bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Nature of Cellular Volume Regulation in Marine Bivalves*
Authors: Pierce Sidney K. , Greenberg Michael J. 
Published: April 2021

ABSTRACT
Regulation of cell volume utilizing intracellular free amino acids has been studied in isolated ventricles from marine bivalves of the genus Modiolus. As in the intact animal, ventricles taken from Modiolus acclimated to various salinities show only a slight change in tissue hydration. This control over cell volume is accomplished by isosmotic intracellular regulation of taurine, alanine, glycine and proline concentrations. When stressed with decreased external salinities the isolated spontaneously beating ventricle becomes quiescent for a period, and then resumes activity. During the period of quiescence ninhydrin-positive substances (NPS) are released. The duration of quiscence and the amount of NPS released increase with increasing dilution of the external medium. The salinity-induced NPS efflux is composed of taurine, alanine, glycine and proline. In molluscs, the amino acids utilized for volume regulation are released from the cells unchanged and are not degraded into keto-acids and ammonia as they are in the crustaceans.
Kinetics of Water and Chloride Exchanges During Adaptation of the European Eel to Sea Water
Authors: Kirsch R. , Mayer-Gostan N. 
Published: April 2021

ABSTRACT
Since Smith (1930) and Keys (1933) studied water and electrolyte exchanges in the eel much work has been done on osmoregulatory problems in teleosts, and the fundamental principles of osmoregulation in this group have now been established. The freshwater teleost drinks little and urinates abundantly to compensate for osmotic water uptake through the gill; the marine teleost drinks abundantly (‘drinks like a fish’ in fact) to make good water loss through the gill. The eel, euryhaline and migratory in varying salinities during its life-cycle, is an excellent choice for the study of osmoregulatory problems.
Transferring an eel from fresh water to sea water results in an increase of plasmatic electrolytes (Oide & Utida, 1968 ; Mayer & Nibelle, 1970; Kirsch, 1972). This increase could be caused by all or any of three factors – factors which it is difficult to dissociate experimentally or to estimate quantitatively. They are: (a) dehydration due to the reversal of the osmotic gradient between internal and external media; (b) an influx of electrolytes temporarily higher than the outflux ; (c) a considerable uptake of water from the digestive tract.
The present work is concerned with the last of these phenomena, with regard to which previous data are contradictory. Oide & Utida (1968) report a gradually increasing ingestion of sea water in vivo with a maximum on the 5th day after transfer, followed by a reduction and stabilization. Kirsch (1972b) isolated the head region of the eel and observed a considerable ingestion of water at the moment of osmotic shock. We have therefore undertaken complete and detailed study of the kinetics of the drinking rate during sea-water adaptation, with a parallel study of the little-known chloride exchanges. Dehydration was also followed indirectly by measurements of body weight.
Water Uptake and Loss in Relation to the Salinity of The Medium in the Amphipod Crustacean Gammarus Duebeni
Authors: Lockwood A. P. M. , Inman C. B. E. 
Published: April 2021

ABSTRACT
The water fluxes across the body surface and the rate of urine production have been studied in the euryhaline amphipod Gammarus duebeni. Urine flow rates (fPOs) have been determined from measurements of loss of [131I]sodium diatrizoate from the body, and the expected urine flow (fPdiff) has been calculated from determinations of the osmotic gradient between blood and medium and the flux of tritiated water. For animals in 2% and 40% sea water the ratio of fPos/fPdiff are 1 ·16 and 1 ·44 respectively, and thus approximate fairly closely to unity. This implies that in these media the water subsequently excreted as urine enters the body by osmosis and that there is little interference with the free diffusion of water at the body surface due to passage through long pores or across unstirred layers. In sea water the ratio fPos/fPdiff is normally (assuming an osmotic gradient of 10 m-oamoles) almost twice unity but urine production is approximately halved when the animals are exposed to sea water saturated with an inhibitor of active sodium uptake (thionine). It is suggested that there is a prima facie case for assuming that part of the fluid subsequently excreted by this species, when in sea water, is taken into the body initially by a process dependent upon active ion transport.
Localization of Ion-Transport in the Intestine of the Migrating River Lamprey, Lampetra Fluviatilis L
Authors: Pickering Alan D. , Morris R. 
Published: April 2021

ABSTRACT
Isolated intestinal preparations from migrating Lampetra fluviatilis re-adapted to 50 % sea water were used to localize ion transport. A large, active, monovalent-ion flux was found in the anterior intestine and its magnitude decreased towards the posterior end of the intestine. The monovalent-ion flux is responsible for a net water flux from mucosa to serosa in the anterior intestine. It is tentatively suggested that both sodium and chloride are actively transported by the mucosa. The divalent ions may be carried along with the monovalent ions to a limited extent. Studies at the light- and electron-microscope levels indicate that columnar cells of the anterior intestine are responsible for ion transport, and there is evidence that the same cells produce mucus.
The Control of Walking in Orthoptera
Authors: Burns M. D. 
Published: April 2021

ABSTRACT
The patterns of leg movements during normal straight-line walking of the locust Schistocerca gregaria and the grasshopper Romalea microptera were recorded and analysed. The ratio of protraction to retraction increased with walking speed except in the prothoracic legs. At any one speed both protraction and retraction durations were variable but the variation was greatest for protraction. The locust employed an alternating tripod gait at all walking speeds recorded (2–8 steps/sec.) It displayed a high level of variability in its leg movements which appeared to be held in check by stabilising mechanisms operating on the first and last leg pairs. The movements of individual legs of the grasshopper were very similar to those of the locust but the gait used was not alternating tripod. Comparisons were made with other insects and it was suggested that the specialization of the metathoracic legs in the locust gave rise to most of the variability in leg movements and that the relative independence of the prothoracic legs reflects an exploratory role in walking.
Central Response to Infra-Red Stimulation of the Pit Receptors in A Crotaline Snake, Trimeresurus Flavoviridis
Authors: Goris Richard C. , Terashima Shin-Ichi 
Published: April 2021

ABSTRACT
Both action potentials and evoked potentials were recorded from the tectum opticum of a crotaline snake, Trimeresurus flavoviridis, in response to infra-red stimulation of the facial pit organs. Action potentials from single units were recorded throughout the tectum. Most units responded to contralateral stimulation, while some responded to both ipsi- and contralateral stimulation. Firing patterns were tonic, phasic, or phasic-tonic, depending on the position of the stimulus and the type of unit being recorded. Sensitivity to stimulus movement was observed. All potentials differed from peripheral potentials in firing patterns. Firing frequency was directly proportional to stimulus intensity. Measurements were made of the vertical and horizontal response fields of single units. Background discharge was noted in all units and its nature discussed. The integrative function of the tectum in regard to infra-red perception was also discussed, as well as the possibility of stereoscopic perception.
Water Relations in An Insect, Thermobia Domestica
Authors: Okasha A. Y. K. 
Published: April 2021

ABSTRACT
The concentrations of Na+ and K+ in the haemolymph remain relatively constant during the moulting cycle. Desiccation, desiccation followed by rehydration and starvation exert little or no effect on the concentrations of Na+ and K+ in the haemolymph. The volume of haemolymph decreases during desiccation and increases after rehydration. More Na+ is voided in the excreta during desiccation. Repeated desiccation and rehydration causes the loss of both Na+ and K+ from the body. The effects of desiccation and rehydration on the concentrations of chlorides and free amino acids in the haemolymph are described.
The Extracellular Space of A Simple Molluscan Nervous System and Its Permeability to Potassium
Authors: Mirolli M. , Gorman A. L. F. 
Published: April 2021

ABSTRACT
The movement of ions through the extracellular space in the tissues surrounding the giant neuron (G cell) of the nudibranch mollusc, Anisodoris nobilis, was studied with anatomical and physiological techniques. The diffusion pathways in the gastro-oesophageal ganglion and nerve were identified anatomically in electron micrographs obtained from preparations which were first incubated in sea water containing lanthanum chloride and subsequently fixed in a basic solution of glutaraldehyde. A lanthanum precipitate was found extracellularly in the connective sheath, in the extracellular clefts between the glial cells and in the space between the glia and the G cell. The rate of diffusion of potassium was estimated from the rate of change of the G cell membrane potential following a change in the potassium concentration of the artificial sea water bathing the preparation. The average half-time for diffusion corresponds to an equivalent diffusion pathway of about 200 μ m. This value is sufficiently close to the average length (70–95 μ m) of the pathways identified with lanthanum to suggest that the restriction to diffusion is minor. The permeability of the extracellular space to potassium is high (5· 7× 10−1 cm/sec), and our calculations show that a difference larger than 2 mM, between the potassium concentration of the external solution and that of the fluid layer adjacent to the G cell membrane, cannot be maintained under most conditions.
Ion and Water Balance in the Ixodid Tick Dermacentor Andersoni
Authors: Kaufman W. R. , Phillips J. E. 
Published: April 2021

ABSTRACT
Of the total meal imbibed by female Dermacentor andersoni during the normal adult feeding cycle, about 80% is excreted. Of the total water excreted by the tick, 75 % is removed by salivation, less than 3 % is evaporated from the integument and spiracles, and the remainder is lost via the anus. Of the total excreted sodium and potassium, 4 and 82 % respectively are lost via the anus. The remainder in each case is presumed excreted via the salivary glands. The ionic and osmotic concentrations of the haemolymph and saliva stabilize at constant values by the third or fourth day of feeding. The volume of extracellular fluid is constantly maintained at 23 % of the body weight, even though the total body weight increases 75 times over the unfed weight, and the volume of excreted fluid passing through the haemolymph is about ten times the haemolymph volume at repletion.
Ion and Water Balance in the Ixodid Tick Dermacentor Andersoni
Authors: Kaufman W. R. , Phillips J. E. 
Published: April 2021

ABSTRACT
The salivary gland of the ixodid tick, Dermacentor andersoni, can be induced to secrete fluid for at least 6 h when bathed in an artificial medium in vitro. Fluid secretion appears to be a consequence of active Cl secretion since (a) it is inhibited by 95 % when nitrate and by 100% when acetate replaces Cl in the bathing medium ; however, bromide can support secretion as well as Cl, (b) the rates of fluid and Cl secretion are linearly related to the concentration of Cl in the medium; and (c) the S/H ratio for Cl is greater than unity at all concentrations despite a transacinar P.D. of 35 mV (lumen negative). Although (in the presence of Na) a low concentration of K in the bathing medium stimulates the rate of fluid secretion fivefold, higher concentrations of K inhibit fluid secretion. The latter is largely due to a direct effect of K ion and not simply to increased osmotic pressure or reduced Na concentration. Fluid secretion is completely inhibited by 10−6 M ouabain. On the basis of these observations we propose that fluid secretion may be dependent on a Na-K activated ‘pump ATPase ‘, which is somehow involved in cation secretion. The S/H ratios of Na and K are greater than unity at all medium concentrations. The saliva secreted in vitro is slightly hypo-osmotic to the bathing medium over a wide range of medium concentration (300–920 mOsm/1). We postulate that the primary saliva is iso- or hyper-osmotic to the bathing medium; the final elaborated saliva is probably rendered hypo-osmotic by a process of solute reabsorption somewhere between the acini and the orifice of the main salivary duct.
Motor Control of Tail Spine Rotation of the Horseshoe Crab, Limulus Polyphemus
Authors: Silvey Gerald E. 
Published: April 2021

ABSTRACT
Limulus polyphemus (L.), the horseshoe crab, rotates its tail spine in order to right tself and to keep itself balanced. Eight muscles, discrete bundles of muscle fibres, move the tail spine. Fibres of the muscles contract in sequence and thereby pull consecutively on the several tendons of each muscle in order to rotate the tail spine in either a clockwise or counterclockwise direction. Motoneurones in nerves to different muscles, fibres within a muscle and units in a nerve to a single muscle fire in different sequences during clockwise and counterclockwise rotation of the tail spine. The firing pattern consists of a major burst of small to large neurons which fire in clusters, and a minor burst of small neurones which appear to fire randomly. Motoneurones in both bursts are excitatory. The major burst develops tension, the minor burst acts during extension of the muscle and presumably impedes relaxation in order to produce stable deflexion and smooth rotation of the tail spine. Muscle fibres respond to motor output with small excitatory junctional potentials of &lt; 5 mV. E.j.p.s sum and show facilitation, and in some cases develop spike-like potentials of 10–20 mV. Both spiking and the greatest increase in tension occur during the clustered firings in major bursts. Muscle fibres have sarcomere lengths of 6·5 ± 0·8 –m and diameters of 10–60 –m. Nerve fibres range from less than 3 to 32 μm in diameter in large nerve branches which contain between 50 and 100 fibres. These findings indicate that two different motor programs evoke contraction of muscle fibres in opposite sequences. Sequential contraction of fibres within a muscle means that muscle fibres which are activated together, rather than whole muscles, are the functional contractile entities.
Sodium Extrusion by A Fish Acclimated to Sea Water: Physiological and Biochemical Description OF A Na-For-K Exchange System
Authors: Evans David H. , Mallery Charles H. , Kravitz Larry 
Published: April 2021

ABSTRACT
The effect of external potassium ions on the extrusion of sodium ions by the seawater-acclimated fat sleeper, Dormitator maculatus, was investigated. Removal of external potassium ions reduced the efflux of sodium from the fish by 22% while addition of io-4 M ouabain reduced the efflux of sodium ions by 14%. Addition of potassium ions to distilled-water baths into which fish were rapidly transferred stimulated sodium extrusion in a manner which could be described by the Michaelis-Menten equation. The Km of this potassium-stimulated sodium efflux was approximately 2 mm-K/1. The calculated rate of sodium extrusion was 10 times the oral ingestion of sodium ions. Biochemical assays of the levels of the enzyme Na-K-activated ATPase extracted from gill tissue determined that seawater-acclimated fish had 3 times the enzymic activity that fish acclimated to freshwater had. In vitro potassium stimulation of the extracted Na-K-activated ATPase showed Michaelis-Menten kinetics with a Km of approximately 2 mm-K/1. It is concluded that the extrusion of sodium ions by Dormitator maculatus acclimated to sea water is coupled with potassium uptake and is mediated by the enzyme Na-K-activated ATPase.
Direct Peristaltic Progression and the Functional Significance of the Dermal Connective Tissues During Burrowing in the Polychaete Polyphysia Crassa (Oersted)
Authors: Elder Hugh Y. 
Published: April 2021

ABSTRACT
Polyphysia excavates its burrow in soft, sublittoral mud by sinusoidal waves of the septate anterior region of the body and the lateral scraping action of the prostomial horns. Associated with discrete, direct peristaltic constrictions, in which the longitudinal muscles shorten to 40%, and the circulars to 80%, of their distended lengths, hydraulic deployment of coelomic fluid converts the periodic advance of the trunk segments into continuous head progression. Direct peristaltic progression advances the body by one-fifth or less of a wavelength per cycle, which is comparable to the figure for earthworm locomotion. A three-dimensional dermal collagen fibre lattice accommodates extensive folding of the cuticle and epidermis while permitting a three-to fourfold increase in the radial dimension of the body wall during peristaltic constriction. Elastic fibre columns oppose the radial distension and control the cuticular folding. These features are seen as adaptations to burrowing in the soft mud habitat. The high degree of body-wall flexibility permits the transition from contracted to distended configuration within the length of one segment. Some three-quarters of the body surface may be in contact with the burrow wall at any one time. Unlike other soft-bodied burrowing animals the force exerted on the burrow wall is unidirectional and the applied pressure is probably small, relatively constant and spread over a wide area.
Nervous Mechanisms Underlying Intersegmental Co-Ordination of Leg Movements During Walking in the Cockroach
Authors: Pearson K. G. , Iles J. F. 
Published: April 2021

ABSTRACT
The activity in identical motoneurones innervating leg muscles of the three thoracic segments of the cockroach has been recorded in (a) normal walking animals, (b) walking animals after lesions to the nervous system and/or amputation of the mesothoracic legs, and (c) restrained de-afferented preparations. The phase of levator motoneurone burst activity of the mesothoracic leg in the metathoracic cycle is almost 0 · 5 for all walking speeds above 2 steps/sec, confirming that a tripod gait is used at all but the slowest speeds. The burst-generating systems in each segment are centrally coupled because in de-afferented preparations there is a tendency for the bursts in the mesothoracic segment to begin near the end of the metathoracic bursts, and vice versa. Sensory input from leg receptors is also important in co-ordinating stepping movements of the different legs since (a) there are some differences in motoneurone activity of de-afferented and walking preparations, and (b) amputation of the mesothoracic legs at the trochanter leads to an immediate change in the co-ordination of the remaining four legs. It is proposed that two mechanisms are important in co-ordinating leg movements in a slow walking cockroach (a) mutual inhibition between levator burst-generating systems in adjacent ipsilateral legs, and (b) an inhibitory reflex pathway from the campaniform sensilla of the trochanter to the burst-generating system of each leg. The second of these two mechanisms may become less important as the walking speed increases.
The Motor Innervation and Musculature of the Antennule of the Hermit Crab, Pagurus Alaskensis (Benedict)
Authors: Snow P. J. 
Published: April 2021

ABSTRACT
The motor innervation and musculature of the medial and distal segments of the hermit-crab antennule have been described anatomically. Intracellular recordings within these muscles and simultaneous monitoring of whole-muscle tension have been used to define the motoneurones and contractile properties of the muscle fibres they innervate. The motor system consists of two fast, two slow and one mixed muscle which are innervated by seven motoneurones. The motor innervation is such that this system may be divided into three components: phasic, phasic-tonic and tonic. The possible involvement of these components in the antennular activities is discussed. The tonic component is adapted to produce fine tonic tension in response to relatively low-frequency (5−10/sec) motoneurone discharge. It is suggested that this may be important for the postural control of appendages which, owing to the density of the environmental medium, are relatively weightless. No evidence of postsynaptic inhibition was found, and this is discussed in relation to the movements of the antennule.
The Mechanism of the Pupal Gin Trap
Authors: Bate C. M. 
Published: April 2021

ABSTRACT
The sensilla inside the gin trap are connected with an intemeurone in the ipsilateral connective above the ganglion in which their axons terminate. This cell is driven by the combined input of many fibres in the afferent bundle; it receives an inhibitory input driven by the contralateral muscle receptor organ and another driven by the contralateral trap sensilla. There is an inhibitory relation between efferent activity on opposite sides of the nervous system. A model is proposed which enhances contrast between the two halves of the nervous system by an inhibitory cross-connexion. The closure mechanism of the gin trap does not fit this model but can be derived from it by a small change in the properties of the ipsilateral junction of triggering sensilla and second-order neurones. A consequence of this theory is that the terminals of the triggering sensilla need not be identified within the central nervous system.
Statocyst-Induced eye Movements in the Crab Scylla Serrata
Authors: Sandeman D. C. , Okajima A. 
Published: April 2021

ABSTRACT
The sensory axons of the thread hair receptors, free hook hair receptors and most receptors of the statolith area of the crab statocyst all project to the same dorsolateral part of the brain. Large sensory receptors which innervate some hairs surrounding the statolith project to a more ventral site, and send some branches across to the contralateral side of the brain. The central projections of oculomotor neurones have a characteristically open branch pattern and their dendritic field corresponds closely with that of the thread hairs. There are no branches extending to the contralateral side of the brain. Intracellular responses from the motor neurones of horizontal eye-movement muscles during nystagmus show that they are probably directly inhibited during a fast-phase movement of the eye opposite to the direction in which they act. During a slow-phase eye movement opposite to their preferred direction the input to the motor neurones is diminished pre-synaptically. Sets of antagonist motor neurones maintain a fairly rigid relationship to one another so that an increase in activity of one set leads to a decrease in the antagonists. Neither this, nor the onset of the fast phase of nystagmus, is governed by proprioceptive input or by the frequency of discharge of the motor neurones themselves.