bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gliding Flight of the Andean Condor in Nature
Authors: McGAHAN Jerry 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.