bluuebunny/crossref_metadata_2025 huggingface dataset:
Osmotic Regulation in the Tadpoles of the Crab-Eating Frog (Rana Cancrivora)
Authors: Gordon Malcolm S. , Tucker Vance A.
Published: April 2021

Salinity tolerance, osmoregulatory mechanisms and some effects of salinity on embryonic development and metamorphosis have been studied in the tadpoles of the euryhaline crab-eating frog (Rana cancrivora). Tadpoles in developmental stages III-XIX survive well in all salinities from fresh water to 32% sea water. They are good osmoregulators over this entire range, plasma osmotic concentration changing by only 250 m-osmoles/1. in the face of environmental concentration changes of 900 m-osmoles/1. Na, Cl, and K account for over 90% of plasma osmotic concentration in all external concentrations. The osmoregulatory mechanisms used by the tadpoles appear to be similar to those used by euryhaline teleost fishes. In hyperosmotic media they probably drink, then excrete salts by an extrarenal pathway. A metamorphosis in osmoregulatory mechanisms occurs simultaneously with morphological metamorphosis. The osmoconforming behaviour of adult frogs is fully developed in the tadpoles by developmental stage XXV. As in other anuran species there probably is no significant urea production before metamorphosis. Both early embryonic development and the completion of metamorphosis beyond stage XIX apparently require low salinities. The pattern of osmoregulation shown by tadpoles of the freshwater R. limno-charis is identical with osmoregulatory patterns found in adult freshwater anurans. Evolutionary and ecological impheations of the data are discussed.
The Spectral Sensitivity of the Goldfish and the Clawed Toad Tadpole Under Photopic Conditions*
Authors: Cronly-Dillon J. R. , Muntz W. R. A.
Published: April 2021

The visual pigments of the vertebrate retina fall into two major classes, depending on whether they are based on vitamin A1 or vitamin A2. The rod pigment in the former case is rhodopsin, and in the latter case porphyropsin, and the scotopic sensitivities of the animals agree well with the absorption spectra of the relevant pigment. Later work led to the view that the photopic sensitivities of animals also fall into the same two classes: those animals with visual pigments based on vitamin A1 are maximally sensitive at about 560 mμ, and those with pigments based on vitamin A2 at about 620 mμ (Granit, 1941, 1947). The first type of photopic sensitivity can be roughly fitted by the absorption spectrum of the pigment iodopsin, the second by the absorption spectrum of the pigment cyanopsin (Wald, Brown & Smith, 1953, 1955). The difference between the rods and cones within each group is due to the opsin part of the molecule.
Neuronal Mechanisms Underlying Control of Sound Production in A Cricket: Acheta Domesticus*
Authors: Ewing Arthur , Hoyle Graham
Published: April 2021

Analyses of neuronal mechanisms underlying instinctive behaviour have long been required (Tinbergen, 1951) but have not been forthcoming. The reason seems to lie in part in a lack of agreement as to suitable experimental animals. There are now signs that certain large insects, which are available in many laboratories, and whose nervous systems are amenable to electrophysiological investigation, have been selected as first-choice subjects for detailed investigations. As examples we may refer to the work of Wilson (1961, 1964) on locust flight mechanisms, Roeder, Tozian & Weiant (1961) on the praying mantis and Hoyle (1964) on general locomotory activity in locusts.
The Formation of Urine by the Prosobranch Gastropod Mollusc Viviparus Viviparus Linn
Authors: Little C.
Published: April 2021

In all aquatic molluscs examined (Anodonta—Picken, 1937; Haliotis—Harrison, 1962; Octopus—Potts & Martin, 1963), blood is filtered through the wall of the heart (or branchial heart appendages in Octopus) into the pericardium. The pericardial fluid passes to the kidney, where secretion and reabsorption modify it to form the final urine. In the terrestrial pulmonates, however (Achatina—Martin, Harrison & Stewart, 1953; Helix pomatia and Archachatina—Vorvohl, 1961), blood appears to be filtered directly into the kidney, and reabsorption takes place in the ureter. In the present paper the inorganic composition of the urine of the freshwater prosobranch Viviparus viviparas is analysed and the rate of urine production is measured. The mechanism of urine formation is then examined in some detail.
The Occurrence and Functional Characteristics of Heteromorph Antennules in An Experimental Population of Spiny Lobsters, Panulirus Argus*
Authors: Maynard D. M.
Published: April 2021

Eyestalks were removed unilaterally from forty-nine Panulirus argus. Twenty-three of the forty-three animals remaining alive to the first moult regenerated a heteromorph antennular outer flagellum in place of the amputated eye. None of the lobsters moulting within less than 3 months of eyestalk ablation regenerated a heteromorph; 70% of those moulting after more than three months recovery regenerated a heteromorph. If the heteromorph did not appear upon the first moult it usually continued to be missing after the second or third moult. Mechanical stimulation of the heteromorph produced a general withdrawal reaction in all lobsters tested, and in most either a specific cleaning reflex directed toward the stimulated heteromorph, or a specific movement of the normal ipsilateral antennule, or both. The withdrawal and antennular movement, when it occurred, resembled responses elicited via stimulation of the normal antennular flagellum. Behavioural responses were followed in a selected subpopulation for periods ranging from one to nearly two years, and over one or two moults. No significant changes in behavioural responses to heteromorph stimulation were detected within that time. The conduction-velocity spectrum of fibres in the heteromorph nerve resembled that in the outer flagellar branch of the normal antennule nerve in having both a fast and a slow component. However, the velocity of the fast component of the heteromorph nerve was often less than normal for the flagellar branch of the antennule nerve, and additional components of intermediate velocity occurred in some animals. According to the direction or nature of the mechanical stimulus both heteromorph and normal flagella elicited inhibitory and excitatory responses in the nerve to the depressor muscle of the outer flagellum of the normal ipsilateral antennule. Responses of the flagellar depressor muscle of the ipsilateral antennule to electrical stimulation of the heteromorph varied among individuals, but in general resembled later components of the response to similar stimulation of the normal antennular flagellum. It is tentatively concluded that at least some of the heteromorph afferents make specific central connexions on neuron pools normally associated with antennular flagellum afferents. The difficulties of drawing such inferences from indirect observation are indicated.
Anelasticity in Bone and Echinoderm Skeletons
Authors: Currey J. D.
Published: April 2021

Bones and echinoderm skeletons have been tested for anelasticity. Bone shows considerable, largely anelastic strains, continuing for at least 54 days, by which time the extra deflexion may be 130% of the original deflexion. The rate at which the anelastic deflexion appears is proportional to the applied stress. Between 2 and 50° C. there is a 300% increase in the rate at which anelastic deflexions in bones appear. Drying seems not to affect irreversibly the anelastic properties of bone. Echinoderm spines show no anelastic deflexion on prolonged loading. The mechanical behaviour of the skeletal materials of the two phyla investigated are such as would be expected from their constitution. The biological significance of these findings is discussed. It is concluded that anelasticity will, except perhaps in a few special cases, be of only marginal importance in vertebrates in life. The adaptive significance of the difference between bone and the skeletal tissue of echinoderms is as yet unknown. It does not lie in their anelastic properties.
Haemolymph Proteins and Yolk Formation in Rhodnius Prolixus Stål
Authors: Coles G. C.
Published: April 2021

There are two adult-specific proteins in the haemolymph of Rhodnius. They appear to be formed in the fat body. The two proteins are absorbed by the oocytes and form the bulk of the soluble egg proteins. The changes in the concentration of total protein in the haemolymph and of four protein fractions, as separated on cellulose acetate, do not reflect egg production. This may be a consequence of the hormonal control of reproduction.
Nerve Pathways and Reflex Siphon Withdrawal in the Surf Clam
Authors: Mellon Deforest
Published: April 2021

Neural pathways controlling reflex withdrawal of the siphons have been examined in the surf clam. Conduction-velocity measurements, coupled with intracellular recordings of postsynaptic responses, indicate that the pathways involved are among the fastest in the relevant nerve trunks. Cell bodies of neurons in the efferent limb of the reflex are located in specific paired regions of the visceral ganglion. Their axons are distributed to ipsilateral effectors via branches of the posterior pallial nerve and input to these cells is derived from a wide area of the periphery involving both sides of the animal. This pronounced sensory convergence can adequately account for symmetrical siphon withdrawal. It is concluded from several lines of evidence that fast reflex pathways within the ganglion are monosynaptic in nature. In addition, the prolonged time course of the postsynaptic response to single volleys, and the capabilities of the synaptic contacts for spatial and temporal summation, make it possible to account for after discharges in the efferent pathways lasting a second or more. Prolonged activity from these cells has not been observed in isolated visceral ganglion preparations, and it is possible that the sustained closure is controlled by pathways involving different groups of neurons.
The Physiology of Excretion in the Cotton Stainer, Dysdercus Fasciatus Signoret
Authors: Berridge M. J.
Published: April 2021

The intestine of Dysdercus is discontinuous in the larval instars, and urine from the Malpighian tubules is therefore uncontaminated by gut contents. Excretion has been studied during the fifth instar, which lasts 8 days. Feeding only occurs in the first 4 days, during which there is a marked fall in water content. In the last part of the instar, when the animal only drinks, the water content returns to its original level. The urine of Dysdercus is always liquid. There is a rapid rate of excretion during the first half of the instar, but when feeding ceases there is no further micturition and urine is retained in the rectum. Therefore there are two phases of excretion, designated excretory and post-excretory phases respectively. The rectal epithelium is incapable of reabsorbing water against an osmotic gradient. The urine which is retained in the rectum during the post-excretory phase acts as a water store ; evaporative water loss is balanced by withdrawing water from this reservoir. During the excretory phase, a large volume of liquid is lost via the excretory system, but the loss is made good by drinking.
Some Experiments on the Chemotactile Sense of Octopuses
Authors: Wells M. J. , Freeman N. H. , Ashburner M.
Published: April 2021

A method of training octopuses to make chemotactile discriminations is described. The animals can readily be taught to distinguish between porous objects soaked in sea water and similar objects soaked in sea water with M/10 KC1 added. Using pairs of objects soaked in solutions with different amounts of KC1 added, minimum distinguishable concentrations were determined over the range M/10−M/100. Effective discrimination broke down when the ratio of the two test concentrations was of the order of 1·3. This approximates to the values found in chemical discrimination experiments with mammals and insects. Attempts were made to determine the minimum detectable concentration of added KC1 by progressive dilution of the M/10 KC1 solution used in the initial training. Additions to sea water down to M/105 were distinguished and there was some indication that octopuses can, in fact, detect added KC1 at much smaller concentrations; the addition of M/1010 KC1 produced a significant decline in the ability of animals under training to discriminate between M/106 KC1 and sea water. Experiments on acid discrimination indicated that acids were distinguished on a basis of their pH, with acetic tasting noticeably more acid than HC1 or H2SO4 at the same pH. Again, the results closely parallel those that have been obtained with mammals and insects.
Influence of Previous Preferences on the Memory of Octopus Vulgaris After Removal of the Vertical Lobe
Authors: Young J. Z.
Published: April 2021

Octopuses from which the vertical lobe had been removed attacked a vertical rectangle more readily than a horizontal one when both shapes were moved vertically. During discrimination training the results differed markedly according to which figure was rewarded with food. When a vertical rectangle was positive the excess of attacks at this figure increased both within and between sessions, the animals showing considerable ability to learn. When a horizontal rectangle was the positive figure the responses to it were at first ‘paradoxical’, the negative shape being attacked more often. There was then improvement within each session, but little if any between the sessions. Octopuses without the vertical lobe quickly ceased to attack crabs shown at 4 min. intervals when shocks were given for attacks, and the effect could still be detected 4 hr. later. When crabs were shown at 8 min. intervals, and shocks given for attacks, there was no decline in attacks over fourteen trials. Fifteen hours later, however, some residual signs of the shocks were evident when trials were resumed at 8 min. intervals. Although all of the animals at first attacked they soon stopped doing so. After a further 15 hr. all attacked again but soon ceased to do so after receiving shocks. Normal animals, by contrast, all ceased to attack the crabs shown at 8 min. intervals after receiving four or five shocks. The memory is much more retentive in normal animals, so that 2 days after receiving shocks the octopuses seldom attacked the crabs.
Directional Sensitivity of the Ears of Noctuid Moths
Authors: Payne R. S. , Roeder K. D. , Wallman J.
Published: April 2021

Noctuid moths of several species were mounted at the tip of a tower of fine tubing in acoustic ‘free space ‘. Recordings were made of the intensity of a brief pulse of ultrasound necessary to produce a constant tympanic nerve response for any angle of sound presentation relative to the moth’s body axis. Such plots of intensity versus angle were made with the wings held in several postures approximating those assumed in normal flight. The data indicate that sound intensity reaching the tympanic organ can vary by as much as 40 db. depending upon: (a) the position of a sound source relative to the moth’s body axis, and (b) the position of its wings. With wings above the horizontal plane each ear reports sounds c. 20-40 db. louder on the ipsilateral side than on the contralateral side. With wings below the horizontal, the lateral asymmetries are replaced by a dorsoventral asymmetry in which each ear reports sounds coming from below the body c. 10-25 db. louder than sounds coming from above. Directional sensitivity plots at 60 kcyc./sec. are more complex than plots at 30 kcyc./sec.—as expected. A theory is presented to explain how a moth could determine the direction of a sound source in three-dimensional space by comparing the intensity reports of both tympanic organs during a complete wing cycle.
An Automatic Diver Balance
Authors: Larsson Sune , Løvtrup Søren
Published: April 2021

An automatic, electromagnetic diver balance is described. The working principle of this instrument is that a small plastic cylinder, the diver, with density less than one is kept floating in an aqueous medium by a magnetic force acting on a permanent magnet enclosed in the diver. In the floating position the diver cuts off a light beam which, through an electronic system, controls the magnetic force acting upon the diver. The latter will move down until its buoyancy is compensated by this force. With this balance one may register the submerged—or reduced—weight of any object placed on the floating diver. The apparatus has hitherto found application in water-permeation studies (D2O-H2O exchange) and in determinations of the cortical tension in the frog’s egg. Potentially the instrument may be used for various other purposes, notably for manometric determinations. Miss Rita Gustafson, Mrs Margareta Jaksch, and Mrs Inger Janson have done all the practical work associated with testing out the method, their excellent assistance is gratefully acknowledged. The work has been supported by grants from Natur-vetenskapliga Forskningsrådet.
Nervous Control of the Mechanical Properties of the Abdominal Wall at Feeding in Rhodnius
Authors: Maddrell S. H. P.
Published: April 2021

When larvae of Rhodnius feed, the abdominal wall rapidly becomes extensible. This change is brought about peripherally by the abdominal nervous supply; as a consequence, abdominal segments which have been denervated fail to stretch as much at feeding as do neighbouring innervated segments. The stimulus for this change originates in the head. It appears that the sensations accompanying feeding are responsible and that they have a cumulative effect, so that the degree of plasticization of the abdominal wall depends on the length of time during which the insect has been sucking. Neurosecretory axons are the only known efferent supply to the abdominal wall and so it is most probable that they cause the localized plasticization. The evidence suggests that the plasticization of the abdominal cuticle is a result of an increase in its water content. The increase in plasticity of the abdominal wall is temporary, the effect decreasing progressively after feeding.
Direct Response of the Crab Carcinus to the Movement of the Sun
Authors: Horridge G. A.
Published: April 2021

One line of evidence points to the conclusion that eye responses should be measurable in a crab, in air, which sees only the movement of the sun in a clear sky. It has been shown in the previous paper, as an extension of earlier work with slowly moving striped drums, that eyestalk movements follow a single light in a dark room when the light is moved with low angular velocities round the crab in the range 10–20°/hr. For horizontal movements which subtend angles of 0·02–1·0° at the crab’s eye, at a lamp velocity of 0·01°/sec., the horizontal eye movement is 20–50% of the light’s movement. The light used gave an illumination of 0·05 lux on a surface in the position of the crab’s eye. These figures remove any doubt that the crab is able to see the movement of the sun directly. The movement of the full moon, with a maximum illumination of 0·24 lux on the earth’s surface, must also be seen by the crab, and possibly some of the brighter stars are also seen directly. Whether the crab responds to these moving lights will depend, not only on whether it sees them, but also on whether there are stationary contrasting objects in the visual field. If the eye begins to follow an isolated moving stimulus, other contrasting objects will move in the opposite direction over the eye, and this will at once diminish the response by an opposite stimulus. Therefore, to make sure of recording a maximum response to celestial movements the animal should see as little as possible besides the object of interest.
The Nervous Control of Ventilation in Dragonfly Larvae
Authors: Mill P. J. , Hughes G. M.
Published: April 2021

Ventilatory movements of the sterna are effected by the paired segmental respiratory dorso-ventral muscles in abdominal segments 4-9 (expiration) and by the natural elasticity of the cuticle aided by two transverse abdominal muscles, the diaphragm and the sub-intestinal transverse muscle (inspiration). The former are innervated by the second segmental nerves, the latter by median nerves. Rhythmic motor discharges were recorded in the nerves to both expiratory and inspiratory muscles. Expiratory bursts consist of a single unit, the firing frequency of which increases during the burst and then normally decreases slightly at the end of the burst. Inspiratory bursts show a rather irregular discharge of the unit(s) within them, the overall frequency of which increases slightly during the first half of the burst. Each spike in the expiratory burst is accompanied by a muscle action potential in the respiratory dorso-ventral muscle it innervates. With increase in frequency of the motor unit facilitation of the muscle action potentials occurs. No such facilitation has been observed in the inspiratory muscles. The mean firing frequency of the expiratory unit increases steadily with increase in burst duration over the normal range of respiratory frequency and a similar minimum interval is attained irrespective of the duration of the burst. Expiratory bursts in second roots of the same ganglion are synchronous and may show a 1:1 relationship. Expiratory bursts start first in posterior segments and the eighth ganglion presumably contains a pacemaker. The duration and number of impulses per burst decrease from behind forwards. However, the expiratory unit reaches its maximum frequency at about the same time in all segments. Stimulation of a first segmental nerve root in the posterior region of the abdomen in an inter-expiratory period causes expiratory bursts to appear in the second roots and consequently re-sets the respiratory rhythm. The inspiratory neurones start to fire very shortly after cessation of the expiratory burst and are closely coupled with the latter. Rhythmic bursts containing many units were recorded in the isolated ventral nerve cord, usually after application of carbon dioxide to the preparation.
Patterns of Ventilation in Dragonfly Larvae
Authors: Hughes G. M. , Mill P. J.
Published: April 2021

A study has been made of the patterns of ventilation in three genera of anisopteran dragonfly larvae by recording simultaneously the pressure changes in the branchial chamber and the dorso-ventral movements of the abdomen. The three main types of ventilation described by Tonner have been confirmed and the characteristic pressure changes during normal, gulping, and chewing ventilation are described. During normal ventilation there is a positive pressure phase of about 4 cm. water followed by a brief negative phase of 12 cm. water. The main expiratory phase is produced by the respiratory dorso-ventral muscles which are found in abdominal segments 4–9. Inspiration, which closely follows expiration, results from the elastic properties of the exoskeleton together with the activity of the two transverse muscles. One of these, lying at the anterior end of the fifth abdominal segment, forms the so-called diaphragm and divides the abdomen into two functional cavities. Gulping ventilation is characterized by a maintained pressure of 20–40 cm. water during which there may be fluctuations associated with the chewing movements, which are mainly due to the intrinsic musculature of the colon and rectum. Despite some differences in detail the main patterns of ventilation are very similar in Aeshna, Anax and Libellula.
Analysis of Formed Bodies in Urine Removed from the Crayfish Antennal Gland By Micropuncture
Authors: Riegel J. A.
Published: April 2021

Two kinds of formed bodies are present in the urine of the crayfish: spheroids, which appear to be produced by the coelomosac cells and appear in all parts of the antennal gland except the bladder; and vesicles, which are produced by the cells of the labyrinth and are found only in the labyrinth. Chemical analysis of the formed bodies show them to contain peptides and amino acids, especially in the more distal portions of the antennal gland. It is suggested that the spheroids also contain proteins, but that this material is inseparable from their structure. The significance of the formed bodies in the excretion process of the crayfish is discussed.
The Pleated Surface of the Undischarged Thread of A Nematocyst and Its Simulation by Models
Authors: Skaer R. J. , Picken L. E. R.
Published: April 2021

The complex appearance in electron micrographs of sections, both transverse and longitudinal, of the undischarged thread of a nematocyst—the large holotrichous isorhiza of Corynactis viridis Allman—is compatible with the pleating of a tubular thread to form a triple-screw surface (Skaer & Picken, 1965). This interpretation of the sections was facilitated by a study of the properties of folded paper models, and by the construction of a three-dimensional wax model following, essentially, the method of His (1887), but with the difference that sections modelled in wax were serial electron micrographs of ultrathin transverse sections (Picken & Skaer, 1966). This wax model being fragile and opaque, it was subsequently cast in more robust and translucent Araldite resin by a cire perdu method.
The Physiology of A Lepidopteran Muscle Receptor
Authors: Weevers R. De G.
Published: April 2021

When a single MRO of a caterpillar is stretched at least 32 motor units show clear reflex changes in activity. The great majority of muscles are excited., and the latency of the reflex differs only slightly from one muscle to another. The response has both tonic and phasic components which reflect more or less faithfully the magnitudes of the same components in the sensory discharge. Muscles are affected on the contralateral side of the stimulated segment and on the ipsilateral side of adjacent segments. The reflex fields of neighbouring receptors therefore overlap; spatial facilitation produces a disproportionate increase in the overall response when two receptors are stimulated simultaneously. The reflex pathway for muscles innervated by nerve 2 is shown to involve synaptic connexions in the ganglion of the segment anterior to the stimulated receptor and responding muscles. The muscles most strongly excited are those which he functionally in parallel with a stretched sense organ. It is concluded that a major function of the caterpillar MRO is to mediate a negative feedback reflex tending to stabilize bodily position independent of load.
The Evaporation of Water from Helix Aspersa
Authors: Machin John
Published: April 2021

Data is presented which suggest that inactive specimens of Helix aspersa are able to regulate evaporative water loss from the mantle. Evaporation is reduced following the cessation of glandular extrusion, by the concentration of solutes in partially dehydrated superficial mucus. Methods are described for determining vapour pressure gradients across living and freshly killed mantle tissue and for calculating permeabilities. Osmotic permeability measurements using isolated and intact body wall were made. The permeability of regulating mantle tissue was 0·039 mg./cm.2/hr. per mm. Hg vapour pressure difference. Living body wall and freshly killed mantle were at least forty times more permeable to water. Low permeability seems to be a unique property of living mantle tissue.
Measurements of Glucose and Amino Acid Concentrations, Temperature and PH in the Habitat of Polymorphus Minutus (Acanthocephala) in the Intestine of Domestic Ducks
Authors: Crompton D. W. T.
Published: April 2021

Measurements have been made on the glucose and amino acid concentrations, temperature and pH in the lumen of the small intestine of the domestic duck in the region inhabited by the acanthocephalan parasite, Polymorphus minutus. The glucose concentration was found to vary from 23 mg./ml. to no detectable glucose, with an average value of about 5·7 mg./ml. for the twenty-four ducks examined. Sixteen amino acids were detected by qualitative and quantitative methods. The temperature in the parasite’s habitat is the same as the other published deep body temperatures of domestic ducks. The pH appears to be about 7·5.
Burrowing in Mercenaria Mercenaria (L.) (Bivalvia, Veneridae)
Authors: Ansell A. D. , Trueman E. R.
Published: April 2021

Burrowing of the bivalve Mercenaria mercenaria has been re-examined using modem recording techniques. Burrowing activity consists of a series of movements, repeated cyclically termed the ‘digging cycle’, involving extension of the foot, closure of the siphons, adduction of the shell valves and retraction of the foot, Final position in the sand is only reached after many digging cycles, constituting a digging period. Closure of the siphons and apposition of the mantle margins temporarily seals the mantle cavity to form a pressure chamber through which forces produced by adduction can be transmitted to act elsewhere. Adduction causes dilation of the distal regions of the foot, aiding pedal anchorage, and ejection of water from the mantle cavity loosens the sand ventrally and laterally. Downward movement is by the passive dropping of the heavy shell into the fluid cavity formed at adduction, and by active movement caused by contraction of the retractor muscles pulling the shell downwards on to the anchored foot. The strength of pedal retraction is 5-6 g. in an animal of 21 g. wt. in water. With the shell completely covered by sand the opening moment of the ligament is shown to be too small to effect complete opening of the valves, and under these circumstances pressures generated by withdrawal of the foot and siphons in a secondary phase of siphonal movements supplement the action of the ligament. Burrowing movements in Mercenaria are compared with those of Tellina, Donax, Macoma, Cardium and Ensis.
The Effect of Hypoxia Upon the Partial Pressure of Gases in the Blood and Water Afferent and Efferent to the Gills of Rainbow Trout
Authors: Holeton G. F. , Randall D. J.
Published: April 2021

The rate of oxygen uptake by rainbow trout does not alter during progressive deoxygenation of the environment. Blood lactate, however, shows a significant increase, indicating an increase in anaerobic metabolism during hypoxia. The percentage utilization of oxygen from the water decreased from 55 % to approximately 20% during hypoxia and was associated with a 13-fold increase in ventilation volume. The arterial blood of a trout resting in aerated water was 95–100% saturated: the was 122 mm. Hg and the was 1−1·5 mm. Hg. The venous blood of a resting trout was 70 % saturated, had a of 35 mm. Hg and a of 2·5 mm. Hg. During hypoxia the percentage saturation of the arterial blood decreased to 37 % and that of the venous blood to 3 %. The in the arterial blood was 10 mm. Hg ; in the venous blood, 6 mm. Hg. The in the arterial blood was 3·5−4 mm. Hg; in the venous blood, 4·5−5·00 mm. Hg respectively. The ability of the fish to withstand hypoxia was related to the oxygen capacity of the blood, which was on average 9 vol. %. The red blood cells swelled during hypoxia, the hematocrit increased, but the red cell count did not alter. Blood pH was 7·7, falling to 7·4 during hypoxia. Cardiac output did not change during progressive hypoxia in the water, stroke volume increased to offset the decrease in heart rate.
Flight in Drosophila
Authors: Vogel Steven
Published: April 2021

In tethered flight in a wind tunnel fruit-flies adjust lift and thrust by shifting the horizontal component of the lower extreme wing position. The upper extreme wing position is nearly constant. Stroke angle and stroke plane are fully interdependent parameters. Angle of attack varies along the length of the wing; no length-wise twisting occurs. Angle of attack varies with flying speed ; pitch is unchanged as speed is increased. These characteristics suggest that the flight machinery of fruit-flies is considerably simpler than that of larger flying animals.
Discharge Patterns of Neurones Supplying Tonic Abdominal Flexor Muscles in the Crayfish
Authors: Evoy William H. , Kennedy Donald , Wilson Donald M.
Published: April 2021

The discharge patterns of tonic flexor motoneurones in the crayfish abdomen have been investigated by simultaneous recording from several nerve roots. The five flexor motoneurones supplying each segment are serially homologous, smaller units have higher discharge frequencies, and the excitability of a given unit is generally higher in more caudal ganglia. Even the smallest axons are capable of generating substantial muscle tension at their spontaneous discharge frequencies. Tension development is extremely tonic. Single motor impulses are without effect, latencies are long, and the frequency/tension relation is steep. The inhibitory axon to each flexor discharges during ‘extension’ reflexes, but has no visible effect upon relaxation time, or upon the response to subsequent excitation. Inhibitory impulses do not relax previously unexcited muscle. Phase histograms for the discharge of pairs of homologous or non-homologous efferent axons across a single ganglion, within the same root, and between adjacent ganglia have revealed several coupling mechanisms. One is mediated by short timeconstant electrotonic junctions between bilaterally paired inhibitory axons. The second involves weaker, more generalized interactions of longer time-constant between non-homologous axons. The third is brought about by common presynaptic sources of excitation. Inputs tend to be common for homologues in adjacent ganglia rather than for non-homologues in a single ganglion, a finding consistent with the selectivity shown by central interneurones in their effects upon motoneurones.
Slow Activity in the Nervous System of the Earthworm, Lumbricus Terrestris
Authors: Roberts M. B. V.
Published: April 2021

Three thresholds are demonstrated in the first segmental nerve and two (sometimes three) in the second and third segmental nerves together. Slow potentials recorded from the ventral nerve cord consist of several peaks. The first peak is composed of three spikes which make their appearance at different thresholds. Transmission of at least some of the slow potentials is decremental. Transmission speeds in the nerve cord and segmental nerves range from 0·4 to 0·6 m./sec. Action potentials in the longitudinal muscle are recorded in response to slow potentials in the nerve cord. Two slow reflexes, one involving elongation, the other longitudinal contraction, are described. The latter has the lower threshold with peripheral stimulation. Slow activity in the nervous system is discussed in relation to reflex activity of the earthworm and the neurone anatomy of the nerve cord and segmental nerves.
The Mechanism of Lung Ventilation in the Tortoise Testudo Graeca Linne
Authors: Gans C. , Hughes G. M.
Published: April 2021

An account is given of the gross structure of the respiratory system and of the principal muscles involved in ventilation of the tortoise, Testudo graeca. The mechanism of ventilation was investigated by electrophysiological methods. Cannulae inserted into the lung through holes drilled in the shell recorded pressure changes during the cycle of ventilation and simultaneous recordings were made of the forelimbs movements. The pressure changes were triphasic in form, consisting of an initial increase in pressure followed by a fall to a level of 7 cm. water below atmospheric, and again returned to the atmospheric level or usually slightly above. During the pause between individual ventilation cycles, any overshoot gradually declined to the base-line. Electromyograms showed that all phases of the respiratory cycle were active. The increase in pressure was accompanied by activity in the transversus abdominis and in the pectoralis muscle which draws the shoulder girdle back into the shell. These activities increase the pressure in the peritoneal cavity, which is transmitted to the lung. During the opposite phase of the cycle, the obliquus abdominis and serratus major muscles are active. This increases the volume of the peritoneal cavity and leads to the reduction in intrapulmonary pressure below atmospheric. Activity recorded from the opener and closer muscles of the glottis showed that the glottis is dilated during the first two parts of the cycle but not during the final recompression phase. The respiratory rhythm does not appear to be composed of brief periods of ventilation activity followed by prolonged pauses, as supposed by many authors. These differences may relate to the species investigated. No evidence was found for significant differences in pressure between the right and left lungs or between the anterior and posterior chambers of the lung on one side. It is concluded that the mechanism producing ventilation in the tortoise takes advantage of the only possible way of changing the volume of the thoracico-peritoneal cavity, namely by altering the position of the limb flanks. Both expiratory and inspiratory movements are active.
Mechanisms for the Production of the Motor Output Pattern in Flying Locusts
Authors: Waldron Ingrid
Published: April 2021

The normal flight pattern consists of alternating bursts of activity in the elevator and depressor motor neurons. However, when sensory input depresses elevator activity, rhythmic bursts of activity in the depressor motor neurons may continue even after all elevator motor neuron activity has apparently ceased. Thus interactions between the antagonistic motor neurons apparently are not necessary for the production of the rhythmic bursts. The proposed mechanism for producing these rhythmic bursts depends on the excitatory interactions among the synergistic motor neurons. Alternative or supplementary explanations for the data seem to be possible only if interneurons participate in the generation of the flight pattern. During flight initiation, when there is a burst of activity in several depressor motor units simultaneously there usually is a pause in the on-going elevator activity ; often the normal flight pattern begins at this time. This reciprocal relationship of activity in the antagonists suggests inhibitory coupling between antagonistic motor neurons or between interneurons which may drive them. This coupling may be responsible for the alternation of the bursts of activity in the antagonists during normal flight. There is no evidence for greater co-ordination within a thoracic ganglion than between ganglia. Some activity in the abdominal C.N.S. is also well co-ordinated with the flight pattern. Thus the anatomical separation into ganglia does not correspond to any interruption of the functional integration of the flight system.
Neural Mechanism by Which Controlling Inputs Influence Motor Output in the Flying Locust
Authors: Waldron Ingrid
Published: April 2021

The central nervous system of the flying locust generates a pattern of alternating bursts of impulses in the elevator and depressor motor neurons (Wilson, 1961). The mechanism by which controlling inputs modify this output pattern is analysed in this paper. During roll turns and other flight manoeuvres the average number of impulses per burst (average burst length) changes in certain motor neurons. Changes in average burst length develop slowly, over tens of wingbeat cycles, even in response to the abrupt changes in input which result from electrical stimulation of sensory nerves. In addition to the slow changes in average burst length which are elicited by controlling inputs, more rapid changes in burst length sometimes occur. During this rapid variation a longer burst is usually followed by a shorter burst, probably because the motor neuron is less excitable after a longer burst of activity. Burst length varies independently in different motor neurons. Both findings suggest that much of the rapid variation in burst length is due to changes occurring within the individual motor neurons, and is not a response to rapid changes in controlling inputs. Under all conditions, changes in the number of impulses per burst are correlated with small changes in the relative timing of the burst; the longer bursts produced by a motor neuron begin slightly earlier in the wingbeat cycle. This implies that the factors which cause variation in the length of the bursts are also responsible for producing the variation in the timing of the bursts. All of the observations can be explained on one assumption: that the only effect of controlling inputs is to cause slow changes in the ‘average excitation’ of individual motor neurons. Thus sensory and central control of the flight pattern generating system appears to be slow control over the average performance, rather than fast control over performance in a particular cycle.
Sequential Changes in the Adenosinetriphosphatase Activity and the Electrolyte Excretory Capacity of the Nasal Glands of the Duck (Anas Platyrhynchos) during the Period of Adaptation to Hypertonic Saline*
Authors: Fletcher G. L. , Stainer I. M. , Holmes W. N.
Published: April 2021

Regardless of the composition of the incubation medium, the nasal gland tissue from ducks adapted to hypertonic saline always released inorganic phosphate from the ATP in the medium at a higher rate than tissue derived from freshwater-adapted ducks. Changes in the nasal gland ATP-ase activities during the period of adaptation to saline followed the same time course as the changes which occurred in the sodium-excretory capacity of the tissue. Adaptation to saline resulted in a three-to fourfold increase in the weight-specific ATP-ase activity which was accompanied by a three-to fourfold increase in the weight-specific sodium-excretory capacity. In the saline-adapted birds a positive correlation was found between the sodium-excretory capacity of the nasal gland tissue and the corresponding ATP-ase activity. The moles of sodium excreted per mole of ATP hydrolysed was constant irrespective of whether the birds were adapted to either fresh water or salt water. Concommitant with the changes in weight-specific sodium excretion and ATP-ase activity, an increase in the sodium concentration of the nasal gland fluid was observed. An approximately twofold increase in nasal gland weight also occurred during this period. All changes which were observed to occur during the period of adaptation to saline were reversed when the birds were returned to fresh water. The observed changes in enzyme activity and sodium excretory rates of the nasal glands are discussed in relation to possible cellular changes which might occur and their importance relative to the birds’s ability to adapt to a marine environment.
Metachronal Co-ordination of the Comb Plates of the Ctenophore Pleurobrachia
Authors: Sleigh M. A.
Published: April 2021

The activity of comb plates of Pleurobrachia was analysed from cine films. The interval between successive beats of a comb plate varied from several seconds to about 50 msec, in normal sea water; this variation in frequency was accompanied by a variation wave velocity. There was an almost linear relationship between wave velocity and frequency, ranging from a minimal wave velocity of about 20 mm./sec. at low frequencies to a maximal wave velocity of about 80 mm./sec. at the highest frequencies. The wave velocity was accelerated at low frequencies by increased Mg2+ concentrations, by ouabain and by curare, and the same substances decreased the wave velocity at high frequencies. The frequency of beat was accelerated by certain concentrations of adrenaline, serotonin, Mg2+, ouabain and curare. Decreases of frequency were found in acetylcholine (and eserine) and strychnine. These substances act on the excitability of the pacemaker. It is concluded that metachronal transmission is by a flow of electric current from one comb plate to the next. Depolarization, either by a recent excitation of the comb plate or by agents like ouabain causes increased excitability and a more rapid transmission. The minimum phase difference between adjacent comb plates was about 5 msec. The comb plates are almost entirely dependent on a conducted impulse for their excitation; occasionally a spontaneous excitation occurs. The membranelles of Stentor depend more on excitation within the ciliary base and less on the conducted impulse. The two systems are believed to share common features, but differ in the relative importance of these features. Reverse waves involving the beating of comb plates in the normal direction were observed. The wave velocity of these waves increased only slightly over a wide frequency range. Reverse waves of this type are believed to be transmitted by mechanical contact between the comb plates.
Active Transport by the Cecropia Midgut
Authors: Nedergaard S. , Harvey W. R.
Published: April 2021

Although the addition of 32 mM/l. choline chloride to the standard bathing solutions depresses the short-circuit current of the isolated midgut, the replacement of the added choline chloride by either sodium or lithium chloride has no further affect on the current. No net flux of either sodium or lithium is measureable by atomic absorption spectrometry. Therefore neither sodium nor lithium is actively transported across the midgut. Rubidium is able to substitute fully for potassium in maintaining a short-circuit current. The net fluxes of rubidium and potassium are approximately in the same ratio as their concentrations in the solutions bathing the blood-side of the isolated midgut. Therefore the midgut is unable to distinguish between potassium and rubidium. Ammonium is unable to replace potassium in sustaining a current. In double-label experiments using 42K to measure one unidirectional flux and 86Rb to measure the other, the net potassium-rubidium flux accounts for about 87 % of the short-circuit current. The short-circuit current increases with increasing potassium concentration, at least in the range from 2 to 64 mM/l., although the exact function depends on the conditions under which the measurements are made. The midgut isolated from the Cecropia silkworm appears to possess a ‘potassium pump’ with the simple ionic requirement that potassium be present in the solution bathing the blood-side and presumably that potassium be present in the cells.
Ionic Regulation of the Baltic and Fresh-Water Races of the Isopod Mesidotea (Saduria) entomon (L.)
Authors: Croghan P. C. , Lockwood A. P. M.
Published: April 2021

The isopod Mesidotea entomon has colonized the Baltic and certain Swedish lakes since the end of the last Ice Age. The ionic regulation of Baltic animals and fresh-water animals (L. Mälaren) has been compared. It has been possible to adapt Baltic animals to very dilute media, but 5 % Askö sea water (5·5 mM/l. Na) appears to be the limit of adaptation. The haemolymph sodium concentration of Baltic animals from the very dilute media was considerably lowered. The haemolymph sodium concentration in Mälaren animals is high (250 mM/l. Na) and comparable with that in Baltic animals in much more concentrated solution. The haemolymph ionic ratios of the Baltic and freshwater animals are similar. The Cl : Na ratio rises slightly in the more concentrated haemolymph samples. From the concentration of ions in the haemolymph and in the total body water, the relative volume of the haemolymph was calculated. Mälaren animals appear to have a much larger haemolymph volume. The permeability of the animals was determined from the rate of loss of sodium into de-ionized water. The permeability of the Mälaren animals is considerably reduced compared to the Baltic animals. Permeability is not related to the medium to which the animals had been adapted. The sodium influx was determined using 22Na. The rate of active uptake was calculated from this. The maximal rate of active uptake was similar in Baltic and Mälaren animals. The sodium concentration of the medium at which active uptake was half maximum (KM) was considerably lower in Mälaren animals than in Baltic animals. The evolution of Mesidotea as a fresh-water animal is interpreted as a result of a reduction in permeability of the external surfaces to NaCl and an increase in the affinity of the active transport mechanism enabling the animal to maintain the haemolymph NaCl concentration in a steady state in fresh water.