bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium Influx and Loss in Freshwater and Brackish-Water Populations of the Amphipod Gammarus Duebeni Lilljeborg
Authors: Sutcliffe D. W. 
Published: April 2021

ABSTRACT
Sodium influx was examined in Gammarus duebeni from freshwater habitats on the Kintyre and Stranraer peninsulas in western Britain, and from a brackish-water habitat in Ireland. The affinity for sodium ions in the uptake mechanism at the body surface was similar in animals from the three localities. Compared with the parent population from Kintyre, an experimental population established for 2 years in water with a lower sodium concentration showed an increased affinity for sodium. Sodium losses in the urine of animals from the above localities were negligible at external salinities below about 2% sea water. In contrast, urinary sodium losses in animals from a brackish-water population in Britain were higher at salinities ranging from 40% sea water to well below 2% sea water. The affinity for sodium ions in uptake mechanisms at the body surface and in the antennary glands of G. duebeni from a wide range of habitats shows a marked correlation with the sodium concentration of the habitat. The permeability of the body surface to outward movement of sodium is similar in G. duebeni from brackish-water and freshwater habitats. It is suggested that most of the observed physiological differences between populations of G. duebeni are phenotypic in origin. The status of the freshwater ‘race’ in Ireland is briefly discussed.
Factors Affecting the Control of Body Volume in the Larvae of the Mosquitoes Aedes Aegypti (L.) and Aedes Detritus Edw
Authors: Stobbart R. H. 
Published: April 2021

ABSTRACT
Control of body volume has been studied in closely related freshwater and salt-water mosquito larvae (Aëdes aegypti and A. detritus). In A. aegypti osmotic inflow of water is equal to the rate of extrusion in urine and is less than the rate of production of Malpighian tubule fluid. Some of this fluid is conveyed to the rectum by intestinal peristalsis dependent on adequate hydrostatic pressure in the pyloric chamber, the rest is conveyed to the midgut by retroperistalses and is resorbed into the haemolymph. Retroperistalses are normally partly inhibited by nervous control probably involving the stomatogastric system and stretch receptors in the body wall. When inhibition is stopped (by interruption of the anterior part of the nerve cord) pressure in the pyloric chamber stays low, intestinal peristalses and hence urine production are curtailed, and the larvae swell. In A. detritus urine production is apparently independent of the slow osmosis and is balanced normally by drinking. Larvae with the mouth sealed shrink in consequence of urine output. Toleration of shrinkage is probably advantageous when the larvae are in concentrated brine.
Behavioural Physiology of the Colonial Hydroid Obelia
Authors: Morin James G. , Cooke Ian M. 
Published: April 2021

ABSTRACT
Electrical, mechanical or chemical (KC1) stimuli produce similar luminescent flashing in Obelia geniculata. Hydranth withdrawal also occurs upon electrical or mechanical stimulation. Luminescent flashes in response to individual stimuli occur in bursts. The first few flashes of the burst facilitate in intensity and then decline. Successive flashes within each burst show a constant shape and duration but a variable intensity. The decay phase of the luminescent flash has a rate constant of 50 s−1 at 20 +1°C and 29 s−1 at 12 ± 1 °C. From these figures an energy of activation of about 12 kcal can be calculated. Upon stimulation, an excitation system, the luminescent potential (LP) system, initiates the luminescent effector flashing. The LPs are monophasic, positive, and slow (duration about 120 ms) and are distinguishable from contraction potentials (KPs) mouth-opening potentials (MOPs) and tentacle contraction potentials (TKPs). LPs are all-or-none, non-decremental, through-conducting (at least over short distances) and show non-polar spread. The LP systems can drive the KPs at the LP frequency. Coupling varies from none to very tight, and the degree of coupling is determined at each hydranth. Several other campanulariids and probably most, if not all, luminescent hydroids possess similar physiological mechanisms for controlling stimulus-initiated luminescent responses.
Innervation of the Abdominal Intersegmental Muscles in the Grasshopper
Authors: Tyrer N. M. 
Published: April 2021

ABSTRACT
The course of the dorsal nerve in the fourth abdominal segment of the grasshopper Melanoplus differentialis is described. Unconventional techniques of making serial sections of the dorsal nerve for examination with the electron microscope are described in detail. The method permits a higher resolution than the light microscope but lower than more conventional electronmicroscope techniques. It has been demonstrated that the median dorsal internal muscles are all innervated from eight axons in the dorsal nerve. Although there is individual variation in the size of these axons there is some indication that they can be divided into four pairs according to their size. Of the remaining 13 axons in the dorsal nerve, two supply the median external dorsal muscle and 11 are concerned with the innervation of the heart.
Desert Snails: Problems of Heat, Water and Food
Authors: Schmidt-Nielsen Knut , Taylor C. R. , Shkolnik Amiram 
Published: April 2021

ABSTRACT
The major physiological problems of survival for desert snails were studied in mcterochila boisseri, a pulmonate snail common in desert areas in the Near East. In summer these snails can be found in a dormant state on the barren soil surface, fully exposed to the sun; in winter they become active during rainy periods, when they feed and reproduce. The lethal temperature of Sphincterochila is between 50 and 55 °C, depending on time of exposure. The temperature of the dormant animal within the shell, exposed to the sun on the soil surface in summer, does not reach a lethal level, although the temperature of the surrounding soil surface far exceeds this temperature. The rate of water loss from dormant snails, exposed in their natural habitat in summer, is about 0·5 mg per day per snail. This rate, if continued unchanged, would give a yearly loss of less than 200 mg. A 4 g specimen contains about 1400 mg water, and since the water loss during the cooler part of the year probably is reduced, several years should elapse before critical levels of water loss would be reached. In snails collected in summer the water content was not reduced, indicating no measurable depletion of water reserves during the hot season. The oxygen consumption of dormant snails varies with temperature (Q10 = 2·4). It is so low that the tissues could support the metabolic rate for several years, thus permitting continued dormancy even during periods of drought extending over more than i year.
Respiration of an Air-Breathing Catfish Clarias Batrachus (Linn.)
Authors: Singh B. N. , Hughes G. M. 
Published: April 2021

ABSTRACT
The respiratory behaviour and the rate of O2 consumption and CO2 elimination has been studied in Clarias batrachus under different environmental conditions which were also designed to test its suitability for life in water and on land. The mean from water and air is about 93 cc/kg/h. It consumes more O2 from air (58·4%) than from water (41·6%). The rate of CO2 release through the air-breathing organs is very low (RQ = 0·11), much more CO2 is released through the gills and skin in water. When the fish is submerged under air-saturated water and prevented from surfacing is low (about 65 cc/kg/h). However, the fish does not struggle to breath air over a period of 6–8 h in aerated water. It exchanges about 17 % of O2 through the skin and the rest through the gills in aerated water. If the fish is maintained in still water in a closed chamber is about 61 cc/kg/h. It starts to search for air once the O2 tension in water is reduced below 100 mmHg and this searching becomes vigorous below 60 mmHg (). When exposed to air its is about 71 cc/kg/h; in air-exposed fish is about 37 cc/kg/h; hence RQ in air is only 0·52. It shows independent respiration in air although in ambient air was reduced to about 80 mmHg and rose to about 51 mmHg. When the fish is kept in deoxygenated water but allowed free access to air, is low, but RQ air is not reduced (0·51) from that of air-exposed fish. It shows dependent respiration under these conditions when aerial is reduced below 80 mmHg and raised above 50 mmHg. Clarias batrachus can live in deoxygenated water for several days if allowed free access to air, and appears to be more suited for life in poorly oxygenated water than Saccobranchus fossilis or Anabas testudineus.
The Swimming Energetics of Trout
Authors: Webb P. W. 
Published: April 2021

ABSTRACT
The wavelength, tail-beat frequency and trailing-edge amplitude have been measured for five groups of rainbow trout at various sub fatigue cruising speeds. Four groups of fish were fitted with extra drag loads. The swimming mode was anguilliform by definition, but is probably best considered as intermediate between this and the carangiform mode. The wavelength of the propulsive wave represented 0·76 of the body length. The specific amplitude (amplitude/length) tended to reach a maximum value of 0·175 at tail-beat frequencies approaching 5/sec. The product of frequency and specific amplitude was found to be linearly related to swimming speed in all five groups of fish. The critical swimming speed for the non-loaded control group was 1·73 body length/sec, and fell in groups 1–4 as the magnitude of the extra drag loads increased. The critical swimming speed for the control group is low for salmonids, probably as a result of the unfavourable history of the fish. A method is described for calculating the drag of a swimming fish from the effects of the extra loads on the characteristics of the propulsive wave. It was found that thrust, T = 7·9 (swimming speed)1 79. The thrust was approximately 2·8 times greater than that required for an equivalent straight rigid vehicle. It was calculated that the power output of the red muscle system would need to be about 0·48–0·77 ergs/sec/g muscle to overcome the drag of the fish at cruising speeds. The power output of the fish was compared with values calculated by means of mathematical models proposed by Taylor and Lighthill. It was found that the fish did not fit the assumptions made in Taylor’s model, and so power output calculations were not comparable with those calculated in the present paper. Lighthill’s model was found to give values which were within 5 % of the values calculated here at higher swimming speeds. At lower swimming speeds the values were up to about 50 % lower than expected because again the fish did not fit the assumptions involved. The relationship between thrust and swimming speed was extended into the sprint-speed range. It was calculated that fish could reach a maximum sprint speed maintained for 1 sec, provided that drag was reduced by about a half, or that the power required was that to accelerate the fish to that speed.
In Vitro Studies on the Environmental Biology of Goniodes Colchici (Denny) (Mallophaga:Ischnocera)
Authors: Williams R. T. 
Published: April 2021

ABSTRACT
Active uptake of water vapour, following previous desiccation, has been studied in the pheasant body louse, Goniodes colchici (Denny). Uptake is not continuous but occurs during limited periods of varying duration. Water vapour is taken up by adult lice at temperatures of 32–44 °C and at humidities of 60–100% R.H. The rate of uptake is not affected by temperature. The amount of uptake is not affected by humidity but is maximal at 36 ·8 °C. Water vapour is not taken up at humidities below 50 % R.H. At 55 % R.H. about half of the lice take up the normal amount, the rest none at all. Immature lice take up either much water vapour or none at all at temperatures of 32–44 °C; there is no temperature of maximal uptake. Lice are unable to take up water vapour during moulting and/or starvation. But within 48 h of moulting they are often able to take up enough to increase the body weight above its pre-moult level. It is concluded that in lice of this species the greater part of their water intake is by active uptake of water vapour. The conditions of temperature and humidity which these lice require for survival and reproduction can be understood on this basis.
The Respiratory Responses of Carcinus Maenas to Declining Oxygen Tension
Authors: Taylor A. C. 
Published: April 2021

ABSTRACT
The degree of respiratory independence shown by Carcinus under conditions of declining oxygen tension is dependent on the animal’s level of activity. Inactive Carcinus are capable of maintaining respiratory independence down to a of 60 –80 mmHg. This is achieved primarily by an increase in ventilation volume such that the amount of oxygen made available at the respiratory surfaces remains constant over a wide range of oxygen tension. The at which this can no longer be maintained corresponds closely to the at which respiratory independence is lost.
Under normoxic conditions the of the post-and prebranchial blood was 97 and 18 mmHg respectively. At the high oxygen tensions prevailing in the postbranchial blood the respiratory pigment is fully saturated. Under conditions of declining oxygen tension the heart rate remains more or less constant until the reaches 60 –80 mmHg, the onset of bradycardia coinciding with the loss of saturation of the haemocyanin. Although cardiac output falls during hypoxia, the capacity rate ratio remains approximately constant, which enables the effectiveness of oxygen uptake by the blood to remain at a high level.
Fluid Secretion by the Malpighian Tubules of the Tsetse Fly Glossina Morsitans: The Effects of Ouabain, Ethacrynic Acid and Amiloride
Authors: Gee J. D. 
Published: April 2021

ABSTRACT
The effects of three inhibitors of sodium transport on the secretion of fluid by the Malpighian tubules of Glossina morsitans have been observed. The cardiac glycoside, ouabain, affects neither the rate of secretion nor the sodium concentration of the fluid secreted when isolated tubules are bathed by solutions containing a range of sodium and potassium concentrations. Secretion is inhibited, however, by ethacrynic acid and amiloride. The results confirm that fluid secretion by the Malpighian tubules of this insect is dependent on the active transport of sodium ions and show that Na+/K+ exchange pumps are not involved in this process.
Temperature Acclimation and Oxygen-Binding Properties of Blood and Multiple Haemoglobins of Rainbow Trout
Authors: Weber Roy E. , Wood Stephen C. , Lomholt Jens P. 
Published: April 2021

ABSTRACT
Acclimation of rainbow trout to 5, 15 and 22 °C for periods exceeding 4 months had no significant effect on the oxygen affinity of whole blood or on the concentration of ATP, which is the main organic phosphate in red cells.
Slight differences were, however, found in the oxygenation properties of the haemolysates, which correlate with changes in the relative concentration of the multiple haemoglobins. The oxygen-binding properties of the main haemoglobin components account for the observed differences in the haemolysates. The possible thermoacclimatory significance of changes in haemoglobin multiplicity and co-factor concentrations is discussed.
Oxygen Dissociation Curves of the Blood of Larval and Adult Lampreys (Lampetra Fluviatilis)
Authors: Bird D. J. , Lutz P. L. , Potter I. C. 
Published: April 2021

ABSTRACT
An electrolytic method was used to plot the oxygen dissociation curves of whole blood from both the larva and adult of the lamprey Lampetra fluviatilis at a temperature of 10 °C and over a pH range of 6·5–8·1. Larval blood has a far higher affinity for oxygen than that of adults, the respective calculated P50’s at a pH of 7·75 being 1·9 and 10·7 mmHg. The high affinity of larval blood is of use to a relatively sedentary animal living in burrows, and the increased oxygen delivery pressure brought about by the shift of the curve to the right in the adult is of advantage to an animal exhibiting greater activity. The n value obtained from the Hill plots increased with increasing saturation and were lower in larvae than adults at the same level of blood saturation. The Bohr effect in larvae at 10 °C over the pH range 6·5–8·1 was – 0·25, a value which did not differ significantly from the –0·22 found in adults.
Electrically Elicited Neurosecretory and Electrical Responses of the Isolated Crab Sinus Gland in Normal And Reduced Calcium Salines
Authors: Cooke Ian M. , Haylett Beverley A. , Weatherby Tina M. 
Published: April 2021

ABSTRACT
The sinus gland (a neurohaemal organ) and its nerve have been isolated from the eyestalk of the crabs Cardisoma carnifex and Portunus sanguinolentus for studies correlating electrical responses recorded extra-cellularly from the sinus gland with hormone release. The appearance of erythrophore concentrating hormone (ECH) in the perfusate was followed by bioassay on leg segments of Ocypode pallidula.
Electrical stimulation of the sinus gland nerve (175 pulses in trains of 5 at 5/s, every 10 s) results in significant amounts of hormone appearing in the perfusate, provided that a propagated compound action potential is recorded from the sinus gland. Release is normally below assayable levels in equivalent unstimulated control periods. A single preparation will release in excess of the equivalent of 20 pg of synthetic ECH in response to the standard routine of 175 stimuli. Many such secretory responses can be obtained over periods extending to as long as 30 h.
Addition of tetrodotoxin (3 × 10−7 M) rapidly abolishes propagated electrical responses and secretion; the effects are reversible.
Perfusion with saline having 30% (7.5 mM) of normal (25 mM) calcium reduces hormone release to about 10%, while the electrical response is often augmented. In 10% normal calcium, release is further decreased, and in 1% is indistinguishable from unstimulated release; electrical responses are reduced. Reduced calcium salines also induce spontaneous unit potentials, which persist in 30% calcium saline but subside after 10 min or longer exposure to salines of lower calcium concentration. All the effects of reduced calcium salines are reversible.
Inhibition of secretion without reduction of electrical responses in 30% calcium saline provides evidence for a direct role of calcium in excitationsecretion coupling. In salines that are more calcium deficient, failure of terminal electrical responses may also contribute to reduction of secretion.
In the crab sinus gland, as in other neurosecretory systems, propagation of action potentials to the terminals causes hormone release for which the presence of external calcium is essential.
Circadian Rhythm of Output From Neurones in the Eye Of Aplysia
Authors: Benson Jack A. , Jacklet Jon W. 
Published: April 2021

ABSTRACT
A relaxation oscillator, feed-back model for the circadian clock in the eye of Aplysia is proposed to account for the experimental findings described earlier. Further data on the effects of light pulses and temperature pulses are reported here to test the hypothesis that light and temperature perturb the clock oscillation at different points in the feed-back loop. The rising phase of the CAP frequency rhythm is postulated to be due to an energy-requiring, synthesis process, and the falling phase to a passive, diffusional process. Synthesis produces a substance, C, which controls CAP frequency, and the level of which oscillates about a reference level, R. The synthesis phase of the oscillation is suggested to be temperature compensated from about 9 °C to at least 22.5 °C. Cooling the eye to 6 °C for long periods therefore inhibits synthesis so that the clock eventually stops at its lowest phase point. 12 h cold pulses of 4 °C applied during the rising phase of the rhythm (i.e. during synthesis) cause large phase delays (9 h), while similar cold pulses applied during the falling phase (i.e. during diffusion} cause only small phase delays (2 h). The action of light is to lower the value of the reference level, R, so that the constant illumination damps the oscillation until the clock is stopped at its lowest phase point. The model predicts that light pulses applied during the rising phase will effectively accelerate the increase in level of C, thus causing phase advances, while phase delays will result from light pulses applied during the falling phase. A phase response curve for 2 h, 1100 lux light pulses confirms this. A rhythm splitting effect due to an appropriately timed light pulse is predicted and tested. Possibilities of clock control of the CAP generating mechanism are discussed with reference to recent findings on the regulation of membrane potential oscillations in molluscan bursting pacemaker neurones.
Salt and Water Balance of the Spiny Lobster Panulirus Argus: the Role of the Gut
Authors: Malley D. F. 
Published: April 2021

ABSTRACT
The rate of drinking of sea water averaged 1·5 ± 0·6 ml/kg body weight per 24 h and accounts for only a minor portion of the uptake of water required to balance estimated urine production. Imbibed water and ions, except Ca2+, are absorbed or diffuse across the gut wall into the haemolymph. The gut appears to be a route of net loss of Ca2+, derived from digestive juice and sea water, from the body. The gut does not appear to be a site of regulation of ionic levels in the haemolymph or a major site of water uptake.
The Time Course of the Electroretinogram of Compound Eyes in Insects and Its Dependence on Special Recording Conditions
Authors: Kugel M. 
Published: April 2021

ABSTRACT
Electroretinograms recorded from slowly moving insects like the mealworm beetle Tenebrio molitor and the stick insect Carausius morosus are shown to be distorted by the use of electrodes of stainless steel and silver/ silver chloride wires, unless they are used in conjunction with amplifiers having extremely high input resistance. Undistorted electroretinograms can also be recorded using micropipettes filled with a suitable electrolyte. The undistorted ERG of Tenebrio molitor is monophasic, as described by Autrum (1950) for Dixippus, and as expected from his rule.
The Neuronal Control of Dragonfly Flight
Authors: Simmons Peter 
Published: April 2021

ABSTRACT
The mechanical action and innervation of the major flight muscles of dragonflies are described. All flight muscles investigated are innervated by at least 3 motor neurones and one by as many as 15. Cell bodies of motor neurones that innervate the same muscle are clustered together, and have similar, widespread dendritic branching patterns. Motor neurones of leg muscles have greater variety in cell body size and position than the major flight motor neurones.
Striking similarities between the positions of cell bodies of motor neurones in dragonflies and the positions of homologous motor neurones in other insects raise interesting questions about the evolution of insect nervous systems.