bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Divalent Cations On Spike Generation in the Longitudinal Somatic Muscle of the Earthworm
Authors: Ito Y. , Kuriyama H. , Tashiro N.
Published: April 2021

Effects of various divalent cations on the spike-generation mechanism in the longitudinal muscle of the earthworm, Pheretima communissima, under sodium-free conditions were observed. In the sodium-free solution the membrane was hyperpolarized from −35 mV. to −55 mV. and the input resistance of the membrane increased from 32 MΩ to 52 MΩ. The spike amplitude was greater in sodium-free solution than in Ringer solution.The amplitude of the spike elicited by intracellular depolarizing currents in sodium-free solution was proportional to the external calcium concentration. The slope of the overshoot potential against tenfold change of the calcium concentration was 26 mV. Similar results could be observed with strontium.The threshold membrane potentials for spike generation varied under various concentrations of calcium. Strontium had nearly the same effect as calcium on the threshold membrane potential.The maximum rates of rise of the spike under various damped membrane potentials were measured in sodium-free solution. The maximum rates of rise of the spike showed sigmoidal curve against the changes of the membrane potential. The half-value of the inactivation curve was estimated to be −32 mV.It was concluded that the spike was elicited by the inward movement of calcium ions, presumably not only in sodium-free solution but also in normal Ringer solution.Strontium and barium ions also carried current during the active state of the membrane.Barium, however, inhibited the potassium conductance of the membrane during the resting and active states, i.e. depolarized the membrane, increased the input resistance of the membrane and prolonged the falling phase of the spike.Magnesium of itself could not elicit the spike in sodium-free solution but prevented spike generation by elevating the threshold membrane potential in the presence of calcium. In the presence of 10 mM Mg, the overshoot potentials recorded in the various concentrations of calcium were not affected, but the maximum rate of rise of the spike was reduced.Cobalt and manganese elevated the threshold membrane potential without changing the resting membrane potential and prevented spike generation. Cobalt was more effective than manganese in preventing spike generations. Cobalt and manganese reduced the amplitude of the overshoot potential and the maximum rate of rise of the spike.
The Direction of the Thrust Produced by the Heterocercal Tails of Two Dissimilar Elasmobranchs: The Port Jackson Shark, Heterodontus Portusjacksoni (Meyer), and the Piked Dogfish, Squalus Megalops (Macleay)
Authors: Simons J. R.
Published: April 2021

It is generally held that the heterocercal tail of elasmobranchs (as well as certain primitive osteichthyans) generates a thrust which is angled upwards. The thrust is thought of as resolved into a horizontal component which drives the animal forward, and a vertical component which aids in the levitation of the creature in the water.
Diagonal Locomotion in De-Afferentated Toads
Authors: Harcombe Elnora Smith , Wyman Robert J.
Published: April 2021

Twenty-eight toads (B. marinus) were de-afferentated by severing all spinal dorsal roots. Every animal made locomotory movements of one kind or another. The normal diagonal pattern was observed fairly often; and, once initiated, this pattern was usually maintained until the animal stopped walking. When a toad made any protraction movement following three steps of the normal pattern, then the fourth step was the appropriate step for the sequence in 66% of cases. When the preceding steps followed the normal pattern, the fifth step was correct in 67% of cases; the sixth in 62%; the seventh in 81% and the eighth in 41%. Random movement predicts 25% in all these cases. It is concluded that spinal afferents are not necessary for the co-ordination of diagonal locomotion.
Body Weight and the Energetics of Temperature Regulation
Authors: McNab Brian K.
Published: April 2021

The interactions of basal rate of metabolism, thermal conductance, body temperature, lower limit of thermoneutrality, and body weight in mammals are compatible with Newton’s law of cooling. A small body weight will normally reduce the level and preciseness of body temperature, but a high basal rate of metabolism or a low thermal conductance may compensate for a small size and permit a high, precise temperature to be maintained. The parameters of energetics that fix the level and preciseness of body temperature in mammals are ultimately correlated in turn with the environmental parameters of climate and food habits. Birds generally have higher temperatures than mammals because the basal rates of metabolism are higher and the conductances lower in birds than in mammals of the same weight.
Extraneuronal Potentials and Potassium Depolarization in Cockroach Giant Axons
Authors: Pichon Y. , Treherne J. E.
Published: April 2021

Elevation of the external potassium concentration resulted in a marked positivation of both intracellularly and extracellularly located micro-electrode tips, in intact connectives, with no appreciable reduction in the amplitude of the recorded action potentials. Sucrose-gap experiments showed that this effect was abolished when tension was applied to the nerve and/or if the connectives were briefly exposed to air. In such preparations continuous and relatively slow potential changes were observed, corresponding to depolarization of the giant axons, with only small extracellular positivations of around 5–6 mV. It is concluded that this effect resulted from the access of potassium ions into the extracellular system most probably as a consequence of the disruption of intercellular occlusions at the inner margin of the perineurium, a situation which contrasts with the restricted intercellular penetration associated with preparations exhibiting extracellular positivation. The possible ionic bases of the latter phenomenon are discussed.
The Viscosity of the Pike’s Endolymph
Authors: Ten Kate J. H. , Kuiper J. W.
Published: April 2021

A micro method, based on Stoke’s law corrected for the influence of adjacent walls, if used for the determination of the absolute viscosity of the pike’s endolymph. Samples of maximally 19 μl were used. The absolute viscosity has an average value of 1·20 ±0·08 cP at 23 °C for ten individual pike labyrinths. The values obtained are compared to those measured by a micro-rolling-sphere viscometer. The absolute values determined by both methods agree within the limits of error. The values obtained for the pike’s endolymph agree with those obtained for other species, if the temperature-dependence of the viscosity of water is taken into account. Though the semicircular canals in mammals are smaller than those in pike of equal body mass, they appear equally sensitive, if the temperature effect on the endolymph viscosity is taken into account.
The Responses of the Marine Amphipods Corophium Arenarium and C. Volutator to Gradients and to Choices of Different Oxygen Concentrations
Authors: Gamble J. C.
Published: April 2021

A gradient or choice apparatus, based on the ‘fluviarium’ principle and suitable for testing the responses of amphipod crustaceans such as Corophium volutator and C. arenarium to different dissolved oxygen concentrations is described. In a gradual oxygen gradient between 6·99 (100% air-saturated) and 0·17 ml O2/l (2·5% air-saturated) C. arenarium shows a significant preference for the oxygenated water while C. volutator is indifferent. The difference between the species is emphasized in experiments with a choice between the above-mentioned oxygen concentrations. Furthermore, in this situation C. volutator shows a greater preference for the deoxygenated water. The response in the choice situation becomes more definite after a period of time. Both Corophium species react immediately at the abrupt oxygen gradient in the choice chamber; C. arenarium is the more sensitive. It is concluded that C. arenarium responds to the dissolved oxygen gradient through an orthokinetic mechanism and that the difference between the two species of Corophium may be correlated with a difference in the oxygen regimes of their respective habitats.
Physiological Basis for Detection of Sound and Vibration in Snakes
Authors: Hartline Peter H.
Published: April 2021

Snakes possess two sensory systems which respond to both air-borne sound and substrate vibration as shown by extracellular slow evoked potentials recorded in the midbrain. One involves the VIII cranial nerve and inner ear (designated ‘auditory system’); the other requires an intact spinal cord and probably originates in skin mechanoreceptors (designated ‘somatic system’). In species of the families Colubridae, Crotalidae, Boidae, the auditory system has a typical U-shaped frequency-threshold curve, similar to those found in other animals, but restricted to a narrow frequency range, c. 150 Hz to 600 Hz. The U-shaped curve has a distinct minimum threshold or best frequency. Frequency-threshold curves for sound and head vibration have only minor differences. The auditory system is not remarkably sensitive to sound. It is about 20 dB less sensitive than the human auditory system for air-borne sound between 200 and 400 Hz. It is remarkably sensitive to head vibration: at the best frequency, 1 Å peak-to-peak amplitude is suprathreshold. The auditory system responds not only to stimuli at the head but to sound and vibration delivered to the body alone. Responses to body stimulation by sound are caused by the same sensory end-organ that responds to head vibration. The role of the body in picking up sound for the auditory system can be substantial; thus the lung plays an important part in snake hearing, a novel situation among land vertebrates. The somatic system is not as sensitive to sound or to vibration as is the auditory system over most of the latter’s frequency range. The somatic system has a relatively flat frequency-threshold curve which lacks a distinct best frequency. The frequency range extends both above and below the range of the auditory system, 50−1000 Hz. The somatic system is insensitive to vibration of the head. Evoked slow potentials fail to show that either spinal or auditory system distinguishes between vibratory energy from the air and from the substrate. It is proposed that intensity information from the auditory system could be compared by the snake’s brain with intensity information from the snake’s somatic system in order to determine the relative amounts of air-borne sound and substrate vibration in an unknown natural stimulus.
The Efference Copy Neurone
Authors: Johnstone J. R. , Mark R. F.
Published: April 2021

Neurones which fire at the same time as saccades are found in the tectal commissure of carp. They are unaffected by visual stimuli or by paralysis of eye muscles and so their activity is not directly related to sensory input. Twenty-two units have been examined. They fire in bursts only during eye movements and only for a particular direction of movement, either eyes-left or eyes-right. They begin to fire a few milliseconds before eye movement begins, slowly at first, reach a maximum frequency of about 300 Hz, then slow again and stop after about 100 ms. In two instances such units have been recorded simultaneously in paralysed fish with a tonically firing unit, presumably visual, which was suppressed during each burst. In one case the tonic activity after each burst was increased, in the other it was decreased. We suggest they are efference copy neurones, responsible for perceptual stability during eye movements. Their possible function is discussed in detail. They are not tectal motoneurones because the same eye movements continue after total removal of the tectum. Neither are they dependent on sensory input resulting from eye movement because their discharge patterns are unaffected by darkness or paralysis.
Dependence of Flight On Temperature Regulation in the Moth, Manduca Sexta
Authors: McCrea M. J. , Heath J. E.
Published: April 2021

Manduca sexta can behaviourally regulate its temperature, but the temperature level is not determined by a simple thermal set-point. Thermoregulation is not localized in a cephalic nervous centre. Both of these characteristics distinguish thermoregulation in M. sexta from thermoregulation as seen in vertebrates. Sustained high temperature is a requisite for flight activity, but regulation of internal temperature is a secondary feature in M. sexta subserving efficient tuning of the flight system.
Experimental Biology, Pure and Applied
Authors: Wigglesworth V. B.
Published: April 2021

THE GEORGE BIDDER LECTURES

The Society for Experimental Biology, with the generous support of the Company of Biologists Ltd., have instituted a series of formal public lectures to be given by distinguished members of the Society, and subsequently to be published in the Journal of Experimental Biology. The series is named after Dr George Bidder, who played an important role in the founding of both the Company and the Society.

A. P. M. LOCKWOOD Hon. Zool. Sec.

N. SUNDERLAND Hon. Bot. Sec.

Society for Experimental Biology

The first George Bidder lecture, given at the Imperial College of Science and Technology, 5 January 1971:
An Analysis Of Pre-Flight Warm-Up In The Sphinx Moth, Manduca Sexta
Authors: Heinrich Bernd , Bartholomew George A.
Published: April 2021

The physiology of pre-flight warm-up in Manduca sexta was analysed with regard to rate of heat production, regional partitioning of heat between thorax and abdomen, and the control of blood circulation.

When moths which have come to equilibrium with ambient temperature undergo pre-flight warm-up, the thoracic temperature increases linearly until flight temperature (37 –39 °C) is approached. The rate of increase in thoracic temperature during warm-up increases directly with ambient temperature from about 2 °C/min at 15 °C to about 7 ·6 °C/min at 30 °C. The temperature of the abdomen remains near ambient throughout the period of warm-up, but during the initial part of post-flight cooling while thoracic temperature declines sharply abdominal temperatures rise appreciably. During warm-up the rate of wing vibration increases linearly with thoracic temperature. At a thoracic temperature of 15 °C the rate is about 8/sec and at 35 °C it is about 25/sec. When resting animals are held by the legs they at once begin to beat their wings through a wide angle. These wing beats at any given thoracic temperature are slower than the wing vibrations characteristic of normal warm-up, but they cause thoracic temperature to increase at almost the normal rate. The removal of thoracic scales causes a decrease in rate of warm-up, but in still air this does not prevent the moths from reaching flight temperature. During cooling the rate of decrease in thoracic temperature is greater in live animals than in freshly killed ones. At any given difference between thoracic and ambient temperatures cooling rates are directly related to thoracic temperature. In resting moths heart pulsations are usually variable with regard to rate, amplitude, rhythm, and sometimes direction, but the records of cardiac activity simultaneously obtained from thorax and abdomen show close correspondence. During warm-up the records of changes in impedance from electrodes in the abdomen indicate that pulsations of the abdominal heart are either absent, greatly reduced, or at a frequency different from that simultaneously recorded from the thorax. The calculated rate of heat production during warm-up is linearly related to thoracic temperature. Our data are consistent with the assumption that heat produced in the thorax during warm-up is sequestered there by reduction in blood circulation between thorax and abdomen. Rates of warm-up in insects are close to the values predicted on the basis of body weight from data on heterothermic birds and animals.
The Swimming of Nymphon Gracile (Pyconogonida)
Authors: Morgan Elfed
Published: April 2021

The organization of the swimming legs of N. gracile has been described. The legs beat ventrally so the animal swims with the dorsal side foremost. The joints between the major segments of the leg are extended for most of the power stroke, but the distal segments articulate sequentially later in the beat, commencing with the flexion of the femoro-tibial joint at the end of the power stroke. Continued flexion reduces the leg radius considerably during the recovery stroke. Animals swimming at constant depth were found to have a leg-beat frequency of about 1 beat/s. Above this the rate of ascent increased rapidly with increasing frequency of beat. Abduction or adduction of the leg usually occurred prior to the start of the power stroke with the femur in the elevated position. Assuming a fixed limb profile at constant angular velocity, maximum lift was calculated to have occurred with the femur inclined at an angle of about 50 ° to the dorso-ventral body axis. The outward component of the lateral thrust decreased to zero at this point, and with further declination of the femur the lateral forces became inwardly directed. Of the different segments of the leg, tibia 2 and the tarsus and propodium contribute most of the hydrodynamic force. The angular velocity of the leg varied during the power stroke, and the actual forces generated during two beats having the same amplitude and angular velocity but of high and low elevation were calculated. Greater lift occurred during the high-elevation beat when the leg continued to provide lift throughout the power stroke, whereas the low-elevation beat acquired negative lift values towards the end of the powerstroke. The lateral thrust was now directed entirely inwards.
Separation of Receptor and Lamina Potentials in the Electroretinogram of Normal and Mutant Drosophila
Authors: Heisenberg Martin
Published: April 2021

In Drosophila the retinula cells and the cells in the lamina ganglionaris contribute to the ERG. This is due to extracellular resistance barriers across these cells ; one of these is situated near the proximal ends of the rhabdomeres separating the retinula cell layer from the rest of the fly, the other is situated either within several layers or homogeneously distributed throughout the lamina. Because of their different origin, two components of the ERG, the receptor potential and the lamina potential can be separated experimentally. At high light intensity the receptor potential is larger than the lamina potential. However, under stimulus conditions where the receptor potential is very small (a) at low light intensity, (b) at high intensity but low flash contrast (ΔI/1), (c) at high frequency of stimulation, the lamina potential exceeds the receptor potential. It is suggested that these properties reflect summation and adaptation of the sensory input within the lamina. The shape of the lamina potential has, under these conditions, the characteristics of a high-pass filter and may improve the fly ‘s response to high stimulus frequencies. The ERGs of the mutants ebony, tan and opm 2 have normal or nearly normal receptor potentials but at the same time demonstrate severe defects in the lamina potentials. In ebony a fast on-effect at high intensity, and in tan a delayed off-effect at high intensity, are still present. The mutant opm 2 shows very little lamina activity at all. The difference of the defects in the three mutants argues against non-specific current leaks in or around the lamina. Therefore it is most likely that the lamina properties of summation, adaptation, and high-pass filtering, are largely lost in the three mutants. This is supported by behavioural experiments.
The Behaviour and Neuromuscular System ofGonactinia Prolifera,a Swimming Sea-Anemone
Authors: Robson Elaine A.
Published: April 2021

In Gonactinia well-developed ectodermal muscle and nerve-net extend over the column and crown and play an important part in the anemone’s behaviour. Common sequences of behaviour are described. Feeding is a series of reflex contractions of different muscles by means of which plankton is caught and swallowed. Walking, in the form of brief looping steps, differs markedly in that it continues after interruptions. Anemones also swim with rapid tentacle strokes after contact with certain nudibranch molluscs, strong mechanical disturbance or electrical stimulation. Swimming is attributed to temporary excitation of a diffuse ectodermal pacemaker possibly situated in the upper column. From the results of electrical and mechanical stimulation it is concluded that the endodermal neuromuscular system resembles that of other anemones but that the properties of the ectodermal neuromuscular system require a new explanation. The size and spread of responses to electric shocks vary with intensity, latency is variable and there is a tendency to after-discharge. There is precise radial localization, for example touching a tentacle or the column causes it to bend towards or away from the stimulus. A model to explain these and other features includes multipolar nerve cells closely finked to the nerve-net which would act as intermediate motor units, causing local contraction of the ectodermal muscle. This scheme can be applied to other swimming anemones but there is no evidence that it holds for sea anemones generally.
Blood Gas Relationships in the Rainbow Trout Salmo Gairdneri
Authors: Eddy F. B.
Published: April 2021

Oxygen dissociation curves were determined using blood from rainbow trout, acclimated for at least 3 weeks to temperatures of 6, 15 and 20 °C. Carbon dioxide tensions in the range 0·3–7 mmHg produced both the Bohr and Root effects in the blood. Increasing temperature, and hydrogen ions, whether raised individually or together, caused a decrease in blood O2 affinity (increased value for P50). Blood at low temperatures had a higher pH than blood at high temperatures. This is related to the fact that the ionization constant of water is diminished with decreasing temperature. When blood was 50 % saturated and was 1 mmHg, the pH value was 8·25 at 6 °C, 7·83 at 15 °C and 7·62 at 20 °C. The factors influencing unloading of oxygen from the blood are discussed. To release the same amount of oxygen from blood, a greater change in carbon dioxid tension is required at 6 °C than at higher temperatures. The Bohr effect expressed quantitatively (ΔlogP50/ΔpH) was –0·54 at 6°C, –0·57 at 15 °C and –0·59 at 20 °C. These values are similar to those for the blood of many mammals, and are within the range reported for fish, where whole blood has been used.
Audition in the Desert Locust: Behavioural and Neurophysiological Studies
Authors: Yinon U. , Shulov A. , Tsvilich R.
Published: April 2021

The auditory responses of the desert locust Schistocerca gregaria were tested using electrophysiological and behavioural methods. The electrical response of the tympanal nerve to pure tone stimuli showed maximum sensitivity between 3 and 5-5 kcyc/sec. The response was the same in both sexes. The flight behaviour was tested as function of pure tone stimuli and measured as the delay period, the number of insects reacting and the time they spent flying. The number of animals which began to fly after the various tones presented was in accordance with the electrophysiological results. The number of animals having a short delay period (under 30 sec) was considerably higher than in the controls for the various sound stimuli. The number of rounds flown (or time spent in flying) was the most affected parameter, although no systematic response was seen as a function of the tone ‘excitation’ by pure tone stimulus and ‘inhibition’ by ‘white’ noise. These two kinds of stimuli were presumably learned by the animal during successive repetition of the stimuli were presumably learned by the animal during successive repetition of the stimulation procedure. The usefulness of sound emission during flight and sound perception (by the hearing organ) was discussed. The auditory neural mechanism of the desert locust is presumably integrated with the visual mechanism for communication purposes between swarming animals.
Variable Responsiveness of A Visual Interneurone in the Free-Moving Locust, and its Relation to Behaviour and Arousal
Authors: Rowell C. H. Fraser
Published: April 2021

Recorded from a dissected immobilized animal, or from an unrestrained animal which is quiescent, the descending contralateral movement detector (DCMD) neurone shows an exponential decremental response to a repetitive stimulus (habituation), reaching a plateau level characteristic of the stimulus conditions. The process is sitespecific on the retina, and movement to a new area of retina gives a complete recovery. In the absence of stimulation responsiveness returns over minutes or hours. Immediate recovery without a rest (dishabituation) can be obtained by a variety of strong sensory stimuli of several different modalities (‘extra-stimuli’) or by non specific electrical stimulation of parts of the CNS. The dishabituating efficacy of all these wanes with repetition. When the habituating stimulus is moved to a new retinal site the previous site is not dishabituated. Dishabituation is not site-specific but affects the whole retina simultaneously. It appears to reverse the original decremental process (‘re-set’) rather than to produce an independent enhancement elsewhere in the pathway, as it does not increase the response from a submaximally stimulated, but unhabituated, retinal site. In unrestrained animals dishabituating extra-stimuli also cause behavioural arousal or other motor activity. When motor activity starts, the DCMD is dishabituated and shows no regular decremental trend thereafter until movement ceases. DCMD background activity is also increased. These effects are not due to the visual stimulus of the moving appendages. The association between motor activity and dishabituation suggests that the latter derives either from motor system collaterals or from mechanoreceptive reafference. Stimulation of the antennal nerve of a totally de-efferented brain cause some dishabituation; this eliminates the lower motor system (below command-fibre level) as the source of dishabituation and suggests it is purely sensory. The activity of a thoracic cord unit (of possibly a wide-field mechanoreceptor interneurone) precedes by 5–20 sec, and closely correlates with, changes in responsiveness of the DCMD. It is either an important input to, or an output from, the dishabituating system. Progressive reduction of sensory input to the brain affects DCMD responsiveness as follows: (i) spontaneous dishabituation is less frequent, (ii) dishabituation is less easily induced and smaller, (iii) rate of habituation is increased, (iv) plateau response level after habituation is lower. Electrical stimulation of the circumoesophageal connective can depress DCMD responsiveness for many minutes. The probable anatomical and physiological bases for modulation of DCMD responsiveness are discussed.
Connective Tissue Mechanics ofMetridium Senile: I. Structural and Compositional Aspects
Authors: Gosline John M.
Published: April 2021

The body-wall connective tissue (mesogloea) of the sea anemone Metridium senile constitutes the highly extensible, tensile container for the hydrostatic skeleton of this animal (Wainwright, 1970). Light-microscopic (Chapman, 1953 a) and electron-microscopic (Grimstone, Horne, Pantin & Robson, 1958) studies of anemone mesogloea show this tissue to be densely fibrillar, with the fibres forming right-handed and left-handed helices around the columnar body wall. The fibrous component has been identified as a collagen on the basis of periodic banding in electron micrographs (Grimstone et al. 1958; Piez & Gross, 1959; Batham, 1960) and of amino acid analyses (Piez & Gross, 1959).
Transepithelial Potential Changes During Stimulation of Isolated Salivary Glands with 5-Hydroxytryptamine and Cyclic Amp
Authors: Berridge Michael J. , Prince William T.
Published: April 2021

The role of cyclic AMP in mediating the action of 5-HT on salivary glands has been studied by measuring transepithelial potentials. The lumen of unstimulated glands is 4 mV positive but becomes 12 mV negative after treatment with 5-HT (10−8M). Both the potential and the secretory responses to 5-HT are dose-dependent over the same concentration range. The electrical response of salivary glands to cyclic AMP is qualitatively different to that of 5-HT; instead of going negative the potential goes more positive. An increase in positive potential is also observed after treatment with theophylline (10−2M), or when glands are stimulated with 5-HT in a chloride-free saline. These results are consistent with the idea that 5-HT has two actions. One is to stimulate the enzyme adenyl cyclase to synthesize cyclic AMP, which, in turn, stimulates cation transport. The other is to increase anion transport by a mechanism which is independent of cyclic AMP.
A Study in Jet Propulsion: An Analysis of the Motion of the Squid, Loligo Vulgaris
Authors: Johnson W. , Soden P. D. , Trueman E. R.
Published: April 2021

A method is presented which allows the jet thrust and motion of a cephalopod to be calculated from basic information on its shape and material properties. A simple model is used to illustrate the technique, and the results are compared with experimental data for Loligo vulgaris. Agreement between theoretical and experimental results is shown to be reasonably good. This approach could be applied to other cephalopods and other animals using jet propulsion.
Central Programming and Reflex Control of Walking in the Cockroach
Authors: Pearson K. G.
Published: April 2021

The activity in identified motor units supplying the coxal levator and depressor muscles of the cockroach have been recorded in intact freely walking animals and in preparations after removal of all sensory input from leg receptors. Reciprocal activity in levator and depressor motoneurones can be evoked, or occurs spontaneously, in the partially de-afferented preparations, thus indicating the existence of a central locomotory rhythm generator. The reciprocal activity patterns recorded in the same motoneurones in intact freely moving animals are not identical to those recorded in partially de-afferented preparations. Thus, the production of normal rhythmic leg movements depends to some extent on sensory input from leg receptors, this input probably exerting tonic and phasic effects on the central rhythm generator. An increase in the resistance to leg retraction during normal walking results in an increase in discharge rate of the levator and depressor motoneurones. This observation further demonstrates that rhythmic leg movements are not exclusively centrally controlled. The receptors responsible for this reflex effect are probably the trochanteral campaniform sensilla.
The Growth of Moniliformis Dubius (Acanthocephala) in the Intestine of Male Rats
Authors: T. Crompton D. W.
Published: April 2021

The helminth Moniliformis dubius forms a convenient source of material for studying the biochemistry and physiology of acanthocephalans because it grows to a relatively large size and its life-cycle is easily maintained in the laboratory. The parasite develops in the haemocoele of the cockroach Periplaneta americana and sexual maturity is achieved in the small intestine of rats. Biochemical work on helminths, however, will progress slowly until the worms in question have been cultured in vitro. One difficulty with culture work is the selection of a trustworthy means of assessing growth. Measurements of the lengths and wet weights are unreliable, and the aim of the work described below was to measure the protein nitrogen, the DNA and the RNA content of M. dubius during the course of its infection in rats. These results could then be used to monitor the growth of worms being kept in vitro and to form the basis for experimental studies of their growth in vivo.
The Corpus Allatum and Oogenesis inRhodnius Prolixus(Stål.)
Authors: Pratt G. E. , Davey K. G.
Published: April 2021

In the ovarioles of both normal and allatectomized females the spaces open between the cells of the follicle layer and vitellogenesis begins as the terminal oocyte grows through the 350–400 μm size range. In both normal and allatectomized ovarioles the growth of the larger oocytes is markedly co-ordinated so that, for example, each ovariole contains only one oocyte in active vitellogenesis. A consideration of the size distribution of the terminal oocytes in normal and allatectomized ovarioles demonstrates that vitellogenesis begins later and proceeds more slowly in allatectomized animals. Allatectomy markedly depresses the number of mitoses in the trophic primordium, but this is held to be a feedback phenomenon resulting from a decreased demand for the products of mature trophocytes. There is a decreased level of yolk protein in the haemolymph of allatectomized animals. This evidence favours the hypothesis that the primary site of action in Rhodnius of the gonadotropin from the corpus allatum is situated at the level of activation, whereby spaces open between the follicle cells and proteins from the haemolymph are allowed free access to the oocyte surface.
The Evolution of Kidney Function in the Neritacea (Gastropoda, Prosobranchia)
Authors: Little Colin
Published: April 2021

Gastropod molluscs of the superfamily Neritacea (or order Neritacea: see Morton & Yonge, 1964) are found in marine, freshwater and terrestrial environments; but despite these wide differences in habitat the general anatomical organization is similar in all the members of the group. In particular the organization of the renal system appears to be very similar in marine and freshwater species, and to be not greatly altered in the terrestrial forms. This is surprising in a group subjected to the apparently different problems posed by life in these various environments.
Respiration, Wing-Beat and Ultrasonic Pulse Emission in an Echo-Locating Bat
Authors: Suthers Roderick A. , Thomas Steven P. , Suthers Barbara J.
Published: April 2021

During flight, echo-locating bats must adjust their pulmonary ventilation to satisfy a variety of requirements. The basic role of respiration, in gas exchange and in the maintenance of physiological homeostasis under exercise stress, must be achieved in a way that is compatible not only with the rhythmic contraction of powerful flightmuscles but also with the continual production of high-intensity vocalizations necessary for acoustic orientation. Moreover, the demand for accurate navigational information is often greatest during the stresses of rapid erratic flight. At such times bats continually emit brief, high-intensity orientation sounds at repetition rates varying from a few to many per second. Nothing is known regarding the relationship between respiration, sound production and wing movements during flight, or the extent to which changes in pulse-repetition rate affects respiration.
Water Content and Water Activity in the Cuticle of Terrestrial Isopods
Authors: Lindqvist Ossi V. , Salminen Inga , Winston Paul W.
Published: April 2021

The water content of the cuticle of both desiccated and non-desiccated terrestrial isopods Porcellio scaber and Armadillidium vulgare was measured. The animals were desiccated for various times (up to 3 h) over silica gel and the mean water content of the cuticle was 54·0 ± 0·78% for P. scaber and 52·7 ± 1·11% for A. vulgare. There was no trend as regards the desiccation time, nor did the body weight affect the water content. The water content of the cuticle remained virtually unchanged as long as the animal was alive in the desiccator. It dropped significantly after the animal had died after having lost some 30 % of its body weight. The cuticular water content of non-desiccated P. scaber tended to be slightly higher than that of desiccated ones. In A. vulgare no significant difference was observed between non-desiccated and desiccated specimens. The water activity of the excised cuticle of the above two species and of Oniscus asellus and Cylisticus convexus was above that of the haemolymph and therefore not in osmotic equilibrium with it. The osmotic equilibrium points were below the osmotic pressures of the blood; the difference amounted from 1·5 to 2·8 atm. in different species. The difference in water activity between blood and cuticle, the maintenance of water content with desiccation, and the drop in water level at death, all indicate the presence of an active mechanism regulating the cuticular water in terrestrial isopods.
The Movement of Gas in the Respiratory System of the Duck
Authors: Bretz W. L. , Schmidt-Nielsen Knut
Published: April 2021

A single inhalation of marker gas (argon) was administered to unanaesthetized ducks. Pargon was continuously monitored in the interclavicular, cranial thoracic, caudal thoracic and abdominal air sacs with a mass spectrometer during the marked inspiration and subsequent respiratory cycles. The sequence of arrival times of the inspired marker at the various sampling sites was determined; ventilation rates of the different air sacs were compared by examining the rate of decrease of Par during washout of each sac. The experimental results agree with previously proposed patterns of air flow in the duck respiratory system. It is proposed that the movement of gas in the respiratory system of birds is a two-cycle event. During the inspiratory phase of the first cycle, inhaled air is drawn into the posterior air sacs ; during the expiratory phase of the first cycle, this air (having mixed with the residual air in the posterior air sacs) is pumped into the secondary and tertiary bronchi of the lung; during the inspiratory phase of the second cycle this air in the lung passage-ways is drawn into the anterior air sacs; and finally, during the expiratory phase of the second cycle, this air is exhaled from the anterior air sacs and the respiratory system.
Electrophysiological Studies on the Heart of the Bivalve Mollusc,Modiolus Demissus
Authors: Wilkens Lon A.
Published: April 2021

Electrical activity from the heart of Modiolus demissus was recorded simultaneously by sucrose-gap and microelectrode techniques, confirming the validity of the extracellular method of assessing the shape of the action potential. Hearts beat in Na-free SW (Tris) but with loss of the plateau and a reduced rise time. Mechanical contractions did not persist, however, for more than 2 h in the absence of sodium, and the viability of the preparation declined rapidly after 3 h. Lithium substitution (for sodium) also failed to support the plateau and tetro- dotoxin had little effect on the spike. Hearts also beat in Ca-free SW. Here, the spike component and contractile activity were lost at nearly the same time although slowly rising plateau-like potentials persisted for over 6 h. EGTA potentiated the effects of Ca-free SW, and manganese had calcium-anta-gonizing effects producing longer plateaus. Spikes and plateau phases could be selectively initiated from hearts made quiescent in Na-free and Ca-free SW by readmitting either ion individually. In Na-free SW spike amplitude and rate of rise were increased by raising calcium concentration. This effect was self-limiting at high levels of calcium, however, and the spike was reduced. In divalent-free solutions (Ca- and Mg-free SW) the membrane was depolarized to near zero potential. In this situation the membrane permeability to sodium exceeded that to potassium, and the membrane behaved as a sodium electrode. It is concluded that the action potential in Modiolus heart is dependent primarily on calcium for the spike component and on sodium for the amplitude of the plateau. Calcium is also important in the control of plateau duration and membrane permeability by reason of its stabilizing properties. A possible correlation exists between the occurrence of the plateau, calcium sensitivity and habitat of three bivalve species. The hearts of Modiolus and of the oyster have plateaus and will beat in Ca-free SW, and these bivalves live in estuarine habitats, whereas Mytilus lives in a subtidal environment and its heart is sensitive to low calcium and has no plateau component.
An Analysis of a Circadian Rhythm of Oviposition in Oncopeltus Fasciatus
Authors: Rankin Mary Ann , Caldwell Roy L. , Dingle Hugh
Published: April 2021

Oviposition in Oncopeltus fasciatus shows a daily periodicity, eggs being laid 4–10 h after light onset. In constant light the inter-ovipositional interval is temperature dependent, being about 12 h at 28 °C and 27 h at 23 °C. Ovariectomized females began to display normal ovipositional behaviour and attempt oviposition after hypertrophy of the fat body. Ovariectomized females attempt to oviposit 4–10 h after light onset, just as do normal intact females, indicating that control of the time of oviposition lies, at least in part, outside the ovary.
The Mechanism of Blood Circulation inAnodonta Anatina(L.) (Bivalvia, Unionidae)
Authors: Brand A. R.
Published: April 2021

The structure of the blood circulatory system of Anodonta anatina is described and the haemodynamics have been investigated by recording pressures in the ventricle, auricle, pericardial cavity and pedal haemocoele at rest and during burrowing. Ventricular systolic pressure is usually 2 − 4 cm in the resting animal; during burrowing it increases to between 6 and 10 cm and this is sufficient to maintain the blood supply to the foot for most of the digging cycle. Auricular and pericardial cavity pressures fall rapidly (by about 1·0 cm) during ventricular systole, confirming the operation of a volume-compensating mechanism for refilling the heart. High peaks of pressure at spontaneous phasic adduction and during the adduction and retraction movements of the digging cycle are generated equally throughout all parts of the animal enclosed within the shell and do not create large gradients of pressure in the haemocoele; the longer duration of these pressure peaks in the pedal haemocoele produces small transient gradients of pressure which could result in the movement of blood out of the pedal haemocoele. At spontaneous phasic adduction contraction of the pedal muscles may assist the flow of blood from the pedal haemocoele. There is some evidence that Keber’s valve limits blood flow from the pedal haemocoele during active burrowing. Although body movements may assist the movement of blood through parts of the peripheral circulation, they do not generate a high venous return pressure. The form of the circulatory system effectively isolates the heart from pressure changes in the pedal haemocoele.
The Median Inferior Frontal Lobe and Touch Learning in the Octopus
Authors: Wells M. J. , Young J. Z.
Published: April 2021

After removal of the median inferior frontal lobe, blinded octopuses already trained to discriminate by touch between rough and smooth spheres continued to do so, but at a lower level of accuracy. Animals without pre-training showed a strong tendency to take rough objects after this operation and learned to discriminate well only when trained to take rough and reject smooth. When animals with intact inferior frontal lobes were given food in the presence of a smooth sphere they learned to take the smooth; in subsequent extinction tests they continued to take the smooth but soon ceased to take rough objects. Animals without median inferior frontal lobes also increased their tendency to take a smooth object associated with food. But they did not behave in the same way as controls in extinction tests; they continued to take the rough objects even if they had not been rewarded for doing so. Operated animals thoroughly pre-trained to take smooth objects showed some capacity to discriminate these from rough objects in subsequent successive training with food and shock, though continuing to take the rough far more than control animals. Animals without brain damage could be taught to take smooth rather than rough objects on one side, and continued to do so when trained in the reverse direction on the other. There was, however, some lateral interference; performance on the unreversed side was worse after the introduction of reversed training. Animals with lesions to the median inferior frontal lobe failed to learn on the reversal (rough+/smooth−) side, responses to both objects declining progressively as training continued. At the same time as this discrimination by the non-reversal (smooth+/rough−) side continued to develop. There was thus no evidence of lateral transfer in these animals. It was confirmed that tactile learning is still possible after removal of the vertical and basal lobes, but with some decrease in the normal preference for smooth objects. The median inferior frontal is thus not essential for tactile learning, but greatly facilitates it, making some contribution to the acquisition of both positive and negative responses, perhaps by spreading information through both sides of the touch-learning system. The effect of its removal in touch learning can be compared with the effect of vertical lobe removal on visual learning. It is concluded that one function of these parts is to compensate for the intensity of stimulation so that animals do not pay undue attention to brightly reflective or texturally rough objects.
Auditory Discrimination between Compressions and Rarefactions by Goldfish
Authors: Piddington R. W.
Published: April 2021

Goldfish were taught to discriminate between a given click and the same click inverted, that is, with the compression and rarefaction phases reversed. The responses were true auditory responses involving the sacculus but not the lateral line. The responses were independent of both waveform (frequency) and intensity and could be elicited with single clicks. Phase was the relevant parameter. Tail flips were found to send a rarefaction wave (rarefaction is the first deflexion) forward from the fish and a compression wave backward. It is proposed that phase analysis of tail-flip sounds is used to tell whether a swimming fish is approaching or receding.
The Swimming of Nymphon Gracile (Pycnogonida)
Authors: Morgan Elfed
Published: April 2021

During the swimming of intact Nymphon gracile the legs beat ventrally in a metachronal sequence starting from the rear, and with a phase delay of approximately one-third between successive appendages. The first and fourth ipsilateral legs thus beat together, usually in synchrony with either the second or the third contralateral leg, rather than halfway between them. The pattern of leg movement in swimming involves a succession of such combinations, e.g. (R4 R1 L2) (R3 L4 L1) (R2 L3), and the preferred gait alternates between this sequence and its mirror-image combination. Amputation of one or both of the third leg pair was followed by a lateral movement of the adjacent legs, but the rhythm of movement was little impaired, to the extent of reducing slightly the phase delay of leg 2 in leg 4 on the same side. The effect of an imposed cycle of movement on the phase relationship of adjacent legs suggests that proprioceptive feedback plays only a little part in entraining the rhythm, but there is some evidence for reflex coupling between adjacent legs. This appears to be strongest within the segment. The results are best explained in terms of negative coupling between oscillators controlling each leg.