bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of Water and Some Ions in Gammarids (Amphipoda)
Authors: Sutcliffe D. W.
Published: April 2021

A comparison was made of the body water contents and the concentrations of sodium, potassium and chloride in the blood and body water of Gammarus zaddachi, G. locusta and Marinogammarus finmarchicus. G. zaddachi had a slightly higher body water content than G. locusta and M. finmarchicus. In all three species the blood chloride concentration was lower than the external chloride concentration in 80–113 % sea water, but the blood sodium concentration was equal to or slightly above the sodium concentration in the external medium. The total body sodium concentration was always greater than the total body chloride concentration. In M. finmarchicus the ratio of body sodium/chloride increased rom 1·2 to 1·3 over the salinity range 100–20% sea water. In G. zaddachi the ratio of body sodium/chloride increased from 1·08 at 100% sea water to 1–87 in 0·25 mM/L NaCl. The total body potassium concentration remained constant. The potassium loss rate and the balance concentration were relatively high in G. zaddachi. The porportion of body water in the blood space was calculated from the assumption that a Donnan equilibrium exists between chloride and potassium ions in the extracellular blood space and the intracellular space. In G. zaddachi the blood space was equivalent to 60% body H2O at 100% sea water, and equivalent to 50% body H2O at 40% sea water down to 0·5 mM/l NaCl. In M. finmarchicus the blood space was equivalent to 38–44% body H2O at salinities of 20–100% sea water. The mean intracellular concentrations of sodium, potassium and chloride were also calculated. It was concluded that for each ion its intracellular concentration is much the same in the four euryhaline gammarids. The intracellular chloride concentration is roughly proportional to the blood chloride concentration. The intracellular sodium concentration is regulated in the face of large changes in the blood sodium concentration.
Oxygen Tension Distribution in Water and Blood at the Secondary Lamella of the Dogfish Gill
Authors: Hughes G. M. , Hills B. A.
Published: April 2021

An analysis is given which makes it possible to trace out the changes in oxygen tensions in the blood and water during their passage along a secondary lamella of the dogfish gill. The analysis depends on a knowledge of the oxygen-dissociation curve of the blood, the shape of the secondary lamella and the oxygen tensions of the two media before and after their passage through the gills. It indicates the differences to be expected according to whether the flows are co-current or counter-current. The method, with modifications, could be applied to the gills of all fishes.
Water Relations in an Insect, Thermobia Domestica
Authors: Okasha A. Y. K.
Published: April 2021

Water uptake is not inhibited by centrifugation, exposure to 45 °C, burning of the integument or by submergence in water for 1 h. Repeated desiccation followed by rehydration does not inhibit water uptake. This, however, results in insects with an extremely high water content. Starvation also results in insects with a very high water content, the latter depending on the length of starvation, and also results in the depletion of dry matter. Desiccation followed by rehydration does not result in any loss in dry matter additional to that caused by starvation. The ability to rehydrate of insects desiccated at various stages of the moulting cycle is described. It is concluded that at the later stages of the moulting cycle water uptake ceases. The results are discussed in the light of current theories of the uptake mechanism. It is suggested that the uptake mechanism is primarily concerned with volume regulation. It is also suggested that anal blockage, which is known to arrest uptake, results in a nervous inhibition bringing about such an effect, rather than the rectum being the site of uptake."
The Swimming Energetics of Trout
Authors: Webb P. W.
Published: April 2021

The oxygen consumption of rainbow trout was measured at a variety of sub fatigue swimming speeds, at a temperature of 15 °C. Five groups of fish were used, a control group and four groups with extra drag loads attached to the body. The logarithm of oxygen consumption was linearly related to swimming speed in all five groups, the slope of the relationship increasing with the size of the extra drag load. The mean standard rate of oxygen consumption was 72·5 mg O2/kg wet weight/h. The active rate of oxygen consumption was highest for the control group(628 mg O2/kg/h) and fell with increasing size of the attached drag load. The active rate for the control group was high in comparison with other salmonid fish, and in comparison with the value expected for the fish. This was not a result of the extra drag loads in the other groups. No explanation for this high value can be found. The critical swimming speed for a 60 min test period was 58·1 cm/sec (2·0 body lengths/sec) for the control group. The values for the critical swimming speeds were slightly higher than those measured for the same species in a previous paper (Webb, 1971). The difference between the two sets of critical swimming speeds is attributed to seasonal changes in swimming performance. The aerobic efficiency was found to reach values of 14·5–15·5% based on the energy released by aerobic metabolism in comparison with the calculated required thrust. The anaerobic contribution to the total energy budget in increasing-velocity tests is considered to be small, and can be neglected. It is concluded that the efficiency of the muscle system in cruising will be approximately 17–20% over the upper 80% of the cruising-speed range, while the caudal propeller efficiency will increase from about 15–75 % over same range. Consideration of the efficiency values for the caudal propeller calculated here, and those predicted by Lighthill’s (1969) model of fish propulsion, suggest that the efficiency of the propeller system will reach an optimum value at the maximum cruising speeds of most fish, and will remain close to this value at spring speeds.
Electrical Activity in the Optic Tectum and Colour Change in the Minnow (Phoxinus Phoxinus L.) *
Authors: Gentle Michael J.
Published: April 2021

The electrical activity of the optic tectum was recorded from the minnow under various conditions to investigate its relationship to colour change. The superficial E.E.G. was found to consist of two rhythms a 6–14 Hz (20–112 V) and a 18–24 Hz (6–18 μV). When the fish were deeply anaesthetized the E.E.G. was reduced virtually to nothing. Almost no activity was present in the optic tectum 30 min after bilateral blinding. There was an increase in activity after 5 h and this continued for 5 or more days but never returned to normal. In darkness the activity of the superficial E.E.G. first increased and then decreased, and when the eyes were re-exposed to light the activity increased again. The E.E.G. patterns were recorded and analysed from various depths and positions in the optic tectum during background reversal. In the stratum plexiforme et fibrosum externum, plexiforme internum and griseum internum no changes were observed. In the stratum fibrosum profundum and griseum periventriculare an increase in the high-frequency activity of approximately 10 Hz was observed on a black background.
The Neuronal Basis of A Sensory Analyser, The Acridid Movement Detector System. I. Effects of Simple Incremental and Decremental Stimuli in Light and Dark Adapted Animals
Authors: Rowell C. H. Fraser , O’shea Michael
Published: April 2021

The response of the movement detector (MD) system to proportionally constant incremental and decremental stimuli has been studied at various degrees of light and dark adaptation. Action potentials in the descending contralateral movement detector neurone were taken as the indicator of response. Over a range of at least six log10 units of adapting luminance, the MD system behaves as an on/off unit, giving responses to both incremental and decremental changes in the illumination of a 5° target. With increasing amplitudes of stimuli, both the on and off responses saturate rapidly. Saturation is reached sooner at higher levels of light adaptation. At all levels of light adaptation, the off response is greater than the on. The ratio for saturating stimuli is approximately constant at around 3:2. At the brightest adapting luminances used (20000 cd/m2) the on response is reduced but not lost. At the lowest (0·004 cd/m2) the off response to a 5° disc fails, but can be regained by increasing the test area to 10°. From what is known of the retina of locusts and other insects, it is thought that light and dark adaptation in the MD system can be adequately explained by events at the retinula cell.
The Neuronal Basis of A Sensory Analyser, The Acridid Movement Detector System. II. Response Decrement, Convergence, and the Nature of the Excitatory Afferents to the Fan-Like Dendrites of the Lgmd
Authors: O’shea Michael , Rowell C. H. Fraser
Published: April 2021

No dendritic spikes occur in the input fan of the lobular giant movement detector (LGMD) neurone. The action potentials are initiated at the point of thickening of the axon, which therefore represents the site of convergence of the retinotopic projection in the MD system. Previous work has shown that the site of decrement in response to repetitive visual stimulation is distal to this point. No change in spiking threshold in the LGMD could be demonstrated, and decrement in the number of LGMD action potentials is completely explained by the observed decrement of EPSPs recorded in the LGMD input dendritic fan. Possible postsynaptic mechanisms which might affect EPSP amplitude are excluded experimentally or shown to be improbable. Latency measurements during electrical stimulation in the second chiasma (which produces a decrementing EPSP in the fan) indicate that the pathway from the chiasma afferents to the LGMD fan is probably monosynaptic. By exclusion, the site of decrement appears to be located at the presynaptic terminal of that synapse. Generalization of habituation of the response to ON and OFF stimuli is demonstrated, showing that the presynaptic neurone at the labile synapse is an ON/OFF unit. The greater part of the previously described sensitivity gradient on the retina, relative to the MD response, appears to be explicable by the geometry of the LGMD fan and of the retinotopic projection. We conclude that the LGMD is fed by a homogeneous population of ON/OFF units running in the second optic chiasma, which form labile synapses on the input fan.
Active Transport of Calcium Across the Isolated Midgut of Hyalophora Cecropia
Authors: Wood John L. , Harvey William R.
Published: April 2021

The net flux of 45Ca from lumen to blood side across the isolated and short-circuited Cecropia midgut was 1·9 ± 0·2 μequiv. cm−2 h−1 in 8 mm Ca and the flux ratio was as high as 56 to 1. The calcium influx was depressed by anoxia; 73 % after 30 min. The kinetics of Ca transport were anomalous; the apparent Km varied with Ca concentration from < 0·2 to > 5·6 mm Ca and the apparent Vmax varied from < 1·3 to > 3·3 μequiv. cm−2 h−1. The calcium influx showed a delay before the tracer steady state was attained, indicating the existence in the transport route of a calcium pool equivalent to 5·7 μequiv/g. wet weight of midgut tissue. High calcium (16 mm) depressed the short-circuit current and potassium transport from blood to lumen side across the midgut. Calcium depressed magnesium transport, from lumen to blood side across the midgut, and magnesium depressed the calcium transport. Ca transport by the midgut does not regulate the Ca level in the haemolymph in vivo; it merely aids the diffusion of calcium down its electrochemical gradient. However, Ca transport may assist the uptake of the nutrients from the midgut contents.
Importance of Air and Water Breathing in Relation to Size of the African Lungfish Protopterus Amphibius Peters*
Authors: Johansen K. , Lomholt J. P. , Maloiy G. M. O.
Published: April 2021

Oxygen uptakes from air and water have been measured in relation to weight of the African lungfish Protopterus amphibius Peters. Combined O2 uptake from air and water ranged from 60 ml O2 kg−1 h−1 STPD, in a 3·7 g specimen, to 30 ml O2kg−1 h−1, in a 255 g specimen. While the combined O2 uptake changed by a factor of 2, within the weight range under study, the aquatic O2 uptake changed 8-fold within the same range. The smaller fish satisfy 70% of their O2 requirement by aquatic breathing compared to 10–15% in the grown specimens. The pattern of bimodal breathing in P. amphibius is discussed in relation to the natural habitat of the species.
Possible Involvement of Monoamines in the Release of Adipokinetic Hormone in the Locust Schistocerca Gregaria
Authors: Samaranayaka Manthri
Published: April 2021

The adipokinetic hormone release, which can be induced by anticholinesterases, is reduced by depleting the content of monoamines in the nervous system. The participation of monoamines in the pathway of release of adipokinetic hormone is studied in vivo and in vitro. A possible mechanism for anticholinesterase-induced release of this hormone involving cholinergic and aminergic transmission is postulated.
Interactions of Membrane Potential and Cations in Regulation of Ciliary Activity in Paramecium
Authors: Machemer Hans
Published: April 2021

Ciliary activity in Paramecium was investigated in different external solutions using techniques of voltage clamp and high frequency cinematography.

An increase in the external concentration of K, Ca or Mg ions decreased the resting potential. It had no effect on ciliary activity.

When the membrane potential was fixed, an increase in external Ca or Mg and, to a lesser extent, an increase in K concentration, raised the frequency of normal beating or decreased the frequency of reversed beating of the cilia. Similar effects resulted from membrane hyperpolarization with constant ionic conditions.

Increase in concentration of Ca, but not of Mg or K, enhanced hyperpolarization-induced augmentation of ciliary frequency. Increase in Ca concentration also specifically augmented the delayed increase in inward current during rapid hyperpolarizing clamp.

The results support the view that [Ca]i regulates the frequency and direction of ciliary beating. It is suggested that the insensitivity of the ciliary motor system to elevations of the external concentrations of ions results from compensation of their effects on [Ca]i. Depolarization itself appears to increase [Ca]i while elevation of the external ion concentrations at a fixed membrane potential appears to decrease [Ca]i.
Aerodynamics of Hovering Flight in the Long-Eared Bat Plecotus Auritus
Authors: Norberg U. M.
Published: April 2021

Steady-state aerodynamic and momentum theories were used for calculations of the lift and drag coefficients of Plecotus auritus in hovering flight. The lift coefficient obtained varies between 3·1 and 6·4, and the drag coefficient between –5·0 and 10·5, for the possible assumptions regarding the effective angles of attack during the upstroke. This demonstrates that hovering flight in Plecotus auritus can not be explained by quasi-steadystate aerodynamics. Thus, non-steady-state aerodynamics must prevail.
Magnetic Fields and the Orientation of Homing Pigeons Under Sun
Authors: Walcott Charles
Published: April 2021

Applying a magnetic field of 0.1 Gs (1 gauss = 10−4T) to the heads of pigeons homing from unfamiliar release sites significantly increased the scatter of the birds’ vanishing bearings. A magnetic field of 0-3 gauss caused no difference between the orientation of birds wearing coils with either their north or south pole up. But a field of 0.6 gauss (equal to that of the Earth) produced a small difference in the vanishing bearings of the two groups. Since an applied magnetic field has an effect on pigeon orientation under sun, it appears that pigeons do not simply switch between a magnetic and a sun compass, but that there is some interaction between the two systems.
Circadian Rhythm of Output From Neurones in the Eye of Aplysia
Authors: Benson Jack A. , Jacklet Jon W.
Published: April 2021

The circadian rhythm of CAP frequency recorded from the optic nerve of isolated eyes at 15 °C was damped out by constant illumination (1100 lux) after several cycles of the rhythm. During illumination (LL) the rhythm was skewed with a rapid rising phase and slow falling phase, and the period was decreased by about 1 h. It is postulated that the circadian clock was stopped by LL at its lowest phase point, and that following cessation of LL, the rhythm was reinitiated from this phase point after a latency of 6-8 h. For light pulses of 80 lux and 1100 lux, the photoresponse of the dark-adapted eye to 20 min light pulses applied beginning at 2 h intervals was not influenced by the circadian clock. At 5 lux there was a periodicity in the magnitude of the photoresponse, in phase with the circadian rhythm of spontaneous CAP production. Small CAPs of non-circadian frequency were recorded together with normal CAPs in about 10% of records of output from isolated eyes. The cells producing the small CAPs had a different temperature sensitivity from those producing normal CAPs. The response of these cells to short light pulses consisted of a phasic burst of activity at light onset, followed by silence during the remainder of the short light pulse, and for 1 or 2 min following cessation of illumination. These small CAPs may be the activity either of H-type receptors or of secondary cells desynchronized from the major population.
Salt and Water Balance of the Spiny Lobster, Panulirus Argus: the Role of the Antennal Glands
Authors: Malley D. F.
Published: April 2021

Panulirus argus in full sea water differs from most other marine isosmotic decapods by regulating Cl− levels in the haemolymph slightly below those in sea water and by having haemolymph K+ levels similar to those in sea water. The species is typical in regulating haemolymph Na+ and Ca2+ above, and Mg2+ and SO42− below, sea-water levels of these ions. Its haemolymph Mg24−and SO42− concentrations are amongst the lowest reported in marine decapods. The antennal glands contribute to this regulation of Mg24− SO42− and Cl− by producing urine with markedly, and approximately equally, elevated Mg24− and SO42− levels, and slightly elevated Cl−levels, compared with those in the haemolymph. The antennal glands show a small tendency to conserve water.
Saltatory Movements of Organelles in Intact Nerves of Rhodnius Prolixus Stål
Authors: Heslop J. P. , Howes E. A.
Published: April 2021

Abdominal nerves of Rhodnius prolixus were studied with the light microscope under high-power Nomarski optics with a minimum of surgical interference. The preparation was perfused with bathing solutions which could be changed during time-lapse cinematography. The structure of the nerve trunks was studied by light and electron microscopy. The movements of intracellular organelles are described and discussed. Saltatory movements of organelles, probably mitochondria, were followed at different temperatures. Rate of saltation varied linearly with temperature. Axonal flow (bulk movement of cytoplasm) did not occur in healthy abdominal nerves.
Ionic Requirements For Non-Synaptic Electrogenesis in the Muscle Fibres of A Lepidopterous Insect
Authors: Yamamoto Daisuke , Fukami Jun-Ichi
Published: April 2021

Study was made of the influence of external sodium, calcium and magnesium concentrations on the directly elicited response of the segmental muscle fibres of the larva of Galleria mellonella, as recorded with intracellular microelectrodes. The graded response caused by an outward current pulse was converted into an all-or-none spike in the presence of 10 mM tetraethylammonium. The amplitude of these spikes increased with increasing external Ca concentration but not with increasing Na or Mg concentration. The spikes were not influenced by tetrodotoxin (3 × 10−5 M) but were suppressed by Mn ions (20 mM). After replacement of TEA-containing saline with an isotonic CaCl2 solution, spikes were still produced in the latter. It appears that only calcium ions act as charge carriers of inward current at the non-synaptic membrane.
The Neuronal Control of Dragonfly Flight
Authors: Simmons Peter
Published: April 2021

The neuronal control of flight in dragonflies has been investigated by making intracellular recordings from identified motor neurones, singly and in pairs, in tethered flying and non-flying animals.

It is concluded that, as in the locust, populations of interneurones generate the flight rhythm and drive motor neurones. The diversity of motor neurone activity in dragonflies is presumably related to their well-known aerial manoeuvres.
Asymmetric Waveforms in Echinoderm Sperm Flagella
Authors: Goldstein Stuart F.
Published: April 2021

Dark-field, multiple-exposure photographs of live spermatozoa of a number of echinoderms were analysed. Bends develop at the base in pairs, as they do in flagella with symmetrical waveforms. However, the angles of these bends do not cancel, so that microtubular sliding – of up to over 50 % of that associated with bend propagation – is transferred distally. This sliding implies that (a) microtubules are not rigidly cross-linked within straight regions, and (b) bends can propagate normally in spite of appreciable extrinsic microtubular sliding. Both the sperm head and the asymmetry of the waveform appear to affect the swim path of a spermatozoon.
CO2-Inhibition of the Amplitude of Bending of Triton-Demembranated Sea Urchin Sperm Flagella
Authors: Brokaw C. J.
Published: April 2021

Demembranated sea urchin spermatozoa were reactivated in solutions containing KHCO3 and observed in a covered well slide. Although KHCO3 itself causes a small inhibition of flagellar beat frequency, the results confirm previous observations of a direct inhibition of flagellar bend angle by CO2 with no effect of CO2 on frequency.

Observation of the effect of pH on the inhibition of bend angle in solutions containing KHCO3 indicates that a given concentration of OH− has a similar effect to the same concentration of HCO3−, as would be expected if CO2-inhibition results from reaction of CO2 with protein-NH3+ groups to form carbamates.

CO2 may interfere with a control mechanism which selectively suppresses dynein cross-bridge activity in order to generate rhythmic bending. This control mechanism may incorporate a feedback control involving a measure of flagellar amplitude, which fails to operate successfully when the amplitude is reduced below a critical level.
Motor Neurone Coordination and Sensory Modulation in the Feeding System of the Mollusc Pleurobranchaea Californica
Authors: Siegler Melody V. S.
Published: April 2021

This study on the marine mollusc, Pleurobranchaea californica, examined the electrophysiological basis of coordinated motor neurone activity associated with the intrinsic feeding rhythm of the buccal ganglion, and the sensory modulation of this rhythm.

Paired intracellular microelectrode recordings from antagonist motor neurones showed that each received alternating barrages of EPSPs and IPSPs; as one of the pair was depolarized, its antagonist was hyperpolarized. PSPs of opposite polarity in antagonists were one-for-one with each other, suggesting that common presynaptic interneurones were responsible. There was no evidence for direct synaptic interaction between antagonist motor neurones. Paired recordings from synergist motor neurones showed that they received similar barrages of PSPs which alternately depolarized and hyperpolarized them. Underlying these parallel changes in potential were one-to-one PSPs of the same polarity, again suggesting driving by common presynaptic interneurones.

The feeding rhythm that was recorded from the buccal ganglion with the buccal mass attached was compared quantitatively with that recorded from the same ganglion after deafferentation. There were significant differences in parameters of the rhythm measured under the two conditions. Rhythmic afferent activity was recorded from the distal stumps of buccal roots, during rhythmic feeding movements of the buccal mass. The spiking of different units was associated with different phases of the movement cycle. Sensory cells with central somata were stimulated individually in the isolated ganglion, and two effects were recorded. Some sensory neurones excited withdrawal motor neurones and inhibited eversion motor neurones; others inhibited withdrawal motor neurones.
Effect of Dehydration and Rehydration on the Water Content and Na+ and K+ Balance in Adult Male Periplaneta Americana
Authors: Tucker Lois E.
Published: April 2021

Changes in live weight and in the water, Na+ and K+ content of the tissues and faeces have been examined in adult male Periplaneta americana in various states of hydration. During dehydration the haemolymph volume decreases markedly, but the Na+ and K+ concentrations rise only slightly. Less than 25 % of the Na+ removed from the haemolymph during dehydration was found to be excreted, but the K+ excreted during dehydration was in excess of that removed from the haemolymph alone. It seems likely that the major tissue for regulating the haemolymph Na+ during dehydration and rehydration is the fat body, in which dehydration causes an increase, and rehydration a decrease, in the Na:K ratio. The Na+ and K+ content of the fat body was found to be variable in both hydrated and dehydrated animals and absolute changes in the ion content of the tissue could not be estimated because of unknown changes in the amount of food reserves and excretory products.
Measurement of Electrogenic-Pump Current in Aplysia Neurones with Constant-current and Constant-Voltage Techniques
Authors: Junge D. , Ortiz C. L.
Published: April 2021

The responses of the abdominal and pleural giant cells to warming and cooling were studied using constant-current and constant-voltage techniques. The potential change upon warming from about 7 °C to 22 °C was reversed by application of maintained inward current. The reversal potential was − 77 ± 12 mV. The membrane conductance increased with warming, but was not affected by pump-blocking agents. The electrogenic-pump current was found to be about 16 nA for a model in which the pump acted across the membrane ionic conductance. This model could explain the reversal of the warming response with hyperpolarization. In voltage-clamped cells, the response to warming was converted from an outward to an inward current by hyperpolarization. The reversal potential for the current response was 31 ± 7 mV more negative than resting, or about − 80 mV. The pump currents measured under voltage-clamp conditions were the same as those calculated for the hyperpolarizing responses in unclamped cells.
The Pattern of Carbon Dioxide Excretion in the Rainbow Trout Salmo Gairdneri
Authors: Haswell M. S. , Randall D. J.
Published: April 2021

Patterns of carbon dioxide excretion were investigated in rainbow trout (Salmo gairdneri). The loss of erythrocytic carbonic anhydrase caused by severe anaemia does not affect acid/base regulation or the ability of fish to excrete CO2. Bicarbonate excretion across the saline-perfused gills of trout is significant even though residence time for the saline in the gills is only 1− 3 s. CO2 excretion across these saline-perfused gills is blocked by the carbonic anhydrase inhibitor, diamox. The excretion of CO2 in fish is via the movement of plasma bicarbonate into the gill epithelium where branchial carbonic anhydrase catalyses the production of CO2. Fish can adjust pH by regulating bicarbonate movement across the gills. The erythrocytic carbonic anhydrase is not necessary for CO2 excretion in the gills but is involved in facilitating Bohr and Root shifts to augment O2 delivery in the tissues.
Induction of Sulphate Transport and Hormonal Control of Fluid Secretion by Malpighian Tubules of Larvae of the Mosquito Aedes Taeniorhynchus
Authors: Maddrell S. H. P. , Phillips J. E.
Published: April 2021

4th stage larvae of A. taeniorhynchus reared in sulphate-enriched sea water drink the medium at the same rate that they do when reared in sulphate-free sea water. They absorb into the haemolymph most of the water and nearly all of the sulphate from the ingested fluid. Larvae are able to keep the concentration of sulphate in the haemolymph at levels well below that of the medium, even when this contains as much as 89 mm sulphate. The Malpighian tubules of larvae reared in sulphate-containing waters soon develop an ability to transport sulphate. The rate of sulphate transport induced varies directly with the sulphate content of the water in which they are reared. This ability is not retained into the adult stage. The rate of fluid secretion by isolated Malpighian tubules is increased by up to 20 times when they are exposed to saline containing 1·5 mm cyclic AMP or concentrations of 5-hydroxytryptamine higher than 10−6M. Tubules isolated from unfed insects into stimulant-free saline secrete fluid only slowly, but similarly treated tubules from feeding insects initially secrete fluid very much faster. Extracts of the brain and of the thoracic ganglia stimulate Malpighian tubules to secrete fluid at a high rate. The brain is about four times as rich a source of stimulant as is the chain of thoracic ganglia. Treatment of the surface of the structures in the head with K-rich saline leads to the release of a factor which stimulates fluid secretion by the Malpighian tubules. The results suggest that the Malpighian tubules in larvae of A. taeniorhynchus are under the control of a diuretic hormone which is elaborated in the brain and possibly also in the thoracic ganglia and which reaches high levels in the circulating haemolymph of feeding animals. The rate of sulphate transport by isolated Malpighian tubules is strongly affected by the rate of fluid secretion. This behaviour is compatible with a passive leak of transported sulphate from the lumen back into the haemolymph through the permeable wall of the tubule.
Dependence of Prolonged Water Absorption by in Vitro Locust Rectum On Ion Transport
Authors: Goh S. , Phillips J. E.
Published: April 2021

An in vitro preparation of the locust rectum, consisting of an everted cannulated sac, is described. After the first hour, the rates of ion and water transport, the electropotential difference and tissue volume do not change significantly over the next 4 h, i.e. a steady-state situation is approximated. The activities and properties of these rectal sacs are reasonably similar to those in vivo; they produce hyposmotic absorbate, exhibit rectification of osmotic flow, and absorb water from pure sucrose solution for 1 h. Inhibition of absorption by KCN + IAA and also ouabain indicates metabolic dependence. Analysis of absorbate shows that tissue ions are secreted to the haemocoel side when water is absorbed over the first hour from pure sucrose solutions. Prolonged transport of water (i.e. from second to fifth hour) requires the presence of ions on the lumen but not the haemocoel side. This is the first direct evidence that water absorption in the insect rectum is coupled to ion transport as previously postulated. The location of the proposed ion recycling suggested by these observations is discussed.
Mechanical Properties of Primary Feathers from the Pigeon
Authors: Purslow P. P. , Vincent J. F. V.
Published: April 2021

The morphology of the primary feather shaft from the pigeon wing has been examined and its salient features noted. The cortex (outer wall) of the shaft appeared to be the most significant feature in relation to bending behaviour and was analysed quantitatively. A model that simulated bending of the shaft was made using this analysis and upon comparison of simulated results with observed bending behaviour it is shown that the shape and size of the cortex does indeed account for the majority of bending behaviour. The model does not include torsional effects and the effects of the pithy medulla and the transverse septa, but the magnitude of these effects is considered to be small in comparison with that of the cortex considered in simple bending. Differences in the shape of the cortex in the outermost primary and those proximal to it are shown to account for different mechanical properties and possible reasons for this are given. The shape and size of the cortex, as measured by its second moment of area, is shown to have some relation to the body weight of the bird.
Control of the Salivary Glands of Helisoma by Identified Neurones
Authors: Kater S. B. , Murphy A. D. , Rued J. R.
Published: April 2021

The neural regulation of an exocrine gland was investigated at the level of identified effector neurones. The salivary gland neuroeffector system of Helisoma consists of a pair of acinous glands innervated by two symmetrically located, identified buccal ganglion neurones (4R and 4L). Neurones 4R and 4L usually are electrically coupled and display synchronous activity. Action potentials in these neurones elicit EPSPs and action potentials in epithelial cells of the salivary glands. Spontaneous miniature potentials similar to those seen at neuromuscular junctions can be recorded from many of the glandular cells. Neurones 4R and 4L, and thus also salivary gland cells, can display bursts of action potentials phase-locked with those seen in buccal mass motoneurones during feeding.
The Distribution of Bumps in the Tail of the Locust Photoreceptor Afterpotential
Authors: Horridge G. A. , Tsukahara Y.
Published: April 2021

An extended tail or prolonged depolarizing afterpotential (PDA) follows the receptor potential of a locust retinula cell when the stimulating light is in the intensity range that saturates the receptor potential. The amplitude and duration of this afterpotential depend on the intensity and duration of the stimulus. As the afterpotential decays, apparently exponentially, it becomes resolved into bumps, which we call light-induced dark bumps (LID bumps).

The intervals between light-induced dark bumps are distributed in a way that is indistinguishable from a random (Poisson) distribution. As previously demonstrated, LID bumps are indistinguishable from bumps directly induced by low intensity light in light-adapted cells, which in turn grade into the slightly larger bumps produced, each by a single photon, in dark-adapted cells.

The light-induced dark bumps continue for up to an hour in darkness, slowly becoming like dark-adapted bumps in amplitude and shape. To account for the random occurrence and discrete features of bumps after so long a latency, we propose that intense light generates a significant amount of an intermediate molecule or packet which decays slowly to start the same process that normally generates bumps with a short delay.
Unusual Step Patterns in the Free Walking Grasshopper Neoconocephalus Robustus
Authors: Graham D.
Published: April 2021

The free walking behaviour of the tettigonid Neoconocephalus robustus provides a unique quantitative description of the interactions that can occur between a rear and middle leg on the same side of the body in an insect. The rear legs step at approximately half the frequency of the anterior legs, and right and left sides of the body can function almost independently. Relative co-ordination produces a slow drift in the timing of the rear and middle leg protractions so that all the possible values of inter-leg phase may be observed.

A statistical examination of this behaviour shows that the duration of the middle leg step cycle is increased by the presence of a rear leg protraction, only when it occurs in the last half of the retraction stroke of the middle leg. If it occurs in the earlier part of the cycle there is no corresponding contraction of the middle leg step period. This and several other features of the walk exclude a ‘magnet effect’ or an ‘excitatory’ interaction between homologous points in the leg cycle and provide a verification of the ascending ‘inhibitory’ interaction proposed by Wilson (1966).

Co-ordinated walking in this insect appears to be a discrete process in which the performance of a protraction stroke activates a co-ordinating influence and, in conjunction with a frequency hierarchy, maintains the required time relationship between the legs.
Factors Affecting Glomerular Function in the Pacific Hagfish Eptatretus Stouti (Lockington)
Authors: Riegel J. A.
Published: April 2021

Single glomerulus filtration rate in Eptatretus stouti averaged 20·3 + 2·13 (S.E.M.) nl min−1. Single glomerulus glomerular filtration rate (GFR) could be correlated with arterial pressure when arterial pressure exceeded about 4 cm H2O. Glomerular filtration was affected by postglomerular resistance brought about by alteration of the volume of urinary spaces. Filtration undoubtedly plays a role in glomerular function. However, average colloid osmotic pressure (COP) of the plasma is almost double the average hydrostatic pressure in the segmental arteries serving the glomeruli. The COP of glomerular fluid is essentially nil, therefore it is difficult to see how pressure filtration alone can account for primary urine formation.

When single glomeruli were perfused with colloid-containing Ringer at pressures within the normal range of blood pressures, GFR was within the normal range. GFR was related inversely to the colloid osmotic pressure of the perfusion Ringer. Colloid entered the urine during perfusion. However, in only a few instances did this result in conditions favourable to pressure filtration.

To assess the role of active processes in glomerular filtration, chemical inhibitors were added to the perfusion Ringer. Amiloride, acetazolamide, cyanide, 2-deoxy-D-glucose, iodoacetate and ethacrynic acid were without marked effect on glomerular filtration. Ouabain and dinitrophenol markedly reduced GFR; inhibition was probably not due to indirect effects upon the renal vasculature.
Short Communication A Note on ‘Clap And Fling’ Aerodynamics
Authors: Lighthill M. J.
Published: April 2021

Weis-Fogh (1973) analysed the ‘Clap and Fling’ mode of hovering flight in the small chalcid wasp Encarsia formosa. He argued that the difficulty of generating wing lift sufficient to support the insect’s weight at the very low Reynolds numbers involved (about Re = 20) is overcome by a substantial enhancement of lift associated with this special mode of flight. Recently, the ‘Clap and Fling’ mechanism has been studied in model experiments by Bennett (1977) at Re = 83000.
On The Respiration of Torpedo Marmorata
Authors: Hughes G. M.
Published: April 2021

The oxygen consumption of resting Torpedo marmorata was measured using three different methods. The results indicate that this species has a much lower oxygen consumption than other elasmobranchs of comparable size. The gills are ventilated by a mechanism similar to that of other rays, but a relatively small spiracular opening seems to be associated with a more important role of the oro-branchial pump. During hypoxia there is a marked increase in both frequency and amplitude of the ventilatory movements. The frequency of the heart beat is low and shows little change during hypoxia, except under extreme conditions when bradycardia occurs. In some individuals, coupling between cardiac and ventilatory pumps is relatively low but seems to increase at lower ventilatory frequencies and when the ratio between the ventilatory and cardiac frequencies is a whole number. Extreme hypoxia can be withstood for many hours but eventually the ventilatory rhythm ceases; it does not recommence immediately following a rise in ambient oxygen tension. The blood has a low oxygen-carrying capacity and a high affinity. The surface area of the gills is smaller than that of other species that have been investigated, but the quantity of oxygen transferred/unit surface area is similar to that known for other species. It is concluded that Torpedo is a sluggish fish adapted to conditions of low oxygen, but the conditions under which this occurs remain to be determined.
Influence of Water Temperature on the Electric Organ Discharge (Eod) of the Weakly Electric Fish Marcusenius Cyprinoides (Mormyridae)
Authors: Toerring M. J. , Serrier J.
Published: April 2021

The influence of different water temperatures on the electric organ discharge (EOD) of a mormyrid fish Marcusenius cyprinoides was studied. The range of the water temperatures was fixed according to the seasonal temperature variations of the rivers in Central Africa, the natural habitat of this species. The EOD activity was characterized using the following parameters: mean EOD rate, EOD pattern in the form of Interpulse Interval Histograms (IIH), IIH range, and shortest pulse interval. These parameters remained constant during control experiments at constant temperature (27 °C) for 4 days. The mean EOD rate increases with increasing water temperatures. The lowest mean EOD rate is always found at 17 °C, the highest between 26 and 33 °C. The characteristics of the IIH are modified by stepwise temperature increases. These IIH show during high temperatures (26−33 °C similar patterns to those previously observed during high level motor activity and excitement. The IIH range diminishes with stepwise temperature increases. The shortest pulse interval has a negative, linear correlation with water temperature. The possible role of water temperature in the reproduction of the mormyrids is discussed. The high discharge rate of M. cyprinoïdes produced by high water temperatures during the rainy season could serve to improve the resolution of the electroreceptors during this period.
Effects of Epinephrine on Branchial Non-Electrolyte Permeability in Rainbow Trout
Authors: Isaia Jacques , Maetz Jean , Haywood Geoffrey P.
Published: April 2021

Using isolated heads perfused at constant pressure, at rates close to those occurring in vivo, the permeability of the gills of the trout Salmo gairdneri to a range of solutes was measured. Under epinephrine-free conditions, butanol and water showed similar high branchial permeability coefficients. Urea, inulin and dextrans (mol. wt 3000 and 20000) were 7−12 times less permeant, and mannitol 60−70 times less permeant than water or butanol. Epinephrine, at 10−6 M, greatly increased the permeability of the gills to the small hydrophilic molecules, water and urea, and to the lipophilic substance, butanol, but did not affect the penetration of the large hydrophilic solutes, mannitol, inulin and dextrans.

In the presence of 10−6 M propanolol, a β-blocker, epinephrine had no effect on the permeation of any of the test substances except that the permeability to urea decreased somewhat.

The results suggest that epinephrine increases the permeability of the membranes of the branchial cells but does not affect the permeation of substances that cross the gill walls by paracellular routes or via an intracellular ‘bulk-transport’mechanism. Such an action would be expected to increase the branchial transfer of oxygen.
Spectral Sensitivities of the Anterior Median Eyes of the Orb Web Spiders, Argiope Bruennichii and A. Amoena
Authors: Yamashita Shigeki , Tateda Hideki
Published: April 2021

Spectral sensitivities of the anterior median eyes of the orb web spiders, Argiope bruennichii and A. amoena have been studied by recording extracellular ERGs and intracellular receptor potentials. The anterior median eyes have three types of visual cells, with maximum sensitivities at about 360 nm (u.v. cell), 480–500 nm (blue cell) and 540 nm (green cell). The blue cells are the most sensitive and have a circadian oscillation of sensitivity. The green cells show a hypersensitivity, i.e. the sensitivity is greater for about 90 s after the cessation of illumination than during dark adaptation. Respiration is necessary for the maintenance of hypersensitivity.
Auditory Masking Patterns in the Goldfish (Carassius Auratus): Psychophysical Tuning Curves1
Authors: Fay Richard R. , Ahroon William A. , Orawski Arthur A.
Published: April 2021

The masking effects of tones on the detection auditory signals were studied in goldfish using the psychophysical tuning-curve paradigm. For signals below 350 Hz, masking is an inverse function of the frequency separation between masker and signal; a finding consistent with previous masking studies on fishes, birds and mammals. For signals above 350 Hz, masking peaks occur both in the 350 Hz region and at the frequency of the signal. Quantitative comparisons with recent neural tuning curves for goldfish saccular neurones suggest that the filtering observed may be determined by mechanical frequency selectivity below 350 Hz, but by a neural analysis of temporal patterns above this range.
Neurones in the Leech That Facilitate An Avoidance Behaviour Following Nearfield Water Disturbances
Authors: Mistick Dyane C.
Published: April 2021

A multimodal, multisegmental interneurone (Röhde’s fibre, RF) and previously identified mechanoreceptors (T-cells) are shown to respond to nearfield disturbances. Both the T-cells and RF can fire for hundreds of milliseconds following a brief stimulus, and both have subthreshold excitatory synapses onto motor neurones that cause longitudinal contraction of the body wall, an avoidance response. Natural stimulation or electrical stimulation of T-cells in one hemiganglion causes synaptic excitation of T-cells in adjacent ipsilateral hemiganglia and re-excitation of T-cells in the hemiganglion stimulated. A model of repetitive T-cell activity that incorporates previously described synapses among T-cells is presented: the T-cells in adjacent ipsilateral hemiganglia form a reverberatory circuit, re-exciting one another via electrical synapses; repetitive firing is terminated by synaptic inhibition onto T-cells provided by an interneurone excited by the T-cells. With repeated stimulation (0·1–0·2 Hz, 0·2 ms pulses) of a segmental root (directly exciting all the T-cells of a hemiganglion), the number of T-cell impulses per stimulus decreases. Facilitation of inhibition may contribute to the response decrement. The T-cell-RF pathway is investigated. T-cell stimulation can elicit RF impulses in the same and in adjacent ganglia. The long delay between mechanoreceptor stimulation and a response in the interneurone suggests that spatial and temporal summation of T-cell inputs may be required to reach firing threshold in the interneurone. The impulse frequency of the RF response was compared for a travelling surface wave that is approaching a segment v. one that is moving away from the segment. It was found that the frequency was greater as the stimulus approaches; this should allow more effective temporal summation of the subthreshold synaptic potentials which RF evokes in motor neurones that cause longitudinal contraction of the body wall. Therefore, the probability of contraction is greater in segments toward which a stimulus is moving.