bluuebunny/crossref_metadata_2025 huggingface dataset:
A Method for Determining Total Carbon Dioxide in Nanolitre Volumes of Liquid
Authors: Little Colin
Published: April 2021

A microdiffusion method is described by which total carbon dioxide can be determined in 2 nl samples of liquid. The standard deviation for 0–30 mm/1 HCO3− is approximately 1 mm/1. The volume of sample can be reduced to o·8 nl, but the S.D. then rises to 1·6 mm/1. With volumes of 0·4 nl, the S.D. is 2·7 mm/1. It is not possible, without modification, to use volumes smaller than about 0·4 nl. In samples where the HCO3− concentration is low, accuracy can be increased by using larger volumes: 10 mm/1 HCO3− can be determined in 6 nl samples with a standard deviation of 0·5 HIM/1.
Pharmacological Induction of Plasticization in the Abdominal Cuticle of Rhodnius
Authors: Reynolds Stuart E.
Published: April 2021

Injections of 5-hydroxytryptamine (5-HT, serotonin) are found to cause plasticization of the abdominal cuticle of Rhodnius larvae. This plasticization is a direct action of 5-HT on some element in the body wall; the central nervous system is not required. It is probable that 5-HT acts directly at a receptor on the epidermal cells. The relationship between structure and plasticizing activity for a number of 5-HT analogues has been investigated. The receptor resembles other ‘classical’ 5-HT receptors in its requirements, but is unlike the 5-HT/diuretic hormone receptor of Rhodnius Malpighian tubules.
Magnesium Regulation in Mosquito Larvae (Aedes Campestris) Living in Waters of High MgSO4 Content
Authors: Kiceniuk J. , Phillips J. E.
Published: April 2021

Although larvae of A. campestris can live in natural waters in which the magnesium content may vary seasonally from extremes of 1 to more than 100 mm, the haemolymph levels of magnesium vary only from 1·5 to 4 mm. Larvae survive in water containing 90 mm-Mg and drink their own body weight every few hours, the ingested fluid and the magnesium ions being largely absorbed into the haemolymph via the midgut. The urinary concentration of Mg2+ ions was always substantially higher than that of the external media and up to 23 times that of the haemolymph. It is suggested that magnesium is not excreted across the general body surface, the Malpighian tubules and hindgut being largely responsible for removing magnesium from the haemolymph. These physiological observations are discussed in relation to the environmental conditions under which larvae are naturally found.
Efferent Regulation of the Abdominal Stretch Receptors of the Crayfish
Authors: Ilyinsky O. B. , Spivachenko D. L. , Shtirbu E. I.
Published: April 2021

Efferent regulation of the activities of the slowly adapting and fast adapting stretch receptors (the MRO1 and MRO2, respectively) of Astacus fiuviatilis was studied. It was shown that the receptors activity is under the efferent control of two central inhibitory neurones: the main inhibitory neurone (MIN) and the accessory neurone (AIN). Their activities were determined by the degree of discharge from the receptors. There was close interaction between the MRO1 and the MIN. The activity of the MIN was determined by the activity of the MRO1 to a higher degree than vice versa; the activity of the MIN was influenced not only by the MRO1 impulses, but by the cessation of those impulses as well (silent periods). The MRO1 could inhibit or excite the MIN, whereas the MIN could inhibit the activity of the MRO1. Interaction between the MRO1 and the MIN could occur during background activity of the MRO1 or of the MIN. In both cases the activity of the initially non-active neurone appeared only after stimulation had been applied to the MRO1. Often each impulse of the MRO1 resulted in a MIN discharge of from 1 to 361 impulses. Sometimes the responses appeared after burst-discharges, induced by mechanical stimulation, of the otherwise inactive MRO1. During interaction between the MRO1 and the MIN, the neurone commencing activity had a higher discharge frequency, if only by 1–2 imp./ sec, than the one firing previously. Under the influence of MIN impulses the response of the MRO1 to stimulation changes from slowly adapting to fast-adapting. The MIN has a slight inhibitory effect on the activity of the MRO2 which is most clearly seen in the course of background activity of the MRO2. The MRO2, however, does not exert much influence on the activity of the MIN. The AIN had much less effect than the MIN on receptors, and the receptors did not naturally evoke AIN impulses. There is, therefore, apparently a more complicated connexion between the receptors and the AIN than between the receptors and the MIN.
Role of active potassium transport by integumentary epithelium in secretion of larval-pupal moulting fluid during silkmoth development
Authors: Jungreis A. M. , Harvey W. R.
Published: April 2021

The exuvial side of the pharate pupal integument is usually positive to the haemolymph-side, both in vivo and in vitro, during the period when the moulting fluid is being secreted. The ratio of potassium flux toward the exuvial space is higher than that toward the haemolymph, under both open-circuit conditions and short-circuit conditions, demonstrating by the Flux Ratio test that potassium is actively transported across the isolated integument during this secretion period. Just prior to ecdysis, while moulting fluid is being reabsorbed, the potassium flux ratios become unity, suggesting that active potassium transport has ceased, but the short-circuit current that remains suggests that some other ion is actively transported at this time. We argue that the potassium salt solution, formed in the exuvial space (as water presumably follows the actively transported potassium), has three functions (1) to accomplish the gel-sol transformation, (2) to activate the gel enzymes and (3) to buffer the enzyme solution at a pH favourable to the activity of the gel enzymes.
Active Transport of Sulphate Ions by the Malpighian Tubules of Larvae of the Mosquito Aedes Campestris
Authors: Maddrell S. H. P. , Phillips J. E.
Published: April 2021

Larvae of Aedes campestris ingest and absorb into their haemolymph large quantities of the sulphate-rich water in which they live, yet they are able to maintain the sulphate content of the haemolymph well below that of the environment. Tracer experiments showed that sulphate regulation was not achieved by deposition of precipitates in the tissues. In vitro preparations of Malpighian tubules secrete sulphate ions actively against both a three times concentration gradient and an electrical potential difference of 20 mV. This transport is half saturated at about 10 mm. The rate of sulphate secretion by the Malpighian tubules is sufficient to remove all of the sulphate ingested by larvae living in waters which contain less than 100 mm of this anion. At higher concentrations, sulphate ions are probably also excreted elsewhere, perhaps by the rectum or anal papillae.
Electrophysiology and Co-ordinated Behavioural Responses in the Colonial Bryozoan Membranipora Membranacea (L.)
Authors: Thorpe J. P. , Shelton G. A. B. , Laverack M. S.
Published: April 2021

There is a colonial retraction response in the Bryozoans Membranipora membranacea and Electra pilosa. The conduction velocity of the response is about 100 cm sec−1. The colonial response will circumnavigate the end of a cut, but will not cross it. The lophophore retraction time is 60–80 msec. The lophophore retractor muscle with a peak contraction rate of 20 + muscle lengths per second is probably one of the fastest contracting muscles known. The colonial responses to successive stimuli under certain circumstances are similar to those of some corals. Nervous pulses can be recorded travelling across the colony at the same velocity as the colonial response. Increases and decreases in the number and frequency of T1 pulses correspond with increases and decreases in the area and duration of the colonial response and are produced in response to the same stimuli. Other pulses can be recorded which correspond to the retraction of the lophophore retractor muscle. The lophophore retractor muscle is apparently under the control of a giant axon from the zooidal ganglion. The colonial nervous system has many of the properties expected of a nerve plexus.
Sperm concentration and fertilization rate in Bufo arenarum (Amphibia: Anura)
Authors: Cabada M. O.
Published: April 2021

The influence of sperm concentration upon the fertilization rate of Bufo arenarum oocytes was determinated. The experimental results were analysed according to the theories of Rothschild and Swann, and Hultin and Hagström for Psammechinus miliaris. The experimental results agreed with the predictions of the latter theory. Since Bufo arenarum and Psammechinus miliaris oocytes differ in both size and disposition of jelly envelopes, the postulations of Hultin and Hagström’s theory appear to have a general validity.
The cardioregulatory system of crayfish: neuroanatomy and physiology
Authors: Field L. H. , Larimer J. L.
Published: April 2021

The anatomical arrangement of the cardioregulatory nerves and their physiological activity during cardiac modulation were analysed in Procambarus clarkii. The bilaterally arranged pairs of cardioinhibitors and cardioaccelerator axons, in nerves SN II and SN III respectively, were physiologically identified by correlating spikes in SN II and SN III with the same spikes in the dorsal nerve, which innervates the heart. The cardioinhibitor neurone fired tonically in varied sporadic bursts. During periods of cardiac inhibition, however, this neurone discharged in a long chain of spikes at a characteristic frequency of 40–50 Hz. The cardioaccelerator neurone fired tonically at 2–3 Hz but on occasion its activity reached 12 Hz. Three inhibitory cardiac reflexes were analysed. The sensory modalities for the reflexes included (a) stretch of the dorsal pericardial wall, (b) chemical stimulation of coxal hair sensilla with glucose and (c) tactile stimulation of hair sensilla in and below the gill chamber, on the antennae, the antennules and on the anterior cephalothorax. The discharge of both cardioinhibitor neurones showed a weak temporal correlation suggesting a common presynaptic drive, while the pair of cardio-accelerators appeared to have a reciprocal relationship With the cardio-inhibitors.
Optic gland implants and their effects on the gonads of Octopus
Authors: Wells M. J. , Wells J.
Published: April 2021

Optic glands transplanted from one Octopus vulgaris into another cause enlargement of the gonads and ducts of the recipient. Enlargement occurs whether or not the gland was secreting when implanted and regardless of the sex of the donor or recipient. Glands derived from Eledone moschata or Octopus macropus implanted into O. vulgaris are as effective as glands derived from O. vulgaris. Implants derived from Sepia officinalis or LoHgo vulgaris appear to be ineffective.
Anaerobiosis: A Possible Source of Osmotic Solute for High-salinity Acclimation in Marine Molluscs*
Authors: Baginski Richard M. , Pierce Sidney K.
Published: April 2021

When stressed with high-salinity exposure, cell volume is restored in ventricles of Modiolus demissus demissus by a rapid accumulation of intracellular free amino acids. Although the total amino acid pool increases and remains at a constant high level thereafter, the pattern and time course of accumulation is different for each major amino acid (glycine, alanine, taurine, and proline). Initially, cell volume is restored by a rapid accumulation of alanine, but later its concentration decreases while glycine and taurine accumulate. Although at first not detected, the proline concentration increases, peaks and subsequently disappears again. Isolated ventricles recover normal activity after large environmental salinity increases. During recovery the intracellular free amino acid changes in isolated ventricles are similar to the initial pattern of accumulation in whole animals, i.e., alanine, and to a lesser extent, proline and glycine accumulate. Finally, isolated ventricles undergo a period of decreased oxygen consumption on exposure to an increased salinity. These results suggest that the initial stages of high-salinity acclimation in molluscs depends upon the synthesis of amino acids via a known anaerobic biochemical pathway.
Habituation and inhibition of the crayfish lateral giant fibre escape response
Authors: Wine J. J. , Krasne F. B. , Chen L.
Published: April 2021

Decrement of the lateral giant fibre escape response was studied in intact, restrained, crayfish and in those with the ventral nerve cord transected at the thoracic-abdominal level. Taps (delivered at rates of 1 per 5 min to the abdomen) depressed responsiveness to about 50% of its initial value in 10 trials, for both intact and operated animals. With additional stimulation, responsiveness dropped to near zero for both groups. Recovery was negligible 2 h later, but nearly complete after an additional 24 h rest. Protection against response decrement in this situation was obtained by directly activating the cord giant fibres 30 msec prior to the tactile stimulus. The directly-elicited giant fibre spikes which follow the tactile stimulus do not influence the course of response decrement. The results establish the decrement as centrally mediated habituation, and minimize the role of receptor alterations or descending neuronal influences in the behavioural change. A comparison is made between the properties of habituation and the homosynaptic depression of afferent to interneurone synapses that is presumed to be the physiological mechanism of habituation in this situation.
Patterns of activity in the antennular motoneurones of the hermit crab Pagurus alaskensis (Benedict)
Authors: Snow P. J.
Published: April 2021

Using electromyogram recordings from the antennular muscles of intact animals and recordings from the antennular nerves of partially dissected preparations, the patterns of activity in specific antennular moto- neurones have been described during antennular flicking and antennular withdrawal. The slow extensor motoneurone A30S is active during flicking in addition to the phasic component of the antennular motor system (A30F, A31F and A32F). The flexion phase of a flick is the result of a burst of variable duration and number of spikes within flexor motoneurones A31F and A32F. The extension phase of a flick is the result of a burst of variable duration and number of spikes in extensor motoneurones A30F and A30S. Extension-withdrawal and slow flexion-withdrawal reflexes, tonic flexion withdrawal and maintained flexion at the MS-DS joint usually result from activity in part of the tonic component of the antennular motor system: moto-neurones A30S, A31S and A32S. Fast flexion-withdrawal reflexes result from a burst of spikes in motoneurone A31F-S which constitutes the phaso-tonic component of the antennular motor system. During high-frequency activity (15–60/sec), reciprocity exists between the slow flexor motoneurones A31S an A32S and slow extensor motoneurone A30S.
The effect of progressive hypoxia on respiration in the dogfish (scyliorhinus canicula) at different seasonal temperatures
Authors: Butler P. J. , Taylor E. W.
Published: April 2021

Dogfish were acclimated to 7, 12 or 17°C and exposed to progressive hypoxia at the temperature to which they had been acclimated. During normoxia, the Q10 values for oxygen uptake, heart rate, cardiac output and respiratory frequency over the full 10°C range were: 2·1, 2·1, 2·1 and 2·5 respectively. Increased acclimation temperature had no effect on cardiac stroke volume or systemic vascular resistance, although there was a decrease in branchial vascular resistance, pHa and . Progressive hypoxia had no effect on heart rate or oxygen uptake at 7°C, whereas at 12°C and 17°C there was bradycardia, and a reduction in O2 uptake, with the critical oxygen tension for both variables being higher at the higher temperature. Cardiac stroke volume increased during hypoxia at each temperature, such that cardiac output did not change significantly at 12 and 17°C. Neither pHa nor changed significantly during hypoxia at any of the three temperatures. The influence of acclimation temperatures on experimental results from poikilotherms is pointed out. Previously-published results show quantitative differences. The significance of the present results with respect to the functioning and location of oxygen receptors is discussed. It is argued that as the metabolic demand and critical oxygen tension of the whole animal are increased at high acclimation temperatures the same must be the case with the oxygen receptor. This would raise the stimulation threshold and could account for the bradycardia seen during hypoxia becoming manifest at higher values of and the acclimation temperature is raised.
The effect of caffeine on calcium efflux and calcium translocation in skeletal and visceral muscle
Authors: Huddart H. , Syson A. J.
Published: April 2021

KCl-induced depolarization resulted in a large stimulation of the 46Ca efflux from both cockroach skeletal muscle and rat ileal smooth muscle. Caffeine (10 mM) induced a large stimulation of 45Ca efflux from skeletal muscle, but a fall in the efflux from ileal muscle, especially if the efflux was previously stimulated by KCl depolarization. Caffeine inhibited calcium uptake by skeletal muscle mitochondria and sarcoplasmic reticulum, was without effect on ileal muscle mitochondria, but significantly increased calcium binding by ileal muscle membrane vesicular preparations. The induction of contractures and stimulation of46Ca efflux in skeletal muscle by caffeine are clearly related to inhibition of intracellular calcium binding by the sarcoplasmic reticulum and mitochondria. The relaxation of ileal muscle by caffeine and the inhibition of fibre calcium efflux correlate well with caffeine enhancement of intracellular calcium binding. These experiments suggest that the membrane vesicular compartment may be the main agency centrally involved in fibre calcium regulation in this muscle during the contraction-relaxation cycle.
The Removal of Sulphate by the Excretory Apparatus of the Blowfly Calliphora Vomitoria
Authors: Knowles G.
Published: April 2021

The excretion of sulphate by the isolated Malpighian tubules of Calliphora vomitoria has been investigated. Contrary to expectation, it was found that the isolated tubules are freely permeable to sulphate. The rate of sulphate secretion is comparable to the rates of secretion of both phosphate and chloride. The excretion of sulphate by the intact fly has also been verified.
The secretion of hyperosmotic fluid by the rectum of a saline-water mosquito larva, Aedes taeniorhynchus
Authors: Bradley T. J. , Phillips J. E.
Published: April 2021

Fourth-instar larvae of the mosquito A. taeniorhynchus (Wiedemann), when living in sea water, drink at a rate of 100 nl h−1 larva−1 and maintain ionic and osmotic levels in the haemolymph at about one-third those of the external medium. Hyperosmotic urine is produced in the rectum by secretion of fluid having an osmotic concentration and ionic composition similar to that of sea water, with the exception that potassium levels are elevated 18-fold in the secretion. The average rate of fluid secretion observed was 19 nl h−1 larva−1 with a maximum of 92 nl h−1 larva−1. The concentration and volume of rectal secretion may be too low to account completely for osmotic balance. The possible role of anal papillae is discussed in this regard.
The effects of calcium on water balance of the brown trout Salmo trutta
Authors: Oduleye S. O.
Published: April 2021

Water space, tritiated water flux, drinking and urine flow rates of the brown trout were decreased by increasing the environmental calcium concentration.

Diffusional and osmotic permeabilities were identical in fresh water. This suggests that water flow across the gill occurs entirely by diffusion. Previous suggestions of a discrepancy between the two permeabilities in freshwater teleosts could have been due to an overestimation of urine flow rate upon which the determination of osmotic permeability coefficient is based.

The wide-ranging effects of calcium on hydro-mineral regulation suggests that the ion interacts with the gills.
Sound localization by the bottlenose porpoise Tursiops truncatus*
Authors: Renaud D. L. , Popper A. N.
Published: April 2021

Sound localization was measured behaviourally for the Atlantic bottlenose porpoise (Tursiops truncatus) using a wide range of pure tone pulses as well as clicks simulating the species echolocation dick. Measurements of the minimum audible angle (MAA) on the horizontal plane give localization discrimination thresholds of between 2 and 3° for sounds from 20 to 90 kHz and thresholds from 2·8 to 4° at 6,10 and 100 kHz. With the azimuth of the animal changed relative to the speakers the MAAs were 1·3–1·5° at an azimuth of 15° and about 5° for an azimuth of 30°. MAAs to clicks were 0·7–-8·8°. The animal was able to do almost as well in determining the position of vertical sound sources as it could for horizontal localization. The data indicate that at low frequencies the animal may have been localizing by using the region around the external auditory meatus as a detector, but at frequencies about 20 kHz it is likely that the animal was detecting sounds through the lateral sides of the lower jaw. Above 20 kHz, it is likely that the animal was localizing using binaural intensity cues. Our data support evidence that the lower jaw is an important channel for sound detection in Tursiops.
The colloid osmotic pressures of invertebrate body fluids
Authors: Mangum C. P. , Johansen K.
Published: April 2021

Colloid osmotic pressures of the body fluids of twenty invertebrate species were measured directly. The results, which are generally lower than predicted values for the same species, pertain to several physiological questions: (1) they do not quantitatively explain the frequently observed hyperosmoticity of body fluids in species believed to be osmoconformers, indicating that the condition cannot be merely a consequence of a Gibbs-Donnan equilibrium; (2) the excess of hydrostatic over colloid osmotic pressure is very small. This result supports the hypothesis that the oxygen transport function of bloods with extracellular haemocyanins and haem proteins is limited by their colligative properties; (3) the pressure relationships and the absence of colloid osmotic activity in urine indicates that filtration contributes to urine formation in several species.
On the Running of the GNU (Connochaetes Taurinus) and other Animals
Authors: Pennycuick C. J.
Published: April 2021

A simple optical method was used to observe speed, stride length and stepping frequency in undisturbed walking or running wild animals. Most measurements were made on the gnu (adult and young calf) and Thomson’s gazelle. The hypothesis that stepping frequency is independent of speed is not tenable for any gait. The data are discussed in terms of , the average number of feet in contact with the ground. It is suggested that the value required of by the animal is the main consideration determining its choice of gait. The height of the vertical jumps in galloping does not need to increase indefinitely with speed, and the power needed for the jumps is not likely to limit the maximum galloping speed. Stepping frequency observations in the walk, trot and canter were analysed for 14 mammal species plus the gnu calf. Stepping frequency was found to vary with about the — 0·5 power of the linear dimensions in all three gaits. It is suggested that only three gaits should be recognized, the walk, trot and canter, and that they should be distinguished on the basis of (a) the symmetry or otherwise of the stepping pattern, (b) the range of over which the gait can be used, and (c) the nature of the energy transformations which occur at each step.
Insect blood-brain barrier: a radioisotope study of the kinetics of exchange of a liposoluble molecule (n-butanol)
Authors: Thomas M. V.
Published: April 2021

About 90 % of the butanol uptake by the cockroach abdominal nerve cord washed out with half-times of a few seconds, in good agreement with an electrophysiological estimate, and the temperature sensitivity suggested an activation energy of 3 Kcal mole−1. The remaining activity washed out far more slowly, with a similar time course to that observed in a previous investigation which had not detected the fast fraction. Its size was similar to the non-volatile uptake, and was considerably affected by the butanol concentration and incubation period. It apparently consisted of butanol metabolites, which could be detected by chromatography.
Acid-base balance in rainbow trout (Salmo gairdneri) subjected to acid stresses
Authors: Eddy F. B.
Published: April 2021

The respiratory properties of rainbow-trout blood were investigated in acid-stressed fish. In the first group acid was introduced into the bloodstream and in the second the carbon dioxide content of the ambient water was increased. Initially the introduction of acid to the blood caused a decrease in blood pH and bicarbonate, and increases in oxygen uptake and ventilation volume. After 2-3 h these values had returned to the control levels. Trout subjected to high ambient CO2 (about 10 mmHg) showed a decrease in blood pH while and bicarbonate increased. After 8 h the trout began to show signs of compensation to the acidosis. In each experiment the blood was little changed but blood O2 content was decreased and tended not to resume the control value even after several hours. The results are discussed in terms of the various acid-base mechanisms thought to be available to the fish. These include branchial ion exchanges and the possible buffering roles of the extracellular and intracellular fluids.
Sodium extrusion by the sea-water-acclimated fiddler crab Uca pugilator: comparison with other marine crustacea and marine teleost fish
Authors: Evans D. H. , Cooper K. , Bogan M. B.
Published: April 2021

Measurements of the blood Na concentration and transepithelial electrical potential (T.E.P.) across Uca pugilator acclimated to sea water indicate that Na is maintained out of electrochemical equilibrium with sea water. The resulting net Na influx as well as the sodium gain due to ingestion of the medium must be balanced by extrarenal Na extrusion. The small T.E.P. (– 0·7 mV) and the ‘transport numbers’ of Na and Cl indicate that the permeability to these ions is equivalent. Removal of external K results in a significant stimulation of unidirectional Na efflux that is dependent upon external Na but is not inhibited by ouabain. Transfer of Uca to K and Na-free sea water results in a 54% decline in unidirectional efflux, which is not due to T.E.P. changes. Readdition of 25 mm-K stimulates Na efflux much more than can be accounted for by changes in the T.E.P. Readdition of 25 mm-Na to potassium-free sea water does not change the Na efflux. The results indicate that Na extrusion by Uca is via a Na/K exchange mechanism which partially inhibits Na/Na exchange. Cessation of Na/K exchange (in K-free sea water) removes this inhibition and allows rapid Na/Na exchange. It is not known whether Na/K and Na/Na exchange are via the same or parallel carrier systems.
The effects of hypophysectomy, prolactin therapy and environmental calcium on electrolyte balance of the brown trout Salmo trutta, L.
Authors: Oduleye S. O.
Published: April 2021

Adaptation of the brown trout to fresh water containing increasing concentrations of calcium resulted in a decrease in plasma electrolyte level and total electrolyte excretion. The electrolyte excretion rate was higher at the beginning than at the end of the urine collection periods.

Hypophysectomized fish had a lower plasma electrolyte concentration than the controls. This deficiency was partially corrected by prolactin therapy. High environmental calcium was only effective to a limited extent. There was no difference in the normal renal sodium output between hypophysectomized and intact fish in fresh water. Environmental calcium did not have any significant effect on renal electrolyte output of hypophysectomized fish.
The initiation of diving apnoea in the frog, Rana pipiens
Authors: West N. H. , Jones D. R.
Published: April 2021

Diving apnoea in Rana pipiens was initiated by submerging the external nares. As the water level was raised above the frog, both buccal and lung pressure increased by an amount corresponding to the water head. During submergence the external nares remained closed, although the apnoeic period was punctuated by ventilation movements which moved gas between the lungs and buccal cavity. Bilateral section of the ophthalmic nerves did not alter the normal pattern of ventilation in air, although it often resulted in the intake of water into the buccal cavity on submergence. Introduction of water into the buccal cavity, either naturally as in denervates or by injection through a catheter in intact frogs, triggered sustained electromyographical activity in some respiratory muscles. Electroneurograms recorded from the cut peripheral end of an ophthalmic nerve showed that receptors in the external narial region were stimulated by movement of a water meniscus across them. Activity could also be recorded in the ophthalmic nerve in response to water flow past the submerged nares. Punctate stimulation of the narial region confirmed that these receptors were mechanosensitive. Bilateral electrical stimulation of the central ends of cut ophthalmic nerves in lightly anaesthetized frogs caused apnoea with a latency of less than 200 ms. The external nares remained closed throughout the period of stimulation although buccal pressure events, resembling underwater ventilation movements, occurred when stimulation was prolonged.
Carbon dioxide combining properties of the blood of the shore crab Carcinus maenas (L.): carbon dioxide solubility coefficient and carbonic acid dissociation constants
Authors: Truchot J. P.
Published: April 2021

The carbon dioxide solubility coefficient, , and the apparent carbonic acid dissociation constants, and , were estimated in the serum of the crab Carcinus maenas at various temperatures and ionic strengths.

At 15 °C, the indirectly determined value is 0·0499 m-mole 1−1 torr−1 for crabs living in normal sea water (salinity ca. 35 ‰). It is apparently independent of the serum protein concentration and of the stage of the moulting cycle.

For crabs living in undiluted sea water, the mean value, determined either gasometrically or titrimetrically, is 6·027 at 15 °C. At the same temperature, . These values approximate to those of sea water at 35‰ salinity. drops as temperature rises; the measured is –0·0053 pH unit °C−1 between 10 and 30 °C. rises as the ionic strength is lowered.

Alignment nomograms have been constructed for the determination of and values in relation to various conditions of temperature and salinity.
Unidirectional ion movements in the hindgut of larval Sarcophaga bullata (Diptera: Sarcophagidae)
Authors: Prusch R. D.
Published: April 2021

Unidirectional Na+, K+, and Cl− fluxes were measured across the isolated hindgut of larval Sarcophaga bullata. Both K+ and Cl− are actively secreted into the hindgut lumen, whereas Na+ is distributed passively. The movements of K+ and Cl− are not entirely independent of each other, and the movement of one ion influences the flux of the co-ion. The NH4+ ion is secreted into the hindgut by a mechanism separate from K+ secretion.
Ciliary propulsion of objects in tubes: wall drag on swimming Tetrahymena (Ciliata) in the presence of mucin and other long-chain polymers
Authors: Winet H.
Published: April 2021

The lubrication effect of three long-chain polymers - mucin, methylcellulose and Ficoll - on ciliary propulsion in tubes is measured by plotting the relative velocities of swimming ciliates as a function of tube bore diameter. Mucin shows the most unequivocal lubrication, which is found at concentrations between 0% and 9·1% (w/v).This observation, coupled with visco-metric measurements which show that ciliary tip shear rates are sufficient to solate mucin, serve as the groundwork for a model of mucin lubrication which explains the optimized lubrication behaviour of thixotropic gelating polymers as an expression of the responses to shear by the various stages of polymer clustering during the gelation process. In addition to the lubricative effect, another wall drag reduction effect by mucin was measured in the clearance region beyond the lubrication layer. This apparent viscosity reduction is optimized in the concentration range between 1·7 and 4·1 % mucin and may also be explained in terms of the properties of gel clustering.
Neural regulation of the heart muscle in an isopod crustacean: acceleration and peripheral inhibition
Authors: Delaleu J. C. , Holley A.
Published: April 2021

In the neurogenic heart of the isopod crustacean Porcellio dilatatus, repetitive electrical stimulation of the cardiac nerves elicited either cardioacceleratory or cardio-inhibitory effects depending on the stimulation parameters. Acceleratory effects were accompanied by a decrease of membrane potential and by changes in the contour of the spontaneous electrical responses: increase in the speed of the rising phase and enhancement of the plateau phase. Inhibitory stimulation acted on rhythmicity and/or contour of spontaneous responses. At stimulation pulse frequencies beyond 25/s a hyperpolarization appeared after the cessation of the inhibitory train. Inhibitory stimulation elicited IJPs in the myocardium. Their reversal potential was found to be close to the value of the resting membrane potential. During inhibitory stimulation, the membrane resistance of the heart muscle was frequently decreased. The effects of changing the external chloride content, and of adding GABA and picrotoxin support the hypothesis that the inhibitory impulses increased the myocardium permeability to Cl−. On the basis of these findings it is assumed that cardio-inhibitory fibres act on both cardiac ganglion and myocardium. Comparisons are established between the wood-louse’s heart and the skeletal or heart muscle of some arthropods. The functional significance of peripheral inhibition is further discussed in relation to the nature of the spontaneous electrical responses and to contraction.
Analysis of burst activity of the buccal ganglion of Aplysia depilans
Authors: Rose R. M.
Published: April 2021

Certain nonlinear properties of molluscan neurones suggest that network activity could be described in relation to nonlinear relaxation oscillators. A specific example is fitted by the Van der Pol equation with an exponentially decaying damping coefficient, and changes in the associated energy and sensitivity are considered. More precise details of the interaction pattern are determined by analysis of a single cycle of burst activity, and it is shown that there are two states of activity, depending on the balance of presumed inhibitory components. Previous results are discussed in relation to an overall decaying oscillation. Changes in subcomponents of a cycle are described for decaying sequences and the constancy of synaptic interaction is demonstrated. The results are briefly discussed in relation to catastrophe theory and learning.
Morphometric study of trout gills: a light-microscopic method suitable for the evaluation of pollutant action
Authors: Hughes G. M. , Perry S. F.
Published: April 2021

Methods are described for the morphometric estimation of parameters of the gill system of trout which are relevant to its function in gas exchange. The methods have been used with 1 μm sections viewed under the light microscope. In particular the diffusion distances between water and blood are measured, which together with determinations of gill area, provide figures for the morphometrically estimated diffusing capacity. The methods have been used to compare the diffusing capacity of gills from control fish and those treated in polluted waters. The concept of relative diffusing capacity (Drol) is introduced which enables comparisons to be made without the need to determine the absolute diffusing capacity. Quantitative estimation of changes in relative volumes and surface areas of components of the secondary lamellae were determined, and employed to explain the possible anatomical causes of changes in Drol. It is suggested that these methods can be of value in the comparison of the gills of fish treated in different waters.
Branchial ion uptake in arctic grayling: resting values and effects of acid-base disturbance
Authors: Cameron J. N.
Published: April 2021

Techniques for the measurement of unidirectional flux rates in fish which require no anaesthesia or surgery are described. Resting values for Cl− uptake at 10 and 17 °C were 8·03 ± 1·11 and 13·52±0·95μ-equiv. 200 g−1 h−1 (±S.E.), respectively; and for Na+ the rates were 15·49±0·40 and 26·30±0·36, respectively. Hypercapnic acidosis caused an increase in Na+ uptake, presumably through Na+/H+ (or ) exchange. It is suggested that this is a com-pensation mechanism leading to the increase in blood buffering observed in response to hypercapnia. Alkalosis was observed following acute temperature increase and was accompanied by an increase in the rate of exchange and also by an increase in Na+/H+ exchange. The role of these branchial ion exchange mechanisms in overall acid-base regulation is discussed.
Flow Visualization with Stereo Shadowgraphs of Stratified Fluid
Authors: Mccutchen C. W.
Published: April 2021

Water stratified thermally or with dissolved material has a refractive index that varies with height. The stratification has no obvious visual effect until the fluid is disturbed, for example by a fish, but then it marks the creature’s wake with a jump in refractive index that is visible in shadowgraphic projection. Two shadowgraphs in stereo display the wake in three dimensions. For a permanent record, or for analysing events too quick for the eye to follow, movies can be taken of the shadowgraphs.
The Effect of Size on the Fast-Start Performance of Rainbow Trout Salmo Gairdneri, and A Consideration of Piscivorous Predator-Prey Interactions
Authors: Webb P. W.
Published: April 2021

The fast-start (acceleration) performance of seven groups of rainbow trout from 9·6 to 38·7 cm total length was measured in response to d.c. electric shock stimuli. Two fast-start kinematic patterns, L-and S-start were observed. In L-starts the body was bent into an L or U shape and a recoil turn normally accompanied acceleration. Free manoeuvre was not possible in L-starts without loss of speed. In S-starts the body was bent into an S-shape and fish accelerated without a recoil turn. The frequency of S-starts increased with size from o for the smallest fish to 60–65 % for the largest fish. Acceleration turns were common. The radius of smallest turn for both fast-start patterns was proportional to length (L) with an overall radius of 0·17 L.

The duration of the primary acceleration stages increased with size from 0·07 s for the group of smallest fish to 0·10 s for the group of largest fish. Acceleration rates were independent of size. The overall mean maximum rate was 3438 cm/s2 and the average value to the end of the primary acceleration movements was 1562 cm/s2. The distance covered and velocity attained after a given time for fish accelerating from rest were independent of size.

The results are discussed in the context of interactions between a predator and prey fish following initial approach by the predator. It is concluded that the outcome of an interaction is likely to depend on reaction times of interacting fish responding to manoeuvres initiated by the predator or prey. The prey reaction time results in the performance of the predator exceeding that of the prey at any instant. The predator reaction time and predator error in responses to unpredictable prey manoeuvre are required for prey escape. It is predicted that a predator should strike the prey within 0·1 s if the fish are initially 5–15 cm apart as reported in the literature for predator-prey interactions. These distances would be increased for non-optimal prey escape behaviour and when the prey body was more compressed or depressed than the predator.
Respiration of the Amphibious Fishes Periophthalmus Cantonensis and Boleophthalmus Chinensis in Water and On Land
Authors: Tamura S. O. , Morii H. , Yuzuriha M.
Published: April 2021

The routine oxygen consumption by Periophthalmus cantonensis and Boleophthalmus chinensis in water increased geometrically, whereas that in air increased logarithmically with temperature. At temperatures of more than 20 °C the oxygen uptake of both species was greater in water than in air. When the fishes were able freely to select either an aquatic or terrestrial habitat, the total oxygen consumption of Periophthalmus and Boleophthalmus was 236 and 110 ml/kg.h at 20 °C respectively; 66% (Periophthalmus’) and 70 % (Boleophthalmus) of the total uptake was from water, and 34 and 30 % of the total uptake was from air at 20 ± 1 °C. Oxygen uptake of fish limited to aquatic or terrestrial life was less than when they could freely select their habitat ; for Periophthalmus, uptake was reduced to 83 % when confined in water and to 50 % in air, and for Boleophthalmus, to 65 % in water and to 43 % in air. The proportion of oxygen uptake by the gill in water was 52% for Periophthalmus and 59 % for Boleophthalmus’, in air the corresponding figures were 27 and 52 %. The proportions of oxygen uptake via the skin in water was 48% for Periophthalmus and 36% for Boleophthalmus; in air the corresponding figures were 76 and 43 %. It is concluded that, on land, Periophthalmus relies mainly on its skin and Boleophthalmus relies mainly on its gills.
Hypersensitivity in the Anterior Median Eye of A Jumping Spider
Authors: Yamashita Shigeki , Tateda Hideki
Published: April 2021

Changes in sensitivity of the photoreceptor cells of the anterior median eye of the jumping spider Menemerus confusus Boes, et Str. have been studied by recording electroretinograms (ERGs) and receptor potentials. The amplitudes of the responses (ERGs and receptor potentials) increase during repetitive stimulation, with a maximum increase at 3−5 s intervals. The sensitivity of the photoreceptor cell is greater for about 60 s following illumination (maximum magnitude at 3−5 s) than it is during complete dark adaptation. This phenomenon, which we call ‘hypersensitivity’, is lost within one day following surgery in physiological saline. Upon loss of hypersensitivity, the sensitivity decrease during light adaptation is greater than for the normal eye and the small increase of sensitivity following the onset of illumination observed for the normal eye is lost.
The Role of Environmental Calcium in Freshwater Survival of the Marine Teleost, Lagodon Rhomboides
Authors: Carrier Jeffrey C. , Evans David H.
Published: April 2021

The marine teleost fish, Lagodon rhomboides, can only tolerate fresh water (5 mm Na) if Ca is also present (10 mm). Transfer to Ca-free fresh water is followed by a substantial increase in radioactive Na efflux with little or no change in the transepithelial potential. Addition of the chelating agent EDTA (2 mm) further increases Na efflux. Fish left in Ca-free fresh water for 2·5 h die with a total body Na less than 50 % of that found in animals acclimated to Ca-supplemented fresh water. Rates of Na uptake were measured on either sea-water-acclimated or Ca-supplemented fresh water-acclimated fish transferred to various low Na media. In both cases Na uptake has a high Km, is saturable, inhibited by external NH4, H and amiloride, and is not related to changes in the transepithelial potential. It is suggested that L. rhomboides is dependent upon external Ca to decrease diffusional Na loss in low salinities so that a relatively inefficient Na uptake can balance diffusional and urinary Na loss.
The Effects of Osmotic Stress on the Electrical Properties of the Axons of A Marine Osmoconformer (Maia Squinado. Brachyura: Crustacea)
Authors: Pichon Y. , Treherne J. E.
Published: April 2021

In contrast to the depolarization observed in hyperosmotic media, exposure of peripheral nerve to hyposmotic conditions induced pronounced axonal hyperpolarization. It is suggested that this hyperpolarization resulted from increased potassium and chloride permeabilities which could assist axonal volume regulation in hyposmotic conditions. The hyperpolarization was readily reversible, but the spike-generating mechanism suffered irreversible damage at hyposmotic concentrations below 665 m-osmoles. It is suggested that this axonal damage contributes to the lethal effects of hyposmotic stress in this crustacean osmoconformer and, possibly, in some euryhaline osmoregulators.
Rhythmic Swimming Activity in Neurones of the Isolated Nerve Cord of the Leech
Authors: Kristan William B. , Calabrese Ronald L.
Published: April 2021

Repeating bursts of motor neurone impulses have been recorded from the nerves of completely isolated nerve cords of the medicinal leech. The salient features of this burst rhythm are similar to those obtained in the semi-intact preparation during swimming. Hence the basic swimming rhythm is generated by a central oscillator. Quantitative comparisons between the impulse patterns obtained from the isolated nerve cord and those obtained from a semi-intact preparation show that the variation in both dorsal to ventral motor neurone phasing and burst duration with swim cycle period differ in these two preparations. The increase of intersegmental delay with period, which is a prominent feature of swimming behaviour of the intact animal, is not seen in either the semi-intact or isolated cord preparations. In the semi-intact preparation, stretching the body wall or depolarizing an inhibitory motor neurone changes the burst duration of excitatory motor neurones in the same segment. In the isolated nerve cord, these manipulations also change the period of the swim cycle in the entire cord. These comparisons suggest that sensory input stabilizes the centrally generated swimming rhythm, determines the phasing of the bursts of impulses from dorsal and ventral motor neurones, and matches the intersegmental delay to the cycle period so as to maintain a constant body shape at all rates of swimming.
Altered Calcium Conductance in Pawns, Behavioural Mutants of Paramecium Aurelia
Authors: Schein Stanley J. , Bennett M. V. L. , Katz George M.
Published: April 2021

Pawns are behavioural mutants (in one of three genes) of Paramecium aurelia that have lost, to varying degrees, the reversal response which is thought to depend on the calcium influx during excitation. This report shows that all of the single and double mutants have reduced active inward (calcium) current, the reduction correlating with the degree of behavioural deficit. All of the mutants display normal resting potential, input impedance and delayed rectification. Mutants in genes pwA and pwC show normal anomalous rectification, but pwB mutants do not show anomalous rectification until the membrane is hyperpolarized further. We suggest that the pwA gene plays a role in depolarization sensitivity (the ‘gate’) and the pwB gene a role affecting either the wall of the channel itself or the total number of channels.
Calcium Channel Stability Measured by Gradual Loss of Excitability in Pawn Mutants of Paramecium Aurelia
Authors: Schein Stanley J.
Published: April 2021

Mutants of Paramecium aurelia that are unable to reverse swimming direction are called pawns. They lack the inward ionic (calcium) current required for the upstroke of the electrically excitable membrane response. By following the progressive loss of reversal response and excitability in cells that are suddenly changed from a heterozygous (wild-type) state to a homozygous mutant state, an estimate of the stability and mean lifetime of the calcium channel has been obtained. During rapid growth, channel dilution due to division occurred, but no channel decay was observed. Under conditions of slow growth, decay could also be observed; channel lifetime was found to be from 5 to 8 days.