bluuebunny/crossref_metadata_2025 huggingface dataset:
The Reactions of the Plaice (Pleuronectes Platessa L.) to Water Currents
Authors: Arnold G. P.
Published: April 2021

Observations were made on the reactions of plaice (2-28 cm. length) to water currents in a small flume (30 × 32·5 × 550 cm.), and a behaviour pattern is described. At a threshold velocity fish turned to face upstream, usually showing burying movements or a clamped-down posture. With increasing current velocity they remained on the bottom, showing a posterior fin-beating response. Fish displaced by the current reacted firstly by moving upstream on the bottom and re-settling and at higher velocities by bursts of swimming in midwater. A velocity was finally reached at which each fish was displaced downstream over the weir. On a sandy bottom small buried plaice did not usually react to the current until the covering layer of sand was eroded away. Observations with an infra-red viewer showed that although the typical optomotor response shown in midwater disappeared in the dark, behaviour on the bottom remained the same as in the fight. The lowest velocity at which fish turned to face the current was o·8 cm./sec. and most fish orientated at a velocity below 8 cm./sec. ; there was no increase in threshold velocity with length. There was great variation in the velocity at which individual fish were finally displaced, but there was a general increase with length from 50 to 70 cm./sec. A displacement velocity was found for anaesthetized fish (24−30 cm. length) heading upstream, which was significantly higher than for those heading downstream. Photographs of the flow patterns over live fish on the bottom showed that they were most effectively streamlined when heading directly upstream. Injection of dye showed that water penetrating beneath the fish was ejected by the posterior fin-beating response, and that the operculum of the ocular surface only was used to exhale water from the gills. Experiments with water jets demonstrated three areas whose stimulation elicited a behavioural response shown in the current. These were the leading edges of the body on either side of the head, including the right nasal papilla, and the tail. The results are discussed in relation to the ecology of the plaice and the contranatant theory of fish migrations. It is concluded that the observed behaviour is hydrodynamically advantageous in maintaining station on the sea-bed.
The Auditory System of Homorocoryphus (Tettigonioidea, Orthoptera)
Authors: McKay J. M.
Published: April 2021

The responses of the auditory interneurones indicate that the tettigoniid ear discriminates frequencies. The T fibre receives strong ipsilateral and weak contralateral excitatory inputs and a strong contralateral inhibitory input, from the tympanic nerves. These inputs are frequency-sensitive, the response being greatest at 30 kcyc./sec. and above. Responsiveness is low in the region of 15 kcyc./sec., which is the dominant song frequency. At 30 kcyc./sec. the T fibre is most sensitive to amplitude increments, and conveys maximal directional information. Both the T fibre and the ear (as judged by the compound potential in the tympanic nerve) respond to steps of 2 dB. The directionality of the ear is enhanced by the contralateral inhibitory connexions of the T fibre. At 15 kcyc./sec. directionality is poor, but is present at 10 kcyc./sec. The T fibre is inhibited by continuous sounds, including the species song. The extent of the inhibitory effect varies with the amplitude of the continuous sound. This may assist in explaining the ‘phasic’ response of the T fibre. There is little habituation to repetitive stimuli. A small interneurone seen in split connectives gives a ‘tonic’ response to song and to continuous sound. It may inhibit the T fibre. Two other auditory fibres are occasionally recorded in the connectives. The T fibre has all the properties required of a warning system responding to pulsed high-frequency sound, and it responds well to bat cries. There is, however, no evidence that it mediates a behavioural response.
Landing Reaction of Musca Domestica: Dependence on Dimensions and Position of the Stimulus
Authors: De Talens A. Fernandez Perez , Ferretti C. Taddei
Published: April 2021

The house-fly exhibits the landing reaction when an expanding optical pattern is placed before it. An expanding pattern which is easy to measure and which keeps the level of illumination constant is created by rotating spirals. In analysing the dependence of landing reaction on the spiral pitch and multiplicity and on the frequency of local stimuli on each ommatidium, (a) interference by the tangential characteristics of the spiral has been observed; (b) stimulus efficiency has been found to depend on stimulus wave-length; (c) the relevance of the above factors and of a temporal parameter influencing both optomotor and landing reactions has been evaluated. The fact that no Moiré effect has been observed is explained in terms of characteristics of stimuli used. The dependence of pattern efficiency on the position of the stimulus in the visual field has been ascertained. Spatial integration of local landing stimuli has been shown in various cases and its threshold excitability and saturation point have been obtained. The dependence of these two last parameters on the position of the stimulus in the visual field has been ascertained.
Further Studies on Synaptic Transmission in Insects
Authors: Pichon Y. , Callec J. J.
Published: April 2021

The dissection of a small length of a giant axon between the 5th and the 6th ganglia of the abdominal nerve cord of the cockroach Periplaneta americana allows extracellular recordings of excitatory post-synaptic potentials (EPSPs) to be made in particularly good conditions. ‘Spontaneous’ or ‘induced’ EPSPs are smaller and slower than those recorded with conventional micro-electrodes. Post-synaptic action potentials are very similar to, or even larger than, those recorded by means of intracellular electrodes. The low impedance of the recording system, together with its stability, allows numerous experiments to be made which were nearly impossible with the microelectrode technique. It is suggested that this technique might be used for other post-synaptic structures.
Water Balance in the Salmon Egg
Authors: Loeffler Clarence A. , Løvtrup Søren
Published: April 2021

The rate of water exchange in the salmon egg was determined by means of the electromagnetic diver-balance. Salmon eggs treated with alcohol to remove the plasma membrane were used to determine the diffusion coefficient, D, for water in the cytoplasm, and untreated eggs to determine the permeability coefficient, E, for water through the plasma membrane. It was found that D is of the same order as that observed in other eggs, whereas the value of E is somewhat lower, but still within the same order of magnitude. The results do not confirm the classical notion that the salmon egg is impermeable to water, but they show that the exchange is extremely slow, the half time being about 24 hr. In order to explain this result the contribution of egg size and environmental temperature must be taken into account. It is concluded that the actually observed rate of swelling corresponds to that anticipated from the recorded permeability coefficient, and that there is therefore no reason to presume that any kind of osmoregulation takes place.
Aerodynamics of Gliding Flight in A Falcon and Other Birds
Authors: Tucker Vance A. , Parrott G. Christian
Published: April 2021

A live laggar falcon (Falco jugger) glided in a wind tunnel at speeds between 6·6 and 15·9 m./sec. The bird had a maximum lift to drag ratio (L/D) of 10 at a speed of 12·5 m./sec. As the falcon increased its air speed at a given glide angle, it reduced its wing span, wing area and lift coefficient. A model aircraft with about the same wingspan as the falcon had a maximum L/D value of 10. Published measurements of the aerodynamic characteristics of gliding birds are summarized by presenting them in a diagram showing air speed, sinking speed and L/D values. Data for a high-performance sailplane are included. The soaring birds had maximum L/D values near 10, or about one quarter that of the sailplane. The birds glided more slowly than the sailplane and had about the same sinking speed. The ‘equivalent parasite area’ method used by aircraft designers to estimate parasite drag was modified for use with gliding birds, and empirical data are presented to provide a means of predicting the gliding performance of a bird in the absence of wind-tunnel tests. The birds in this study had conventional values for parasite drag. Technical errors seem responsible for published claims of unusually low parasite drag values in a vulture. The falcon adjusted its wing span in flight to achieve nearly the maximum possible L/D value over its range of gliding speeds. The maximum terminal speed of the falcon in a vertical dive is estimated to be 100 m./sec.
A Method for Determining Total Carbon Dioxide in Small Volumes of Liquid
Authors: Little Colin , Ruston Gary
Published: April 2021

A microdiffusion method for estimating total dissolved carbon dioxide in volumes of approximately 1·5 μl. is described. The principle of the method is to displace the CO2 with acid, to absorb it in barium hydroxide solution and to measure the change ;n the freezing-point depression of this solution. The range of measurement is 0–30 mm/1. HCO3− with a standard deviation of ± 0·3–0·4 mm/1. In its present form the method cannot be used with smaller volumes without correcting for errors arising from the diffusion of water vapour between the sample and the barium hydroxide solution.
Kinetics of Fertilization in the Sea Urchin: A Comparison of Methods
Authors: Presley R. , Baker P. F.
Published: April 2021

A method is described for the direct counting of male pronuclei in recently fertilized sea-urchin eggs. Using this method, fertilization rate determinations were made to compare 30% artificial sea water (A.S.W.), isotonic KC1, sea water containing lauryl sulphate, calcium-free and magnesium-free A.S.W. containing EDTA, and sea water containing uranyl nitrate, as agents blocking fertilization but permitting further development of previously fertilized eggs. 30% A.S.W. was found to be less satisfactory than the other agents, lacking instant effect, and tending to promote polyspermy. The other agents all gave sigmoid rate curves, that of uranyl nitrate lagging 15– 25 sec. behind the others. Evidence was found that uranyl nitrate acts at a later stage in fertilization than the other agents. Sigmoid rate curves were found, except with 30% A.S.W., when eggs with the bulk of the jelly coat removed, and nicotine-treated eggs, were fertilized. Analysis of sperm distribution among eggs from samples fertilized for more than 40 sec. confirmed that re-fertilization takes place at a lower rate than primary fertilization. The processes blocked by KC1 and uranyl nitrate were found to precede the cortical responses to fertilization, and the termination of nicotine sensitivity.
Wettability and Phylogenetic Development of Feather Structure in Water Birds
Authors: Rijke A. M.
Published: April 2021

The water repellency of feathers is determined mainly, but not exclusively, by a structural parameter which can be expressed in terms of diameter and spacing of the barbs and barbules. Effective waterproofing properties result from the optimal balance of structural parameter and resistance to water penetration. Comparison of the structural parameters for water birds with the geological time interval of their earliest fossil record shows a phylogenetic tendency toward optimizing waterprooftng properties with the course of time. Several behavioural patterns are discussed which may have evolved under the selective pressure of the quality of water repellency and resistance to water penetration.
The Mechanics of Stridulation in Bush Crickets (Tettigonioidea, Orthoptera)
Authors: Bailey W. J.
Published: April 2021

A method has been devised by which the isolated tegmina of bush crickets can be actuated in such a manner as to simulate the insect’s natural song. The actuator was used to make a detailed analysis of the mechanics of sound production, with particular reference to the emission of the more or less pure tone at 15 kHz., characteristic of Homorocoryphus nitidulus. Results involving damping and cautery indicated that the area of the right tegmen responsible for the radiation of this sound was the mirror frame, the vein enclosing the classical mirror membrane. Further experiments involving transduced sound and a probe microphone led to the construction of sound radiation maps of the right tegmen which supported the above view. The cantilever hypothesis, involving the mirror frame with the axis of the vestigial file as the cantilever’s rotational axis, was considered in the light of the Homorocoryphus type. The Homorocoryphus type differed from the Conocephalus type (on which the cantilever hypothesis was based) in that a simpler cantilever is formed in a line direct from the plectrum to the tip of the frame arm.
Sensory Control of Abdomen Posture in Flying Locusts*
Authors: Camhi Jeffrey M.
Published: April 2021

Flying locusts use their abdomens as rudders when executing a variety of flight manoeuvres. In the previous paper (Camhi, 1970) I described the lateral deflexions of the abdomen, which locusts presumably use in yaw correction. The sensory cue evoking this response is a change in the direction of the relative wind, monitored by the cephalic wind receptor hairs. The response appears in tethered locusts only while the wings are flapping in flight, suggesting that the activation of the flight mechanisms closes a neuronal switch, which permits wind-direction information from the cephalic hairs to be processed and translated into an abdominal movement.
Relative Growth, Nucleic Acid Content and Cell Numbers of the Brain in Octopus Vulgaris (Lamarck)
Authors: Packard A. , Albergoni V.
Published: April 2021

The brain of Octopus vulgaris grows allometrically with respect to body weight from 12 mg. at the beginning of post-larval life to 1·95 g. at a body weight of 8·5 kg. The two optic lobes contribute 64% to the wet weight total at the beginning of the growth range and 44% at the end. The 150−fold increase in brain weight is accompanied by a 40−fold increase in total DNA content, 80−85 % °f which is in the optic lobes. DNA concentrations of the order of 20 mg./g. wet weight are found in the vertical lobes. An average of 1 mg. DNA is yielded by 1·9 × 108Octopus sperms and this figure is used to calibrate the nucleic acid content of the optic lobes, and of the suboesophageal and supraoesophageal divisions of the brain in terms of their ‘diploid equivalent’. The ratio between the ‘diploid equivalent’ and the numbers of neurones counted histologically is highest for the suboesophageal division and lowest for the vertical lobes and probably indicates a high glia/neurone index in brain areas with many large cells and low index in those with a homogeneous population of small cells. The brain cells of O. vulgaris do not appear to be polyploid. The RNA/DNA ratio is less than 1·0 in the optic and supraoesophageal lobes, higher than 1·0 in the suboesophageal lobes. The ratio increases during growth, especially in the suboesophageal division.
Salt and Water Balance in Salmon Smolts
Authors: Potts W. T. W. , Foster Margaret A. , Stather J. W.
Published: April 2021

Salmon smolts adapted to sea water maintain a high rate of turnover of both sodium and chloride, but when adapted to fresh water the rate of turnover is low. Only a small part of the influx takes place through the gut. On immediate transfer from sea water to dilute sea water or to fresh water the influxes decline rapidly, but on transfer from fresh water to sea water the restoration of the fluxes takes place slowly. The alternative hypotheses that the rapid changes are due to exchange diffusion or to rapid adjustments of the sodium pump are discussed.
Water Flow Through the Gills of Port Jackson Sharks
Authors: Grigg Gordon C.
Published: April 2021

It has been said that the presence of interbranchial septa in elasmobranchs prevents counter-current flow of water and blood at the respiratory surface. In contesting this opinion, attention is drawn to the importance of the septal canals as ducts carrying respiratory water in the Port Jackson shark. Observations made on the passage of dye through the gills and on water pressures in the orobranchial cavity, septal canals and parabranchial cavity, indicate that water flows unidirectionally between the secondary lamellae and into the septal canals. This provides a counter-current flow between water and blood at the respiratory surfaces.
Use of the First Gill Slits for Water Intake in a Shark
Authors: Grigg Gordon C.
Published: April 2021

The use of the first gill slits as an alternate or accessory route for the intake of respiratory water in the Port Jackson shark is described. This pattern of ventilation is an effective means of oxygenating the blood, but not as effective as normal respiration using the mouth. The use of the first gill slits for water intake is thought to allow respiration to continue during either the crushing of food or obstruction of the mouth while scavenging for food on the bottom. This therefore provides an interesting parallel with the use of the spiracles in skates and rays.
Gas Tensions in Tissues of Trout and Carp Exposed to Diurnal Changes in Oxygen Tension of the Water*
Authors: Garey W. F. , Rahn H.
Published: April 2021

When an artificial gas pocket is formed by injection of air into a tissue space the gases equilibrate with the tissue-blood environment and assume a state of constant composition which is maintained until all the gas is eventually resorbed. In man (Rahn, 1957) and in rats (Van Liew, 1968) evidence has been presented that the O2 and CO2 tensions of gas in such pockets are virtually the same as those of the venous blood draining these tissues provided that air or gases of lower O2 concentrations are breathed (see also review by Piiper, 1965). Since the techniques required for sampling and analysis of the equilibrated gas are relatively simple, this method provides a convenient approach for the determination of gas tensions of the blood-tissue environment of unanaesthetized, unrestrained animals.
Substrate Discrimination in Pectinatella Magnifica Leidy (Bryozoa)
Authors: Hubschman Jerry H.
Published: April 2021

This study is concerned with the role of particle size in habitat selection by the larvae of the colonial bryozoan Pectinatella magnifica Leidy. All experiments were conducted at 25° C. with a 14/10 LD photoperiod. When larvae are provided with a clean glass surface only, they settle and metamorphose with no apparent difficulty. If natural pebbles are provided, the larvae will favour the stone over the glass surface. As the size of substrate particle is reduced, the selective favour is likewise reduced. If larvae encounter only sand-size particles, the preference will return to the glass surface. In experiments in which larvae are offered various other surfaces, settling larvae clearly favoured naturally occurring surfaces over manufactured materials.
Hormonal Control of the Malpighian Tubules of the Stick Insect, Carausius Morosus
Authors: Pilcher Diana E. M.
Published: April 2021

Urine secretion by isolated Malpighian tubules of Carausius is accelerated by a diuretic hormone which can be extracted from the brain, corpora cardiaca and suboesophageal ganglion. The level of this hormone in the haemolymph varies according to the state of hydration of the insect. The hormone is inactivated by the tubules, and a mechanism is proposed whereby the tubules might be controlled by the hormone in vivo.
Chemotactic Turning Behaviour of Tubularia Spermatozoa
Authors: Miller R. L. , Brokaw C. J.
Published: April 2021

Chemotaxis of spermatozoa to female gonophores has been shown to occur in Campanularia, Tubularia and other hydroids (Miller, 1966 a, b). Cinemicrographic records of the movements of Campanularia spermatozoa in the vicinity of female gonophores or of glass capillary pipettes containing extracts of female hydranths have shown that chemotactic aggregation of the spermatozoa occurs because the spermatozoa turn and swim toward the source of chemotactic stimulation (Miller, 1966 a). In the present paper the turning behaviour of hydroid spermatozoa during chemotaxis is examined in greater detail, using multiple-exposure dark-field photomicrography under conditions where the spermatozoa are swimming at an interface between sea water and a glass surface. Under these conditions the changes in bending behaviour of the sperm flagellum can be photographed, in addition to the changes in the path of the spermatozoon. Although this report deals exclusively with spermatozoa of Tubularia, similar results have been obtained from less extensive attempts to photograph the turning behaviour of Campanularia spermatozoa.
Control of Preparatory Feeding Behaviour in the Sea Anemone Tealia Felina
Authors: McFarlane I. D.
Published: April 2021

Dissolved food substances elicit preparatory feeding behaviour in the sea anemone Tealia felina. This behaviour takes the form of expansion of the oral disk and lowering of the margin of the disk. Food may also cause mouth opening and pharynx protrusion. This pre-feeding response may increase the chance of food capture. The expansion and lowering of the oral disk can also be elicited by electrical stimulation of a slow conduction system, the SS1, thought to be located in the ectoderm. SS1 activity is seen when the anemone is exposed to dissolved food substances. It is concluded that preparatory feeding behaviour in Tealia is mediated in part by the SS1.
Osmoregulation of Lampetra Fluviatilis L. and Petromyzon Marinus (Cyclostomata) in Hyperosmotic Solutions
Authors: Pickering Alan D. , Morris R.
Published: April 2021

Freshly caught migrating lampreys were placed in 50% sea water and their method of osmoregulation was analysed. Some osmoregulated more successfully than others. Water balance is maintained by a mechanism involving the drinking of large quantities of water (up to 99·5 ml/kg/day). Sodium, potassium and chloride are absorbed by the intestine (often against a concentration gradient) with the subsequent uptake of water. Divalent ions are not readily absorbed by the intestine and there is some evidence for the secretion of magnesium and sulphate into the gut lumen. The limited urine flow (up to 6·2 ml/kg/day) is used for the excretion of calcium, magnesium and sulphate in high concentrations, but the urine is never hyperosmotic to the blood. The urinary excretion of monovalent ions is not sufficient to eliminate those entering by the intestine and extrarenal excretion at the gills must presumably occur. The breakdown of this osmoregulatory mechanism during the anadromous migration involves: an increase in the permeability of the integument to water, a breakdown of the swallowing mechanism which is not dependent upon the occlusion of the alimentary canal, a reduction in the ability to absorb monovalent ions and water from the ingested 50% sea water, and a loss in the large mitochondria-rich ‘chloride output cells’ of the gills. The similarities between the mechanisms of ‘marine’ osmoregulation of lampreys and teleosts are discussed in terms of the evolution of the two groups, and it is concluded that almost identical osmoregulatory mechanisms have evolved independently.
Oxygen Consumption in Ammocoetes of the Lamprey Ichthyomyzon Hubbsi Raney
Authors: Hill B. J. , Potter I. C.
Published: April 2021

A continuous flow respirometer suitable for measuring oxygen consumption in some small burrowing aquatic animals is described. Rates of oxygen consumption in ammocoetes of the lamprey Ichthyomyzon hubbsi are low, with mean values at 15·5°C ranging from 38·8 to 97·1 μl/g/h for large (3·44 g) and small (0·14 g) animals respectively. A Q10 of 3·6 was found for medium-size animals (1·18g) between 3·5 and 22·5°C. The slope of the logarithmic linear regression relating weight and oxygen consumption was 0·718 at 15·5°C. The rates of oxygen consumption are discussed with respect to the ecology of ammocoetes and compared with those obtained for other lower vertebrates.
Survival and Behaviour of Ammocoetes at Low Oxygen Tensions
Authors: Potter I. C. , Hill B. J. , Gentleman Susan
Published: April 2021

Survival and behaviour studies were made on ammocoetes subjected to water of various tensions of oxygen and carbon dioxide. Ammocoetes can tolerate, for at least 4 days, oxygen tensions as low as 7–10 mmHg at 5°C, 12-16 mmHg at 15·5°C and between 13–16 and 19–21 mmHg at 22·5°C. A limited ability to acclimate to low oxygen tensions was found in some animals. A characteristic emergence behaviour is evoked by low partial pressures of oxygen that approach the lethal level and by high concentrations of carbon dioxide. Ammocoetes respond to low oxygen and high carbon dioxide by an increase in the rate and amplitude of beating of the branchial basket. This increase is maintained in animals able to survive at low oxygen tensions. A high affinity of the blood for oxygen is evident from oxygen equilibrium curves determined on erythrocytes suspension. There was an insignificant Bohr effect at 15·5°C in the pH range 7·68–6·70, although a change occurred in the n value. Haemoglobin concentration, haematocrit and oxygen equilibria suggest that the characteristics of the blood contribute significantly to the ability of ammocoetes to survive in low oxygen conditions.
Electrophysiological and Endocrinological Correlates During the Metamorphic Degeneration of A Muscle Fibre in Galleria Mellonella (L.) (Lepidoptera)
Authors: Runion H. I. , Pipa R. L.
Published: April 2021

Excitatory postsynaptic potentials (e.p.s.p.s), membrane resting potentials, and intensity of birefringence were measured from the two principal planta retractor muscles (PPRMs) of the first pair of prolegs during metamorphosis of Galleria mellonella. This was done to determine whether cessation of efferent nerve impulses to these single fibres signals their degeneration. E.p.s.p.s were elicited reflexively by brushing the insect’s last abdominal segment. Though they become attenuated, e.p.s.p.s can be recorded until 11-12 hr. after pupal ecdysis. By this time the membrane resting potential has dropped from c. 55 mV. to less than 18 mV., and the intensity of birefringence has become minimal. Continuous electromyographic records taken during the initial 18 hr. after pupal ecdysis suggest that the PPRMs are being excited regularly as they degenerate. No ‘sparing effect’ on the degeneration of the PPRMs could be detected when programmed, current-limited stimuli were administered to pupae via chronically implanted electrodes. Removing all acknowledged endocrines by transecting newly emerged pupae has negligible effect on the decrease of the PPRM birefringence, but greatly retards the degradation of the membrane resting potential and e.p.s.p.s. This retardation can be alleviated by injecting the steriod hormone 20-hydroxyecdysone.
Chloride Regulation at Low Salinities by Nereis Diversicolor (Annelida, Polychaeta)
Authors: Smith Ralph I.
Published: April 2021

Evaluation of the chloride exchanges of Nereis diversicolor in the steady state has shown that this worm ‘cuts its losses’, i.e. reduces the fluxes, of chloride at very low salinities (Smith, 1970a), and that this reduction of chloride loss takes place mainly in the urinary component of the efflux, as has also been suggested by previous authors. Jorgensen & Dales (1957) measured the rates of osmotic gain or loss of water, and concluded that at low salinities N. diversicolor could reduce its permeability to water by over 60%. Assuming a comparable reduction in permeability to chloride, they calculated that the observed reduction of chloride efflux could be accounted for by reduction of urine volume, without the necessity of postulating the production of a urine rendered hypotonic to the body fluids by recovery of solutes by the nephridia. Potts & Parry (1964), on the other hand, in their review of the previous authors’ work, felt unable to accept the evidence for a reduction of permeability to water and, on the assumption of no permeability changes, drew up a balance sheet in support of the hypothesis that reduction of chloride loss was achieved in N. diversicolor by recovery of ions from a consequently hypotonic urine. These views are not mutually exclusive, and the problem is not to choose between them but to obtain evidence to indicate the extent to which each postulated mechanism may be operative. In the previous paper (Smith, 1970a), evidence was presented compatible with the concept that the urine of N. diversicolor may be hypotonic in chloride to the coelomic fluid at low salinities, although this evidence was indirect and not conclusive. In a subsequent paper (Smith, 1970b) direct evidence will be presented that the urine of N. diversicolor is hypo-osmotic. In order fully to evaluate the hypothesis of Jorgensen & Dales it would be necessary to measure both permeability to water and urine volume. So far, it has not been possible to measure urine volume, but data on permeability to water have been obtained, and an estimate of water fluxes attempted.
The Effects of Prolactin and Divalent Ions On the Permeability to Water of Fundulus Kansae
Authors: Potts W. T. W. , Fleming W. R.
Published: April 2021

Measurements have been made of the rate of exchange of tritiated water in both intact and hypophysectomized Fundulus kansae in a variety of media. Hypophysectomy reduces the rate of exchange in fresh water. Low doses (30 mu) of ovine prolactin stimulate water turnover in hypophysectomized fish in fresh water. The rate of exchange declines in both intact and hypophysectomized animals with increasing salinity. Experiments with synthetic solutions show that the decline in the rate of exchange in sea water and in higher salinities is due mainly to the effects of calcium ions. Fishes maintained in synthetic sea water containing a low concentration of calcium have both a higher rate of exchange of tritiated water and a higher drinking rate than fish in normal sea water. Supported in part by National Science Foundation Grant GB 7200, and by Biomedical Support Grant Fr-07053 from the General Research Support Branch, Division of Research Resources, Bureau of Health Professional Education and Manpower Training, National Institutes of Health. Visiting Professor, Zoology Department, University of Missouri, Columbia. Professor Potts’s travel and research was supported by the Faculty Improvement Programme. Prolactin (NIH-P-S9) was generously supplied by the National Institute of Arthritis and Metabolic Diseases.
Responses of the Respiratory Pumps to Hypoxia in the Rainbow Trout (Salmo Gairdnert)
Authors: Hughes G. M. , Saunders R. L.
Published: April 2021

Unanaesthetized rainbow trout, when subjected to a lowered Po2 of the inspired water, show an increase in amplitude of pressures recorded from the buccal and opercular cavities. Pressure amplitudes were commonly found to be 0·5 cm of water in resting trout and increased 4-or 5-fold as inspired Po2 was reduced. Differential pressures across the gills also increased with hypoxia. Typically the minute volume in a 400–600 g trout increased from about 0·2 to 0·6 1/kg/min when the inspired was lowered from 150 to 80 mm Hg, but rose to 1–5 1/kg/min at lower Po2. Increased minute volumes are mainly due to increases in stroke volume; respiratory frequency remains fairly constant at Po2’ s above about 80 mm Hg. The relation between differential pressure and minute volume is fairly linear over much of the range, but minute volume increases more rapidly than differentia] pressure. Oxygen consumption of the non-swimming fish increases during hypoxia and is related to the increased ventilation and differential pressure across the gills. Estimates of the oxygen cost of breathing were made from the increased oxygen consumption during hyperventilation. Comparison of these estimates with estimates of the work done, using the pressure and volume measurements, gave figures for the overall efficiency of the pumping mechanism of about 10%.
Fluorescence Localization of Monoamines in Crab Neurosecretory Structures
Authors: Cooke I. M. , Goldstone Martha W.
Published: April 2021

The pericardial organs and anterior ramifications (both neurohaemal structures) of six species of crabs have been examined as whole mounts by the histochemical method for monoamines based on formaldehyde-induced fluorescence. A small number of specifically fluorescing axons (not more than six green and six yellow) innervate the pericardial organ; one of the green-fluorescent and one yellow-fluorescent axon branches and also innervates the anterior ramification. All of the fluorescing axons enter via segmental nerves 1, 2 and 3 from the ventral ganglion. One large, brilliant green-fluorescing axon, and the small green-fluorescing axon which branches to the AR, have been traced in Carcinus to cell bodies in the circumoesophageal connective ganglion. These cells may give rise to the entire population of green-fluorescing axons and terminals in the neurohaemal organs. Each axon, throughout its course in the pericardial organ, supplies a dense array of varicosities (blebs) at surfaces which are directly exposed to the haemolymph. The anterior ramifications are also supplied with blebs. Lack of fluorescence in controls not exposed to paraformaldehyde, reversible quenching of fluorescence by treatment with sodium borohydride, and depletion of the fluorescence by reserpinization of the crabs, all confirm that the fluorescence is specific and represents the intracellular localization of monoamines. With the aid of data available elsewhere we conclude that there are distributed, in parallel with peptide-secreting axons and terminals in the pericardial organs and anterior ramifications, a group of dopamine-containing and a group of 5-hydroxy-tryptamine-containing axons and terminals.
Release of A Neurosecretory Hormone as Peptide by Electrical Stimulation of Crab Pericardial Organs
Authors: Berlind A. , Cooke I. M.
Published: April 2021

Saline which had bathed an isolated crab pericardial organ was chromatographed on a column of Sephadex G-25. The fractions were divided and assayed for cardioexcitor activity and for ninhydrin colour following hydrolysis. Fluid from pericardial organs which had been stimulated electrically to give a maximum propagated compound action potential showed both cardio-excitor activity and ninhydrin colour. These were always in the same fractions, which corresponded to the volume for elution of small peptides. Fluid from unstimulated preparations gave negative assays. The cardio-excitor activity of fluid from stimulated pericardial organs and of distilled-water homogenates of pericardial organs behaved identically in Sephadex G-25 chromatography. No evidence could be obtained of the cardio-excitor peptide binding to a protein. This work provides evidence that neural stimulation of crab pericardial organs results in release to the bathing fluid of cardio-excitor hormone as free peptide.
Axonal Localization of An Excitatory Post-Synaptic Potential in A Molluscan Neurone
Authors: Gorman A. L. F. , Mirolli M.
Published: April 2021

Stimulation of the lateral nerve gives rise to an excitatory post-synaptic potential (EPSP) in the Anisodoris G cell. The amplitude of this EPSP is either unchanged or slightly reduced by moderate hyperpolarization of the soma membrane, whereas stronger hyperpolarization produces an increase. Two factors contribute to this paradoxical behaviour. First, the conductance of the G cell membrane increases when it is hyperpolarized. Second, the apparent changes in cell conductance associated with the EPSP are small relative to the input conductance of the G cell. There are two major regions of the G cell where presumed synaptic contacts can be demonstrated anatomically. The first is on branches of the stem process of the soma in the gastro-oesophageal ganglion neuropile, and the other is on the main trunk of the axon and on axonal branches in the gastro-oesophageal nerve. Presynaptic fibres from the lateral nerve are present in the latter region. No synaptic contacts are found on the soma surface. A comparison of the effects of axonal and somatic polarization on the behaviour of the lateral nerve EPSP indicates that the EPSP occurs on the axon or on axonal branches.
Circadian Rhythm of Locomotion and Its Temperature Dependence in Blattella Germanica
Authors: Dreisig Hans , Nielsen Erik Tetens
Published: April 2021

The activity in Blattella germanica was investigated under standard conditions. Periods of latency and increment were recognized. The free-running rhythm in continuous darkness was determined at different temperatures and showed about the same period. The free-running rhythm in confinons light could not be determined unless the light intensity was extremely low. The period of activity was not released immediately after a change from light to darkness if this was advanced in relation to the normal time. The activity was then only slightly advanced. Delay of the onset of darkness caused the activity to diminish gradually after the usual time of change from light to dark. If the temperature was lowered some time before the expected time of activity in continuous darkness the activity was advanced much more than normally. If the temperature was raised the activity was delayed. Based upon these and other studies, a theory is advanced which explains the activity rhythms in insects as being the result of the interaction between a gradually increasing, temperature-dependent sensitization and different thresholds of release determined by light and temperature. A theory is propounded concerning the temperature-independence of the free-running rhythm in continuous darkness, assuming a temperature-dependent threshold of release.
Innervation of Coxal Depressor Muscles in the Cockroach, Periplaneta Americana
Authors: Pearson K. G. , Iles J. F.
Published: April 2021

The innervation of the mesothoracic and metathoracic coxal depressor muscles has been investigated using intracellular microelectrodes. Five motor axons have been found to innervate the coxal depressor muscles; the largest is a fast axon, the second largest a slow axon and the three smallest are all inhibitory axons. The fast axon innervates the anterior and posterior coxal depressor muscles as well as parts of the coxal branches of the main leg depressor muscle. The slow innervates all fibres in the coxal branches of the main leg depressor muscle. The three inhibitory axons innervate only those parts of the coxal branches of the main leg depressor muscle which are not innervated by the fast axon. The three inhibitory axons were found to be branches of three different common inhibitory motoneurones.
Active Transport of Sodium by the Isolated Midgut of Hyalophora Cecropia
Authors: Harvey W. R. , Zerahn K.
Published: April 2021

Sodium and lithium are actively transported by the isolated midgut of Hyalophora cecropia. The short-circuit current in 32 mM sodium solution is about half of that in 32 mm potassium solution. The sodium flux measured with 22Na from blood-side to lumen accounts for all of the short-circuit current and is 19 times the flux from lumen to blood-side. In a solution containing 16 mm potassium and 16 mm sodium there is no transport of sodium, although a large current remains. The sodium transport mechanism is not sensitive to ouabain.
The Central Nervous Control of Colour Change in the Minnow (Phoxinus Phoxinus L.)
Authors: Gentle Michael J.
Published: April 2021

The colour of the minnow Phoxinus phoxinus L. and its ability to undergo colour change were studied after partial and complete blinding. The blinding was accomplished either by section of the optic nerve or by tectal ablation. Following bilateral section of the optic nerve the blinded minnows darken. After the initial darkening, half of the fish pale and the other half remain dark. The colour of the fish blinded by bilateral section of the optic nerve could not be affected by external conditions. Following complete removal of the optic tectum the fish at first paled, but after 24 h they darkened to very variable tints. Unilateral section of the optic nerve coupled with unilateral tectal removal on the same or opposite side did not affect the ability of the fish to change colour. The bilateral removal of the anterior tectum from a blinded darkened fish did not affect its colour. The bilateral removal of the posterior tectum of a darkened fish caused maximal pallor.. By a series of lesions an area in the dorsal posterior part of the optic tectum was found to cause darkening in the blinded fish because following its removal the fish paled. It is suggested that the fibres from the tectum may act by exciting or inhibiting the neurones of the paling centre in the anterior medulla
Rhythmic Activity in the Insect Nervous System
Authors: Miller P. L.
Published: April 2021

Mechanical or electrical stimulation of widely separated parts of the body or appendages of Sphodromantis lineola produces a premature expiratory stroke with coupled spiracle movements when the ongoing frequency is low. The rhythm is then normally reset. Flashes of light directed at the eyes produce the same results. The responses may become phase-locked to repeated stimuli but usually soon habituate. Similar stimulation during CO2-evoked hyperventilation produces at most tonic effects. Electrical stimulation of thoracic or abdominal connectives with single shocks at up to 3 Hz can produce non-habituating phase-locked ventilation. Such stimulation also produces miniature bursts in spiracle 1 which follow shocks on a 1:1 basis sometimes at up to 45 Hz. It is suggested that they result from the stimulation of an interneurone which co-ordinates ventilatory activity in the insect.
Calcium Regulation in the Freshwater Mollusc Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)
Authors: Greenaway Peter
Published: April 2021

Three major calcium compartments have been identified in L. stagnalis: the shell, the blood and the fresh tissues. The distribution of 45Ca, absorbed from the medium, in the tissues of L. stagnalis has been studied. Absorbed calcium appears first in the blood and then in the shell and other tissues. 30% of the total fresh tissue calcium and about 20% of mantle calcium exchanges with blood calcium. A continual exchange between shell and blood calcium occurs. During net calcium loss from L. stagnalis a net movement of calcium from shell to blood occurs at a rate similar to the rate of net loss. During net calcium uptake, the reverse movement from blood to shell at a rate similar to the rate of net uptake occurs. A simple mechanism which might account for the control of blood calcium concentration has been proposed.
The Pharmacology of Efferent Synapses in the Lateral-Line System of Xenopus Laevis
Authors: Russell I. J.
Published: April 2021

The nature of the transmitter substance released at the lateral-line efferent synapses was investigated by histochemical techniques in Xenopus and Acerina and by pharmacological methods in Xenopus. The bases of lateral-line hair-cells and fine fibres in the lateral-line nerves reacted positively for acetylcholinesterase in Acerina and to a lesser extent in Xenopus. Acetylcholine (10−6M, and acetyl-β-methyl choline (5×10−6M), which has a muscarinic action, caused strong reversible inhibition of afferent impulses when pipetted on to the undersides of lateral-line stitches. Carbachol (5 × 10−4 to 5 × 10−6M) caused a smaller reversible inhibition of spontaneous afferent impulses, but other nicotinic substances (propionylcholine and buterylcholine) had no effect. Physostigmine (5 × 10−8M) prolonged inhibition of afferent impulses by electrical stimulation of efferent fibres, but atropine (5 × 10−6M) blocked it. Calcium and magnesium interact at the efferent synapses in a way similar to that found at the amphibian neuromuscular junction. Arguments are put forward to support the hypothesis that acetylcholine is released at lateral-line efferent synapses.
Behavioural Physiology of the Colonial Hydroid Obelia
Authors: Morin James G. , Cooke Ian M.
Published: April 2021

The bioluminescent system of Obelia responds to stimulation by producing a burst of excitatory potentials (luminescent potentials, LPs) with each stimulus except the first. These LPs initiate flashes from the coupled luminescent effectors. There is temporal facilitation between the applied stimulus and the LP-system ; the LP-system shows adaptation to stimulation by a rise in threshold as well as fatigue. There is facilitation within the LP-system that is temporal at a given point and spatial (in the distance of spread) between two or more points. The result is a limited spread of the first potentials and decreasing numbers of potentials with increasing distance but often a through-conduction of the final potentials. The conduction velocity of the LPs is about 22 cm/s at 12 ° C; the refractory period is about 60 ms at 20 ° C and 150 ms at 12 ° C; the latency from stimulation to the first LP in a stimulus train first decreases from 130 – 600 ms to 20 – 80 ms and then increases again to 150 – 600 ms at 20 ° C. The latency between LP and the flash is about 20 + 9 ms. The intervals between LPs in bursts evoked by stimuli applied at 1/s gradually increase from about 65 ms to about 135 ms at 20 ° C. The absolute LP intervals are temperature-dependent (the relative ratios are not) but independent of the stimulus frequency. The number of LPs in a burst is frequency dependent. The facilitation curve of the LP-system-luminescent effector junctions, as determined from flash intensity, shows a rapid rise between 60 and 80 ms, a fairly rapid decay between 80 and 200 ms, and a long residual decay which lasts for several hundred milliseconds.
Pharmacology of the Malpighian Tubules of Rhodnius and Carausius: The Structure-Activity Relationship of Tryptamine Analogues and the Role of Cyclic Amp
Authors: Maddrell S. H. P. , Pilcher D. E. M. , Gardiner B. O. C.
Published: April 2021

5-Hydroxytryptamine (5-HT) and a few of its derivatives will cause an acceleration of secretion by the isolated Malpighian tubules of Rhodnius prolixus and Carausius morosus. Substitution in the terminal amino group of 5-HT causes little loss of effect, but changes in the indole ring and the hydroxy group in general abolish activity. Most derivatives of 5-HT which do not stimulate secretion, and many other related amines, act as inhibitors of secretion in Rhodnius. This inhibition is probably of the competitive type. Substances which stimulate secretion in Rhodnius are easily washed off the Malpighian tubules, although they will stimulate secretion at very low concentrations By contrast, competitive inhibitors wash away relatively slowly and inhibit only at much higher concentrations. It is suggested therefore that stimulation involves only momentary interactions between stimulant and receptor sites, but that competitive inhibitors spend considerably longer attached to the sites. Cyclic 3 ′,5 ′ -adenosine monophosphate (cyclic AMP) will stimulate secretion by tubules of both Rhodnius and Carausius. Tubules of both species are very sensitive to cyclic AMP, measurable effects being produced at concentrations of 4×10−5 M/ l in Rhodnius and 10−4 M/ l in Carausius. Aminophylline (theophylline ethylene diamine) at a concentration of 10−4 M/ l stimulates secretion by Carausius tubules. This compound and other inhibitors of phosphodiesterase have no stimulatory action on Rhodnius tubules, but any such effect may be masked by the adverse reaction of the tubules to the high concentrations necessary. Inhibitors of 5-HT action such as tryptamine and tyramine also inhibit secretion by Rhodnius Malpighian tubules induced by cyclic AMP. This may be due to a dependence of the action of cyclic AMP on the state of the diuretic hormone receptor site. The evidence is consistent with the idea that 5-HT, other stimulant molecules related to 5-HT and the diuretic hormones interact with Malpighian tubule cells of Rhodnius and Carausius at specific sites, probably on the cell membrane facing the haemolymph. As a result of this, secretion is induced, possibly through the action of intracellular cyclic AMP produced as a response.