bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Salinity Changes on the Water Content and Respiration of Marine Invertebrates
Authors: Beadle L. C. 
Published: April 2021

ABSTRACT
Schlieper’s theory of the function of increased oxygen intake by “homoi-osmotic” marine invertebrates in dilute sea water in maintaining their body fluids hypertonic to the surrounding water is discussbd, and objections are brought forward to the methods used in the experiments on which his conclusions were based. By periodic weighings, and measurements of respiratory rate (under narcotic) by Barcroft manometers, it was found that the weight of N. diversicolor, on transference to water of low salinity, at first increases and then falls, and that the respiratory rate is at first increased and later tends to decrease. With N. cultrifera the weight increases to a higher value and does not subsequently fall, and the respiratory rate is also increased but to a lesser extent than with N. diversicolor. These differences in the amount of increase in respiratory rate are more marked in water containing only 16·6 per cent, sea water than in water containing 25 per cent, sea water. N. diversicolor maintains its activity while N. cultifera becomes practically inert in dilute water. The latter does not actually die in 25 per cent, sea water after 100 hours, but dies in 16·6 per cent, sea water after about 50 hours. Exposure to Mjiooo KCN or to anaerobic conditions in dilute water tends to break down the mechanism by which the free osmotic inflow of water in N. diversicolor is prevented, and the weight curves under these conditions approach the N. cultrifera form. The respiratory rate of G. ulvae increases progressively with dilution of the sea water, and is roughly proportional to the initial difference of osmotic pressure inside and outside the animal. The swelling of Gunda in dilute water is due to swelling of the gut cells, which become much vacuolated. The other tissues appear unaltered. M/1000 KCN or anaerobic conditions cause a greater amount of swelling in Gunda in a given salinity than normally occurs. These experiments seem to give reasonably good support to Schlieper’s hypothesis. The mechanism responsible for this “osmotic resistance” in N. diversicolor must be of a somewhat different nature from that in G. ulvae. A rigid distinction between “homoiosmotic” and “poikilosmotic” marine animals cannot be supported.
Growth in the Larvae of Tenthredinidae
Authors: Miles Herbert W. 
Published: April 2021

ABSTRACT
From a study of the larvae of some twenty-eight species of Lepidoptera, Dyar(1) concluded that growth, as indicated by the growth of the head in successive instars, follows a regular geometrical progression. Fisher (2), working on Tortrix pronubana Hb., applied the findings of Dyar and worked out the growth ratio, which he found to be 1·37. The following table indicates how the growth ratio is arrived at: Table I.(Fisher, 1924.)
In the above table the measurements are given in millimetres, and the modes of the observed widths of the head capsules of the first and second larval instars are taken as the basis of calculation. By dividing the mode for the head widths of the second instar larvae by that for the first instar larvae, a figure representing the ratio of increase is found. By further calculation it is possible to estimate the width of the head capsule for any subsequent instar. The close approximation of calculated and observed measurements furnishes the student of life history of Lepidoptera with a means of checking larval ecdysis and development.
Morphologically the larvae of Tenthredinidae bear a close resemblance to those of Lepidoptera, hence it seemed possible that the same general laws with regard to growth might be followed. Material was obtained, therefore, to test the application of Dyar’s law for growth in the larvae of Lepidoptera to growth in the larvae of the Tenthredinidae.
The Influence of Temperature on the Rate of Growth of Sporotrichum Garnis, From −10° C. TO +30° C
Authors: Haines R. B. 
Published: April 2021

ABSTRACT
This mould is of frequent occurrence on stored carcases and in cold stores. The lean portions of carcases which have been kept for eight or ten weeks below zero centigrade but above –10° C. are frequently covered with mould growth. No such growth has been so far observed on carcases stored at – 20° C. Brooks and Hansford, in reviewing mould growth on cold-store meat, found that some strains of Cladosporium herbarum developed and grew at – 6° C. (Brooks and Hansford, 1923). They also suggested that other moulds including Sporotrichum, would probably grow between o° C. and – 6° C. It is therefore of interest to attempt to determine the precise growth limits of this mould. Two cases have to be investigated: the influence of temperature upon growth per se, and also the effect of physical changes in the medium consequent upon freezing. The present communication is concerned with the first of these only, all measurements below zero having been made on supercooled media: i.e. media cooled below their freezing-points but from which ice crystals had not separated.
The Physiology of Excretion in A Blood-Sucking Insect, Rhodnius Prolixus (Hemiptera, Reduviidae)
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
A theory of uric acid excretion is put forward according to which potassium or sodium acid urate is secreted in solution in the upper part of the Malpighian tube, and water and base reabsorbed from the lower part of the tube, leading to a precipitation of free uric acid; so that the same water and base are circulated and used repeatedly. The evidence for this theory is presented under four heads:
General evidence from the histology of the Malpighian tube and the relative solubility of uric acid and urates. Experiments with vital dyes. Thus, neutral red is taken up from the blood by the upper segment of the Malpighian tube, and from the lumen of the tube in the lower segment. It is suggested that water follows the same route. The application of ligatures to the tubes at different levels shows that uric acid is not secreted by the lower segment. Experiments with indicators show that the contents of the tube are faintly alkaline (pH 7·2) in the upper segment, and acid (pH 6·6) in the lower segment. Uric acid in solution has a pH about 6·5.
It is suggested that the terminal ampullae of the Malpighian tubes, and possibly the rectal glands, also play a part in the reabsorption of water.
Direct Measurements of Instantaneous Lift in Desert Locust; Comparison with Jensen’s Experiments on Detached Wings
Authors: Cloupeau M. , Devillers J. F. , Devezeaux D. 
Published: April 2021

ABSTRACT
Instantaneous values of lift in the locust Schistocerca gregaria, flying in a wind tunnel, were measured by means of a piezo-electric probe. The airflow velocity was adjusted to be equal to that which would have been experienced by the freely flying insect.
In order to obtain the true aerodynamic forces, the inertial forces must be subtracted from the gross forces measured. These inertial forces were calculated from the movement of the centre of gravity and from the mass of the different wing sections.
The lift curves obtained have a shape similar to the curves deduced by Jensen from measurements on isolated wings in steady flows, but an approximately doubled amplitude. These amplitude differences appear to be caused by the existence of significant unsteady effects.
The Relationship of the Central Motor Pattern to the Feeding Cycle of Lymnaea Stagnalis
Authors: Rose R. M. , Benjamin P. R. 
Published: April 2021

ABSTRACT
Electromyographic recordings from the buccal muscles of Lymnaea during feeding has shown that there are 4 component phases in the feeding cycle. Cinephotography of feeding cycles has confirmed that these correspond to protraction, 2 phases of retraction, and an inactive phase. The 4 phases of muscle activity can also be related to the cycle of neural activity described previously (Benjamin & Rose, 1979). Thus types 6, 4 group, and type 8 cells are motoneurones involved in protraction and the two retraction phases, while the type 5 cell fires in the inactive period. The combination of physiological and anatomical approaches has led to the suggestion that the single and double input cells described by Benjamin & Rose (1979) are involved with the control of buccal and oesophageal activity respectively.
Inhibition and Excitation in the Locust DCMD Receptive Field: Spatial Frequency, Temporal and Spatial Characteristics
Authors: Pinter Robert B. 
Published: April 2021

ABSTRACT
The descending contralateral movement detector (DCMD) of the locust responds vigorously to small target (ca. 5°) stimuli; this response is inhibited by simultaneous or subsequent rotation of a radial grating (windmill) pattern (subtending 19-90° of visual angle) and suppressed by earlier rotation, The excitation produced in the DCMD by rotation of a radial grating pattern depends only on the spatial frequency of the stripes of the pattern, and is independent of pattern size, and of temporal frequency over the range of low values used. The inhibition produced by this same stimulus similarly depends only on the spatial frequency of the stripes of the pattern, independent of pattern size, and of temporal frequency over the range of low values used. As the radial grating excitation decreases with increasing spatial frequency, the inhibition increases until limited by optical and neural resolution. For spatial frequencies of the radial grating pattern below 0·05 cyc/deg the radial grating patterns become excitatory. Above 0·05 cyc/deg they are inhibitory. This is the point in spatial frequency below which inhibitory grating ‘backgrounds’ become excitatory targets. Inhibition decreases as the size of the radial grating pattern is decreased below 19° visual angle; at 8° or less no inhibition can be found at any spatial frequency. Inhibition is greater in the posterior than anterior regions of the receptive field, and greater in the ventral than the dorsal regions. Inhibition decreases as the distance between small target and the radial grating is increased, but this is influenced by the local variations of excitation and inhibition. Habituation is often greater for small target and low-frequency radial grating response than for inhibited small target and high frequency grating response. These results substantiate previously proposed lateral inhibition models of the acridid movement detector system.
Epithelial Conduction in Salps: I. Properties of the Outer Skin Pulse System of the Stolon
Authors: Anderson Peter A. V. 
Published: April 2021

ABSTRACT
The Outer Skin Pulse (OSP) system of the stolon of Salpa fusiformis was studied histologically and electrophysiologically. The cells of the conducting epithelium are cuboidal, 4–10 μm in diameter and are connected by gap and tight junctions (Fig. 1). They have resting potentials of − 75 to − 96 mV. Outer Skin Pulses are conducted as overshooting action potentials 84–104 mV in amplitude which are characterized by the absence of a hyperpolarizing undershoot during the repolarizing phase (Fig. 2 A). When OSPs are evoked at frequencies in excess of 2 s−1 a pronounced plateau appears in the repolarizing phase (Fig. 2C). Tetrodotoxin blocks OSPs in a manner which suggests that a sodium current is responsible for activation of the action potential. Addition of 15 mM manganese to the bath blocks OSPs. This effect was initially accompanied by a reduction in OSP amplitude and an increase in duration (Fig. 5). This observation was interpreted as indicating the presence of a calcium influx during the action potential. The results are compared with those obtained from epithelial conduction systems in other organisms, other embryonic tissues and excitable cells in other non-vertebrate chordates.
Epithelial Conduction in Salps: II. The Role of Nervous and Non-Nervous Conduction System Interactions in the Control of Locomotion
Authors: Anderson Peter A. V. , Bone Quentin , Mackie George O. , Singla Chaman L. 
Published: April 2021

ABSTRACT
The control of locomotion in Salpa fusiformis was studied by intracellular recordings from motor neurones and swimming muscles. Regular, synaptically driven, volleys of action potentials were recorded from motor neurones. This pattern of activity was consistent with that expected from the waveform of the compound junctional potentials associated with contraction of the swimming muscles. A second class of brain neurone was identified. These cells were synaptically driven. In some, their firing rate was increased while in others it was decreased by activity in an epithelial conduction system, the Outer Skin Pulse (OSP) system. Cells of the outer epithelium were impaled and OSP’s were recorded intracellularly as conventional action potentials. The records from many of these cells showed many depolarising synaptic potentials. Numerous gap junctions were observed throughout the outer epithelial layer and several neuroepithelial synapses were found. The distribution of these synapses coincided with that of the epithelial cells from which synaptic events were recorded.
Ventilatory Mechanisms of the Amphibian, Xenopus Laevis; The Role of the Buccal Force Pump
Authors: Brett S. S. , Shelton G. 
Published: April 2021

ABSTRACT
Lung pressures, buccal pressures, lung volumes, and EMGs from respiratory muscles were measured in unrestrained Xenopus laevis to analyse their roles in the lung ventilation cycle. Lung pressure was always maintained above atmospheric levels and a buccal pumping mechanism was used to fill the lungs in Xenopus, as in other Amphibia. Xenopus, unlike other amphibians, does not ventilate the buccal cavity between lung ventilations. Expiration of gases from the buccal cavity is aided by muscles which decrease buccal cavity volume. Other anurans increase buccal cavity volume during expiration. The buccal phase of inspiration occurs after expired air has passed from the lung and buccal cavity, in comparison to the ranids and bufonids which inspire fresh air into the buccal cavity before expiration.
Ventilation, Oxygen Uptake and Haemolymph Oxygen Transport, Following Enforced Exhausting Activity in the Dungeness Crab Cancer Magister
Authors: McMahon B. R. , McDonald D. G. , Wood C. M. 
Published: April 2021

ABSTRACT
Scaphognathite and heart-pumping frequencies, ventilation volume, cardiac output, oxygen uptake and oxygen transport by haemolymph have been studied in unrestrained Dungeness crabs (Cancer magister) before, immediately after, and during recovery from 20 min of enforced exhausting activity. Exercise increased oxygen uptake 4-fold. This increase was achieved by more than 2-fold elevation of both ventilation volume and cardiac output and by greater participation of haemocyanin in oxygen delivery. The elevated ventilation volume resulted entirely from an increase in scaphognathite pumping frequency, while the rise in cardiac output resulted largely from increase in stroke volume. Prior to exercise haemocyanin accounts for less than 50% of the oxygen delivered to the tissues. Following exercise this increases to over 80%, the additional oxygen release being mediated by a depression of prebranchial oxygen tension and a substantial Bohr effect resulting from build up of lactate ion in the haemolymph and subsequent fall in pH. These changes allowed% oxygen extraction from branchial water to be maintained at 28% despite a 2-fold increase in ventilation volume, and allowed an increase in%. oxygen extraction by the tissues. Despite these changes oxygen supply fell below demand during exercise, and considerable anaerobic metabolism resulted, as evidenced by a 9-fold increase in haemolymph lactate concentration. The resulting oxygen debt required 8–24 h for repayment. Aerobic metabolic scope, and mechanisms of increasing oxygen uptake and transport in this crab are compared with those of a range of fish species.
Thermoacclimatory Changes in the Ionic Microenvironment of Haemoglobin in the Stenothermal Rainbow Trout (Salmo Gairdneri) and Eurythermal Carp (Cyprinus Carpio)
Authors: Houston Arthur H. , Smeda John S. 
Published: April 2021

ABSTRACT
Haematological characteristics (erythrocyte number, haematocrit, haemoglobin, mean erythrocytic volume and haemoglobin content) and plasma and packed red blood cell water and electrolyte (Na+, K+, Ca2+, Mg2+, Cl−) levels were determined in summer and winter populations of rainbow trout acclimated to 2, 10 and 18 °C, and for carp held at 2, 16 and 30 °C. Erythrocyte electrolyte concentrations and ion: haemoglobin ratios were calculated from these data. Modest increases in red cell abundance and reductions in mean erythrocytic volume were the most obvious haematological changes accompanying acclimation to higher temperatures. Haemoglobin levels in carp also tended to increase with temperature. In winter trout plasma sodium and potassium were elevated following acclimation to increased temperature. No significant changes in plasma composition were observed in summer fish. Carp held at higher temperatures were characterized by increases in plasma chloride and calcium and reductions in sodium and magnesium levels. Red cell potassium and magnesium and K+:Hb and Mg2 +:Hb ratios tended to be higher in winter than in summer trout, with the converse being true of chloride and calcium and Cl−:Hb and Ca2+. Hb. Only potassium and K+: Hb were significantly altered following acclimation; rising at higher temperatures. In carp, potassium and K+:Hb were relatively thermostable, but sodium and chloride and Na+:Hb and Cl∼:Hb increased with temperature while magnesium and Mg2+:Hb decreased. Changes in the ionic composition of carp red cells support the suggestion that cellular pH is reduced in the warm-acclimated animal. These variations may be of adaptive value. Increases in chloride and hydrogen ion commonly reduce haemoglobin-oxygen affinity, and should facilitate oxygen unloading at the tissue level. Reductions in cellular magnesium, by maximizing organophosphate modulator levels, should produce much the same effect. In both species reductions in mean erythrocytic volume took place at higher temperatures despite increases in cellular ion content which exceeded those of plasma. It is probable that reductions in cellular volume, which should favour branchial oxygen loading, were achieved by export of some as yet unidentified solute or solutes.
Aerodynamics and Hydrodynamics of the ‘Hovering’ Flight of Wilson’s Storm Petrel
Authors: Withers Philip C. 
Published: April 2021

ABSTRACT
Wilson’s storm petrel (Oceanites oceanicus) characteristically feeds by ‘hovering ‘over the water surface, but its technique for this is unlike that of other flying vertebrates. The kinematics and aerodynamics of this ‘hovering’ flight were investigated to determine the possible sources of lift ; various nonaerodynamic sources of lift were discounted. It is suggested that the storm petrel soars into an ambient, horizontal wind, and thus is not hovering in the usual sense. Such soaring into a horizontal wind is only possible if some thrust component counteracts the bird’s aerodynamic drag, and it is shown that the hydrodynamic drag of the feet through the water is adequate to balance aerodynamic drag. The bird is thus analagous to a kite, where the tension in the string counterbalances the aerodynamic drag of the kite.
The movements of the storm petrel’s wings during ‘hovering’ suggest that the bird may use the wing-flip mechanism for generation of high lift coefficients (Weis-Fogh, 1973, 1976). Such high lift coefficients are required for the bird to ‘hover’ under calm conditions, when ambient wind velocity is less than 5 m s −1. Use of the wing-flip mechanism would enable the bird to ‘hover’ at lower ambient wind velocities. Ground effect also contributes to the bird’s ability to ‘hover’.
This analysis of the flight behaviour of Wilson’s storm petrel indicates that its ‘hovering’ is an energetically inexpensive foraging stragegy which is probably available only to small, surface-feeding birds with low wingloading.
Central Generation of Bursting in the Feeding System of the Snail, Lymnaea Stagnalis
Authors: Benjamin P. R. , Rose R. M. 
Published: April 2021

ABSTRACT
The central generation of burst activity was investigated in the buccal ganglia of Lymnaea. Eight different patterns of burst activity were generated by one or two consecutive phases of compound synaptic potentials resulting from activity of neurones outside the population of recorded neurones. These inputs acted upon the different endogenous properties of buccal neurones such as post-inhibitory rebound and spike adaptation. Effects of synaptic inputs were reinforced by electrotonic coupling of some buccal neurones of the same type.
Metabolic Control of Neuronal Pacemaker Activity and the Rhythmic Organization of Central Nervous Functions*
Authors: Chaplain R. A. 
Published: April 2021

ABSTRACT
The endogenous rhythmic activity of isolated pacemaker neurones of Aplysia californica appears to be controlled by the operation of a substrate cycle. The recycling of fructose-6-phosphate is mediated by two membrane-bound enzymes: phosphofructokinase (PFK) and fructose-1,6-diphosphatase (FDPase). Allosteric effectors which promote the PFK-FDPase system either increase the regular beating activity or induce bursting discharges, while inhibitory effectors reduce pacemaker activity. Associated with the PFK-FDPase cycle are slow oscillations in membrane potential, the postulate being that changes in amplitude and time period of the waves are brought about by the cyclic fluctuations of H+ ions and ATP in the immediate vicinity of the membrane. Other enzyme reactions which affect the concentrations of gluconeogenic substrates or PFK effectors can modulate the oscillatory driving input, a good example being the neurogenic amino acid glutamate. Modifiers of FDPase and PFK are equally effective in changing pacemaker activity within the intact neuronal network and, hence, the rhythmic body function connected to this network. This has been demonstrated with pacemaker neurones governing cardiovascular activity in Aplysia, blood pressure or heart beat in the cat, and respiration or thermo-regulation in the rabbit. Nature appears to have achieved a functional differentiation between different pacemaker neurones by altering their response to at least one or two of the PFK and FDPase effectors. New periodicities can be entrained by current stimuli on the pre-existing rhythms of isolated Aplysia pacemaker neurones. Stimulus-induced resetting of the discharges is in fact accompanied by a redistribution between two kinetically distinct forms of PFK, and modifiers of this enzyme can stabilize the new periodicities or facilitate the conditioning effect of a stimulus. Memory facilitation and consolidation under PFK modifiers could also be demonstrated in avoidance and discrimination learning trials with honey bees and rats, which are consistent with the metabolic nature of the slow-wave rhythmicity in vertebrate microneurones thought to be the site of memory storage.