bluuebunny/crossref_metadata_2025 huggingface dataset:
Central patterning and reflex control of antennular flicking in the hermit crab Pagurus alaskensis (Benedict)
Authors: Snow P. J.
Published: April 2021

The effects of altering sensory input on the motoneuronal activity underlying antennular flicking have been tested. Removal of the short segments of the outer flagellum results in a reduction of the number of spikes/burst in the fast flexor motoneurones A31F and A32F. During a flick the delay between the burst in motoneurone A31F and the burst in motoneurone A32F is insensitive to alteration of sensory input. Sensory feedback from the flexion phase of a flick is necessary for the activation of either extensor motoneurone. Evidence is presented to suggest that this feedback is primarily from joint-movement receptors at the MS-DS and DS–OF joints. The results are incorporated into a model in which the patterns of flexor activity result from some specified properties of three components: a trigger system, a follower system, and the spike initiating zone of the flexor motoneurones. The trigger system determines when a flick will occur. The follower system determines the number of flexor spikes during a flick. Properties of the spike initiating zone determine the spike frequency and the timing between bursts in the flexor motoneurones. Extensor activity in the model is reflexively elicited by feedback from phasic, unidirectional receptors sensitive to joint flexion. The functional significance of reflex control of extensor activity is discussed in relation to the form and proposed function of antennular flicking. It is suggested that this form of control is adapted to the function of antennular flicking because flexion at the MS-DS joint is not always necessary for the fulfilment of the function of a flick.
Oxygen consumption, ventilatory frequency and heart rate of lampreys (Lampetra fluviatilis) during their spawning run
Authors: Claridge P. N. , Potter I. C.
Published: April 2021

The standard rate of oxygen consumption, ventilatory frequency and heart rate of adult Lampetra fluviatilis were measured during the light phase of the photoperiod and at times corresponding to various stages in the upstream migration. All three parameters increased during the spawning run but only in mature individuals were significant differences found between the sexes. The regression coefficients for the logarithmic relationship between oxygen consumption and body weight of immature animals were 0·912 and 0·925 at 9·5 and 16 °C respectively. Both the standard rate of oxygen consumption and the amount of oxygen taken up during activity increased greatly during the hours of darkness. Oxygen consumption, ventilatory frequency and, to a lesser extent, heart rate increased significantly at 9·5 °C over the 100–20% range of saturation with air. Below 20 % saturation with air, lampreys no longer remained attached by their oral disc for prolonged periods and the ventilatory frequency rose even more rapidly to reach a maximum of 175 beats/min at 12·5 %. Exposure to 7·5 % resulted in death within 5–8 h.
A technique for repeated sampling of the blood of individual resting fish
Authors: Soivio A. , Nynolm K. , Westman K.
Published: April 2021

A dorsal cannulation technique is described. It has been employed for repeated blood sampling in unanaesthetized rainbow trout (Salmo gairdneri) kept singly in special receptacles described in the paper. The level of the studied haematological parameters (Haematocrit, Hb, glucose, lactate, K+, Na+, Ca2+) differed between fish kept in receptacles for 1 week and free-swimming fish, most probably owing to differences in the motility of the fish. The receptacle seems to minimize visual and handling disturbances, and permits both the standardization of experimental conditions and quick and easy sampling via the dorsal aorta cannula. The general variation in the blood parameter values was very small compared with the previously reported variation in such values for rainbow trout.
Patterns and bilateral coordination of scaphognathite rhythms in the lobster Homarus americanus
Authors: Wilkens J. L. , Young R. E.
Published: April 2021

The bilateral patterns of forward and reversed scaphognathite (SG) pumping are described for the American lobster. During forward pumping the two SGs usually function synchronously, but may also function independently. The nine muscles of one SG are arranged into four functional groups which are sequentially active during forward pumping. During reversed beats, motor neurones to one group of muscles are inactive while bursts to another are either delayed or missing. Reversal beats do not appear to alter the phasing of thec entral oscillators that generate the basic SG rhythm.

Phase analysis of bilateral SG beating demonstrates two types of relationship : phase coupling or phase drifting with a tendency to couple. An animal may remain in one state for long periods of time or may alternate between states. Coupling can occur at more than one phase indicating phase multistability. The coupled state may remain constant at markedly different frequencies of beating, indicating phase rather than latency coupling between SGs. During the drifting state each SG tends to assume its ‘intrinsic’ rate of oscillation. The drift state reflects the inherent asymmetry of the two SG systems. The influence of several parameters of sensory stimulation on phase and frequency of SG beating are analyzed.
Micropuncture study of the renal responses of the urodele amphibian Necturus maculosus to injections of arginine vasotocin and an anti-aldosterone compound
Authors: Garland H. O. , Henderson I. W. , Brown J. A.
Published: April 2021

Necturus maculosus kidney function has been examined using standard clearance techniques and renal tubular micropuncture methodology. Throughout, cyanocobalamin (vitamin B12) has been used to monitor glomerular filtration rate (GFR) and tubular water movements. It was established that this substance was handled by the Necturus kidney in a similar manner to inulin. It can be readily analysed, together with renal electrolytes, by electron microprobe techniques. Profiles of transtubular gradients (TF:P ratios) along the nephron were established for osmolarity, sodium, potassium, calcium and cobalt (of cyanocobalamin). Ureteral urine is always hyposmotic with respect to plasma and the site of dilution of the plasma ultrafiltrate is within the distal segment. Up to 30 % of the filtrate is isosmotically reabsorbed along the proximal tubule ; the tubular fluid : plasma ratio for osmolarity and sodium is around 1, and the TF : P for cobalt of cyanocobalamin is about 1·4 by the end of this segment. The renal effects of the neurohypophysial hormone arginine vasotocin (AVT) and an aldosterone antagonist (SC14266; Soldactone) have been examined. AVT was consistently antidiuretic causing both a decreased GFR and an enhanced distal tubular reabsorption of water. SC14266 also increased distal tubular reabsorption of water. Such an effect differs from that found in higher vertebrates, and may indicate a ‘glucocorticoid-type’ of renal action for aldosterone in amphibians.
Potassium exchange between bathing solution and midgut of Hyalophora cecropia and time delay for potassium flux through the midgut
Authors: Zerahn K.
Published: April 2021

Exchange between potassium of the isolated midgut of the American silkworm Hyatophora cecropia and the bathing solutions has been determined by different authors, but with contradictory results. Therefore the experiments were repeated with another technique and the exchange determined for varying time intervals. It was found that the exchange was fast -half of the midgut K was exchanged in 2–3 minutes, which confirms the earlier findings by Harvey & Zerahn (1969).
Electrophysiological analysis of potassium and sodium movements in crustacean nervous system
Authors: Abbott N. J. , Moreton R. B. , Pichon Y.
Published: April 2021

An electrophysiological method was used to estimate the half-times for sodium and potassium entry to, and efflux from, the extra-axonal space in peripheral nerve and central nervous connectives of two species of crustacean. Results from crab (marine) and crayfish (fresh water) were qualitatively similar. Peripheral nerve showed no evidence for diffusion barriers, potassium entry and efflux being rapid, and proceeding at comparable rates. In connective, potassium entry was extremely slow, with a half-time greater than 100 min, while potassium efflux was relatively rapid . Sodium movements were less restricted, but sodium entry was more rapid than sodium efflux. The potassium experiments were compared with the behaviour of a theoretical model system. Evidence is presented for diffusional restriction to potassium at the connective perineurial layer. The mechanism of restriction may involve changes in permeability or activation of an ion pump in the perineurial layer. The physiological significance of these findings is discussed.
Active transport of potassium by the Cecropia midgut; tracer kinetic theory and transport pool size
Authors: Wood J. L. , Harvey W. R.
Published: April 2021

Tracer influx kinetics have been analysed theoretically to determine the size of the transport pool with no assumptions regarding the transport pathway. For a calculation of the size of the transport pool to be made, the following six conditions are required by the theory: tracer steady state attained, tissue steady state attained, Isc measures net flux, small magnitude and constant time-course of efflux, and correction for decay in pumping rate. The size of the pool, S1 is given by the steady state influx, J∞, divided by the mixing-time constant, α. Some experimental results are analysed by three different graphical methods, and it is shown that these three methods are equivalent. Specifically, a is equal to the reciprocal of the 75 % mixing time, divided by In 4 and is equal to the reciprocal of the lag time, X. The tracer kinetic theory is applied to active potassium transport across the isolated short-circuited midgut: the transport meets the six conditions required by the theory. The size of the transport pool of potassium in one midgut is calculated to be 80·5 μequiv./g wet weight under high-K steady-state conditions. A value as high as this suggests that the pool is intracellular.
Active transport of magnesium across the isolated midgut of Hyalophora cecropia
Authors: Wood J. L. , Jungreis A. M. , Harvey W. R.
Published: April 2021

The 28Mg-measured net flux of magnesium from lumen-side to haemolymph-side of the isolated and short-circuited midgut was 1.97 + 0.28 µ-equiv cm−2 h−1 in 8 mM-Mg2+. The magnesium-influx shows a delay before the tracer steady-state is attained, indicating the existence of a magnesium-transport pool equivalent to 6.7 µ-equiv/g wet weight of midgut tissue. Magnesium depresses the short-circuit current produced the midgut but not the potassium transport, the depression being equal to the rate of magnesium transport. Magnesium transport yields a linear Lineweaver-Burk plot with an apparent Km of 34 mM-Mg2+ and an apparent Vmax of 14.9 µ-equiv cm−1 h−1. Magnesium is actively transported across the midgut and contributes to the regulation of the haemolymph magnesium concentration in vivo.
Cation distributions across the larval and pupal midgut of the lepidopteran, Hyalophora cecropia, in vivo
Authors: Harvey W. R. , Wood J. L. , Quatrale R. P. , Jungreis A. M.
Published: April 2021

The levels of potassium, sodium, magnesium and calcium in leaves, midgut contents, midgut tissue, and blood were analysed in seven developmental stages between feeding, fourth-instar larvae and new pupae of the Cecropia silkworm. Three dramatic changes in cation levels were found: the K level in the contents drops from 284 ±51 mEquiv./l tissue water in the fifth-instar larva to 51 ± 6 mEquiv./l in the new pupa ; the Mg level in the midgut tissue increases from 28 ± 3 mEquiv./l at the time of gut evacuation to 1093 ± 104 mEquiv./l in the new pupa; and the Ca level in the contents drops temporarily from 56 ± 12 mEquiv./l in the feeding fourth instar larva to 17 ± 5 mEquiv./l in the new fifth instar larva. The Na level was never higher than 2·8 ± 0·5 mEquiv./l. The relative levels of the four cations were different for each tissue studied, but each tissue maintained the same relative levels during the developmental stages studied. The sequences are: leaf, Ca > K > Mg > Na; midgut contents, K ⪢ Ca > Mg > Na; midgut tissue, K ⪢> Mg > Ca > Na; and blood, Mg ⪢ K > Ca > Na. There were three large concentration gradients across the midgut ; the K level in the midgut contents is approximately 10 times the level in blood; the Mg level in contents is one-half to one-sixth the level in blood; and the Ca level in contents is 3—4 times the level in blood. The K gradient and the Ca gradient are opposed and the Mg gradient is favoured by the electrical gradient across the larval midgut, the contents being 100 mV positive with respect to the blood. The K gradient and the electrical gradient are not present across the pupal midgut while the Mg gradient and the Ca gradient persist. The K gradient is presumably maintained by the midgut K pump, the Mg gradient is aided by the midgut Mg pump, and the Ca gradient suggests that the midgut may possess a Ca pump.
A quantitative analysis of ventilation tachycardia and its control in two chelonians, Pseudemys scripta and Testudo graeca
Authors: Burggren W. W.
Published: April 2021

In both the turtle, Pseudemys scripta, and the tortoise, Testudo graeca, lung ventilation is closely accompanied by a tachycardia of predictable magnitude and duration. Efferent vagal activity progressively decreases as heart rate increases with the onset of lung ventilation. Atropine increases heart rate during apnoea to those levels observed during prolonged breathing series when vagal tone is negligible, β-adrenergic blockade of the heart does not affect the development, duration or magnitude of ventilation tachycardia. It is thus concluded that heart rate change during chelonian lung ventilation is mediated solely by alterations in vagal tone. Peripheral sensory reflexes involving pulmonary stretch receptors, arterial chemoreceptors and baroreceptors, and receptors stimulated by water immersion do not affect heart rate during breathing. It is suggested that ventilation tachycardia in these chelonians is the result of the spread of activity between the respiratory and cardiac centres of the medulla.
Diuresis in the tsetse fly Glossina austeni
Authors: Gee J. D.
Published: April 2021

After taking a blood meal, the tsetse fly Glossina austeni excretes the excess water and salts of the meal in approximately 30 min. During this period a volume of fluid equivalent to 80% of the unfed weight of the fly passes through the haemolymph, whose composition nevertheless remains almost constant. The fluid excreted has a higher sodium and lower potassium concentration than the haemolymph, indicating that sodium may be the prime mover in urine formation in Glossina.
The Permeability to Ions of the Neural Lamella and the Extracellular Spaces in the C.N.S. of Anodonta Cygnea
Authors: Sattelle D. B. , Howes E. A.
Published: April 2021

Rapid axonal depolarization follows the elevation of [K+]o in the Ringer bathing the surfaces of the connectives of both intact and desheathed cerebro-visceral connectives of Anodonta cygnea. Potassium movements between the blood or medium bathing the surface of the connectives and the axonal membranes can be accounted for in terms of a first-order diffusion process. No visible structural barriers to prevent free movements of materials through the neural lamella and the extracellular spaces can be detected in electron micrographs of the cerebro-visceral connectives. In desheathed preparations fast action potentials are conducted in sodium-free (dextran) Ringer. Mechanisms of axonal function and ionic regulation in this and other inverte-brate central nervous tissues are discussed in the light of these observations.
Extrinsic modulation of crayfish escape behaviour
Authors: Krasne F. B. , Wine J. J.
Published: April 2021

Extrinsic systems were shown to control the excitability of the neurones which mediate tail-flip escape in the crayfish. Restraint suppresses the escape mediated by giant fibres and some, but not all, categories of non-giant mediated escape; autotomy of claws increases the excitability of non-giant mediated escape without affecting the lateral giant reflex.

The effects of restraint on the lateral giant reflex result from inhibition rather than reduced facilitation. The inhibition descends from thoracic and higher levels, and the lateral giant escape command neurone appears to be its primary target. Inhibition may serve to shift the control of escape behaviour from short latency ‘reflex’ systems to more flexible ‘voluntary’ ones which can produce responses at times most opportune for successful escape.
Effects of helium and other inert gases on Echinosphaerium nucleofilum (protozoa, heliozoa)
Authors: Miller J. B. , Aidley J. S. , Kitching J. A.
Published: April 2021

The effects of helium, nitrogen, argon and krypton on Echinosphaerium nucleofilum (Heliozoa) have been studied at partial pressures of 10–130 atm. Additional experiments have been carried out with hydrostatic pressure alone. Helium causes shortening of the axopods over the whole range of pressures, and damage to the cell body at pressures of 60–90 atm, both with a maximum at 80 atm. These effects cannot be explained in terms of hydrostatic pressure alone; a ‘pressure reversal’ effect may be operating, causing the peak at 80 atm. Nitrogen also causes both cell damage and axopod shortening, the severity increasing with increasing pressure. Argon and krypton cause cell damage but no shortening. The order of potency for cell damage is krypton > argon > nitrogen > helium. It is suggested that there may be tuo sites of action, possibly the microtubules (for axopod shortening) and the cell membrane (for cell damage). In appropriate mixtures of helium and argon, both the cell damage usually caused by argon, and the axopod shortening usually caused by helium, are prevented. Possible mechanisms include the effects of hydrostatic pressure on gas solubility coefficients, reversal of the effects of the gases by the increase in total pressure, and competition for sites of action.
Physical and adrenergic factors affecting systemic vascular resistance in the rainbow trout: a comparison with branchial vascular resistance
Authors: Wood C. M. , Shelton G.
Published: April 2021

The passive distensibility and adrenergic reactivity of the systemic vascular resistance (Rs) in Salmogairdneri have been studied using perfused trunk pre-parations, and the data compared with previous results on the branchial resistance (Rg). At normal levels of efferent blood pressure, Rs is relatively more distensible than Rg in response to afferent pressure increases, but this difference may not be important in vivo, α-adrenergic constrictory receptors predominate in Rs, in contrast to β-adrenergic dilatory receptors in Rg; a significant a-adrenergic tone in Rs is lost during perfusion. Rs is far less sensitive than Rg to circulatory catecholamine levels. It is suggested that the sympathetic nervous system, rather than plasma catecholamines, provides the effective adrenergic control of Rs in vivo.
An electrophysiological analysis of chemoreception in the sea anemone Tealia felina
Authors: Dawn I. D.
Published: April 2021

Electrophysiological techniques have been employed to examine the nature of the response observed in the ectodermal slow-conduction system (SS1) when dissolved food substances contact the column of Tealia felina. The response seems to consist entirely of sensory activity which may continue for periods of many minutes, provided that the stimulatory chemicals remain contacting the column. The interval between each evoked pulse gradually increases as the sensory response progresses. This does not result from fatigue in the conduction system but involves a genuine process of sensory adaptation. This may occur over a period of several minutes, which is much longer than comparable adaptation in higher animals. Physiological evidence suggests that the chemoreceptors involved are dispersed throughout the column ectoderm and are absent from the pedal disc, oral disc, tentacles and pharynx. The basic role of the SS1 in coordinating behavioural activity in sea anemones is reviewed. It is concluded that it functions primarily as a single, diffuse-conducting unit responsible for transmitting frequency-coded sensory information from ectodermal chemoreceptors to ectodermal (and perhaps endodermal) effectors.
Control of Mouth Opening and Pharynx Protrusion During Feeding in the Sea Anemone Calliactis Parasitica
Authors: McFARLANE I. D.
Published: April 2021

Activity in all three known conducting systems (the nerve net, SS1, and SS2) may accompany feeding in Calliactis. The most marked response is an increase in pulse frequency in the SS2 (the endodermal slow conducting system) during mouth opening and pharynx protrusion. Electrical stimulation of the SS2 at a frequency of one shock every 5 s elicits mouth opening and pharynx protrusion in the absence of food. A rise in SS2 pulse frequency is also evoked by food extracts, some amino acids, and in particular by the tripeptide reduced glutathione, which produces a response at a concentration of 10−5 M. Although the SS2 is an endodermal system, the receptors involved in the response to food appear to be ectodermal. The epithelium that lines the pharynx conducts SSi pulses, but there is some evidence for polarization of conduction.
The significance of palpation by the maxillary palps of Locusta migratoria (L): an electrophysiological and behavioural study
Authors: Blaney W. M. , Duckett A. M.
Published: April 2021

Palpation increases the amount of sensory input reaching the central nervous system compared with that obtained from sustained contact but that increase is not essential to allow discrimination.

During a meal on favoured food, phagostimulatory input from the palps is not needed to drive feeding. When less favoured food is taken, phagostimulatory input from the palps may enhance feeding. Even with favoured food, the palps are important in registering inhibitory substances.
Induction of transport of organic anions in Malpighian tubules of Rhodnius
Authors: Maddrell S. H. , Gardiner B. O.
Published: April 2021

The ability of Rhodnius Malpighian tubules to transport organic anions such as p-aminohippuric acid (PAH) and amaranth depends on the physiological state of the insect. Unfed insects progressively lose this ability, but the transport mechanisms rapidly become activated after a blood meal. This induction occurs in adults as well as larval instars and is not prevented by decapitation. No increase in rates of excretion of organic anions follows a meal of Ringer’s solution or a single injection of 0·1 μmoles of PAH into the haemolymph. Accelerated PAH excretion is induced in insects fed (a) blood plasma alone or a suspension of red blood cells in saline, (b) solutions of serum albumin or casein, and (c) whole or diluted milk. These results show that the ingestion of a protein-rich meal is sufficient to induce an accelerated transport of organic anions such as PAH and they suggest that this induction is not controlled by a hormone released in response to abdominal distension but depends instead on the continued presence in the haemolymph of some product of digestion of the meal.
Form of developing bends in reactivated sperm flagella
Authors: Goldstein S. F.
Published: April 2021

Dark-field, multiple-exposure photographs of reactivated tritonated sea urchin sperm flagella swimming under a variety of conditions were analysed. The length, radius and subtended angle of bends increased during bend development. The pattern of development was essentially the same under all conditions observed. The angles of the two bends nearest the base tend to increase at the same rate, cancelling one another, so that the development of new bends causes little if any net microtubular sliding. The direction of microtubular sliding within a bend is initially in the same direction as that within the preceding bend, and reverses as the bend develops.
Contribution of an electrogenic pump to the resting membrane polarization in a crustacean heart
Authors: Delaleu J. C. , Holley A.
Published: April 2021

In the neurogenic heart of the isopod crustacean Porcellio dilatatus, external K+ removal depolarized the membrane (K0 effect) whereas subsequent restoration of K+ resulted in a rapid hyperpolarization (K1 effect). The amplitude of the K1 effect depended on the duration of the prior K+ deprivation and on the subsequent K+ concentration. The membrane resistance slightly increased during the K0 effect; during the K1 effect, it only returned to its control value. Ouabain, cooling and replacement of external Na+ by Li+ also produced depolarization. The Kj effect was suppressed by ouabain and markedly depressed by lowering the temperature to 4–6 °C. It was abolished if Li+ replaced Na+ during the prior privation of K+; moreover Li+ was unable to act as a substitute for external K+ in generating the K1 effect if used at equivalent concentration, but enhanced the effect at high concentration. The findings are consistent with the presence of an electrogenic sodium pump in the myocardium of Porcellio contributing to the resting membrane potential. Changes in the spontaneous rhythm observed during K0 and K1 are further suggestive of the presence of an electrogenic Na+ pump in the pacemaker neurons of the cardiac ganglion. Another explanation is also proposed. The magnitude of the spontaneous contractions of the heart was increased during the K0 effect and markedly decreased during the K1 effect. An indirect effect of the changes in internal Na+ concentration on the contractile processes is suggested.
Physiological properties of eel haemoglobin: hypoxic acclimation, phosphate effects and multiplicity
Authors: Weber R. E. , Lykkeboe G. , Johansen K.
Published: April 2021

Unlike the whole blood oxygen affinity, which adapts readily to environmental oxygen tensions, haemoglobins prepared from normoxic-and hypoxic-acclimated eels (Anguilla anguilla) show no adaptive changes in oxygenation properties or in multiplicity. Hypoxic acclimation is, however, accompanied by a strong decrease in red cell nucleoside triphosphates, particularly guanosine triphosphate (GTP), which depresses oxygen affinity of the composite and component haemoglobins more strongly than does the concurring ATP. The effects of pH, temperature and salts on the oxygenation properties of the (isolated) haemoglobins are reported, discussed in relation to the varying environmental conditions encountered by eels, and compared with data on American and Japanese eels (A. rostrata and A. japonica, respectively).
Excretion of Alkaloids by Malpighian Tubules of Insects
Authors: Maddrell S. H. , Gardiner B. O.
Published: April 2021

Nicotine is transported at high rates by Malpighian tubules of larvae of Manduca sexto, Pieris brassicae and Rhodnius prolixus and the transport persists in the absence of alkaloid from the diet. In the fluid-secreting portion of Rhodnius tubules this transport is not coupled to ion transport, nor is it dependent on the physiological state of the animal. The transport, which can occur against a steep electrochemical gradient, shows saturation kinetics with a maximal rate of 700 pmol. min−1 per tubule and is half saturated at 2–3 mm. Nicotine transport independent of ion movements also occurs in the lower resorptive parts of Rhodnius tubules. Both portions of Rhodnius tubules can transport morphine and atropine. These alkaloids and nicotine compete with one another and are presumed to be carried by the same transport system. Nicotine transport in Rhodnius was unaffected by organic anions, such as amaranth and benzyl penicillin, or by the organic anion transport inhibitor, probenecid. Fluid secretion in 5-HT-stimulated tubules was reduced by atropine and nicotine, probably by blocking the 5-HT receptors. The Malpighian tubules of adult Calliphora erythrocephala and Musca domestica remove nicotine from bathing solutions, an unknown metabolite accumulating in the tubules. Adult P. brassicae and M. sexta do not exhibit transport of nicotine by their Malpighian tubules.
Active transport of sodium by the malpighian tubules of the tsetse fly Glossina morsitans
Authors: Gee J. D.
Published: April 2021

Isolated Malpighian tubules of Glossina morsitans are able to transport sodium against its concentration gradient. Their rate of secretion is dependent on the sodium concentration of the bathing medium. Potassium must be present in the bathing solution for rapid secretion to be maintained, but it does not play an active role in fluid secretion. Lithium and ammonium ions are able to substitute partially for sodium, other monovalent cations cannot. Ouabain does not affect rapid secretion by Glossina tubules in vitro. Conclusions drawn from the results are incorporated into a model of Malpighian tubule cell function in this insect.
The unreliability of mammalian glomerular markers in teleostean renal studies
Authors: Beyenbach K. W. , Kirschner L. B.
Published: April 2021

The assumption that [3H]methoxy inulin, [14C]polyethylene glycol (PEG) and [128]iothalamate (glofil) are reliable volume and glomerular markers in teleosts was tested. PEG occupied smaller volumes than inulin and glofil in sea-water-adapted Salmo gairdneri. Ureteral clearances of PEG were about 22 % higher than those of inulin and glofil, and urine-to-plasma ratios were significantly greater for PEG than for the other two markers. After introduction into the urinary bladder the three macro-molecules appeared in the plasma, PEG at the lowest rates. These observations indicate that mammalian glomerular markers can penetrate the bladder and possibly the ureters and renal tubules. Therefore, their clearances may not give a true measure of glomerular filtration rates in teleosts.
Two slow conduction systems co-ordinate shell-climbing behaviour in the sea anemone Calliactis parasitica
Authors: McFarlane I. D.
Published: April 2021

Pulses in two slow conducting systems, the ectodermal SS 1 and the endodermal SS 2, were recorded during shell-climbing behaviour. The mean pulse interval of SS 1 pulses was 7·4 s and that of SS 2 pulses was 6·4 s. Activity in both systems may arise as a sensory response of tentacles to shell contact, but the SS 1 and SS 2 may not share the same receptors. Electrical stimulation of the SS 1 and SS 2 together, at a frequency of 1 shock every 5 s, elicits shell-climbing behaviour in the absence of a shell. Low-frequency nerve-net activity (about 1 pulse every 15 s) accompanies column bending during both normal and electrically elicited responses. This activity probably arises as a result of column bending and is not due to a sensory response to the shell.
The effects of transecting the IXth and Xth cranial nerves on hydromineral balance in the eel Anguilla anguilla
Authors: Mayer-Gostan N. , Hirano T.
Published: April 2021

The IXth and the Xth cranial nerves in Anguilla anguilla were transected, and the effects upon ion and water balance were studied in fresh water and sea water, and during transfer from fresh water to sea water and vice versa. In fresh water there is a slow demineralization due to an excess loss of Na and Cl ions. During freshwater to seawater transfer the eel survives only for 4–5 days. The fish do not drink and Na efflux does not increase enough to extrude excess ions. In sea water the glossopharyngeal and vagus nerves are necessary for the maintenance of the hydromineral balance. Denervation is followed by an increase in plasma ion concentrations. Na fluxes are not modified and increased water loss is not compensated by drinking.

The rapid reduction of Na efflux during transfer from sea water to fresh water is not modified by denervation.
The series elastic component and the force-velocity relation in the anterior byssal retractor muscle of Mytilus edulis during active and catch contractions
Authors: Tameyasu T. , Sugi H.
Published: April 2021

The length changes of the anterior byssal retractor muscle (ABRM) of Mytilus edulis, following step changes in load, were studied at various phases of active and catch contractions produced by acetylcholine. The load-extension curves of the series elastic component (SEC) were found to be scaled down in proportion to the isometric tension immediately before step changes in load, but remain unchanged irrespective of whether the ABRM was in active or in catch contraction. In hypertonic solutions the compliance of the SEC was reduced in the same manner as that of the SEC in frog skeletal muscle. These results seem to favour the linkage hypothesis for the catch mechanism, though the SEC in the ABRM is suggested to be composed not only of the cross-linkages, but also of the compliance of the myofilaments.
Flight energetics of sphinx moths: power input during hovering flight
Authors: Casey T. M.
Published: April 2021

The energetic cost of hovering flight was measured in sphinx moths from five species. Mean power input per unit mass (Pi/M) varied from 237·2 W kg−1 in Manduca sexta (Subfamily: Sphinginae), mean body mass 1·2 × 10−3 kg, to 327·9 W kg−1 in Deilephila elpenor (Subfamily: Macroglossinae) mean body mass 7×3 × 10−4 kg. Mean Pi/M for the five species was inversely proportional to mean body mass and directly proportional to mean wing loading. For any given body mass, Pi/M was greater in Hyles lineata than in M. sexta. This difference is correlated with higher wing loading at any given mass in H. lineata. Energy expenditure per unit mass of thorax was 1018 W kg−1 in H. lineata and 694 W kg−1 in M. sexta. Within each of these species, Pi per unit mass of thorax does not vary with body mass. Power input data are compared with calculated power requirements based on momentum theory and blade-element theory of helicopter aerodynamics. Absolute efficiency, the ratio between calculated power requirements and measured energy expenditure, appears to vary directly with body mass. These data provide an energetic basis for observed correlates between thoracic temperature and flight effort in flying sphinx moths.
Heat exchange in relation to blood flow between thorax and abdomen in bumblebees
Authors: Heinrich B.
Published: April 2021

The narrow passage within the petiole between thorax and abdomen is anatomically constructed so that counter-current exchange should retain heat in the thorax despite blood flow to and from the cool abdomen. However, the counter-current heat exchanger can be physiologically circumvented. Exogenously heated bumblebees prevented overheating of the thorax by shunting heat into the abdomen. They also regurgitated fluid, which helped to reduce head temperature but had little effect on thoracic temperature. Temperature increases in the ventrum of the abdomen occurred in steps exactly coinciding with the beats of the ventral diaphragm, and with the abdominal ‘ventilatory’ pumping movements when these were present. The ability to prevent overheating of the thorax by transport of heat to the abdomen was abolished when the heart was made inoperative. At low thoracic temperatures the ventral diaphragm beat at a wide range of rates and with varying interbeat intervals, while the heart beat at a high frequency relative to the ventral diaphragm, but at a very low amplitude. However, when thoracic temperature exceeded 43 °C the amplitudes of both were high, and the interbeat intervals as well as the beating frequencies of the two pulsatile organs became identical in any one bee. Furthermore, heated bees engaged in vigorous abdominal pumping at the same frequency as that of their heart and ventral diaphragm pulsations. The results indicate that the anatomical counter-current heat exchanger is reduced or eliminated during heat stress by ‘chopping’ the blood flow into pulses, and the blood pulses are shunted through the petiole alternately by way of a switch mechanism.
The Effect of Partial Pressures of Inert Gases on the Behaviour and Survival of the Heterotrich Ciliate Spirostomum Ambiguum
Authors: MacDonald S. , Kitching J. A.
Published: April 2021

A study has been made of the effects of helium, nitrogen and argon at partial pressures of 10–120 atm on the swimming speed, behaviour and survival of the heterotrich ciliate Spirostomum ambiguum. Experiments have also been carried out with hydrostatic pressure alone. Hydrostatic, helium and nitrogen pressures reduced the swimming speed approximately equally but pressure of argon reduced it to an even greater extent. Hydrostatic, helium, nitrogen and argon pressures caused a reduction in the number of reversals in a given time but the number of reversals/distance travelled did not change significantly. All the treatments increased the durations of individual forward movements. Pressures of helium, nitrogen and argon also increased the durations of reversals but at high hydrostatic pressures the durations of reversals were reduced.

Argon caused cytolysis at 30–40 atm and nitrogen at 80 atm; helium did not cause any visible cell damage over periods of 1 h at 120 atm. Addition of substantial partial pressures of helium protected Spirostomum against partial pressures of argon which would otherwise have caused cytolysis. The increase of hydrostatic pressure may have been responsible.
A study of the unidirectional fluxes of Na and Cl across the gills of the dogfish Scyliorhinus canicula (Chondrichthyes)
Authors: Bentley P. J. , Maetz J. , Payan P.
Published: April 2021

The gills of the dogfish Scyliorhinus canicula are more permeable to Cl than to Na. In sea water, influx of Na and Cl exceeded the efflux of these ions. Under these conditions the fish were slightly electronegative, by about 2 mV, to the external solution. The net accumulation of Cl could be accounted for by diffusion along the observed electrochemical gradient but the movement of Na into the fish was more consistent with an electrically neutral active Na transport mechanism (using the Ussing flux ratio criterion). When the external pH was changed from 7·8 to 6·9, influxes of Na and Cl were depressed, while the effluxes were unaffected, and the fish became slightly less electronegative. In artificial solutions, in which the concentrations of Na and Cl were lowered and replaced with urea to maintain the total osmotic concentration, Na influx displayed saturation kinetics, while Na efflux increased with decreasing Na concentrations. Cl influx decreased linearly, while Cl efflux remained constant. The efflux of Cl could not be reconciled with a process of passive diffusion along any of the observed electrochemical gradients and thus could reflect the presence of an active transport mechanism.
The actions of some putative neurotransmitters on the cockroach salivary gland
Authors: Bowser-Riley F. , House C. R.
Published: April 2021

Certain putative transmitters were applied to the innervated cockroach salivary gland and their effects on the resting potential and the neurally evoked secretory potential of the acinar cells were observed. γ-Aminobutyric acid, glutamate, glycine, aspartate and alanine had no significant effect on the resting potential. However, γ-aminobutyric acid and glutamate reduced the neurally evoked secretory potential but only at concentrations above 10−3 M. Acetylcholine and carbachol appeared to act by modifying transmitter output from the salivary nerves. These substances failed to have any effect on the resting potential. The biogenic amines, adrenaline, dopamine, noradrenaline, 5-hydroxy-tryptamine and octopamine, produced hyperpolarizing responses, graded according to concentration, It is suggested that dopamine, the most potent of the biogenic amines tested, is the transmitter at this junction.
Electrical activity of the proventriculus of the polychaete worm Syllis spongiphila
Authors: Anderson M. , del Castillo J.
Published: April 2021

The striated myoepithelial cells of the proventriculus of Syllis spongiphila are composed of only one or two sarcomeres that may reach 40 µm in length. Experiments were performed to study some of their electrophysiological properties and their synaptic control. The mean resting potentials recorded in two different bathing media were 59·1 ± 5·5 mV (S.D., n = 91) and 62·5 ± 6·3 mV (S.D., n = 98). At rest the membrane potential is determined largely by permeability of the membrane to K + ions, but the membrane is also permeable to other ions. On a semilogarithmic plot of membrane potential v. [K]o the mean slope of the data points from 9 to 90 mm-[K]o was 48 ± 3 mV for a 10-fold change in [K]o. The anterior end of the animal was stimulated with a suction electrode to elicit activity of nerve fibres that innervate the proventriculus. Single indirect stimuli usually evoked hyperpolarizing or biphasic responses, and occasionally depolarizing responses, from the myoepithelial cells. The depolarizing synaptic potentials exhibited a faster time course than the hyperpolarizing ones. The rise time to peak ranged from 20 to 35 ms for simple depolarizations (n = 32) and 25−75 ms for simple hyperpolarizations (n = 103). Time to decay to half amplitude ranged from 20 to 55 ms for depolarizations (n = 29) and 62−135 ms for hyperpolarizations (n = 87). Low frequency (⩽ 4 Hz) trains of indirectly applied stimuli elicited mainly hyperpolarizing responses; higher frequency (5−40 Hz) trains elicited complex responses composed of hyperpolarizations and depolarizations. Hyperpolarizations were selectively and reversibly abolished in chloride-free solutions. The reversal potential of the hyperpolarizing synaptic potential was —104 ± 3 mV (S.D., n = 8, 2 preparations). In calcium-free solution both hyperpolarizations and depolarizations were almost completely abolished. 4 mm-Mn2+ added to the bath almost completely abolished the depolarization but not the hyperpolarization. It was not clear whether Mn2+ acted at the presynaptic membrane, the postsynaptic membrane or both. The myoepithelial cells are electrically coupled. The mean space constant of five preparations was 0·52 mm (range 0·40−0·66 mm).
Pressure Difference in Adjacent Segments and Movement of Septa in Earthworm Locomotion
Authors: Seymour Malcolm K.
Published: April 2021

The nature and timing of septal movements during gentle crawling have been examined in relation to the coelomic pressure (Pc) in and between adjacent segments. Between neighbouring anterior segments the phase lag was 0·05−0·1 s and the maximum Pc difference 3·3 cm water. The mean Po in a leading segment exceeded that in a trailing segment by 0·9 ± 0·06 cm water. In forward crawling, the septa bulged maximally backward and forward when segments were half elongated and half shortened respectively, and were flat when segments were longest and shortest: the area of a septum in an elongated segment was one quarter that in a shortened one and thus a septum is strongest (small and thick) when the Pc to be longitudinally confined is highest. Bulging of septa is closely related to the intersegmental Pc difference. Bulging forces acting on a septum range from o to about 1 g wt. The pressure drop along a worm is not linear and the ventral foramina may act as ‘septal valves’ to equalize coelomic volume and pressure when required. The influence of gut, septum and body wall movements on each other is discussed.
The cardiac responses to shell opening and closure in the bivalve Arctica islandica (L.)
Authors: Taylor A. C.
Published: April 2021

Shell closure in Arctica islandica is followed by an exponential decrease in the oxygen tension of the mantle cavity water and is accompanied by an initial increase in heart rate which is followed at lower oxygen tensions by a bradycardia. Prior to shell opening there is a slight increase in heart rate before any movement of the shell valves can be detected. However, once the shell opens and pumping activity recommences there is a rapid increase in heart rate, often to levels above normal.

Perfusion of the mantle cavity with water of high and low oxygen tension resulted in the cardiac responses normally associated with shell opening and closure. Recordings of the of the blood in the ventricle, made simultaneously with cardiac recordings, showed that the changes in heart rate were recorded only after the of the blood had changed. These experiments suggest that changes in the of the mantle cavity water may be primarily responsible for the cardiac responses to shell closure in Arctica.
Acoustical Properties of the Flight Activities of the Caribbean Fruit Fly
Authors: Webb J. C. , Sharp J. L. , Chambers D. L. , Benner J. C.
Published: April 2021

The waveforms generated by the flight sounds of the Caribbean fruit fly Anastrepha suspensa (Loew) were recorded and analysed. These analyses included measurements of wingbeat frequency (WBF), sound pressure level (SPL) and harmonic content. The WBF and SPL were similar for both sexes but varied with fly maturity. A power spectral density (PSD) plot was made of the waveforms produced by each fly. These PSD plots showed waveform differences between young 1- to 4-day-old) flies and older flies, but these differences decreased with age. In flies more than 4-6 days old the waveforms remained relatively constant throughout the test period and were similar, for both sexes in that each contained discrete, narrow-band spectral lines in both the fundamental frequency and the harmonics.
The effect of caffeine on excitation-contraction coupling in skeletal and smooth muscle
Authors: Syson A. J. , Huddart H.
Published: April 2021

For cockroach skeletal muscle, 2 mm caffeine considerably lowered the mechanical threshold without affecting the membrane potential. Contractures were induced by 8−10 mm caffeine. In rat ileal smooth muscle, 1−10 mm caffeine inhibited spontaneous contractile behaviour, abolished spike activity and reduced KCl-induced contracture tension. Enhanced spike activity associated with the KCl-induced phasic contraction was abolished by caffeine, the degree of caffeine-induced relaxation being proportional to the concentration employed. These relaxations were not accompanied by membrane hyperpolarization. The present results accord with previous work which has shown that caffeine increases myoplasmic free calcium in the skeletal muscle and lowers it in the smooth muscle. It is suggested that caffeine releases bound calcium in the former muscle and promotes binding in the latter. It is further suggested that in the smooth muscle caffeine may reduce the membrane permeability to calcium.
Receptor Units Responding to Movement in the Octopus Mantle
Authors: Boyle P. R.
Published: April 2021

A preparation of the mantle of Octopus which is inverted over a solid support and which exposes the stellate ganglion and associated nerves is described. Afferent activity can be recorded from stellar nerves following electrical stimulation of the pallial nerve. The latency and frequency of the phasic sensory response is correlated with the contraction of the mantle musculature. It is proposed that receptor cells located in the muscle, and their activity following mantle contraction, form part of a sensory feedback system in the mantle. Large, multipolar nerve cells that were found between the two main layers of circular muscle in the mantle could be such receptors.
Neural Excitation of the Larval Firefly Photocyte: Slow Depolarization Possibly Mediated by A Cyclic Nucleotide
Authors: Oertel Donata , Case James F.
Published: April 2021

In firefly larvae, extracellular recordings from the light organ nerve show that a volley of action potentials elicits a glow similar to the glow of an intact animal. Intracellular recordings from the photocytes show that they respond to nerve stimulation with a slow, graded depolarization which precedes light emission. The depolarization begins about 0·5 s after the nerve is stimulated ; it peaks about 1 s after stimulation; and subsides about 2·5 s after the stimulus. The glow increases fastest when the photocyte depolarization is at its peak and lasts 5–15 s. Photocyte depolarization is associated with a decrease in the input resistance of the cell. Adrenergic receptors in the light organ are pharmacologically similar to vertebrate α-receptors. Phosphodiesterase inhibitors, aminophylline and theophylline, cause the light organ to glow, suggesting that cyclic nucleotides may mediate the effect of the adrenergic nerve transmitter.