bluuebunny/crossref_metadata_2025 huggingface dataset:
Specific Re-Innervation of Limbs Transplanted Between Segments in the Cockroach, Periplaneta Americana
Authors: Young D.
Published: April 2021

The connexions of single, identified motor neurons have been studied in the thoracic ganglia of the cockroach, Periplaneta americana. Selected cell bodies were identified on purely morphological criteria from one animal to another. Similarly, serially homologous cell bodies were identified from one ganglion to another. Their connexions to particular limb muscles were demonstrated by intracellular stimulation through the cell body and subsequent marking with procion yellow dye. Serially homologous cell bodies in the mesothoracic and metathoracic ganglia innervate serially homologous muscles in the mesothoracic and metathoracic limbs. Metathoracic limbs transplanted to the mesothoracic segment retain their metathoracic characteristics. They become functionally incorporated in the mesothoracic segment and are used normally during walking movements. These transplanted metathoracic limbs become re-innervated from the mesothoracic ganglion. Identified mesothoracic cell bodies make specific connexions with those metathoracic muscles which are the serial homologues of their own muscles.
Light-on Effects and the Question of Bimodality in the Circadian Flight Activity of the Mosquito Anopheles Gambiae
Authors: JONES M. D. R. , CUBBIN C. M. , MARSH D.
Published: April 2021

1. The pattern of non-specific flight activity in Anopheles gambiae females appears to be bimodal, with an initial peak followed by about 12 h of secondary activity, with a maximum 6-10 h after the main peak.

2. The secondary activity is more apparent when the activity level is high, and can account for over 60% of the total activity. When D < 12 h activity is curtailed by the inhibitory effect of light, but there may be a minor peak in the light period, 8-9 h after light-off.

3. The main peak normally follows light-off, but is delayed in LD 3:21 and 1:23.

4. There may also be a peak at light-on if it is abrupt and occurs during the active half of the cycle. The peak is not observed if the light-intensity is changed slowly.
The Landing Response and Visual Processing in the Milkweed Bug, Oncopeltus Fasciatus
Authors: Coggshall John C.
Published: April 2021

The landing response of the milkweed bug Oncopeltus fasciatus consists primarily of extension at one leg joint (femur-tibia) of each of the front four legs upon presentation of the appropriate visual stimulus. Small-field peripherally directed angular motion in the frontal visual hemisphere is sufficient to elicit the landing response. Movement from the periphery is not an effective stimulus. Response latency to a large-field peripherally moving striped pattern decreases monotonically with increasing angular velocity. This decrease is consistent with what is known of the dynamics of motion-detecting neurones in other insects. It is suggested that motor mechanisms controlling the landing response, opto-motor turning reactions and flight-power behaviour receive inputs from a common neural motion-detection system.
Spatial Organization of Respiratory Neurones in the Medulla of Tench and Goldfish
Authors: Waldron Ingrid
Published: April 2021

A minimum of 2000 neurones in the medulla of the tench have cyclic activity that is phase-locked to the respiratory cycle. These respiratory neurones are not uniformly distributed throughout the medullary region where they occur. They tend to occur in two bilateral groups, each of which, toward its rostral end, tends to be split into a dorso-lateral and ventromedial group. Specific patterns of activity are more common in some regions than in others. No evidence was found for anatomically localized groups of neurones with interactions primarily within the group. Neurones within 0·2 mm of each other are more often either synchronous or anti-synchronous than are neurones separated by a distance of 0·5–1·0 mm, but so are neurones separated by 1·0–2·0 mm. Contrary to a speculation by Shelton, respiratory neurones are not bunched into anatomical clusters with a diameter of 0·6 mm or less.
Expansion and Contraction of the Oral Disc in the Sea Anemone Tealia Felina
Authors: Mcfarlane I. D. , Lawn I. D.
Published: April 2021

Electrical stimulation of the SS 1 of Tealia felina causes inhibition of spontaneous activity and increase in length of oral disc radial muscle preparations. This response is elicited over a wide stimulus frequency range (1 every 2 sec to 1 every 30 sec). The response shows a slow onset and a long recovery period. Stimulation of the nerve net at frequencies between 1 shock every 5 sec and 1 shock every 20 sec produces slow contraction. The radials also show fast contractions to shocks less than 2 sec apart. Dissolved food substances excite the SS 1 in the column. The sensory response to application of food extract to a small area of the column shows evidence of sensory adaptation. These observations are related to the pre-feeding response of Tealia and a model for oral disc expansion is described.
Brightness Discrimination in Larvae of Plaice and Sole
Authors: Blaxter J. H. S.
Published: April 2021

The brightness discrimination of larvae of plaice and sole was tested by subjecting them to a choice of moving phototactically to one of two horizontally opposed light sources.

At higher light levels, above 100– 10−1 m-candles, they moved to the brighter of the two lights; below 10−1– 10−2 m-candles they moved to the dimmer.

Brightness discrimination, expressed as the increment (ΔI) discriminated as a percentage of the dimmer light (I) (the Weber fraction), was of the order of 60– 200 %.
The Eye and Colour Change in the Minnow (Phoxinus Phoxinus L)
Authors: Gentle Michael J.
Published: April 2021

Counts were made of the retinal receptors and observations were made of the colour of the minnow, Phoxinus phoxinus L., following the surgical removal of parts of the dorsal and ventral retina. It was found that there were greater numbers of retinal receptors in the temporal field than in the rostral field of the eye. There were very few triple and quadruple cones but a large number of double and single cones in the ventral retina compared to the dorsal. Surgical removal of the dorsal retina or only part of it resulted in the fish being fully dark-adapted on a black or white background. Surgical removal of the ventral retina resulted in the fish assuming an intermediate colour on a white background and a darker tint on a black background.
The Burst Activity of Different Cell Regions and Intercellular Co-Ordination in The Cardiac Ganglion of the Crab, Eriocheir Japonicus
Authors: Tazaki Kenro
Published: April 2021

Various patterns of burst activity in the cardiac ganglion cells of the crab Eriocheir japonicus were observed by means of intracellular electrodes. The pacemaker for burst initiation is located among small cells, and it induces small synaptic potentials in the large cells, increasing their excitability. The anterior large cells generate slow potentials by synaptic activation. The slow potential is the spike generator. The anterior large cells are capable of initiating slow potentials in their own somata without synaptic activation from the small cell. Non-synaptic maintained depolarization takes place in the anterior large cell membrane. The after-depolarizations are cumulative and can develop the slow potential, leading to repetitive firing. The posterior large cell is innervated by two pre-synaptic nerve fibres, one being the small pacemaker cell and the other the anterior large cell, showing that it is a follower. Electrical interaction is present among ganglion cells. Positive feedback through electrical connexions is observed between large and small cells. The cardiac ganglion of the crab has some features common and similar to those found in the ganglia of both the lobster and Squilla.
Sound Discrimination by the Bicolor Damselfish, Eupomacentrus Partitus
Authors: Myrberg Arthur A. , Spires Juanita Y.
Published: April 2021

Males of laboratory and field colonies of the bicolor damselfish, Eupomacentrus partitus, showed significantly greater response to playback of courtship sounds of conspecifics than to playback of structurally similar and fully analogous sounds of two closely related and sympatric congenerics, E. leucostictus and E. planifrons. Relative levels of responsiveness by these colonies differed, however, in that laboratory males showed a significant difference in courtship during playback periods of congeneric sounds (recorded in the laboratory) whereas field males showed no such difference. Field males, though responding well to typical laboratory sounds from conspecifics during tests which did not include playback of field sounds from conspecifics, failed to respond well when playback periods did include such field sounds. Present evidence demonstrates that male bicolors possess an excellent discriminative ability within the acoustic modality and that such discrimination is based on some factor of the structural patterning, in time, of the experimental sounds. Present evidence also indicates that the observed response differentials noted during experiments were the result of a slight, but important, difference in at least one typical parameter, i.e., the pulse interval.
A Comparison of Transmitter and Synephrine on Luminescence Induction in the Firefly Larva
Authors: Carlson Albert D.
Published: April 2021

The pharmacological effects of neural transmitter and synephrine are compared with respect to induction of luminescence in extirpated larval firefly lanterns. Transmitter and synephrine show many similarities of action. They are as follows : They both act directly on the lantern. Their response latencies are relatively constant. Both stimulate ATP production. Neither induces a persistent intermediate in anoxic lanterns. No monoamine oxidase enzyme appears to act on them. The luminescence-inducing action of both is rapidly blocked by chlorpromazine. They show identical responses in the presence of dichloroisoproterenol. Luminescence induced by transmitter is much more rapidly extinguished than that induced by synephrine. The possible reasons for the difference in luminescence extinction rate between the two agents are discussed and their different modes of delivery are emphasized.
Factors Affecting Diastolic Blood Pressures in the Systemic and Pulmocutaneous Arches of Anuran Amphibia
Authors: Jones David R. , Shelton Graham
Published: April 2021

During rhythmic lung ventilation systolic blood pressures in the pulmocutaneous and systemicarches were more or less the same although diastolic pressures in the former were some 3– 4 cm H2O lower than in the latter. During prolonged apnoea (20– 35 min) the pulse pressures became identical. Venous pressures in both lung and body circuits were little affected by these procedures. Raising or reducing systolic pressure by application of drugs to the exposed ventricle caused no change in the relationships of the pressure pulses in the systemic and pulmocutaneous arches. Removal of the conus arteriosus and spiral valve caused a significant reduction in diastolic pressure in the systemic but not in the pulmocutaneous arch. After conus removal differences in diastolic pressures in the systemic and pulmocutaneous arches were only recorded when valves at the apex of the conus were functional. Bilateral occlusion of both systemic arches produced a greater increase in systolic blood pressure in the systemic and pulmocutaneous arches than bilateral occlusion of the pulmocutaneous arches, although pressure changes following the latter were more variable. Blood flow in the pulmocutaneous arch was extremely variable, lowest stroke flows being recorded when the pressure pulses in the systemic and pulmocutaneous arches were identical. The role of the conus arteriosus, spiral valve, arterial compliance and peripheral resistance in maintenance of diastolic pressures in the systemic and pulmocutaneous arches is discussed.
The Influence of Environmental Salinity on the Water Fluxes of the Amphipod Crustacean Gammarus Duebeni
Authors: Lockwood A. P. M. , Inman C. B. E. , Courtenay T. H.
Published: April 2021

It has been known for a number of years that removal of the eyestalks of decapod crustaceans disturbs the maintenance of the water balance of the animals during and after ecdysis (Scudamore, 1947; Carlisle, 1955; Passano & Jyssum, 1963; Bliss, Wang & Martinez, 1966). More recently it has been shown that ligaturing or removal of the eyestalks of crayfish (Procambarus clarkii) results in an increased urine output and this has been interpreted as indicating an increase in permeability to water at the body surface (Kamemoto & Ono, 1967). The semi-terrestrial crab Metopograpsus messor shows a similar effect (Kato & Kamemoto, 1969).
Statocyst-Induced Eye Movements in the Crab Scylla Serrata*
Authors: Sandeman D. C. , Okajima A.
Published: April 2021

The fast and slow eye movements of nystagmus in crabs can be produced by moving a striped pattern around the animal or by rotating the animal in complete darkness. The discharges in the eye muscles are the same regardless of the method used to produce nystagmus. Controlled irrigation of the statocyst in isolated eye-brain preparations of the crab produces activity in the eye muscles which is equivalent to the slow and fast phases of normal nystagmus. When stimulated together, both statocysts combine to produce a greater excitation of the appropriate eye muscles than that produced by the stimulation of a single statocyst. Anticlockwise rotation of the fluid in the left statocyst produces greater muscle activity than clockwise rotation of the fluid in that statocyst. Clockwise rotation of the fluid in the right statocyst is more effective than anticlockwise rotation in the right statocyst. In a model of the system the mutual inhibitory effect between the systems driving the eyes in opposite directions is placed on the output side. The fast-phase system operates through the slow-phase systems, driving one side vigorously while inhibiting the other.
Gliding Flight of the Andean Condor in Nature
Authors: McGAHAN Jerry
Published: April 2021

Derived in a vector analysis with measurements of wind velocity and ground velocity of the bird, the following mean air speeds were obtained for birds crossing a Peruvian beach: 15 m/sec for 15 gliding Andean condors, 14 m/sec for 42 condors that flapped during the crossing, and 10 m/sec for five turkey vultures that flapped. For the 15 gliding condors a mean lift coefficient of 0 · 7 and a mean induced drag force of 3 N were computed. Implausibly low values derived for parasite drag coefficient of the condor appeared to be due to (a) unmeasured forces of deceleration and (b) an undetected vertical component of the wind at the level of the flight path. Field data, adjusted by introducing a coefficient of parasite drag determined for the black vulture in a windtunnel study provided corrected estimates of drag. I secured an adjusted value of 14 for the L/D ratio of a condor gliding with wings fully extended. A moderate flexion of the wings reducing the span by 20% is estimated to increase the optimum air speed from 13 · 9 to 15 · 2 m/sec for an adult male condor and from 12 · 6 to 13 · 8 m/sec for an adult female.
Spontaneous Electrical Activity in the Sea Anemone Calliactis Parasitica
Authors: McFarlane I. D.
Published: April 2021

Activity in the three known conduction systems in Calliactis parasitica (nerve net, SS 1, SS 2) has been monitored for periods up to 2 h. The ectodermal slow system (SS 1) shows irregular activity and many of the observed spontaneous pulses may in fact result from undetected external stimuli. The SS 2 shows rhythmic changes in frequency (approximate range 0·2–7·5 pulses/min.) During periods of low-frequency SS 2 activity a short (up to 10 pulses), high-frequency (up to 15/min) burst of activity in the through-conducting nerve net is seen. A slow contraction of the sphincter muscle is often seen after a nerve net burst.
Bioelectric Activity During the Startle Response of A Hemichordate Worm
Authors: Pickens Peter E.
Published: April 2021

When the proboscis of a hemichordate worm is prodded, two or more nerve pulses travel along the ventral cord to trigger the large, compound muscle potential that precedes the startle response. Nerve pulses also may be compound or they may be all-or-none spikes. Compound pulses decay in size as they travel from their point of origin, but spikes are generally through-conducted to the posterior end and are seen most often during the repetitive discharge evoked by a strong stimulus. Repetitive discharge produces facilitation of conduction velocity so that a burst of closely spaced spikes is generated. The same pulses that trigger the startle response initiate waves of retreat peristaltic contractions, but in the latter activity there is less summation of the spike-like muscle potentials. Although conduction of the waves toward the anterior end depends on the presence of the ventral cord, waves that follow the initial contraction are not preceded by nerve spikes.
On The Function of the White Muscles in Teleosts at Intermediate Swimming Speeds
Authors: Hudson Richard C. L.
Published: April 2021

The swimming performance of rainbow trout, Salmo gairdneri, and the electrical activities, recorded extracellularly, of its red and mosaic muscles have been studied at different swimming speeds. A linear relationship was found between the specific velocity (body lengths/sec) and the frequency of tail beating at frequencies up to 5/sec. The red muscles are active at all swimming speeds at which the fish swim by tail oscillations. Discharges from this muscle decrease in duration with frequency up to 3·5−5·0 beats/sec and then increase while the interburst interval decreases linearly with tail-beat frequency. Mosaic muscle becomes active at 3·05−3·60 tail beats/sec and increases slightly with increasing frequency of tail oscillations. Greatly increased activity was recorded in response to struggling and rapid accelerations. The white (mosaic) muscle mass of teleosts is concluded to be involved at intermediate swimming speeds and to be active at the higher range of cruising speeds.
Control of Ciliary Activities by Adenosinetriphosphate and Divalent Cations in Triton-Extracted Models of Paramecium Caudatum
Authors: Naitoh Yutaka , Kaneko Hiroki
Published: April 2021

Cilia of Paramecium candatum extracted with Triton X-100 were reactivated in the presence of ATP and Mg2+. The beating frequency of the reactivated cilia is a function of both the ATP and Mg2+ concentrations. The reactivated cell models swam forward when the Ca2+ concentrations in the ATP-Mg2+ medium was kept below 10−7 M. They swam backward when the Ca2+ concentration was above 10−6M. This was due to a reversed orientation of the effective power stroke of the reactivated cilia. In the absence of Mg2+ the cilia failed to beat, even though ATP was present. If Ca2+ was then added the cilia assumed a new orientation, pointing toward the anterior without beating. Ni2+ inhibited ciliary beating in the reactivated models, but has no influence on changes in the orientation of the cilia produced by ATP and Ca2+. This suggests that one ATP-activated system is responsible for beating, while another governs the direction of the effective stroke. Mn2+ is half as effective as Mg2+ for inducing ciliary beating in the extracted models in the presence of ATP. Salyrgan strongly inhibits Mg2+-ATP activated ciliary activity of the model. Bioelectric control of ciliary activity by the cell membrane of live animals is discussed.
Release of Transmitter From Degenerating Locust Motorneurones
Authors: Usherwood P. N. R.
Published: April 2021

When the motorneurones to the femoral part of the retractor unguis muscle of the locust Schistocerca gregaria are severed, the changes in impulse-linked release and spontaneous release of transmitter which take place at the synapses between the motorneurones and the retractor unguis muscle fibres can be related to known changes in the numbers and distribution of synaptic vesicles at these synapses. Impulse-linked transmitter release fails when the synaptic vesicles aggregate to form clumps of vesicles, and at this time the miniature discharge recorded from the muscle fibres become characterized, initially, by bursts of miniature excitatory post-synaptic potentials (min. EPSPs) and, eventually, by ‘giant’ intracellular min. EPSPs up to 15 mV in amplitude. The appearance of ‘giant’ potentials is accompanied by an overall fall in the frequency of the miniature discharge, which continues to decline thereafter until spontaneous transmitter release fails. The miniature discharge ceases at a time when the axon terminals are engulfed by glial tissue or become devoid of synaptic vesicles. The parallel changes in temporal arrangement of min. EPSPs and spatial arrangement of synaptic vesicles seen during degeneration of locust nerve-muscle synapses provide further support for the ‘vesicle hypothesis’.
An Oxygen Electrode Microrespirometer
Authors: Atkinson H. J. , Smith L.
Published: April 2021

A constant-temperature microrespirometer, based on a Clark-type oxygen electrode, is described. The apparatus was designed for use with small, individual nematodes weighing 60–380 μg body weight. The experimental procedure for accurate and reliable measurements of oxygen consumptions of the order of 0·02–0·2 mm3 O2/h is given.
The Respiratory Physiology of the Marine Nematodes Enoplus Brevis (Bastian) and E. Communis (Bastian)
Authors: Atkinson H. J.
Published: April 2021

The rate of oxygen consumption of individual males of Enoplus brevis and E. communis was measured at 15 °C and at each of four oxygen tensions, 135, 75, 35, and 12 Torr, after at least 12 h experience of these conditions. It was clearly demonstrated that the level of oxygen consumption of both species was reduced by each lowering of the imposed oxygen tension. In all cases the oxygen consumption of each species fell with increasing body size. On a unit dry-weight basis the oxygen consumption of E. brevis is greater than that of the larger E. communis, but after allowing for the difference of body size the two species have more or less similar oxygen uptakes at all oxygen tensions. In E. brevis oxygen tension influenced the relationship of body size and metabolism, the slope relating oxygen consumption and body weight becomes steeper with decreasing oxygen tension. This effect was not shown by E. communis. Some general factors influencing the availability of oxygen to nematodes are considered.
Hibernation and Osmoregulation in the Diamondback Terrapin Malaclemys Centrata Centrata (Latreille)*
Authors: Gilles-Baillien M.
Published: April 2021

Two batches of diamondback terrapins have been kept for a whole year, one in sea water the other in tap water, and seasonal variations have been recorded in the composition and osmotic pressure of the blood plasma. All year round the sea-water animals have a higher osmotic pressure and higher concentrations of Na, K, Cl and urea than fresh-water animals. It is in July, however, that these differences are the least marked. The seasonal variations recorded are linked in particular to the conditions of osmotic stress imposed by the environment. The results are discussed within the framework of hibernation and of the evolution among chelonians from fresh water to sea water.
An Electrophysiological Study of the Sodium and Potassium Permeabilities of Insect Peripheral Nerves
Authors: Pichon Y. , Treherne J. E.
Published: April 2021

Experiments carried out in situ, using suction electrodes, and in vitro, using the ‘sucrose-gap’, have demonstrated a restricted access of sodium and potassium ions to the axon surfaces in crural nerves of the cockroach Periplaneta americana and the locust Schistocerca gregaria. Elevation of the external potassium concentration produced appreciable extraneuronal potential changes in intact crural nerves of the locust. In the locust the presence of the over lying fat body sheath was found to alter the time course of potassium-induced d.c. potential changes. In particular, an initial lag period in the d.c. response is described and tentatively interpreted in terms of a cation reservoir effect.
Quantitative Studies of Muscle Glycogen Utilization During Sustained Swimming in Crucian Carp (Carassius Carassius L.)
Authors: Johnston I. A. , Goldspink G.
Published: April 2021

The relationship between the wet weight of superficial red muscle and the wet weight of the remaining trunk musculature was found to have the form y = 0·036x + 0·339. The average weight of superficial red muscle accounted for 7·4% of the myotomal mass. A technique is described which allows quantitative studies to be made on glycogen utilization in these muscles for short periods of swimming. A total of 120 Crucian carp (Carassius carassius L.) were studied at six different swimming speeds ranging from 2·0–4·2 bodylengths/s. The log10 of the total glycogen utilization of the superficial red muscle was found to be linearly related to swimming speed. Statistically significant glycogen utilization from the remaining myotomal musculature only occurred at speeds in excess of around 3 bodylengths/s. At these speeds the superficial red muscle only accounted for 15–20% of the total glycogen mobilized by the swimming musculature. The significance of these results is discussed in relation to the division of labour between the myotomal muscles of fish.
Visual and Multimodal Interneurones in the Ventral Nerve Cord of the Cockroach, Periplaneta Americana
Authors: Cooter R. J.
Published: April 2021

Visual and multimodal units were recorded from the thoracic nerve cord of the cockroach, Periplaneta americana, using glass microelectrodes. Compound-eye units could be classified as ON-, OFF-or ON-OFF-units according to their response to visual stimulation. Some were multimodal, firing to both visual and tactile stimulation of the antennae. Although some units were found to be either fired by ipsilateral or by contralateral stimulation only, others were fired by both types of stimulation, often in different ways. Ocellar units were invariably OFF-units, mainly phasic, but one type showed tonic dark-firing in addition to the phasic OFF-burst. The general properties of cockroach visual units are discussed and compared with those reported by other workers for different insects.
Kinematics of Pectoral Fin Propulsion in Cymatogaster Aggregata
Authors: Webb P. W.
Published: April 2021

The kinematics of pectoral-fin propulsion have been measured for Cymatogaster aggregata, 14-3 cm in length, during an increasing-velocity performance test. Acclimation and test temperature was 15 °C, similar to the fishes’ normal environmental temperature for the time of year of the tests. Locomotion was in the labriform mode. Within this mode two pectoral-fin patterns were observed, differing only in the details of fin kinematics. These differences resulted from the length of the propagated wave passed over the fin. At low swimming speeds, up to about 2 L/sec, the wavelength was relatively short, approximately twice the length of the trailing edge of the fin. At higher speeds, a wave of very much longer wavelength was passed over the fin. The pectoral fin-beat cycle was divisible into abduction, adduction and refractory phases. Abduction and adduction phases were of equal duration, and the proportion of time occupied by these phases increased with swimming speed. The duration of the refractory phase decreased with increasing speed. The kinematics indicated that thrust was generated throughout abduction and adduction phases, together with lift forces that cancelled out over a complete cycle. As a result of lift forces and the refractory phase the body moved in a figure-8 motion relative to the flow. Pectoral fin-beat frequency and amplitude increased with swimming speed, and the product of frequency × amplitude was linearly related to swimming speed. Interactions between pectoral fin-beat frequency, amplitude, refractory phase and kinematic patterns were interpreted as a mechanism to permit the propulsive muscles to operate at optimum efficiency and power output over a wider range of swimming speeds than would otherwise be possible. Pectoral-fin propulsion was augmented by caudal-fin propulsion only at swimming speeds greater than 3·4 L/sec. The mean 45 min critical swimming speed was 3·94 L/sec, and compares favourably with similar levels of activity for fish swimming by means of body and caudal-fin movements.
A Simple Technique for Monitoring the Synaptic Actions of Pharmacological Agents
Authors: Callec J.-J. , Sattelle D. B.
Published: April 2021

A simple electrophysiological method for the pharmacological investigation of synaptic transmission in insects is described. By means of this technique synaptic potentials and ganglionic polarization can be recorded from the sixth abdominal ganglion of Periplaneta americana L. for long periods. In the absence of stimulation, spontaneous excitatory (EPSP) and inhibitory (IPSP) postsynaptic potentials can be recorded. The mechanical stimulation of cereal receptors demonstrates the summation of EPSPs leading to spike generation. Electrical stimulation of the cereal nerves (X, XI) enables the recording of a monosynaptic EPSP (XI) and a bisynaptic IPSP (X). The action of acetylcholine on synaptic transmission, including a dose-response curve, is described. The potential of this technique as a tool in pharmacological research is discussed.
The Action of Isotonic Salt Solutions on the Unfertilised Eggs of Thalassema Neptuni
Authors: Hobson A. D.
Published: April 2021

The action of isotonic solutions of single salts in causing artificial parthenogenesis was first described by R. S. Lillie (1910, 1911 a, 1911 b). He found that while the salts of sodium and potassium caused development, those of calcium and magnesium were ineffective. Addition of calcium or magnesium inhibited the action of sodium or potassium. In a later paper (1916) Lillie showed that activation of the egg, whether by fertilisation or by artificial methods, is accompanied by an increase in permeability of the surface membrane of the egg to water.
The Growth of Fish
Authors: Gray J.
Published: April 2021

According to Minot (1908) the amount of new tissue formed per gram of mammalian embryo per unit time falls with decreasing velocity as the embryo gets older, so that for very young embryos this specific growth-rate is astonishingly high, whilst the decrease in its value is not in any obvious way associated with a scarcity of the raw materials for growth. How far such an inherent decline characterises the specific growth-rate of a cold blooded animal is entirely unknown. Within more recent years, Robertson (1923) has suggested that the growing period of an animal’s life can be resolved into one or more independent cycles and during each of these cycles the growth-rate is controlled by two factors. One of these factors is always proportional to the size of the organism, and therefore constantly increases; the other factor is a linear function of the size of the organism, but decreases as the animal grows, so that the rate of growth (δx/δt) is proportional to x (a − x) where x is the weight of the organism and a is a constant representing the maximum weight reached by the animal at the end of a particular phase of growth. If this be so, it follows that the growth-rate must reach a maximum when the animal is half grown.
On The Structure of the Cells Bearing the Velar Cilia of the Nudibranch Veliger
Authors: Carter G. S.
Published: April 2021

The object of the present paper is to extend the previous observations of the author (3) on the nervous control of the cilia of the Molluscan velum and to provide a description of the cytoplasmic structure of the cells which bear these cilia. It is hoped that a revision of this subject, based as far as possible on observations made on the living cell rather than on fixed material, may be of use in the study of the mechanism of ciliary activity from both the chemical and structural points of view.
Studies in the Metabolism of Insect Metamorphosis
Authors: Frew J. G. H.
Published: April 2021

The present study constitutes an attempt to correlate the processes of insect metamorphosis with certain of the more obvious metabolic changes characteristic of larval and pupal life. Throughout this work it has become obvious that the chemical constitution of different batches of larvae or pupae may be very different although all composed of individuals of the same age. One particular instance of this may be cited at the outset. Two batches of larvae, A and B, were reared under almost identical conditions, A being from slightly earlier ovipositions and reaching maturity about two days before B. Both were reared at a somewhat low temperature until nearly mature and the only differences between the two batches were that the higher temperature would commence nearer maturity for batch A than for batch B, and that the sand in which A were reared was somewhat more moist than was the case for larvae B. Both batches pupated very slowly. In each case samples of the body fluid were taken on the day when the majority of the larvae had evacuated the gut, and again two days later. Not only was there marked differences in the physical properties of the body fluids but there was also a difference in colour: the fluid of specimens A being yellow and deeply pigmented, whereas that of B had the normal greenish tinge and was less pigmented.
Respiratory Responses to Long-Term Hypoxic Stress in the Crayfish Orconectes Virilis
Authors: McMahon B. R. , Burggren W. W. , Wilkens J. L.
Published: April 2021

Changes in the rate and force of scaphognathite beating, irrigation volume, oxygen utilization, oxygen consumption and heart rate during acclimation in response to the experimental conditions and in response to long-term hypoxic exposure have been measured in the crayfish Orconectes virilis. Immediately following placement in the experimental chamber the animals exhibited very high levels of respiratory and circulatory performance. These levels decreased slowly and stable minimal performance levels could be measured only after 2–3 days. A 3-day acclimation period under normoxic conditions thus routinely preceded hypoxic experiments to ensure measurement of unmasked hypoxic responses. Two responses to hypoxia were routinely observed: an initial hyperirrigation response maintained oxygen consumption by increased branchial water flow. This response was not maintained, but oxygen consumption remained at pre-hypoxic levels while pumping rates decreased. Possible mechanisms of acclimation to hypoxia are discussed.
Directional Sensitivity of Echolocation System in Bats Producing Frequency-Modulated Signals
Authors: Shimozawa T. , Suga N. , Hendler P. , Schuetze S.
Published: April 2021

Radiation patterns of the 55, 75 and 95 kHz components in frequency-modulated sounds emitted by the grey bat (Myotis grisescens) were studied. FM sounds similar to species-specific orientation sounds were elicited by electrical stimuli applied to the midbrain while the head of the animal was immobilized by a nail cemented to its skull. The main beam was emitted 5–10° downward from the eye-nostril line. The radiation angle at one half of maximum amplitude was 38° lateral, 18° up and 50° down at 55 kHz, 34° lateral, 8° up and 32° down at 75 kHz, and 30° lateral, 5° up and 25° down at 95 kHz. At 95 kHz, two prominent side lobes were present. The directional sensitivity of the auditory system (DSA) measured in terms of the potential evoked in the lateral lemniscus was studied with the grey bat (M. grisescens) and the little brown bat (M. lucifugus). The maximally sensitive direction moved toward the median plane with the increase in frequency from 35–95 kHz. The slope of the DSA curve increased from 0·3–0·6 dB/degree with frequency. The directional sensitivity of the echolocation system (DSE) was calculate using both the DSA curve and the radiation pattern of the emitted sound. The maximally sensitive direction of the echolocation system was 15° lateral to the median plane at 55 kHz and 2·5° lateral at 95 kHz. The slope of the DSE curve increased from 0·6 to 1·0 dB/degree with frequency. Thus, the higher the frequency of sound, the sharper was the directional sensitivity of the echolocation system. The interaural pressure difference (IPD), which appeared to be the essential cue for echolocation in Myotis, changed linearly with the azimuth angle from 0–30° lateral regardless of the frequency of sound, at respective rates of 0·4, 0·7, 0·3 and 0·4 dB/degree for 35, 55, 75 and 95 kHz sounds. Beyond 30°, the change in IPD was quite different depending on frequency. For 75 and 95 kHz sounds, the IPD stayed nearly the same between 30° and 90°. Thus, the 75–95 kHz components in FM orientation sounds were not superior to the 35 and 55 kHz components in terms of the IPD cue for echolocation. Assuming the just-detectable IPD and ITD to be 0·5 dB and 5 μsec respectively, as in man, the just-detectable azimuth difference of Myotis around the median plane would be 0·7–1·7° with the IPD cue and 11° with the ITD cue.
Blood Gases of the Tench (Tinca Tinca) in Well Aerated and Oxygen-Deficient Waters
Authors: Eddy F. B.
Published: April 2021

The respiration of tench at 13 °C was investigated, particular attention being given to the role of the blood in uptake and transport of oxygen. In well aerated water the mean value for arterial blood was 36 mmHg, for 3·3 mmHg and for pH 8·16; the respective venous values were 7 mmHg, 5 mmHg and 8·08. Arterial blood averaged about 75 % and venous blood about 40 % oxygen saturation. The mean value for oxygen uptake was 0·5 ml/min/kg and for ventilation volume 132/ml/min/kg. The oxygen tension and the percentage saturation of the blood determined in vivo are discussed in terms of the oxygen dissociation curve determined in vitro. When the environmental was decreased, tench responded by increasing breathing rate and ventilation volume. Arterial and decreased but arterial pH tended to remain steady. There was also a significant increase in blood lactate. That tench can withstand severe hypoxic conditions is attributed to blood of high oxygen affinity and the ability to maintain a favourable acid-base status in the blood for oxygen transport. Respiration in tench is compared with that in other fish species.
Changes in Critical Temperature During Nymphal and Adult Development in the Rabbit Tick, Haemaphysalis Leporispalustris (Acari: Ixodides: Ixodidae)
Authors: Davis Minh-Tam Bui
Published: April 2021

During the developmental period from nymphal to adult engorgement of the rabbit tick, Haemaphysalis leporispalustris, critical temperature changed with developmental stage and nutritional state, but was similar in the two sexes. Critical temperature was low in engorged nymphs one day after drop-off (in the range of 36–40 °C), increased during the following 15 days (46–47 °C), slightly decreased just after ecdysis (42–43 °C), remained constant in unfed females for the next 2 months (42–43 °C) and then decreased again during engorgement of adult females (from 42–43 to 37–38 °C then to 35–36 °C). The rates of water loss also changed with the developmental period. The hypothesis that evaporative water loss might initiate the rapid engorgement phase is supported, although not confirmed, by a close correspondence between the host body temperature and the critical temperature of the tick just prior to the rapid engorgement phase.
The Water Balance of a Serpulid Polychaete,Mercierella Enigmatica(Fauvel)
Authors: Skaer Helen Le B.
Published: April 2021

The electrical activity of the two types of longitudinal muscles of an osmoconforming polychaete worm, Mercierella enigmatica, have been studied in media of widely varying osmotic and ionic composition. Activity persists practically unaltered in both types of muscle cell. The possible effects of osmotically induced changes in cell volume on the ionic gradients across the cell membranes are considered. It is concluded that the normal gradients are unlikely to be maintained as a result of such changes. The involvement of ion pumps in the maintenance of the normal gradients across the muscle cell membranes has been studied using specific and metabolic poisons. It is evident that the persistence of electrical activity in media of altered ionic content does not depend on the sodium-potassium exchange pump. The ionic basis of the overshoot of action potentials recorded from cells of the small resting potential type has been studied. It is concluded that calcium ions but not sodium ions are responsible for the inward current although there is a component of the inward current carried by some other as yet unidentified ion. Alterations in the external concentrations of chloride ions are found to alter both the height of the overshoot and the length of the action potential. Profound alterations in the overshoot height are produced only when the normal ratio of calcium to chloride concentration in the external medium is altered. Possible mechanisms to explain these effects are discussed. It is suggested that the stability of the action potential in the muscle cells of M. enigmatica, despite large fluctuations in the salinity of the external medium, depends on the constancy of the ratios between the concentrations of the ions in the fluids bathing the cells and not on the absolute concentrations of the ions.
Excitatory and Inhibitory Control of Inherent Contractions in the Sea Anemone Calliactis Parasitica
Authors: McFarlane I. D.
Published: April 2021

Bursts of nerve-net activity are always followed by a contraction cycle involving parietal and circular muscle contractions in isolated preparations of Calliactis parasitica. Both muscle groups can, however, also contract in the absence of nerve-net activity. These contractions, termed inherent, seem to follow periods of reduced activity in the endodermal slow conduction system (SS2). Electrical stimulation of the SS2 inhibits inherent contractions of parietal and circular muscle preparations. Electrical stimulation of the nerve net excites parietal muscles but seems to have both excitatory and inhibitory effects on circular muscles. A model for control of parietal and circular muscle contractions proposes that both the nerve net and the SS2 are responsible for directing the inherent muscular activity into the observed contraction cycle. It is suggested that when the action of these antagonistic muscles is strongly opposed the SS2 pulse frequency rises, resulting in inhibition of further muscular activity.
The Permeability to Water of the Cuticle of the Larva of Opifex Fuscus (Hutton) (Diptera, Culicidae)
Authors: Nicolson Susan W. , Leader John P.
Published: April 2021

Fourth-instar larvae of Opifex fuscus were found to have a mean body weight of 7·61 mg, a water content of 85·2%, and a mean cuticular surface area of 29·3 mm2. Larvae ligatured at neck and anus were found to lose 1 % of the body weight per hour when immersed in sea water. The osmotic permeability coefficient of the cuticle was calculated from these data to be 2·4 × 10− 2 cm. h− 1. Measurement of the diffusional permeability coefficient (Pd) by means of tritiated water and Deuterium oxide gave a value for this parameter of 4·8 × 10− 3 cm.h− 1. The diffusional permeability of the cuticle of Opifex fuscus is thus less than that of typical freshwater insects, as predicted by Shaw & Stobbart.
The Passive Permeability of Insect Malpighian Tubules to Organic Solutes
Authors: Maddrell S. H. P. , Gardiner B. O. C.
Published: April 2021

The permeability of Malpighian tubules of five insect species to a range of organic solutes has been measured by both in vitro and in vivo techniques. Nearly all the substances tested were found, in in vitro experiments, to penetrate the walls of Malpighian tubules in a manner which, on several criteria, was judged to be passive. The walls of Malpighian tubules are more permeable to small molecules than to large ones; but even inulin (MW 5200) penetrates fast enough to reach concentrations which, in tubules secreting fluid slowly, can be as high in the secreted fluid as 50 % of its concentration in the bathing fluid. Inulin injected into Schistocerca and L-fucose injected into Rhodnius appeared in the excreta at rates which could be accurately predicted from the in vitro behaviour of Malpighian tubules of these insects. Taken with the fact that the cuticular lining of the rectum of insects is thought to be not very permeable, the high permeability of insect Malpighian tubules means that the reabsorption of useful compounds of the order of size of disaccharides must to some extent occur before excretory material reaches the rectum. It is suggested that the circulation of lipids and hormones in the form of complexes with proteins is a device to prevent their rapid loss through the excretory system.
The Electrophysiology of Photoreceptors in the Nudibranch Mollusc, Tritonia Diomedia
Authors: Chase Ronald
Published: April 2021

Tritonia has two eyes, each lying beneath the integument at the base of the rhinophore. Three cell types are present in the eye: large photoreceptors with nuclei up to 50 μ m in diameter, pigment cells, and epithelial cells. A count of nuclei revealed a total of five receptors in each eye. All receptors produced depolarizing generator potentials in the presence of light, regardless of intensity within the responsive range. Responses usually consisted of a fast early depolarization followed by a more slowly rising component. Spikes were uncommon in receptor somata. When present, spikes were superimposed on the slower phase of the response and measured no more than 12 mV. Depolarization was maintained at a steady level when illumination was sustained. The receptors are coupled electrotonically, and synaptic inhibition was evident in a few cells. The functional consequences of these interactions are considered to be minimal. Morphologically, the eye of Tritonia is very similar to that of the nudibranch, Hemissenda. But there are significant differences in the electrophysiology of the two eyes, particularly with respect to cell interactions. Although the maximum recorded sensitivity was about five orders of magnitude less than that considered to be necessary for the detection of sunlight in Tritonia’s natural habitat, a visual role in the regulation of periodic behavioural patterns cannot be definitely excluded. The eye may also function in the location or identification of luminescent pennatulids, the major source of food for Tritonia.
Co-Ordination of two Kinds of Flight Activity in an Aphid
Authors: Kennedy J. S. , Ludlow A. R.
Published: April 2021

The interaction between ‘migratory flight’, defined as flight oriented vertically and horizontally towards a large overhead light source, and ‘targeted flight’ oriented towards a yellow leaf-like object seen to one side against a dark background, has been analysed in Aphis fabae in a laboratory flight chamber. Landings were prevented by regulating a down-current of air so as to balance the flier’s rate of climb and by momentary withdrawal of the target when the flier came close. The longer an aphid had flown before the target appeared the more persistently it homed-in on the target and the more its rate of climb was depressed by the presence of the target. This ‘priming’ of targeted flight during migratory flight could be counteracted by suitably repeated bouts of presentation of the target. Such a treatment tended rather to prime migratory flight responses to the target stimulus, that is avoidance of the target and increase in the rate of climb. The visual stimulus from the target had both excitatory and inhibitory effects on the rate of climb, mixed in varying proportions. Antecedent events in the behavioural chain governed the magnitude and relative timing of these effects. The excitatory effect usually followed an inhibitory one but it could occur first or even alone, and was thus a separate effect not comparable with post-inhibitory rebound.