bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium Spike in the Longitudinal Muscle of the Lobworm, Tylorrynchus Heterochaetus, (Nereidae)
Authors: Ito Y. , Tashiro N.
Published: April 2021

The mechanical and electrical activities of the longitudinal somatic muscle of the nereid Tylorrynchus heterochaetus were studied by intra-and extracellular stimulating methods. The contraction elicited by electrical stimulation under isometric conditions consisted of two components, i.e. early phasic contraction and sustained contraction. The sustained contraction lasted more than 1 min after the cessation of the tetanic stimulation. The membrane potential was 62·8 mV, and spontaneous discharges with overshoot (mean 18 mV) were recorded. A similar amplitude of the spike could be recorded by the intra-cellular polarizing method. The maximum slope of the membrane potential change against a tenfold change in [K]o was 39 mV in the presence of Na+ and 48 mV in the absence of Na+. The membrane was hyperpolarized by reduction of [Na]o but not by reduction of [Cl]o. Tetrodotoxin (10−5 g/ml) blocked neither spontaneous spike generation nor spikes evoked by electrical stimulation. The spike amplitude (overshoot) was proportionally increased with increased [Ca]o in the absence of Na+. The electrical threshold and the membrane potential remained the same in the ranges of 2 and 200 mM [Ca]o in the absence of Na+. Sr2+ and Ba2+ could produce spike generation in the absence of Na+ and Ca2+. Prolongation of the spike (plateau) was observed when 20 mM Ba2+ was added to the solution containing no Na2+ and Ca2+. The electrical and mechanical properties of the muscle were discussed in comparison with those observed of the longitudinal muscle of the earthworm.
Activity Patterns and Energetics of the Moth, Hyalophora Cecropia
Authors: Hanegan James L. , Heath James Edward
Published: April 2021

The time of activity and the duration of active periods (flight) of moths of the species Hyalophora cecropia has been determined by monitoring thoracic temperature. The metabolic cost of flight per day and per adult life has been determined directly by measuring O2 consumption and indirectly by analysis of cooling curves of individual moths. An energy balance sheet has been derived which gives the metabolic cost of flight and maintenance (during torpor) over the insect’ s adult life. The metabolic stores mobilized for daily activity appear to be fixed and independent of air temperature. This mobilization of fat stores may be under hormonal control. It is metabolically more expensive for moths to be active at low air temperatures. The number and duration of active periods at low air temperatures is reduced, but, the metabolic expenditure for activity is equal to that of animals held at higher air temperatures. Females have a smaller total energy reserve than males. The number of active periods per day is not significantly different between the sexes at any given temperature, but in females the active periods are significantly shorter in duration. The flight speed has been determined, and estimates of the flight range per day and per adult life have been calculated. The ecology of H. cecropia has been discussed with respect to the timing and duration of active periods, the range and speed of flight, and the energetic cost of flight and maintenance metabolism.
Do the Monoamines in Crab Pericardial Organs Play A Role in Peptide Neurosecretion?
Authors: Berlind A. , Cooke I. M. , Goldstone Martha W.
Published: April 2021

Pericardial organs of Libinia emarginata and L. dubia were isolated, the nerves from the thoracic ganglion were stimulated electrically, and propagated electrical activity was recorded. Fluid which bathed the neurohaemal organ was assayed for cardio-excitor effects on the isolated crab heart, when necessary, made tachyphylactic to drugs. Neither 10−6 M 5-hydroxytryptamine (5-HT), 10−6 M dopamine (DA), nor 10−5 M UML applied directly to the pericardial organ evoke release, nor do DA or UML alter release in response to stimulation. The rate of cardio-excitor release is normal in pericardial organs taken from reserpinized animals. Histochemical examination of the pericardial organs by the formaldehyde-induced fluorescence method confirmed depletion of the monoamines. These experiments, taken together, provide strong evidence against a role of monoamines in the release of cardio-excitor hormone from this neurosecretory structure.
The Mechanism of Burrowing of the Mole Crab, Emerita
Authors: Trueman E. R.
Published: April 2021

The mechanism used by the mole crab Emerita for burial in sand has been studied by the analysis of cine film and electronic recordings. Digging is initiated by tactile stimulation of the base of the telson and is carried out by the fourth thoracic legs and uropods continuously excavating a cavity in the substrate. The crab moves into this in a series of steps by the action of the first three pairs of legs. These limbs function in the manner of oars, being feathered during the recovery stroke. The efficiency of locomotion and the power required for burial are determined.
The Involvement of Sodium Transport in the Volume Regulation of the Amphipod Crustacean, Gammarus Duebeni
Authors: Lockwood A. P. M.
Published: April 2021

The effect on sodium influx of reduction in the fluid volume of the amphipod Gammarus duebeni has been investigated. Removal of water and sodium by exposure to isotonic sucrose or mannitol results in no significant change in blood concentration but is followed subsequently by a marked increase in sodium influx. The increased influx is due, at least in part, to increased active uptake of sodium. Physical removal of blood by pipette stimulates a greater degree of increased uptake in some individuals by comparison with the controls. For technical reasons the increases as measured are smaller than in §2 above and in some individuals there is no response. When the blood concentration is caused to rise at the same time as body volume is reduced there is subsequent decrease in sodium influx. It is concluded that a mechanism is present which initiates an increase in sodium uptake on reduction of blood volume. This mechanism may be of value in replacing fluid loss resulting from haemorrhage, if water uptake accompanies sodium uptake. The evolutionary significance of such a mechanism is discussed in relation to development of active transport mechanisms in present-day freshwater and brackish-water forms.
Water Flow and Gas Exchange at the Gills of Rainbow Trout, Salmo Gairdneri
Authors: Davis John C. , Cameron James N.
Published: April 2021

Ventilation volume was measured directly in rainbow trout using a rubber membrane attached to the mouth which separated inspired and expired water and allowed collection of the latter. Mean ventilation volume at 8·6°C for 18 trout weighing approximately 200 g was 37±1·8 ml/min/fish. Mean ventilation rate and ventilatory stroke volume averaged 74 breaths/min and 0·5 ml/breath respectively. Ventilation volume could be increased nearly sevenfold during moderate, shortterm hypoxia as a result of a large increase in ventilatory stroke volume and a small increase in ventilation rate. The ratio between the flow rates of water and blood through the gills was approximately 10. Percentage utilization of oxygen from inspired water had a mean of 46 ± 1·5% and ranged from 23 to 64%. Artificial perfusion of the gills with water at different flow rates was achieved by tying a tube into the mouth of trout. Perfused fish could not saturate their arterial blood with oxygen at a perfusion rate of 45 ml/min but could do so at rates ranging from 85 to 1200 ml/min. Low arterial tensions at a perfusion rate approximating the mean of fish with oral membranes are probably the result of a poor pattern of water flow over the gills during perfusion. Opercular movements occurred only at perfusion rates below 700 ml/min and increased in frequency as perfusion rate dropped. This ventilatory activity may have resulted from receptors sensitive either to water flow over the gills or to arterial . As perfusion rate went up cardiac output and oxygen uptake increased. These changes were accompanied by a drop in dorsal aortic pressure which reflected vasodilation of the gills and peripheral circulation. This change in the pattern of blood flow through the gills contributed to a 50% increase in oxygen transfer factor across the gills. At the highest perfusion rates there was no apparent impairment of gas exchange even though anatomical deadspace was probably high.
Bird Respiration: Flow Patterns in the Duck Lung
Authors: Bretz William L. , Schmidt-Nielsen Knut
Published: April 2021

A heated thermistor probe was designed to determine the direction of air flow in the respiratory system of birds. The probes did not significantly affect the respiratory rates, tidal volumes, or body temperatures of birds implanted with the probes as compared to unimplanted birds. Air-flow directions were determined in the primary bronchus, the craniomedial secondary bronchi, and the caudodorsal secondary bronchi in the lungs of ducks which were either unanaesthetized and at rest, anaesthetized, or panting due to heat load. The recorded air-flow directions suggested the following patterns of air flow in the duck lung for resting respiration. During inspiration air flows to the posterior air sacs directly from the primary bronchus (the most direct route), without passing through the tertiary bronchi, while air flows towards the anterior air sacs via the caudodorsal secondary bronchi and the tertiary bronchi (thus by-passing the most direct route, the craniomedial secondary bronchi connecting these sacs to the primary bronchus). During expiration air flows from the anterior sacs to the primary bronchus via the craniomedial secondary bronchi (the most direct route), but from the posterior sacs through the tertiary bronchi and through branches of the craniomedial secondary bronchi to the primary bronchus (by-passing the most direct route, the portion of the mesobronchus posterior to the craniomedial bronchi). The patterns established for panting and anaesthetized respiration were very similar to those described for resting respiration. There was no indication of an effective shunt operating during panting to avoid excessive ventilation of the exchange surfaces of the lung. Flow in the tertiary bronchi appeared to be in the same direction during both inspiration and expiration (from the caudodorsal secondary bronchi towards the craniomedial secondary bronchi). Such unidirectional flow would permit the operation of a counter-current exchange system, provided that the blood vessels are arranged appropriately around the parabronchi.
Orientation by Jumping Spiders in the Absence of Visual Feedback
Authors: Land M. F.
Published: April 2021

Jumping spiders turn to face moving objects. These turns are mediated by the lateral eyes. They can be accomplished accurately whether or not the spider sees the relative movement of the stimulus across the retinae which would normally result from such a turn. The spider’s response to an adequate stimulus may be: (i) to make a ‘complete’ turn resulting in fixation by the antero-median eyes; (ii) to make a ‘partial’ turn of 10–20°, whose magnitude is independent of stimulus position, and which does not result in fixation, or (iii) to ignore it. To be seen, a stimulus must subtend more than 0–7° (slightly less than the distance between receptors) and must move through a minimum angle of about i°. The probability of a turn being made is greatest for stimuli 40–90° from the spider’s front, and decreases to a low value for stimuli behind the animal, and immediately in front of it. Repeated presentation of a stimulus to one part of the retina results in a rapid decrease to zero of the probability of a turn being made, but turns can still be evoked by moving the stimulus a few degrees to a previously unstimulated part of the retina. Habituation does not affect the sizes of the few turns that are made. Dishabituation can be caused by mechanical stimulation, or it may occur spontaneously. The fields of view of the lateral eyes have been measured in the horizontal plane by blinding each eye and determining the parts of the visual field from which turns could not be evoked. Three kinds of response mediated by the lateral eyes, in addition to turns towards the stimulus, are described.
Temperature Regulation of the Sphinx Moth, Manduca Sexta
Authors: Heinrich Bernd
Published: April 2021

The sphinx moth, Manduca sexta, maintained an average thoracic temperature of 40–42°C during free flight in ambient temperatures (TA) of about 16·33°C. In the extremes, the excess of thoracic temperature TTh over TA varied from a mean of 25°C at 12·5°C, to a mean of 8°C at a TA of 35°C. During tethered flight TTh increased directly with TA, and the excess of TTh over TA varied from about 11-4°C. The oxygen consumption was about 45-50 c.c. Oa/g h during free flight from ambient temperatures of 15 –30°C. During captive flight the oxygen consumption was about 21 c.c. O2/g h. The wing-beat frequency and amplitude during both free flight and captive flight did not vary significantly with TA. The wing-beat frequency was about the same during free flight and captive flight but the wing-beat amplitude was significantly less in the latter. The moths showed little variation of flight speed with respect to TA on the flight mill. The difference between TTh and TA was strongly correlated with flight speed at low, but not at high, TA. The cooling rate of dead moths was only slightly correlated with air speeds from 2 to 5 m/s. The cooling rate of thoraces without scales was 2·4 times as great as with scales intact at an air flow 2 m/s, but the cooling rate of the abdomen was only slightly increased after the removal of its scales. The data suggest that the rate of metabolism during flight is altered with regard to the flight effort, but not with regard to temperature-regulation. Heat is actively dissipated from the thorax during flight at high TA, or during fast flight when TTh reaches 40°C or above.
Temperature Regulation of the Sphinx Moth, Manduca Sexta: II. Regulation of Heat Loss by Control of Blood Circulation
Authors: Heinrich Bernd
Published: April 2021

The circulatory anatomy of Manduca sexta is such that heat loss from the thorax is minimized when the flow of blood is reduced, and maximized when it is increased. Abdominal temperatures immediately after flight suggested that blood flow was substantially increased during flight at high TA, and greatly reduced during flight at low TA. When the thorax was artificially heated, the pulsation rates of the abdominal blood vessel increased, the amplitudes-of the pulsations became large, and the pulsations were always in the posterior-anterior direction. Heating of the abdomen often resulted in the constriction of the abdominal vessel and a reduction in the amplitude of the pulsations. Transection of the ventral nerve cord reduced the frequency of the high-amplitude pulsations and abolished the ability of the abdominal heart to respond to thoracic heating. When the heat was applied to the thorax, but not to the abdomen: (a) TTh increased while remained near TA, (b) TAb then increased while TTh stabilized near 40–42°C; (c) finally, if the heat input was not excessive, TAb also stabilized at a temperature above TA. Neither stabilization of TTh nor increase of TAb were observed during thoracic heating of dead moths or those with transected nerve chords. The distribution of temperature observed in the abdomen during thoracic heating is not explicable in terms of heating by conduction from the thorax. During modest thoracic heating, decreases of TTh were correlated with intervals during which there were full-length pulsations of the dorsal vessel. During periods where movement of the vessel was observed only at the anterior end of the abdomen, the temperature of the thorax increased. Calculations of blood flow and heat flux indicate that the regulation of TTh in the observed range is physically reasonable by blood circulation alone.
Evidence for Na+/H+ and Cl−/HCO3− Exchanges During Independent Sodium and Chloride Uptake by the Larva of the Mosquito Aedes Aegypti (L.)
Authors: Stobbart R. H.
Published: April 2021

Ionic movements into and out of the starved salt-depleted fourth instar larvae of Aëdes aegypti have been studied during independent uptake of Na+ and Cl−. About 33% of the Na+ taken up from Na2SO4 is balanced electrically by a loss of K+, about 49% is exchanged for H+, and about 17·5% is accompanied by SO4−2. About 36% of the Cl− taken up from KCl is presumably balanced electrically by a loss of unknown and possibly organic ions, about 41% is exchanged for HCO3− (and possibly OH−) and about 23% is accompanied by K+.
Calcium Regulation in the Freshwater Mollusc, Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)
Authors: Greenaway Peter
Published: April 2021

Calcium regulation in normal and calcium-depleted snails has been investigated. L. stagnalis has an uptake mechanism with a high affinity for calcium ions and shows a positive calcium balance in media containing more than 0·062 mM Ca/l. Influx and net uptake of calcium are related to external calcium concentration in a non-linear manner. The uptake mechanism is half-saturated and near-saturated in external media containing 0·3 and 1·0–1·5 mM Ca/l respectively. Calcium uptake from external concentrations of less than 0·5 mM Ca/l is against a small electrochemical gradient whereas from external concentrations greater than 0·5 mM Ca/l there is no adverse gradient. Calcium depletion does not significantly alter the normal influx or net uptake rate of calcium from 1·o mM Ca/l. The calcium concentration in the blood remains constant during net uptake from, and net loss to, the medium. A comparison is made between the mechanisms of sodium regulation and calcium regulation in L. stagnalis.
Sodium Influx and Loss in Freshwater and Brackish-Water Populations of the Amphipod Gammarus Duebeni Lilljeborg
Authors: Sutcliffe D. W.
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Diel Changes in Potassium Activity in the Haemolymph of the Cockroach Leucophaea Maderae
Authors: Lettau Janine , Foster W. A. , Harker J. E. , Treherne J. E.
Published: April 2021

A technique is described for continuous measurement, with ion-selective microelectrodes, of K+ and Na+ activity in the blood of a free-walking cockroach Leucophaea maderae(Fab.).Measurements can be made for periods of up to 96 h. In LD 16:8, there is a marked and consistent pattern in the diel variation of K+ activity, with minima 1 h before dusk and 2 h after dawn. The mean diel range in K+ activity covers a drop of 67 % below the maximum daily value. The maximum range in K+ activity for an individual cockroach in 24 h was from 4·5 to 25·0 mm-K+. Simultaneous records of K+ activity and locomotor activity show that the first minimum in K+ activity occurs 1–2 h before the main, sharp peak in locomotor activity at dusk, and the second minimum 1–3 h after the subsidiary, broad peak in locomotor activity at dawn. Diel fluctuations in whole-blood potassium concentration follow a roughly similar pattern to the K+ activity changes. Comparison of the concentration and activity changes allows some speculations about the diel movements of potassium within the blood. Diel fluctuations in Na+ activity show no clear overall pattern.
The Swimming of Nymphon Gracile (Pycnogonida): the Vertical Lift Forces Generated While Swimming at Constant Depth
Authors: Morgan Elfed , Hayes Stephen V.
Published: April 2021

The vertical lift forces generated by the legs of Nymphon while swimming at constant depth have been estimated graphically using drag constants determined by a sedimentation method. Drag both normal and tangential to the different segments of the leg has been considered. When holding station Nymphon characteristically employs a low elevation beat in which the upward force produced during the power stroke of each leg only just exceeds the predominantly downward force generated during the recovery. An upward lift component is also produced late during the recovery stroke. The legs beat in a vertical plane and an investigation of the moments at the joints of the leg suggests that much of the power stroke is gravity assisted. The upward lift produced by all eight legs agreed fairly well on average with the sinking force due to the animal ‘s weight in water, and the vertical lift fluctuates rhythmically throughout the leg beat cycle. The relationship between the swimming gait and the amplitude of these fluctuations has been investigated. During the gait most frequently used by the animal fluctuations in vertical lift were found to be minimal.
The Swimming of Nymphon Gracile (Pycnogonida): The Energetics of Swimming At Constant Depth
Authors: Morgan Elfed
Published: April 2021

The mechanical power required by Nymphon for swimming at constant depth has been calculated from drag forces acting on the legs. For an adult male this was found to be 3·4 W kg. Only about 60 % of this is used to support the animal’s weight in water. The metabolic rate fluctuates spontaneously over a tidal cycle, being greatest during the ebb-tide period. The mean rate of oxygen consumption during the animals least active phase was found to be about 0·1 µl O2 mg−1 h−1. The total carbohydrate and lipid immediately available for combustion have been estimated at 4·64 and 16 µg/mg wet wt respectively. These quantities should be adequate for about 42 h periodic swimming in an adult Nymphon.
Electrophysiology and Luminescence of An Ophiuroid Radial Nerve
Authors: Brehm Paul
Published: April 2021

All-or-none single unit spikes were recorded from an ophiuroid radial nerve cord. The spikes propagate non-decrementally over the entire radial nerve cord (RNC) length at rates as rapid as 78 cm−1. The neurones responsible for single unit activity reach lengths of 4−6 cm. Therefore, interneural transmission must occur for single units to be recorded over 315 cm long RNC. The electrical activity in the RNC is not affected by the removal of Na. However, all recordable electrical activity is blocked by the removal of Ca and restored by return of Ca or addition of Ba. A number of cells within and surrounding the RNC are capable of luminescing. These cells flash all along the RNC in response to RNC stimulation. The propagation of the flash is non-decremental along the RNC and travels at a rate similar to electrically recorded single unit activity in the RNC. The luminescence within the RNC and surrounding tissue requires Ca and does not require Na. Membrane fractions prepared from luminescent tissue flash in response to depolarization by KC1 or addition of the ionophore A23187 only in the presence of Ca or Sr. Neither Mn, Mg, nor Na will activate the luminescence and Ba will only slightly activate the luminescence. The coexistence of both neurones and luminescent cells within the RNC, the similar morphology of the two, and the similar ionic dependency of luminescence propagation and recorded electrical activity suggests that luminescent cells may be modified neurones. The rapid conduction velocity of both recorded spikes and propagated luminescence suggests that large neurones are present in the RNC. A small number of neurones were identified in the RNC which are 8 µm in diameter, which is considerably larger than any axons described in asteroids or echinoids. The large neurones themselves, however, have never been observed to be luminescent.
Peripheral Control of Responsiveness to Auditory Stimuli in Giant Fibres of Crickets and Cockroaches
Authors: Orida N. , Josephson R. K.
Published: April 2021

Auditory stimuli initiate ascending activity in large fibres of the ventral nerve cord of the cricket, Acheta domesticus, and the cockroach, Periplaneta americana. This auditory responsiveness is reduced during locomotion. An earlier study concluded that the depression of responsiveness was mediated by descending inhibition. However, the auditory responsiveness is reduced during locomotion even after section of the ventral nerve cord anterior to the abdominal recording electrodes. Further, auditory responsiveness of isolated abdomens attached to intact animals is inhibited during locomotion of their hosts. Laminar wind streams over the cerci depress responsiveness to sound, but only at velocities markedly higher than those encountered by freely walking animals. Although the exact mechanism is not known, the depressed auditory responsiveness can occur independently of any descending influences.
Ion-Selective Electrode Studies on the Effects of 5-Hydroxytryptamine on the Intracellular Level of Potassium in an Insect Salivary Gland
Authors: Berridge M. J. , Schlue W. R.
Published: April 2021

Potassium-sensitive microelectrodes were used to measure the intracellular level of potassium in Calliphora salivary glands. During stimulation with 1·10−8 M 5-HT, the potassium concentration increased from a resting level of 133·2 to 139·0 mm. When the external concentration of potassium was reduced below 2 mm there was a rapid loss of potassium which could be partially reversed by 5-HT. During 5-HT stimulation, the addition of ouabain had no effect on a number of parameters including the rate of fluid secretion, the ionic composition of the saliva and the intracellular level of potassium. The possibility that potassium enters the cells passively is discussed.