bluuebunny/crossref_metadata_2025 huggingface dataset:
Photobiology of the Chloroplast Hosting Mollusc Elysia Timida (Opisthobranchia)
Authors: Rahat M. , Monselise Edna Ben-Izhak
Published: April 2021

Photoreactive behaviour of Elysia timida was examined with regard to the posture of its parapodia, covering or exposing its symbiotic chloroplasts. In the dark, the parapodia are held dorsally close together, but they open and spread out in light, at 3 × 103 to 3 × 105 ergs. cm−2. s−1. At higher light intensities (up to 6×105 ergs. cm−2. s−1) the parapodia close up again. This behaviour is identical in normal and eyeless individuals. At a wavelength of 540 nm, the slugs open their parapodia as above, but the eyeless E. timida will not close their parapodia at the higher light intensities at this wavelength. At 445 and 650 nm, no photoreaction is observed.

It is postulated that E. timida has three photoreceptor systems. (1) An extraocular photoreceptor that differentiates between light and dark, which causes, respectively, opening or closing of parapodia. (2) The eyes, which can differentiate between optimal and above optimal light intensities (the latter causing closure of the parapodia). These photoreceptors perceive light at 540 nm, and could thus contain carotenoid photoreactive pigments. (3) An extraocular photoreceptor, which, like the eyes, can differentiate above optimal light intensities and cause parapodial closure, but only in ‘white’ light. An interaction of the first two photoreceptors could be an alternative for the function of the latter.

The form or location of the extraocular photoreceptors is unknown. It is proposed that although the symbiosis of algal chloroplasts and E. timida might be of recent evolution, this symbiosis has already affected the behaviour of the slug.
The Integration of the Patterned Output of Buccal Motoneurones During Feeding in Tritonia Hombergi
Authors: Bulloch A. G. M. , Dorsett D. A.
Published: April 2021

Three phases of activity may be recognized in the buccal mass of Tritonia hombergi during the feeding cycle. These have been termed Protraction, Retraction and Flattening. Each phase is driven by a group of motoneurones along the posterior border of the buccal ganglia. The patterned bursting observed in the motoneurone groups during feeding activity is phased by synaptic inputs which are common to two or more groups. Evidence is presented which indicates these inputs are derived from three unidentified multi-action interneurone sources within each buccal ganglion, and whose action primarily determines the patterned output of the motoneurones. Electrical coupling between between synergistic motoneurones and, in one case, post-inhibitory rebound, contribute to the synchronization of group activity. Proprioceptive input to the motoneurones was not identified, but may project to the interneurones.

Some small neurones having synaptic inputs on the motoneurones appropriate to two of the interneurones were found, but require confirmation in this role. The cerebral giant cells synapse on representatives of three motoneurone groups, and also activate the buccal interneurones driving the feeding cycle. The patterned activity of the motoneurones can occur in the absence of cerebral cell activity.
Direct Measurements of the Stiffness of Echinoderm Sperm Flagella
Authors: Okuno Makoto , Hiramoto Yukio
Published: April 2021

The stiffness (flexural rigidity) of some echinoderm sperm flagella was measured, using a flexible glass microneedle. Values of 0·3–1·5 × 10− 21 N m2 were obtained for the stiffness of live flagella which were immobilized with CO2-saturated sea water. The immobilized live flagellum was uniform in stiffness along its entire length, except in a particular plane of imposed bending in which flexible regions were observed. Demembranated flagella (Hemicentrotus pulcherrimus) in an ATP-free solution were about ten times stiffer (1·1 × 10− 20 N m2) than immobilized live ones (0·5–0·9 × 10− 21 N m2). The stiffness was decreased by addition of ATP to the solution and became equivalent to that of live ones when the solution contained 10 mm ATP. In the demembranated flagella, the effects of ADP and ATP on the stiffness were similar. Other nucleotide phosphates and inorganic phosphate did not reduce the stiffness. Young’s modulus of microtubules is estimated to be 2–5 × 10− Nm2 on the basis that the microtubules have no tight connexion with one another in immobilized live flagella.
Do Frogs Drink?
Authors: Bentley P. J. , Yorio T.
Published: April 2021

Drinking in response to dehydration and exposure to saline solutions was measured in adult Rana pipiens, Bufo marinus and Xenopus laevis, and tadpoles of Rana catesbeiana. These animals normally occupy quite different types of environments where the possible advantages of drinking may differ. Small amounts of the external media were swallowed by all the animals and the quantity usually increased when they were placed in hyperosmotic NaCl solution. However, no relationship between the oral intake of water and the particular conditions, such as the degree of dehydration, was observed. Usually 80–90% of the total water uptake occurred by absorption across the skin. Thus although ‘secondary’ type drinking takes place, ‘primary’ drinking did not appear to occur. These results directly confirm the general popular impression that amphibians, in contrast to other tetrapods and marine teleosts, do not drink in order to rehydrate.
An Analysis of Acid-Base Disturbances in the Haemolymph Following Strenuous Activity in the Dungeness Crab, Cancer Magister
Authors: McDonald D. G. , McMahon B. R. , Wood C. M.
Published: April 2021

Enforced activity causes a marked depression of haemolymph pH in Cancer magister. Both lactate concentration and PCO2 of the haemolymph are elevated immediately following exercise but resting PCO2 is restored within 30 min whereas resting lactate levels are not restored for at least 8 h. The haemolymph acid-base disturbance is caused largely by elevated haemolymph lactate levels but a Davenport analysis based on measurements of pH and total CO2 reveals a marked discrepancy between the amount of metabolic acid buffered by the haemolymph and the lactate anion concentration. This appears due to a more rapid release of lactate from the tissues than H+ ions produced with lactate.
Reactions of the spiny lobster Palinurus Vulgaris to substrate tilt
Authors: Neil Douglas M. , Schöne Hermann
Published: April 2021

The input-output properties of the eyestalk responses of Palmurus vul­garis to substrate tilt are described in both the time and frequency domains. Trapezoidal substrate movements elicit phaso-tonic eyestalk move­ments which decay from the phasic peak to the tonic plateau with time constants of 9-2 s (tilt) and 6⋅ι s (return) (Fig. 1). Average eye excursions for tilt and return are equivalent (Fig. 2). The relationship to tilt amplitude is non-linear (Fig. 3), and with step­wise tilts in opposite directions a marked hysteresis is evident (Fig. 4). Sinusoidal stimuli produce consistent eyestalk responses (Fig. 5), and a frequency analysis reveals a high gain, phase-leading region below 0-25 Hz (Fig. 6). Around this frequency the eyestalk response is effectively a compensation with respect to both amplitude and phase position. The results are considered in relation both to the experimental arrange­ment with fixed body and vision excluded, and to the normal biological situation.
Iodine Compounds and Fertilisation
Authors: Carter G. S.
Published: April 2021

In a previous paper (Carter, 1930) it was shown that the presence of thyroxine produces effects upon the oxygen consumption of suspensions of the spermatozoa of Echinus miliaris which are in some respects similar to those produced by the secretions of the eggs of the same species. It was suggested that the secretions contain a body which has similar physiological action to thyroxine, and may be related to it in chemical structure.

The observations to be recorded in the present paper form a part of an investigation undertaken with the object of comparing the action of these substances on the phenomena of fertilisation more widely. In this paper the results of further experiments on the oxygen consumption of suspensions of spermatozoa are given. Other aspects of fertilisation will be considered in later papers. Although it is clear that such an investigation should not be confined to the gametes of one species or of one group of animals, it is also clear that the study of each species should be as complete as possible. For this reason the present paper is confined to two species of Echinus, E. esculentus and E. miliaris, the spermatozoa of which behave very differently. The experiments discussed in the previous paper were concerned with the second of these two species, and the results on that species here given are intended to extend those given in that paper.
Latitude and Relative Growth in the Razor Clam, Siliqua Patula1
Authors: Weymouth F. W. , McMILLIN H. C. , Rich Willis H.
Published: April 2021

The present paper is a study of the growth of a clam (Siliqua patula) under natural conditions and over a wide range of latitude. Various constants derived from the growth data are compared for the different localities. For this species, over the range considered, growth in the southern localities as compared with the northern is initially more rapid but less sustained, leads to a smaller total length and is associated with a shorter life span. Reasons are presented for considering the relative growth-rate as a particularly significant constant leading to more sound biological conclusions than the use of the absolute growth-rate. On the basis of the relative growth-rate, current mathematical expressions for the course of growth are discussed and a formula used which emphasises Minot’s conception of a growth-rate constantly declining with age.

This expression in which L = length at time t, e = base of natural logarithms, and B, c and k are constants, is found to graduate the extensive data in clam growth with significant accuracy.
The Thermal Death-Point of Rhodnius (Rhynchota, Heteroptera) Under Controlled Conditions of Humidity
Authors: Buxton P. A.
Published: April 2021

It has been felt for some time that the relations between insects and atmospheric humidity must often be responsible for determining the places and seasons at which particular species can exist, or be abundant. But it is not easy to devise experimental methods of testing this view, and investigating the water balance of an insect. One way of approaching the problem is explored in the present paper. I have set myself to delimit the precise conditions of temperature and humidity which are fatal to a particular insect: I hope to discover whether evaporation into dry air cools the insect and so allows it to survive higher air temperatures than it can in moist air; or whether evaporation kills the insect by causing undue loss of water; or whether the humidity of the air has little effect on the insect, even at temperatures which are nearly fatal. A serious objection to the method is that it is so laborious; allowing for preliminary work with imperfect apparatus, and for experiments with an exposure of 5 minutes which are not reported in full, I have performed over 200 experiments, using ten insects in each; as the rate of reproduction of Rhodnius (Buxton, 1930) is not very high, the work has occupied a part of my time for three years.
The Distribution of the Insoluble Nitrogen in Beta Leaves of Different Ages
Authors: Pearsall W. H.
Published: April 2021

The distribution of nitrogen in the proteins of Beta leaves of widely varying ages has been examined. The basic N fraction is relatively abundant in the youngest stages of leaf growth, but shows no significant variations in leaves of full size. The amide N fraction rises very suddenly at the beginning of the photosynthetic stage. Its subsequent decrease has been confirmed. Possible explanations of these changes are examined.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Smith Michael
Published: April 2021

The infertile egg shows no measurable consumption of oxygen.

Carbon dioxide is liberated from it at a rate which rapidly falls off from the time the egg is laid, and which varies with the temperature at which the egg is kept.

There is still an appreciable output of carbon dioxide (from 0.1 to 0.2 mg. per day per egg) from eggs kept for 100 days at 10°C.

The total amount of carbon dioxide obtained from a fresh egg (about 50 c.c.) appears too great to be accounted for on a basis of simple de-solution from the egg contents; in all probability some of it is actually generated during the storage of the egg, perhaps by the action of an acidic substance on the calcium carbonate of the shell.

There is no evidence from gas exchange for the existence of a respiratory activity, in the infertile egg, which might supply energy for maintaining an osmotic disequilibrium between yolk and white.
Influx Theory and Size of Potassium and Rubidium Pools in the Midgut of Hyalophora Cecropia
Authors: Wood John L. , Harvey William R.
Published: April 2021

The midgut contains a ‘pool’ which must mix with tracer added to the blood-side, before the transported potassium reaches a steady specific activity. The size and mixing time of the pool can be deduced from the timecourse of rate of appearance of tracer on the lumen-side, the tracer influx. The theory has been extended to cover cases where the pool-size and the transport rate vary with time. By using 42K and 86Rb together, it is shown that the midgut treats potassium and rubidium differently, rubidium being transported nine-tenths as fast as potassium, when both are present in equal concentration. The influx pool for potassium is one-third larger than that for rubidium, but mixes four-fifths as fast with blood-side tracer. The size of the potassium pool decreases with time, but that for rubidium does not, and the ratios of mixing times and transport rates are constant. The implications of the results are discussed, both in terms of the accuracy of previous investigations and with respect to the probable intracellular location of part of the influx pool.
Compartmental Osmotic Pressures in the Rectal Complex of Tenebrio Larvae: Evidence For A Single Tubular Pumping Site
Authors: Machin J.
Published: April 2021

The distribution of osmotic pressures derived from melting points of frozen sections of mealworm rectal complex is described. Animals rapidly frozen during atmospheric absorption show radially increasing values from lumen to Malpighian tubules suggesting that water uptake is driven by a single pump located in the area of highest solute concentration. Volume–concentration relationships of isolated rectal cuticle and perirectal fluid are consistent with their transmitting water passively to an area of lower solvent activity.

The rectum of animals frozen with some delay after atmospheric absorption show high osmotic pressures with no radial gradients, a condition which is thought to exist when the rectum is in its faecal dehydration mode. Rectal osmotic pressures in all absorbing animals increased towards the posterior end. Several, presumably extreme posterior tubular, osmotic pressures agree well with the 6·7 osmol.kg−1 value expected for an 88% R.H. threshold for atmospheric absorption.
Thermodynamic and Hydrodynamic Studies Relating to the Mechanochemical Cycle in the Flagellum of Crithidia Oncopelti
Authors: Holwill M. E. J. , Wais J.
Published: April 2021

The motile response of the flagellum of Crithidia oncopelti to changes in the temperature, pressure and viscosity of the environment were studied. The dependence of beat frequency on temperature and pressure can be interpreted in terms of the theory of reaction rates by making the assumption that the frequency is proportional to the rate constant of a chemical reaction within the flagellum. For viscosities below a characteristic value, which depends on the temperature, increasing the pressure causes a reduction in the beat frequency. At the characteristic value, pressure changes do not affect the frequency while above this value an increase in pressure causes an increase in the frequency. Pressure and temperature changes directly affect chemical reactions within the flagella whereas alterations in viscosity produce changes which can be attributed to a modification of the microtubule sliding rate. The time for which detergent-treated flagella remain active following addition of ATP depends upon the environmental conditions. It appears that these in vitro preparations can convert only a limited amount of chemical energy into mechanical work.
The Energetics of Hovering in the Mandarin Fish (Synchropus Picturatus)
Authors: Blake R. W.
Published: April 2021

The influence of the ground effect on the energetics of hovering in Synchropus picturatus Peters, a negatively buoyant, demersal teleost was studied. Changes in pectoral fin kinematics, the ultimate water velocity in the wake below the fins, the calculated minimum induced thrust and power required to hover are related to the height at which the animal hovers above the substrate. The profile power required to overcome the frictional drag on the fins has been calculated for the case of both a laminar and a turbulent boundary layer over the fins. Reductions in the total power needed to hover (as compared with that required out of ground effect) of 30–60% have been calculated for Synchropus when hovering at commonly observed heights above the bottom. Results are discussed in relation to the hovering flight of birds, insects and helicopters.
Continuous Evaluation of In Fish: Recording and Data Processing
Authors: Belaud Alain , Trotter Yves , Peyraud Claude
Published: April 2021

In the eel (Anguilla anguilla L.), the dorsal and ventral aortas and the subhepatic vein were catheterized to provide an external circulatory shunt. in the shunted blood was continuously recorded using a polarographic measuring device. Spontaneous interruptions in the eel’s ventilatory activity result in rapid changes in . The period of these oscillations is sometimes less than 1 min. However, the response time of the measuring system is so great under the conditions of these experiments that only slow variations of , of a period greater than 5 min, are faithfully recorded. In view of the impractibility of technical improvement in the recording system, a data processing method was developed to reconstitute the real physiological variations from the distorted experimental recordings. Through this method of data correction, it is demonstrated that apnoeic or active ventilatory phases in the eel’s breathing pattern are not triggered by constant low values of . Other physiological applications are suggested.
The Role of Lactic Acid Accumulation in Muscle Fatigue of Two Species of Anurans, Xenopus Laevis and Rana Pipiens
Authors: Putnam Robert W.
Published: April 2021

Fatigue produced a marked increase in the lactic acid content of hind-limb muscles, the blood, and the whole animal. After 15 min of rest there was little decline of lactic acid levels but the animals could be stimulated into about 3 min of intense activity. This re-fatigue produced a further increase in lactic acid levels. Gastrocnemius muscles removed from fatigued frogs and stimulated in vitro were able to generate initial tensions similar to those in control muscles; total tension was about a third of the control value. In vitro stimulation of these muscles from fatigued frogs led to additional accumulation of lactic acid. Fatigue produced little decrease in the glycogen content of muscles in X. laevis but a marked decrease in R. pipiens. Considerable glycogen stores remained even in the muscles of re-fatigued animals. These data show that accumulation of lactic acid in muscle or blood, depletion of glycogen in muscle, or change in blood pH cannot account for fatigue in these species. Possible other causes of fatigue are discussed.
Short Communications How Honey-Bees Know Their Distance From A Near-By Visual Landmark
Authors: Cartwright B. A. , Collett T. S.
Published: April 2021

Insects generally have eyes that are close together and lenses with a very short focal length. In consequence neither stereoscopic nor focus cues can be used to measure the distance of objects that are further than a very few centimetres. To do this insects must rely on information provided by retinal image size or by motion parallax. If an insect knows how large an object appears to be at one distance, it can use image size to compute any other object distance. This method is probably used by some male hoverflies when tracking conspecifics (Collett & Land, 1975). Bulldog ants snap at an image of constant retinal size, and so open their jaws when an appropriately sized prey object comes within range (Via, 1977). The distance of an object can also be specified by the way in which its image travels across the retina or changes size when an insect moves a known distance or at a known speed. To date only stationary locusts have been shown to exploit motion parallax, which they do by performing a specialized side-to-side head and body movement (Wallace, 1959; Collett, 1978). Very little, however, is known about the ways in which freely flying insects measure their distance from stationary objects. We were interested in studying this question in honey-bees because they clearly have a good appreciation of the arrangement of stationary features in their environment, which they will demonstrate all day long as they fly between a food source and their hive. Bees can learn to locate a source of food using near-by landmarks and to do this they must know their distance from such landmarks (Lauer & Lindauer, 1971 ; Anderson, 1977). In this paper we show that honey-bees use both motion parallax and image size or change in image size in determining how far they are from a single landmark.
Measurement of Calcium Ion Concentrations in the Lateral Line Cupulae of Xenopus Laevis
Authors: McGLONE F. P. , Russell I. J. , Sand O.
Published: April 2021

Ion selective microelectrodes were used to measure the distribution of Ca2+ in the cupulae of Xenopus laevis, and to observe the effects of the Ca2+ blocker, La3+, and a Ca2+ chelating agent (EGTA) on the endocupular potential and K+ concentration. Measurements of the endocupular Ca2+ and potential were found to be in the range of 2–30 μM and 55–10 mV respectively, and their relationship indicates that Ca2+ is passively distributed in the cupula. The concentration of endocupular K+ and endocupular potential was found not to be influenced by addition of either 1 mM EGTA or 100 μM–La3+ to the bathing solution.
Neuromuscular Transmission In Peripatus
Authors: Hoyle Graham , Del Castillo José
Published: April 2021

The electrical and mechanical responses of body, leg and jaw muscle of Peripatus to electrical excitation of their motor-nerves were examined. A small twitch was obtained from each muscle, whose strength increased stepwise with increasing stimulus strength. In jaw and body muscles as many as ten increments in height were obtained with increasing stimulus strength. Only a single twitch height was obtained from the claw retractor muscle. Tetanus:twitch ratio under supraminal stimulation was less than 2:1 for jaw muscles, about 50:1 for the claw retractor and about 6:1 for muscles moving the legs. The jaw-muscle twitch duration was 0·6 s, that for the leg muscles 1·2 s and for body muscles about 3·0 s. Large miniature junctional potentials were frequently recorded regardless of electrode location. Responses to neural stimulation consisted of small junctional potentials whose height was progressively increased with increasing stimulus strength, generally with three steps. With repetitive stimulation, facilitation of the second and third junctional potentials occurred, plus summation. A few fibres gave spikes to a single shock : most gave a few spikes sporadically, during repetitive stimulation only. No abrupt tension increments occurred in whole muscles when individual fibres spiked. We saw no evidence for peripheral inhibitory axons. The excitation of Peripatus muscle is by local graded junctional potentials at distributed nerve-on-muscle fibre synapses, together with action potentials. The latter are initiated only by larger junctional potentials compounded of multiple smaller ones summated and/ or facilitated. The details of neuromuscular physiology are not compatible with the phylogenetic status commonly proposed for Peripatus.
Non-Simultaneous Auditory Masking in the Goldfish, Carassius Auratus
Authors: Popper Arthur N. , Clarke Nancy L.
Published: April 2021

Auditory thresholds were determined for 500 Hz pure tone pulses of 15, 25 and 50 ms duration presented leading, following or simultaneously with noise pulses of 50 or 250 ms duration. Masking by the noise decreased : (i) with an increase in tone pulse duration; (ii) with a shortening of the noise pulse duration; and (iii) as the interval between tone and noise pulses was increased from o to 3 50 ms. The effect of the noise was independent of whether the noise led or followed the pure tone. It is suggested that the most significant factor affecting masking was the duration of the interval between tone and noise, and that the site for the interactions between signals is central to the inner ear.
Behavioural and Physiological Aspects of Swimming in Cercariae of the Digenetic Trematode, Proterometra Macrostoma
Authors: Prior David J. , Uglem Gary L.
Published: April 2021

Cyclical swimming behaviour of the cercariae of the digenetic trema-tode, Proterometra macrostoma, involves a highly regular alternating swim-sink sequence. During periods of swimming the cercariae are propelled upward through the water by alternating lateral contractions of the tail. Following each burst of swimming the cercariae passively drift downward. Suction electrode recordings from the tail during swimming reveal that a single biphasic potential precedes each contraction in a burst. The site of initiation of the rhythmic activity is the transverse band at the junction of the furcae and body of the tail. Sensory feedback does not play a major role in maintenance of the rhythm. A burst of swimming can be initiated by tactile stimulation of the tail. At no time is a cercaria refractory to tactile stimulation. The tail of P. macrostoma cercariae is an autonomous locomotor organ specialized for the brief free-living period between emergence from the snail host and infestation of the primary host.
Occlusable Yellow Corneas in Tetraodontidae
Authors: Appleby S. J. , Muntz W. R. A.
Published: April 2021

In three species of brackish-water puffer fish (Tetraodontidae) the corneas are colourless in the dark but become yellow in the light, through the migration of pigment in chromatophore cells lining the corneal margirts. Spectrophotometry indicted the pigment to be a carotenoid. The threshold and time course of pigment migration were determined, and the effects of Unilateral illumination and optic nerve section suggest that the movement is under local control. It is shown that the increase in optical sensitivity obtained by clearing the eye of pigment should be advantageous for fish living in clear water.
Chemical Recognition and Nematocyte Excitation in A Sea Anemone
Authors: Lubbock Roger
Published: April 2021

The response of nematocytes in the anemone Stichodactyla haddoni to contact with complex organic compounds varies according to the substance concerned and in most cases according to the level of accompanying mechanical stimulation. Compounds with a proteinaceous moiety differ in their capacity to excite nematocytes, but usually tend to induce a stronger response than polysaccharides or lipids. Nematocyst discharge against foreign animals appears to be the result of a sophisticated cellular recognition process in which the nematocytes, and/or cells closely associated with them, respond to physical contact with a surface of appropriate chemical composition.
High Density Cell Water in Amphibian Eggs?
Authors: Mild Kjell Hansson , Løvtrup Søren , Forslind Erik
Published: April 2021

The exchange of isotopic water, 2H2O and H218O, has been studied in amphibian eggs. The experiments were carried out with ovarian and body cavity eggs of Rana temporaria and unfertilized eggs of Ambystoma mexicanum. The cytoplasmic diffusion coefficient for H218O was found to be 4·6 × 10− 4 cm2/s, somewhat higher than that for 2H2O, 3·4 × 10−6 cm2/s. The total change in reduced weight, ΔRW;, during the isotope experiments was compared with the total amount of water in the egg cell, m. The ratio &RW/m was significantly higher than would be expected from calculations using ordinary water density values. The results are discussed in terms of different phases of structured cell water.
Neurophysiological Correlates of the Dopaminergic Cilio-Inhibitory Mechanism of Mytilus Edulis
Authors: Catapane Edward J. , Stefano George B. , Aiello Edward
Published: April 2021

The neurophysiological regulation of gill ciliary activity by the CNSof the bivalve mollusc Mytilus edulis was studied by recording electrophysiological activity of the branchial nerve while simultaneously observing ciliary activity of the lateral ciliated cells of the gill by stroboscopic microscopy. The addition of dopamine to the visceral ganglion slowed and stopped ciliary activity by increasing the firing rate of the cilio-inhibitory dopaminergic neurones of the visceral ganglion which innervate the gill. This could be antagonized at the ganglion by pre-applications of ergonovine or methysergide, or by prior treatments of intact animals with the neurotoxin 6-hydroxydopamine. The study confirms earlier work showing the inhibitory functioning of dopaminergic neurones of the CNS and demonstrates the manner in which they may exert their effects.
Haemolymph-Volume Changes in Rhodnius Prolixus During Flight
Authors: Gringorten J. L. , Friend W. G.
Published: April 2021

Exhaustive flight in male Rhodnius prolixus Stål (Hemiptera : Reduviidae) can cause up to a 50% decrease in haemolymph volume. Insects urinate during the flight period which may account for this decrease. The percentage water in the haemolymph does not appear to change substantially during exhaustive flight.
A Novel Mechanism For Salt and Fluid Transport Across Epithelia
Authors: Edwards H. A.
Published: April 2021

Some salt transporting epithelia can absorb inorganic ions from extremely low external concentrations. Salt depleted frogs, for example, can absorb sodium ions from freshwater at concentrations down to 0·01 mM (Krogh, 1939) while freshwater mosquito larvae can maintain haemolymph sodium at 30 mM in external media containing as little as 1·55 × 10−3 mM sodium (Stobbart, 1974). The ability of the frogskin to absorb ions, into the blood, from such low external concentrations has been held to present difficulties (Hansen & Zerahn, 1964) for the classical model, which proposes a passive entry of external sodium ions into the cells and pumping at the inner epithelial membrane (Koefoed-Johnsen & Ussing, 1958). At least two current hypotheses exist to explain how net sodium transport from low external concentrations is achieved. The first postulates an involvement of ion pumps located on the outer epithelial membrane (Hansen & Zerahn, 1964; Leblanc, 1972) and the second that the electrical potential across the outer membrane is large enough to create an inwardly directed electro-chemical gradient to induce a passive entry of sodium ions from media containing as little as 1 mM sodium (Nagel, 1977). This communication proposes an alternative model for unidirectional salt transport from dilute environments which may be applicable to the uptake of cations and anions in a variety of salt absorptive epithelia.
Pharmacological Properties of Axonal Sodium Channels in the Cockroach Periplaneta Americana L.
Authors: Sattelle D. B. , Pelhate M. , Hue B.
Published: April 2021

Voltage-clamp experiments on isolated giant axons of the cockroach Periplaneta americana L. show that chemically synthesized saxitoxin specifically and reversibly blocks the transient inward sodium current without affecting the steady-state outward potassium current. From the concentration dependence of sodium, current suppression it is concluded that individual sodium channels are blocked by single molecules of synthetic saxitoxin which bind reversibly to part of the channel with a dissociation constant of 3·0 × 10−9 M. Synthetic saxitoxin blocks sodium channels in cockroach axons at a lower concentration than tetrodotoxin. Sodium channel block by synthetic saxitoxin is more readily reversed than tetrodotoxin-induced block.
Energy Metabolism of Dragonflies (Odonata: Anisoptera) at Rest and During Endothermic Warm-Up
Authors: May Michael L.
Published: April 2021

Energy metabolism at rest and during pre-flight warm-up was measured in a variety of anisopterous dragonflies. Resting oxygen consumption was similar in its relation to body temperature (Tb) and body mass to that of other insects. At 30 °C, log M = 0·91 log m + 0·44, where M is metabolism (W) and m is body mass (kg). Metabolism during warm-up was calculated both from measurements of Tb and from oxygen consumption. By the former method, log M = 1·01 log m + 2·22 at the maximum Tb attained during warm-up, and log M= 0·90 log m+ 1·87 at Tb = 30 °C. Oxygen consumption measurements mostly gave values of M about 15% higher. Total energy cost of warm-up is directly related to mass, thermal conductance and Tb at takeoff, and inversely related to warm-up rate.
Electrical Interactions Between the Giant Axons of A Polychaete Worm (Sabella Penicillus L.)
Authors: Mellon DeForest , Treherne J. E. , Lane N. J. , Harrison J. B. , Langley C. K.
Published: April 2021

Intracellular recordings demonstrated a transfer of impulses between the paired giant axons of Sabella, apparently along narrow axonal processes contained within the paired commissures which link the nerve cords in each segment of the body. This transfer appears not to be achieved by chemical transmission, as has been previously supposed. This is indicated by the spread of depolarizing and hyperpolarizing voltage changes between the giant axons, the lack of effects of changes in the concentrations of external divalent cations on impulse transmission and by the effects of hyperpolarization in reducing the amplitude of the depolarizing potential which precedes the action potentials in the follower axon.

The ten-to-one attenuation of electronic potentials between the giant axons argues against the possibility of an exclusively passive spread of potential along the axonal processes which link the axons. Observation of impulse traffic within the nerve cord commissures indicates, on the other hand, that transmission is achieved by conduction of action potentials along the axonal processes which link the giant axons. At least four pairs of intact commissures are necessary for inter-axonal transmission, the overall density of current injected at multiple sites on the follower axon being, it is presumed, sufficient to overcome the reduction in safety factor imposed by the geometry of the system in the region where axonal processes join the giant axons.

The segmental transmission between the giant axons ensures effective synchronization of impulse traffic initiated in any region of the body and, thus, co-ordination of muscular contraction, during rapid withdrawal responses of the worm.
Asymmetrical Muscle Activity During Feeding in the Gar, Lepisosteus Oculatus
Authors: Lauder G. V. , Norton S. F.
Published: April 2021

Prey capture in the spotted gar, Lepisosteus oculatus, was studied by high-speed cinematography synchronized with electromyographic recordings of cranial muscle activity. Muscle activity patterns were recorded during each of the three major phases of feeding: the initial strike at the prey, manipulation of the prey following capture, and swallowing. With one exception, the obliquus superioris, all muscles at the strike are active in a bilaterally symmetrical pattern. During the manipulation phase two distinct muscle activity patterns occur: one is characterized by symmetrical activity in the epaxial muscles and obliquus inferioris, the other by complete asymmetry between the right and left sternohyoideus, obliquus superioris, and epaxial muscles. Low-amplitude manipulatory movements are characterized by activity in one side of the sternohyoideus only, all other muscles being generally inactive. The adductor mandibulae and obliquus inferioris are always active symmetrically. Asymmetrical activity in the sternohyoideus, epaxial muscles, and obliquus superioris correlates with lateral head movements during feeding and acts to rotate prey into the preferred orientation for swallowing. The pattern of asymmetrical activity between right and left side muscles is discussed in relation to previous studies of feeding which utilized only unilateral muscle recordings.
Ionic Bases of Resting and Action Potentials in Salivary Gland Acinar Cells of the Snail Helisoma
Authors: Hadley Robert D. , Murphy A. Don , Kater Stanley B.
Published: April 2021

Values for resting and action potentials of Helisoma salivary gland cells are much the same as in most neurones and muscle cells. The resting potential is primarily due to the distribution of potassium ions across the membrane, with a small contribution by an electrogenic sodium pump. Estimated values for intracellular potassium concentration and the relative membrane permeabilities to sodium and potassium ions correspond to similar estimates in other excitable tissues. The inward current of the salivary gland action potential is carried predominantly by calcium ions and possibly serves as a mechanism of calcium entry for stimulus-secretion coupling.
Morphology and Electrophysiology of the Ovulation Hormone Producing Neuro-Endocrine Cells of the Freshwater Snail Lymnaea Stagnalis (L.)
Authors: De Vlieger T. A. , Kits K. S. , Ter Maat A. , Lodder J. C.
Published: April 2021

The ovulation hormone producing neuro-endocrine cells of Lymnaea stagnate, the caudo-dorsal cells (CDC), are comparable to the bag cells of Aplysia. Both cell types are capable of the production of a long-lasting activity (afterdischarge) during which an ovulation hormone is released. The CDC (30 cells in the left cerebral ganglion and 70 cells in the right) are usually electrically silent but an afterdischarge can be brought about in all cells of both groups by direct, repetitive electrical stimulation of single CDC. This is not possible in every preparation, indicating that the CDC can be in different states of excitability.

All cells participate in the afterdischarge and fire approximately synchronously. All CDC are electrotonically connected. Results of experiments in which neurones were injected with horseradish peroxidase suggest that the demonstrated electrotonic connexions between the two opposite groups of CDC are brought about by 10–12 special axons.
The Effects of Enforced Activity On Ventilation, Circulation and Blood Acid-Base Balance in the Aquatic Gill-Less Urodele, Cryptobranchus Alleganiensis; A Comparison with the Semi-Terrestrial Anuran, Bufo Marinus
Authors: Boutilier R. G. , McDonald D. G. , Toews D. P.
Published: April 2021

A combined respiratory and metabolic acidosis occurs in the arterial blood immediately following 30 min of strenuous activity in the predominantly skin-breathing urodele, Cryptobranchus alleganiensis, and in the bimodal-breathing anuran, Bufo marinus, at 25 °C, In Bufo, the bulk of the post-exercise acidosis is metabolic in origin (principally lactic acid) and recovery is complete within 4-8 h. In the salamander, a lower magnitude, longer duration, metabolic acid component and a more pronounced respiratory acidosis prolong the recovery period for up to 22 h post-exercise. It is suggested that fundamental differences between the dominant sites for gas exchange (pulmonary versus cutaneous), and thus in the control of respiratory acid-base balance, may underline the dissimilar patterns of recovery from exercise in these two species.
The Giant Axon Escape System of A Hydrozoan Medusa, Aglantha Digitale
Authors: Roberts Alan , Mackie G. O.
Published: April 2021

Aglantha digitale (Hydrozoa) has a ring giant axon, up to 35 μm in diameter, which runs all round the margin of the bell in the outer nerve-ring. Running from the margin, up the inside of the bell towards the apex are eight motor giant axons, up to 40 μm in diameter. These synapse with the sub-umbrellar myoepithelium and are therefore motoneurones. The myoepithelial cells line the inside of the bell and have striated muscular tails running circumferentially. Contraction of this circular musculature forces water out of the bell and propels the medusa through the water. A large axon (up to 7 μm in diameter) runs on the aboral side of each tentacle. The tentacles retract during swimming and contain longitudinally aligned striated muscle tails. Intra- and extracellular recordings from the giant axons indicate that they are involved in the rapid escape swimming response of Aglantha. Stimuli which evoke escape swimming lead to a brief burst of two to six impulses (2–3 ms in duration) in the ring giant axon. These propagate round the margin (at up to 2·6 m s−1). The large tentacle axons fire one-to-one with the ring giant axon and the tentacles contract. The motor giant axons are excited at chemical synapses (blocked by divalent cations and with a synaptic delay of 1·6 ± 1 ms), where large, facilitating epsps evoke an impulse which then propagates up the bell at up to 4 m s−1. The overshooting motor giant axon impulses are Na+ dependent, 2–3 ms in duration, and excite the myoepithelium at synapses with a 1·6 ± 1 ms synaptic delay. A regenerative muscle impulse is evoked. It is of long duration (15–70 ms), Ca2+ dependent, overshoots zero, and propagates through the myoepithelium at 0·22 to 0·29 ms−1. A nearly synchronous contraction of the whole subumbrellar circular musculature is evoked. Isolated strips of muscle can reach peak tension in 40 ms. In the absence of sarcoplasmic reticulum, Ca2+ for excitationcontraction coupling probably enters the muscle during the impulse. This preparation has allowed a clear understanding of how the two types of axon co-ordinate escape behaviour. It should also be valuable for the study of synaptic transmission, previously very inaccessible in Cnidarians.
Cockroach Giant Interneurones Stained by Cobalt-Backfilling of Dissected Axons
Authors: Harrow I. D. , Hue B. , Pelhate M. , Sattelle D. B.
Published: April 2021

Detailed neuroanatomical information is an essential prerequisite for functional analysis of specific neurones in the central nervous system. In this investigation we have combined the dissection of single axons with cobalt-backfilling to reveal the structural organisation of a class of interganglionic giant intemeurones in the central nervous system of the cockroach, Periplaneta americana (L). Each giant interneurone possesses a cell body, neurite and dendrites within the sixth abdominal ganglion and also has a giant axon which ascends the ventral nerve cord (Harris & Smyth, 1971). Cereal sensory neurones provide monosynaptic input to at least some giant interneurones (Callec et al., 1974). Furthermore the cereal afferent, giant interneurone pathway has proved to be a useful system for quantitative pharmacology of putative cholinergic synapses (Callec & Sattelle, 1973; Callec, 1974).
Membrane Currents of Pawn Mutants of the Pwa Group in Paramecium Tetraurelia
Authors: Satow Youko , Kung Ching
Published: April 2021

Membrane currents were recorded from the wild type and two pawn mutants of the pwA complementation group in Paramecium tetraurelia under a voltage clamp. Most currents are not changed by the mutations. Transient inward currents of a leaky mutant, puA132, upon step depolarizations are less than those in the wild type. The inward transient is completely lacking in a non-leaky mutant, pwA500. The time course of the residual inward currents in the leaky mutant is not significantly different from that of wild type. The voltage sensitivity of the Ca channels in the leaky mutant is also similar to that of wild type. The inward currents upon membrane hyperpolarizations in the mutants show normal characteristics in the presence or absence of external K+. With sufficiently large, prolonged depolarization, outward currents progressively develop in the wild type but decay in the mutants.

The simplest conclusion we can draw is that the pwA mutations reduce the number of functional Ca channels but do not change the channel characteristics. From the conductance measurements, 45 % of the Ca channels remain in the leaky mutant pwA132, and none remain in the non-leaky mutant pwA500..

By subtracting the outward currents of pwA132 from the slow and prolonged outward currents of the wild type, we have tentatively separated a Ca-induced K+ current from the voltage-dependent K+ current. The time courses of these two currents differ by two orders of magnitude.
The Mechanism of Fluid Absorption at Ecdysis in the American Lobster, Homarus Americanus
Authors: Mykles Donald L.
Published: April 2021

The mechanism of fluid absorption at ecdysis was investigated in the stenohaline marine decapod, Homarus americanas. Sea-water uptake began approximately 1 h before ecdysis, increased rapidly during ecdysis, and was completed 2 h after ecdysis. Increased drinking rates were measured during and just after ecdysis. The quantity of water ingested was equal to the total amount of water absorbed during moult, indicating that fluid entered the haemolymph exclusively via the lining of the digestive tract. It was estimated that 91 % of the ingested sea water appeared in the haemolymph by 2·5 h postecdysis. The midgut appeared to be the principal part of the digestive tract involved in the absorption of fluid into the haemolymph. X-radiography of lobsters that ingested a suspension of barium sulphate during ecdysis demonstrated that accumulation and concentration of this compound occurred within the midgut during the 2·5 h of haemolymph expansion following ecdysis. Elevated net water fluxes across perfused midgut were observed in late proecdysis and 0-5 h after ecdysis.
A Micropuncture Study of Kidney Function in the River Lamprey, Lampetra Fluviatilis, Adapted to Fresh Water
Authors: Logan A. G. , Moriarty R. J. , Rankin J. C.
Published: April 2021

Micropuncture techniques have been used to investigate the role of each nephron segment in the river lamprey. The proximal segment reabsorbed no more than 10% of filtered water and tubular fluid here was iso-osmotic to plasma, at about 250 m-osmol. Further water reabsorption occurred in later nephron segments so that 44% of all filtered water was reabsorbed. Dilution of tubular fluid began in the ascending limb of the nephron loop and continued in the distal and collecting segments, so that 96% and 97· 5% °f filtered sodium and chloride, respectively, was reabsorbed by the kidney. Lampreys produce 337 ml kg−1 day−1 of a dilute urine (31·2 m-osmol) and the urinary ducts appear not to modify the composition of this urine.