bluuebunny/crossref_metadata_2025 huggingface dataset:
The Acid-Base Status of Prenatal Pups of the Dogfish, Squalus Acanthias, in the Uterine Environment
Authors: Kormanik Gregg A. , Evans David H.
Published: April 2021

The acid-base status of late-term Squalus acanthias L. pups in the uterine seawater environment was examined. Blood values for pH, total CO2, partial pressure of CO2, urea and sodium concentrations in late-term pups were not significantly different from those of the mothers. Haematocrit was slightly lower, while total plasma lipid and ammonia concentrations were several times higher.

The uterine environment in which these pups reside and maintain normal acidbase status is nevertheless quite remarkable. In the later months of gestation, up to six pups (approx. 60 g each) reside in each horn of the uterus, in about 100 ml of seawater, in which they ventilate. While the major ion concentrations of the uterine fluid resemble normal seawater, the pH may be as low as 5·9, and the ammonia concentration as high as 22 mmol 1−1.

This system provides a unique opportunity to study acid-base balance, respiration and nitrogenous waste excretion in developing elasmobranchs under quite unusual conditions.
Fracture Toughness Design In Horse Hoof Keratin
Authors: Bertram J. E. A. , Gosline J. M.
Published: April 2021

An engineering fracture mechanics approach was applied to the analysis of the fracture resistance of equine hoof-wall. The relationship between fracture toughness and the morphological organization of the keratin hoof tissue was investigated. Fracture toughness was evaluated using the J-integral analysis method which employs the compact tension test geometry. Tensile tests were also conducted to evaluate the effect of the morphological organization on the stress-strain behaviour. Hoof-wall has greatest fracture resistance for cracks running proximally, parallel to the tubular component of the wall keratin. For fully hydrated material tested in this direction the mean critical J-integral value at failure was 1·19× 104 J m−2. This was nearly three times greater than the value determined for the weakest orientation, in which the crack ran parallel to the material between the tubules. The lower fracture toughness of the intertubular material dominates the fracture behaviour of this tissue. The tubular components of the wall appear to reinforce against fracture along the weak plane and the entire wall organization provides the mechanical capability for limiting and controlling fracture in this tissue.
Intrinsic Mechanical Properties of the Perfused Rainbow Trout Heart and the Effects of Catecholamines and Extracellular Calcium Under Control and Acidotic Conditions
Authors: Farrell A. P. , MACLEOD K. R. , Chancey B.
Published: April 2021

A perfused rainbow trout heart was developed which generated its own intrinsic heart rate and a physiological power output. This preparation wàs used to examine the intrinsic mechanical properties of the trout heart, the dose-response effects of catecholamines and extracellular calcium on these properties, and the effects of catecholamines and extracellular calcium during exposure to acidotic conditions. The trout heart was relatively pressure-insensitive to a physiological range of ventral aortic pressures. Preload exerted an important control over cardiac output through the Starling response. Heart rate was independent of both these intrinsic mechanisms. The intrinsic mechanical capabilities of the trout heart were greater than those observed previously in less active, benthic teleosts. Physiological concentrations of catecholamines significantly improved cardiac contractility through positive inotropy and chronotropy. Adrenaline was more potent than noradrenaline, indicating that these effects were mediated by β2-adrenoceptors. Elevated extracellular calcium produced only a modest improvement of cardiac contractility compared to that produced by adrenaline. Positive inotropy and negative chronotropy were observed with elevated extracellular calcium. Extracellular acidosis always reduced cardiac contractility through negative chronotropy and inotropy. Extracellular calcium improved the inotropic state of the acidotic heart and restored contractility, but the overall improvement of cardiac performance was compromised by an accompanying negative chronotropy. Physiological levels of adrenaline improved cardiac performance during extracellular acidosis. The roles of catecholamines and extracellular calcium are discussed with respect to post-exercise cardiac performance in trout.
An Approach to the Mechanics of Pleating in Dragonfly Wings
Authors: Newman D. J. S. , Wootton R. J.
Published: April 2021

A structural engineering approach to the pleated wings of Odonata has been developed during a functional study of wing morphology in the group. The wing can be regarded as a folded plate structure within which each pleat-side acts as a deep plate-girder. Small cross-veins act as stiffeners within the girders, allowing the membrane to carry web shearing forces as pure tension, through a stressed-skin effect. Bending experiments confirm that the membrane significantly increases the rigidity of wing components. The properties of the membrane are unknown. It lacks birefringence, is very thin, and may be pure epicuticle. The advantages of stressed-skin construction are discussed, and possible modes of structural failure considered. The wing seems adapted to yield reversibly to unpredictable heavy loads.
Neural Correlates of Colour Change in Cuttlefish
Authors: Messenger J. B. , Miyan J. A.
Published: April 2021

This paper presents the first direct demonstration in a living cephalopod of neural activity associated with chromatic behaviour. It has long been known that colour change in these molluscs is unique in that it is brought about by chromatophores controlled neurally rather than hormonally (e.g. Hofmann, 1907). The chromato-phore muscles are innervated directly by nerves whose cell bodies lie in the brain itself (Sereni & Young, 1932; Boycott, 1953); the muscles respond tetanically when these motoneurones are stimulated above 10-15 Hz (Florey, 1966) ; electrical stimulation in the chromatophore lobes of the brain causes darkening of the skin (Boycott, 1961) ; stimulation in the optic lobes can elicit patterning (the expansion of some sets of chromatophores and the simultaneous retraction of others) (Boycott, 1961; Chichery & Chanelet, 1976). Darkening, paling and patterning can also be elicited by introducing specific neurotransmitters into the blood supplying the brain (Andrews, Messenger & Tansey, 1983). But until now no-one has successfully recorded from the nerves supplying a specific set of chromatophores in the living animal and shown changes in activity as the display is switched on and off.
Classification of Ocellar Interneurones in the Cockroach Brain
Authors: Mizunami Makoto , Tateda Hideki
Published: April 2021

Nine types of ocellar interneurones with arborizations in the ocellar tract have been identified in the cockroach, Periplaneta americana. These neurones are classified into (1) five types of ‘PS-neurone’, which project into the posterior slope, (2) two types of ‘OL-neurone’, which project into the lobula and medulla of the optic lobe, and (3) two types of ‘D-neurone’, which descend to the thoracic ganglia. When recordings were made in the ocellar tract, all types of neurones exhibited similar responses: a tonic hyperpolarization during illumination and one or a few transient depolarizations at the end of illumination. However, these neurones are classified into several physiological types from the responses recorded in their axons or terminal regions.
Phase-Dependent Modulation of Auxiliary Swimmeret Muscle Activity in the Equilibrium Reactions of the Norway Lobster, Nephrops Norvegicus L.
Authors: Neil Douglas M. , Miyan Jaleel A.
Published: April 2021

The activity of swimmeret muscles of the lobster Nephrops norvegius during beating in the upright and tilted animal has been examined. The responses to tilt are produced primarily by stimulation of the statocysts. The anatomy of the swimmeret muscles is described. Although essentially similar to previous descriptions, important new aspects are presented. The arrangement of the main powerstroke and retumstroke muscle groups in relation to the peg-and-hook articulation of the swimmeret produces a segregation of action, with different muscles contributing progressively to force production. The auxiliary muscles of the basipodite, M9, M10 and M13 act to twist the swimmeret laterally. The auxiliary muscle Ml 1-12-14—15 acts to maintain a rearward powerstroke. The innervation of swimmeret muscles and the location of their motoneurone cell bodies in the abdominal ganglia have been revealed by cobalt staining. There is a clear segregation of powerstroke and returnstroke motoneurones. Intraganglionic fibre tracts as well as four interganglionic fibres are identified. Intracellular studies on the twister muscles show that M9 receives at least three excitatory units, and M10 at least six. No inhibitory activity was ever recorded in these muscles. M9 and the medial bundle of M10 receive tonic excitatory inputs, while the lateral bundle of M10 receives phasic inputs and is normally silent in the absence of lateral beating. In the absence of swimmeret beating, body roll about the long axis induces tonic motor activation of the lateral twister muscles (M9 and M10) and the return-stroke muscles in the swimmerets on the side tilted upwards. When beating occurs it is predominantly in the swimmerets tilted upwards, and there is an entrainment of phasic activity in M9, M10 and M13 to the powerstroke phase of the beats. Tonic units to the retumstroke muscle remain unaffected. The results are discussed with particular reference to the interaction of descending statocyst information with the central pattern generator for swimmeret beating.
Swimmeret Proprioceptors in the Lobsters Nephrops Norvegicus L. and Homarus Gammarus L.
Authors: Miyan Jaleel A. , Neil Douglas M.
Published: April 2021

The morphology, sensory responses and reflex effects of two proprioceptive systems in the swimmerets of the Norway lobster Nephrops norvegieus are described. Two bipolar cells embedded in an elastic strand (strand B) which spans from the sternal rib to the proximal edge of the basipodite respond to stretch of the strand, applied directly or through swimmeret protraction. Powerstroke motoneurones are excited by a negative feedback reflex, and the transition from retumstroke to powerstroke movement is thereby sharpened. When protraction movements of the swimmeret are blocked, the intensity of beating is reduced both in the blocked swimmeret, and in neighbouring (particularly posterior) swimmerets. A second receptor strand, the twisting muscle receptor (TMR), stretches from the sternal rib wall to the proximal end of the twisting muscle M10 in both the lobsters Nephrops norvegieus and Homarus gammarus. It contains the sensory endings of two cells which have somata in the abdominal ganglion. The axons of these cells convey conventional spikes in response to strand stretch, which occurs on release of M10 from imposed extension or following active M10 contraction. They produce a specific activation of M10 motoneurones, which represents a positive feedback reflex. This reinforces the twist of the swimmeret blade, so that the beat is directed laterally to its greatest extent throughout the powerstroke. It is suggested that the TMR is homologous with the crayfish non-spiking swimmeret receptors, which also have central cell bodies. However, the receptors differ in their location, mode of afferent transmission and reflex actions. The discovery of these differences resolves anomalies between previous studies on lobsters and crayfish. The results are discussed in terms of the homologies of all limb proprioceptors with central cell bodies in decapod crustaceans, and of the proprioceptive control of swimmeret beating.
Monitoring the Metabolic Rate and Activity of Free-Swimming squid With Telemetered Jet Pressure
Authors: Webber D. M. , O’Dor R. K.
Published: April 2021

Measurements of oxygen consumption and mantle cavity pressure (P, kPa) of squid, Illex illecebrosus, of various masses (M,kg), swimming at various speeds (U, ms−1) in a tunnel respirometer yielded two relationships: Both jet frequency and peak pressures increase with increasing speed. Patterns varied considerably between individuals, but total area under the pressure curve (P) was well correlated with oxygen consumption and speed. A differential pressure transducer linked to an ultrasonic transmitter carrying average pressure data encoded on impulse frequency was designed to be carried inside the mantle cavity. It was tested in both the swim-tunnel and in video-taped free-swimming animals. The relationships above held over a range of speeds from 0 to 1·4ms−1, the maximum speed observed, indicating that such transducers could provide direct estimates of both the metabolic rates and activities of these pelagic carnivores in nature; their use to test hypotheses about several energy-saving strategies is discussed. Average thrusts, calculated from pressure data, are consistent with rigid body drag predictions and with overall locomotor efficiencies of 5 %, which are also consistent with the relative costs of transport and efficiency estimates for fish.
Blood pressure control during exercise in the Atlantic cod, Gadus morhua
Authors: Axelsson M. , Nilsson S.
Published: April 2021

Atlantic cod were subjected to 12–15 min swimming exercise at 2/3 body lengths s−1 in a Blazka-type swim tunnel. Pre-and postbranchial blood pressures, cardiac output (ventral aortic blood flow) and heart rate were continuously recorded, and blood samples for measurement of arterial and mixed venous oxygen tension were taken before and at the end of the exercise period. In a second group of fish, subjected to similar exercise regimes, blood samples were taken for analysis of the plasma concentrations of catecholamines.

Pre-and postbranchial blood pressures and cardiac output increase during exercise, while the mixed venous oxygen tension decreases. The effect on cardiac output is due to an increase of both heart rate and stroke volume. There are no significant changes in either systemic or branchial vascular resistances, or in the plasma concentrations of catecholamines.

Injection of the adrenergic neurone-blocking drug bretylium produces a decrease in postbranchial blood pressure in resting cod, due to a decrease in the systemic vascular resistance. Exercising cod treated with bretylium have a significantly lower pre-and postbranchial blood pressure than exercising control cod. This is due mainly to a dramatic reduction in the systemic vascular resistance. The α-adrenoceptor antagonist phentolamine does not further affect the blood pressure in cod treated with bretylium.

It is concluded that the exercise hypertension observed in cod depends on the effect of adrenergic vasomotor fibres maintaining the systemic vascular resistance, and also on the increase in cardiac output. An adrenergic innervation of the heart may play some role in the control of cardiac performance both at rest and during exercise, but the main cardioregulatory mechanism is likely to be non-adrenergic, most probably including cardiac control via variation of the cholinergic vagal cardio-inhibitory tonus.
Motor correlates of learning behaviour: feeding on novel prey by pumpkinseed sunfish (Lepomis gibbosus)
Authors: Wainwright P. C.
Published: April 2021

The functional basis of learning in prey capture was investigated in the pumpkin-seed sunfish (Lepomis gibbosus). Feeding performance of sunfishes was assessed when the fish were first fed a novel, elusive prey (guppies) and compared with their performance after several weeks of experience with capturing guppies. During these feedings electromyographic recordings were made to document the pattern of activity in four jaw muscles at the strike. With experience, the L. gibbosus improved their ability to capture guppies, and several changes in the pattern of muscle activity were associated with this improved performance. Average duration and maximum amplitude of activity in all muscles increased between trials. Previous studies of muscle activity modulation in fishes indicate that these changes could improve feeding performance on an elusive prey. Thus, specific modifications of muscle activity appear to be one functional determinant of feeding success in fishes.
Heat loss from deer mice (Peromyscus): evaluation of seasonal limits to thermoregulation
Authors: Conley K. E. , Porter W. P.
Published: April 2021

This paper investigates the influence of seasonal adaptations to thermoregulatory heat loss for deer mice (Peromyscus) during summer and winter. A general, mechanistic model of heat transfer through fur was evaluated for the structural properties of the fur of deer mice. The model was validated against heat production determined from mice exposed to a range of radiative (wall) temperatures (tr) at air temperatures (ta) of 15, 27 and 34°C. Calculated heat loss from the appendages was subtracted from the measured heat production to yield heat loss from the furred torso. This calculated torso heat loss agreed closely with the predicted fur heat loss for all conditions, as shown by a regression slope near 1 (0·99). Simulations using models of fur and appendage heat loss reveal that the winter increase in thermogenic (heat production) capacity has a greater effect than changes in fur properties in expanding the limits to thermoregulation. Both wind and a clear night sky increase heat loss and can limit thermoregulation to air temperatures above those found in deer mice habitats during winter (—25°C). Thus, despite seasonal adaptations, these simulations indicate that thermoregulation is not possible under certain winter conditions, thereby restricting deer mice to within the protected environment of the leaf litter or snow tunnels.
The Physiology of Dehydration Stress in the Land Crab, Cardisoma Carnifex: Respiration, Ionoregulation, Acid-Base Balance and Nitrogenous Waste Excretion
Authors: Wood Chris M. , Boutilier R. G. , Randall D. J.
Published: April 2021

Air-breathing Cardisoma carnifex, collected in Moorea, French Polynesia, were held in fresh water similar in chemical composition to that in their burrows. Under control conditions, which allowed branchial chamber flushing but not ventilation of the medium, crabs demonstrated net Na+ and Cl− uptake, and ammonia, urea and base excretion (= acidic equivalent uptake). Throughout 192 h of water deprivation, crabs dehydrated slowly at a rate of 0·55 gH2Okg−1 h−1, eventually reaching a near lethal 18% loss of total body water. Increases in haemolymph osmolytes were quite variable (0–29%); electrolyte excretion was negligible. and both decreased by approximately 55%, maintaining an unusually low gas exchange ratio (R = 0·53), and suggesting general metabolic depression. There was no evidence of internal hypoxia as haemolymph lactate remained at hydrated levels and actually increased. The dominant acid-base response was a progressive metabolic alkalosis accompanied by a partially compensating rise in . Alkalosis was probably caused by blockage of the normal aquatic excretion of base produced by the metabolism of this herbivore. Other possible causes were eliminated: i.e. alkalaemia due to contraction of the ECFV; entrainment via strong ion shifts; CaCO3 mobilization; and ammonia accumulation in the haemolymph. In the absence of water, net ammonia production and excretion both appeared to cease, and alternate end products (urea, uric acid) did not generally accumulate. Within 2h of rehydration, crabs regained more than half the lost water, and increased above control levels, and ammonia excretion and haemolymph concentration both exhibited a prolonged (56 h) 4- to 6-fold rise. At the same time, metabolic alkalosis was reversed in association with elevated net base excretion into the water; the latter was correlated with an increase in the strong ion difference (SID) flux ([Na+ + K+4-Ca2++Mg2+-Cl−]).
Effects of flow rate, duration of stimulation and mineralocorticoids on the electrolyte concentrations of mandibular saliva from the red kangaroo (Macropus rufus)
Authors: Beal A. M.
Published: April 2021

Mandibular saliva was collected at eight flow rates ranging between 0·052 ± 0·0059 (S.E. of mean) and 4·294 ± 0·0717 ml min−1 from anaesthetized red kangaroos receiving ipsilateral intracarotid infusions of acetylcholine. The concentrations of sodium (4·04 ± 0·759 to 75·9 ± 4·64 mmol 1−1) and chloride (51·2±2·46 to 85·0 ± 6·90 mmol 1−1) and the osmolality (99·7±4·88 to 178·9 ± 13·50 mosmol kg ‘) were positively correlated with salivary flow rate over most or all of the flow range, whereas the concentrations of potassium (50·3 ±2·03 to 19-7 ±3·16mmol 1−1), calcium (5·43 ± 1·696 to 1·26 ± 0·055 mmol 1−1), magnesium (259·8 ±49·3 to 19·0 ± 1·88 μmoll−1), hydrogen ions (457·7 ± 107·3 to 69·3 ± 5·64 nmol 1−1) and phosphate (2·22 ± 0·171 to 0·27 ± 0·040 mmol 1−1) were negatively correlated with flow rate. Salivary bicarbonate concentration (15·6 ± 1·76 to 2·19 ± l·83mmoll−1) showed little flow dependency except possibly at high levels of stimulation. Spontaneous secretion was not observed during anaesthesia.

During continuous stimulation of flow at two rates (0·5 and 2·0 ml min−1) for periods of 90 min, rest transients were observed for sodium, potassium, calcium, chloride and phosphate in the initial sample and the sodium concentration rose by 17·56 % during the first 60 min of steady-state flow and stimulation.

Indications that the gland was capable of responding rapidly to changes in endogenous mineralocorticoid levels were confirmed by intracarotid infusion of aldosterone at 80μgh−1. With the mean salivary flow rate lying between 1·3 and 1·4 ml min−1, the salivary Na+/K+ ratio began to fall at 45-60 min of aldosterone infusion and after 4h of infusion had fallen to 0·62 ±0·116. Administration of deoxycorticosterone acetate (DOCA) for 21 days at 0·25 or 0·3mgkg−112h−1 caused a further lowering of the Na+/K+ ratio to 0·09 ± 0·013 at similar flow rates. Biopsy showed this increase to be associated with a moderate level of hypertrophy of the intralobular ducts of the gland. Two types of intralobular duct were identified on the basis of glycogen granulation after DOCA administration.

It was concluded that the mandibular gland of the red kangaroo, with its high secretory capacity, its responsiveness to low levels of mineralocorticoids and its saliva being essentially a markedly hypotonic sodium/potassium chloride solution, is functionally better adapted to act as the primary source of saliva used as an external coolant than is the parotid gland.
Calcium-dependent action potentials in the prothoracic gland of Manduca sexta
Authors: Eusebio EJ , Moody WJ
Published: April 2021

The physiological changes which occur during insect moulting are brought about by the steroid hormone 20-hydroxyecdysone (Riddiford & Truman, 1978). The prohormone ecdysone is secreted by the bilaterally paired prothoracic glands (PGs) in response to prothoracicotropic hormone (PTTH) released from the brain (Bollenbacher, Agui, Granger & Gilbert, 1979). Recently, Smith, Gilbert & Bollenbacher (1985) demonstrated that Ca2+ is required for PTTH-stimulated ecdysone synthesis and, consequently, proposed the existence of a hormone-dependent calcium channel associated with the PTTH receptor. In the present study, we show for the first time the existence of voltage-dependent calcium channels in PG cells. Furthermore, we have observed electrical coupling between the cells which appears sufficiently strong to permit the propagation of an action potential throughout the gland in response to stimulation at a single location.
Acquisition of potential for sperm motility in rainbow trout and chum salmon
Authors: Morisawa S. , Morisawa M.
Published: April 2021

The male reproductive organ of rainbow trout and chum salmon consists of a pair of testes and sperm ducts. Spermatozoa in the distal portion of the sperm ducts exhibit full motility in the K+-free medium. However, spermatozoa from the testis were almost immotile in this medium. This suggests that the spermatozoa acquire a capacity for movement during their passage from the testis along the sperm duct. In chum salmon migrating into a bay, the sperm duct was almost empty. However, after the fish have travelled upstream for 1 km to their spawning ground in the river, the spermatozoa have left the testis, moved into the sperm duct and are capable of becoming motile. Thus it is probable that the process of acquiring the ability to move occurs within a relatively short period in this simple reproductive organ. Additionally, testicular spermatozoa demembranated with Triton X-100 exhibited motility, although the motility was less than that of demembranated spermatozoa from the sperm duct, suggesting that the acquisition of motility may correspond with the development of some function of the plasma membrane.
Presynaptic Depolarization Mediates Presynaptic Inhibition at a Synapse Between an Identified Mechanosensory Neurone and Giant Interneurone 3 in the First Instar Cockroach, Periplaneta Americana
Authors: Blagburn Jonathan M. , Sattelle David B.
Published: April 2021

Intracellular microelectrodes were used to study presynaptic inhibition at a cholinergic synapse between identified neurones: the lateral filiform hair sensory neurone (LFHSN) and giant interneurone 3 (GI 3) in the terminal ganglion of the first instar cockroach Periplaneta americana. The LFHSN-GI3 synapse was shown to fulfil physiological criteria for monosynaptic transmission : the latency of the EPSPs was 1·4ms and was constant during high-frequency firing of LFHSN; transmission was progressively and reversibly abolished by replacement of Ca2+ with Mg2+.

Movement of the lateral filiform hair towards the cereal tip produced a burst of spikes in LFHSN and a burst of EPSPs in GI 3. Movement of the medial filiform hair towards the base of the cercus produced a burst of spikes in the medial filiform hair sensory neurone (MFHSN) and a burst of EPSPs in GI2. EPSPs evoked in GI 3 by LFHSN spikes were inhibited during bursts of EPSPs in GI 2 which were evoked by MFHSN spikes. LFHSN was depolarized and its spikes were reduced in amplitude during spike bursts in MFHSN. Reduction in LFHSN spike amplitude reduced GI 3 EPSPs. This phenomenon was attributed, therefore, to presynaptic inhibition. The occurrence of presynaptic inhibition was dependent upon the degree of delayed rectification exhibited by the LFHSN axon. Hyperpolarization of LFHSN increased spike height, but did not increase the amplitude of GI 3 EPSPs.

The delay between the onset of MFHSN-evoked EPSPs in GI2 and MFHSN-evoked depolarizations in LFHSN suggested that MFHSN does not synapse directly onto LFHSN. Neither depolarization nor hyperpolarization of GI 2 had any effect on MFHSN-mediated presynaptic inhibition of LFHSN-GI 3 transmission, therefore it was considered unlikely that GI2 synapses onto LFHSN. Prolonged hyperpolarization lowered the LFHSN spike threshold and temporarily abolished presynaptic inhibition.

Bursts of spikes in LFHSN mediated presynaptic inhibition of MFHSN-GI2 EPSPs. Mutual presynaptic inhibition by the FHSNs may have a functional significance in sharpening the boundaries of the GIs’ directional sensitivities.
The Telson Flexor Neuromuscular System of the Crayfish: I. Homology with the Fast Flexor System
Authors: Dumont J. P. C. , Wine J. J.
Published: April 2021

We describe the phasic neuromuscular system of the crayfish telson and establish its homology with the abdominal flexor system that provides the power stroke for tailflip escape responses. Three paired phasic telson muscles are innervated by 11 paired neurones which have somata in the terminal (sixth) ganglion and axons in the sixth nerve. These are the posterior and ventral telson flexors and the anterior telson muscle. Studies of embryonic ganglia provide evidence that the sixth ganglion is a fusion product of two ancestral ganglia, plus a partial ganglion that is not homologous with the segmental ganglia. Two of the telson flexor motor neurones are homologues of the single motor giant found in each anterior hemiganglion. Among the shared features which led to this conclusion are: size, soma position, distribution of terminals to the muscles, dendrite morphology, pattern of direct inputs from the giant axons, and the marked tendency for low-frequency depression of the neuromuscular synapse. Two of the telson flexor neurones are homologues of the single flexor inhibitor found in each anterior hemiganglion. In addition to numerous morphological similarities, these two cells produce IPSPs in the telson flexor muscles. Six of the seven remaining motor neurones were identified as homologues of the non-giant fast flexor excitors of anterior ganglia. These can be divided into two uneven groups according to their ganglia of origin. The sixth segmental group of fast flexor motor neurones consists of four neurones (one less than expected) and the seventh segmental group consists of two neurones (three less than expected). The remaining neurone provides the sole innervation of the anterior telson muscle. Although previously classified as a telson flexor muscle, we found that the anterior telson muscle moves the uropod but not the telson. The innervation of this muscle and the pattern of inputs to the anterior telson motor neurone from identified interneurones are unlike that of any fast flexor muscle or motor neurone. We conclude that the anterior telson muscle and its motor neurone are not homologues of anterior components of the fast flexor system. In anterior ganglia, a prominent premotor neurone known as the segmental giant is presynaptic to all fast flexor motor neurones except the motor giants and flexor inhibitors. We identified a single paired cell in the sixth ganglion which appears to be the segmental giant homologue.
The Telson Flexor Neuromuscular System of the Crayfish: III. The Role of Feedforward Inhibition in Shaping a Stereotyped Behaviour Pattern
Authors: Dumont J. P. C. , Wine J. J.
Published: April 2021

The telson flexor system is homologous to the fast flexor system of anterior ganglia (Dumont & Wine, 1986a), but important differences exist in connections to the telson motor giants (MoGs) (Dumont & Wine, 1986b). In this paper, we describe additional differences in connections to the telson non-giant fast flexor (FF) motor neurones and to the telson flexor inhibitor (FI). The telson FF motor neurones in ganglion 6 (G6) receive inputs similar to those in G4 and G5 (Miller, Hagiwara & Wine, 1985). The escape command neurones (lateral giants, LGs, and medial giants, MGs) in common provide weak disynaptic input via the telson segmental giant (SG6), and relatively strong tri-synaptic input via SG2, SG3 and the corollary discharge interneurones 12 and 13. There may also be some direct input from the MGs, but it, as well as the connections from SG6, appears to vary in different preparations. The compound PSP produced in telson FFs by a single LG or MG impulse was suprathreshold in only five of 55 experiments in isolated abdominal nerve cords, but the probability that a motor neurone would fire increased with additional giant axon impulses, showing that temporal summation of excitation outweighed the possible recruitment of inhibition. Firing probability was higher in semi-intact preparations, where at least one posterior telson FF was fired by a single LG impulse 50% of the time. As was pointed out previously (Dumont & Wine, 1986b), telson flexion would disrupt the behaviour pattern expected from LG commands. Two pathways of feedforward inhibition were found which prevent such disruption. The sensory input that recruits the LG also recruits powerful feedforward inhibition of the telson FF motor neurones, which reduces the probability that they will be fired by the LG. The same sensory stimulus also evokes inhibition of FFs in G5, excitation of FFs in G2 and G3, and mixed excitation and inhibition of FFs in G4. In addition, the telson FIs fire at short latency during LG-mediated tailflips. This occurs because the telson FIs are excited by sensory input. In fact, the firing threshold of the telson FIs to sensory input is lower than that of the LGs, at least for electrical stimulation of nerves. When the LGs do fire, they produce additional excitation of the FIs. The telson FIs also are excited by the LGs but not by the MGs. In contrast’ the anterior homologues of the telson FIs receive equivalent, delayed excitation from both MGs and LGs, and weaker sensory input, so that they tend to fire only after the peak of flexion (Wine & Mistick, 1977). The predicted net effect of these connections is that the telson flexor muscles should not contract during naturally elicited LG tailflips, and this is consistent with observed behaviour. The results can be interpreted as providing additional examples of potentially maladaptive central connections which are not expressed in behaviour because of feedforward inhibition.
Thermoregulation by Winter-Flying Endothermic Moths
Authors: Heinrich Bernd
Published: April 2021

Noctuid moths of the subfamily Cuculiinae fly in any month of the winter in the north-eastern United States when air temperatures are at least 0°C. At lower temperatures they hide under leaf litter rather than perching on trees like many summer-flying noctuid moths. Like moths of similar mass and wing-loading that fly in the summer or that reside in tropical regions, the nocturnal cuculinids fly with a thoracic temperature of 30–35°C. The generation and maintenance of such high thoracic temperatures at low air temperatures depends on (1) the ability to begin shivering at very low muscle temperatures, (2) a thick insulating pile, and (3) counter-current heat exchangers that retard heat flow to the head and to the abdomen, respectively.
The Effects of Reduced Gill Area and Hyperoxia on the Oxygen Consumption and Swimming Speed of Rainbow Trout
Authors: Duthie Garry G. , Hughes George M.
Published: April 2021

Rainbow trout with a cautery-induced 30 % reduction in functional gill area showed significant proportional reductions in maximum oxygen consumption in comparison to controls, but oxygen consumption at rest and at subcritical swimming speeds was not affected. This corroborates suggestions that total gill area is utilized for oxygen uptake only under conditions of maximum aerobic demand. During swimming trials, hyperoxia (, 300mmHg) neither increased of control fish nor compensated for the reduced apparent in fish with reduced gill area. Therefore a direct limitation on oxygen uptake at the gills is implied.
A Comparative Study of the Flight Mechanism of Diptera
Authors: Ennos A. Roland
Published: April 2021

The mechanism of dipteran flight has been investigated in a comparative study involving thorax manipulation, analysis of high-speed films and direct observation of tethered flies under stroboscopic illumination. The click action observed in CCl4-anaesthetized Calliphora was found to be due to an interaction between the radial stop and the pleural wing process at the top of the upstroke. The movements occurring during unanaesthetized tethered flight were quite different as these structures were vertically separated except towards the bottom of the downstroke (Miyan & Ewing, 1985a,b). Results of observations on tethered insect flight and on morphology did not give full support to either the click mechanism (Boettiger & Furshpan, 1952) or the model of Miyan & Ewing. A novel model for the wingbeat is proposed. Distortion of the thorax brought about by the flight muscles results in upward and outward movement of the lateral scutum during the downstroke and inward and downward movement during the upstroke. In more advanced flies flexion lines result in a differentiated scutellar lever and parascutal shelf. Distortion is thereby limited largely to the posterior scutum. The parascutal shelf moves as a part of the scutal distortion, not as an independent element in the articulation, and the system is not bistable. The automatic changes in angle of attack are caused by inertial and aerodynamic forces acting around the torsional axis of the wing during the beat, which twist the compliant wing base.
Hydric Conditions During Incubation Influence Locomotor Performance of Hatchling Snapping Turtles
Authors: Miller Kirk , Packard Gary C. , Packard Mary J.
Published: April 2021

Locomotor performance of hatchling snapping turtles (Chelydra serpentina) was assessed while turtles were running on land and swimming in water. Hatchlings from eggs incubated on a relatively wet substrate were faster than hatchlings from eggs incubated on a drier medium, both in absolute distance and in body lengths moved per unit time. The superior performance of turtles from the wet substrate was not due to differences in hydration of tissues, because differences in performance persisted after turtles from both groups had been fully hydrated. The superior performance of turtles from the wet substrate may stem from a greater aerobic capacity, because these animals accumulated lactate more slowly during locomotion than did turtles from eggs incubated on the dry substrate. These observations may provide a physiological basis for the improved survival of larger hatchlings of many species of reptiles.
The Wake of a Kestrel (Falco Tinnunculus) in Gliding Flight
Authors: Spedding G. R.
Published: April 2021

The wake of a kestrel gliding down a 36 m long corridor was examined using multiple-flash stereo photographs of small bubbles of helium in soap solution. Qualitatively and quantitatively, the wake is very similar to that which would be measured behind an elliptically loaded aerofoil of the same span. The significance of this close agreement with classical aerodynamic theory is briefly discussed and the results are compared with others measured or assumed in the bird flight literature.
The Wake of a Kestrel (Falco Tinnunculus) in Flapping Flight
Authors: Spedding G. R.
Published: April 2021

The structure of the wake behind a kestrel in medium-speed flight down a 36 m length of corridor was analysed qualitatively and quantitatively by stereophoto grammetry of multiple flash photographs of the motion of small soap-covered helium bubbles. The wake consists of a pair of continuous, undulating trailing vortices. The upstroke is therefore aerodynamically active and the circulation appears to remain constant along the wing whose geometry is altered during the course of the wing stroke. It is argued that the flight kinematics, and so the wake structure, of the kestrel may be typical of flapping flight at medium speeds and a flight model based on this wake geometry is presented. Rough estimates of the rate of momentum generated in the wake balance the weight almost exactly and a direct estimate of the induced power requirement from the wake measurements is obtained. The significance of these results for the various alternative aerodynamic descriptions and energetic predictions of models of flapping animal flight is briefly assessed.
Discontinuous Carbon Dioxide Release and Metabolic Depression in Dormant Land Snails
Authors: Barnhart M. Christopher , McMahon B. R.
Published: April 2021

The respiration of dormant land snails (Otala lactea Müller) is characterized by periodic retention and release of CO2. Rates of oxygen uptake and CO2 release of individuals were recorded continuously for up to 21 days. was usually low (5·6μlg−1tissueh−1) but increased up to five-fold at intervals between 20 and 50h. Snails hypoventilated and retained CO2 when was low, while periods of elevated commenced with hyperventilation and net CO2 release. The ratio varied between about 0·2 and 4·8 during these cycles. Calculated whole body CO2 content fluctuated over a range of about 4·3 mmol I−1 H2O, and was inversely correlated with .

Cycles of CO2 retention and release might be the result and/or the cause of changes in metabolic rate during dormancy. Ventilation is sensitive primarily to O2, and O2 transport appears to be diffusion-limited. A simple model based on these characteristics predicts hypoventilation and consequent CO2 retention when is reduced. Also, the close correlation of and whole-body CO2 content in snails suggests that CO2 or acid-base balance might influence metabolic rate during dormancy. The relationship between discontinuous CO2 release and respiratory water loss in insects and snails is discussed.
The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri: II. Branchial solute fluxes
Authors: Vermette M. G. , Perry S. F.
Published: April 2021

Rainbow trout were infused continuously for 24 h with epinephrine in order to elevate circulating levels to those measured during periods of acute extracellular acidosis (about 5× 10−8 mol I−1). Concomitant effects on branchial solute fluxes were evaluated. Epinephrine infusion caused complex and differential adjustments of Na+ and Cl− unidirectional fluxes (influx and efflux) resulting in a significant elevation of the arithmetic difference between Na+ and Cl− net fluxes . A significant correlation existed between and net branchial acid excretion , thereby suggesting a role for epinephrine in piscine acid-base regulation. The stimulation of by epinephrine was due primarily to a reduction in the excretion of titratable acid (JTA) accompanied by non-significant changes in ammonia excretion (JAmm) The results are discussed with respect to a role for epinephrine in regulating acid-base disturbances by interacting with branchial ionic exchange mechanisms.
Mobilization of a Coordinated Escape Response by Giant Axons in the Ophiuroid, Ophiopteris Papillosa
Authors: Yee Audrey , Burkhardt James , Gilly W. F.
Published: April 2021

The escape response of Ophiopteris papillosa to contact by a predatory asteroid consists of a fast withdrawal of the stimulated arm, completed in less than 1 s, followed by rapid locomotion carried out by coordinated rowing of the two arms opposite the one stimulated. Electrical activity recorded from the radial nerve cord (RNC) during the locomotory phase consists of small-amplitude spikes (<5μV). The initial arm jerk response is mediated by sequential activation of segmental intervertebral muscles, and the onset of activation progresses centrally at a rate of <10cms-1 commencing 100-200ms after stimulation. Electrical activity recorded from the RNC immediately after tubefoot stimulation consists of a burst of large-amplitude spikes (50-100 μV) that propagate centrally at approximately 50cms-1. Electrical activity in the RNC with the lowest threshold to direct electrical stimulation consists of large spikes propagating at a mean velocity of 55cms-1 at 13 °C, and this activity persists in a Ca2+-free medium. Electrical and tubefoot stimulation of the arm tip in the same preparation both trigger a burst of large action potentials that propagate at approximately 50cms−1. The identity of the giant axons activated by tubefoot stimulation, the path-ways they follow and their role in mobilizing the coordinated escape response are discussed.
Pharyngeal movements during feeding sequences of Navanax inermis (Gastropoda: Opisthobranchia) in successive stages of dissection
Authors: Susswein A. J. , Achituv Y. , Cappell M. S. , Bennett M. V.
Published: April 2021

Feeding in Navanax inermis Cooper was filmed and analysed after various dissections. In preparations with a cut through the body wall exposing the pharynx and buccal ganglia, completely normal feeding was observed. In addition to seven motor acts previously described in intact animals, an eighth act, peristalsis, was observed. In preparations with the pharynx excised from the animal but attached to the buccal ganglia, four motor acts were observed: flaring, expansion, contraction and peristalsis. In addition to increasing information about the nature of feeding movements in Navanax, these data indicate that preparations suitable for neuro-physiological studies are capable of producing a variety of feeding acts.
Short Communication: Critical Comments on a ‘Novel Mechanical Model of Dipteran Flight’ (Miyan & Ewing, 1985)
Authors: Pfau Hans K.
Published: April 2021

According to the classical investigation of Boettiger & Furshpan (1952), the wing beat of flies is accompanied by a bistable mechanism, the ‘click mechanism’. This mechanism is controlled by the pleurosternal and tergopleural muscles (see Heide, 1971 ; Pfau, 1978; Pfau, Schroeter & Steitz, 1977). Recently doubts have been raised concerning the existence of the click mechanism during flight (Miyan & Ewing, 1985a,b). The authors suspect that the click mechanism is an artefact of CCl4 anaesthesia and propose a novel mechanical model of dipteran flight. In the following I analyse this model critically.
Suppression of sensory to motor synaptic transmission and narrowing of the sensory neurone action potential by arginine vasotocin in Aplysia californica
Authors: Goldberg J. , Colmers W. , Edstrom J. , Lukowiak K.
Published: April 2021

The vertebrate neurohypophysial peptide arginine vasotocin (AVT), which may be endogenous to the Aplysia central nervous system, was tested for its effect on sensory to motor neurone synaptic transmission. In the semi-intact preparation, superfusion of AVT (10−6moll−1) over the abdominal ganglion decreased the amplitude of both the gill withdrawal reflex and the short-latency excitatory postsynaptic potentials (EPSPs) evoked in gill and siphon motor neurones by single action potentials elicited in sensory’ neurones. AVT slowed the rate of rise of the EPSP, enhanced the rate of homosynaptic depression, and reversibly decreased the duration of the action potential of mechanosensory neurones in isolated, perfused abdominal and pleural ganglia. Frequency-dependent prolongation of action potentials of pleural sensory cells was also decreased by application of AVT. Because this peptide has been shown to modulate the gill withdrawal reflex and its subsequent habituation, the hypothesis that AVT plays a physiological role in the expression of the suppressed behavioural state is proposed. In addition, it is proposed that modulation of the reflex by AVT occurs in part by shortening the duration of the sensory neurone action potential.
A New Field of Wing Campaniform Sensilla Essential for the Production of the Attractive Calling Song in Crickets
Authors: Schäffner Karl-Heinz , Koch Uwe T.
Published: April 2021

A field of 10–15 campaniform sensilla located ventrally on the cubital vein of the cricket’s wing is described for the first time. This field of cubital campaniform sensilla (CCS) is only found in male crickets. When the afference from the CCS was removed by lesions of the cubital nerve, the syllable pattern was disturbed: syllables were shortened, shifted or omitted, resulting in severe irregularities of the song time pattern. The songs of crickets with lesions of the CCS are shown to be significantly less attractive to the female in quantitative phonotaxis experiments. In choice tests, the song of a lesioned male must be 20 dB louder to be as attractive as an intact song.
Extracellular accumulation of proline, serine and trehalose in the haemolymph of osmoconforming brackish-water mosquitoes
Authors: Garrett M. A. , Bradley T. J.
Published: April 2021

Larvae of Culex tarsalis, a mosquito, are capable of surviving and developing in dilutions of sea water ranging from 0 mosmol l−1 to 700 mosmol l−1. In waters more dilute than 400 mosmol l−1, the larvae osmoregulate, whereas in those more concentrated than 400 mosmol l−1, the osmotic strength of the haemolymph parallels that of the medium, i.e. the larvae osmoconform. Over the full range of external concentrations tested, the larvae regulate the levels of Na+, K+, Mg2+, Ca2+ and Cl− in the haemolymph. Analyses of haemolymph samples from larvae adapted to media of 50 mosmol l−1 or 600 mosmol l−1 indicate that the increase in haemolymph osmotic concentration observed in media above 400 mosmol l−1 is due to the accumulation of organic compounds, particularly proline, serine and trehalose.