpaired median (DUM) cells isolated from the sixth abdominal ganglion of the cockroach Periplaneta americana were studied with the whole-cell clamp technique in the presence of Ca2+ and K+ channel blockers. In about 80% of the cells, the current activated at –35 mV, was maximal at –10 mV and reversed at +48mV (Vrev), very close to VNa, the equilibrium potential for Na+ (+47.9mV). Vrev followed VNa when the external Na+ concentration was varied and the current was entirely suppressed by 1.0×10−7mol l−1 saxitoxin (STX), indicating that it was carried by Na+. In the remaining cells, an STX-sensitive maintained current was observed, the peak current–voltage relationship having almost the same characteristics except that an additional small shoulder was present between –90 and –35 mV, suggesting the existence of two types of Na+ channels. Na+ channels were half-inactivated at –41.1 mV and half-activated at –25.8mV. The overlap of inactivation (h∞) and activation (m∞) parameters was important (–70 to + 10mV). h∞ was not well fitted by a single Boltzmann distribution for potentials more negative than –70mV, indicating more than one process of inactivation. The half-times of activation and of inactivation of the Na+ current were voltagedependent, strongly decreasing with increasing pulse amplitude. The time courses of both inactivation and recovery from inactivation were best described by the sum of two exponentials. The two components of inactivation did not contribute equally to the decay of the current; the fast component accounting for more than 90% of the inactivation at positive potentials. Taken together, the results suggest that the Na+ channels of DUM neurones have more than one open state and/or more than one inactivated state.
Do Cicadas Radiate Sound through their Ear-Drums?
Authors: Young David
Published: April 2021

Sound output was investigated in males of two cicada species, Cyclochila australasiae Donovan and Macrotristria angularis Ståhl. These are large insects, about 4·5 cm in length, with a typical arrangement of sound-producing organs. Songs produced by both species consist of continuous trains of sound pulses, with a fundamental frequency close to 4 kHz. Higher harmonics fall below the 4 kHz peak by 20–30 dB. These songs are the loudest yet recorded among insects: 110 dBSPL at 20cm for the protest songs of both species, and values as high as 115 dB for the vigorous calling songs of C. australasiae (mean 113 dB). The male tympanum (ear-drum) is between 3·3 (M. angularis) and 5·5 (C. australasiae) times greater in area than that of the female, which does not sing. The tympana and folded membranes, as well as the sound-generating tymbals, vibrate vigorously during singing; other parts of the insect do not vibrate. Sound output is greatest at the gap between the tympana and their protective coverings, the opercula. High values are also found close to the tymbals but not over the rest of the body. When the gap between tympana and opercula is held closed, rather than open, sound output falls by 11 dB. In the field, calling males adopt a characteristic posture, which keeps this opercular gap wide open. Ablating the tympana makes no difference to the sound output. But ablating the posterior half of the abdominal air sac produces a mean fall of 8.6 dB, together with a great broadening of the song’s frequency content. The above results support the conclusion that the majority of sound is radiated through the tympanal opening in typical cicadas, with the tympana being driven passively by the resonant vibrations of air in the air sac. This system can be modelled as a Helmholtz resonator, with the tympanal opening representing the neck of the resonator.
Scaling Effects on Muscle Function: Power Output of Isolated Fish Muscle Fibres Performing Oscillatory Work
Authors: Altringham John D. , Johnston Ian A.
Published: April 2021

Bundles of 3–10 live fast fibres were isolated from the abdominal myotomes of cod (Gadus morhua L.) 13–67 cm in length. The preparations performed work under conditions simulating their activity during swimming: sinusoidal length changes were imposed about in situ fibre length, and the fibres were stimulated at a selected phase in each cycle. Strain amplitude, and the number and timing of stimuli were chosen to give maximum power output over a wide range of cycle/tailbeat frequencies. For each preparation power output was maximal at a particular frequency, although the peaks were rather broad. As the size of the fish increased the cycle frequency for maximum power output (fopt) decreased, from 12.5 Hz (13 cm fish) to 5 Hz (67 cm fish) (fopt=1.67 L−0.52, where L is body length).
Electrolyte and Gas Exchange During the Moulting Cycle of a Freshwater Crayfish
Authors: Wheatly Michele G. , Ignaszewski Lori A.
Published: April 2021

Whole-animal net electrolyte fluxes (Ca2+, apparent H+, titratable acidic equivalents, ammonia, Na+, Cl−, K+, Mg2+, phosphate and sulphate) and respiratory gas exchange were monitored throughout the moulting cycle in juvenile freshwater crayfish Procambarus clarkii (Girard) at 21 °C. Intermoult crayfish were essentially in ion balance. As crayfish approached ecdysis (–3 days, where t=0 is the day when the cuticle is shed), there was a net efflux of Ca2+ (–1000μmol kg−1 h−1) correlated with a corresponding uptake of acidic equivalents (or base output) of +2000 μmol kg−1 h−1. Following ecdysis, both fluxes switched vector; uptake of Ca2+ (+2000/mol kg−1 h−1) and basic equivalents (+4000μmol kg−1 h−1) were completed within 6 days. The moulting cycle also affected fluxes of electrolytes other than those involved in CaCO3 resorption and deposition. Crayfish remained in Na+ and Cl− balance from intermoult up to ecdysis. Following ecdysis, both were taken up actively at rates of around +500μmol kg−1 h−1 for 3 days, presumably restoring the haemodilution that would have resulted from water loading. A premoult efflux of K+ was partially offset by postmoult uptake. Meanwhile, crayfish experienced increased efflux of phosphate following ecdysis, probably because of increased integumentary permeability. Rates of O2 uptake and CO2 excretion increased to peak values (double intermoult rates) immediately prior to ecdysis. While recovered during postmoult, dropped precipitously, significantly reducing the gas exchange ratio. Since the deficit agreed well with the postmoult basic equivalent uptake, the latter is probably attributable to HCO3− uptake for calcification.