bluuebunny/crossref_metadata_2025_split huggingface dataset:
Respiratory Regulation in Ephemera Simulans Walker and Hexagenia Limbata (Serville) (Ephemeroptera)
Authors: Eriksen Clyde H. 
Published: April 2021

ABSTRACT
This study shows that Ephemera simulans and Hexagenia limbata are respiratory regulators and how it is that regulation is attained and maintained. Nymphs, 17-24 mm. in length, were acclimated in the laboratory at 13·0° C. for 24 hr. Oxygen consumption experiments employed the ‘closed-bottle’ technique and several modifications. When studied in bottles containing no substrate, both species appeared to be respiratory adjustors. Using ‘optimal substrates’ and a wide range of oxygen concentrations, both species proved to be respiratory regulators. As the oxygen concentration decreased, respiratory regulation was attained by initiating and increasing a flow of water past the body surfaces by the bailer action of beating gills. The volume passed was proportional to the number of gill beats which, in turn, was influenced by the size of the gills. The larger gills of Hexagenia beat at a slower rate to produce the same current as Ephemera and potentially they were capable of producing a significantly greater current and, hence, could regulate to a lower oxygen concentration.
An Electrophysiological Study of the Anatomical Relations of Two Giant Nerve Cells in Aplysia Depilans
Authors: Hughes G. M. , Tauc L. 
Published: April 2021

ABSTRACT
Histological studies of the central nervous system of invertebrates using methylene-blue and silver-staining techniques, alone or in conjunction with degeneration experiments, have provided a considerable amount of information about neuronal pathways. The use of electrophysiological methods, however, makes it easier to trace the path of individual neurones over long distances and can be especially helpful in invertebrates where the path of an axon is complicated by its passage through the neuropiles. In addition, they may give some insight into the types of functional connexion which exist between neurones.
The Localization of Function in the Root of An Insect Segmental Nerve
Authors: Fielden Ann 
Published: April 2021

ABSTRACT
The roots of the segmental nerves in nymphs of Anax imperator originate from separate dorsal and ventral tracts in the ganglionic neuropile. Axons forming the dorsal part of the nerve root can sometimes be traced to ganglion cells and tend to be large and thick-walled compared with the ventral axons which are smaller and thin-walled. In the roots of the fifth nerves of the last ganglion the two parts can be separated by dissection. Recording from each part under various conditions of stimulation shows that sensory activity occurs predominantly in the ventral part of the nerve root whilst motor spikes are recorded almost entirely from the dorsal part. It is concluded that there is a functional localization of motor and sensory fibres in the root of an insect nerve comparable to that in the dorsal and ventral roots of vertebrate nerves.
Organic Constituents of the Seminal Plasma ofBalanus Balanus
Authors: Barnes H. 
Published: April 2021

ABSTRACTThe seminal plasma of Balanus balanus has been analysed for a number of organic substances including total nitrogen, protein, urea, protein-bound hexose, hexosamine, fucose, ‘sialic acid’, glycogen, and RNA. The material was separated into soluble and insoluble fractions by precipitation with ethanol. A large part of the ethanol-soluble material is inorganic salts and glycine; it contains a small quantity of protein-like material which on hydrolysis yields largely glycine and glutamic acid. The alcohol-precipitated material contains protein, protein-bound hexose, hexosamine, lipids, and RNA. Glycogen, fucose, and ‘sialic acid’ are absent. It is suggested that the plasma contains glycoproteins of a mucoid nature: the absence of both fucose and ‘sialic acid’ suggests that the mucoid may be of a relatively simple character. Attention is drawn to the similarity of this seminal plasma, which is produced in the absence of accessory male organs, to that of higher animals.
Sensitivity of Neurones inAplysiato Temporal Pattern of Arriving Impulses*
Authors: Segundo J. P. , Moore G. P. , Stensaas L. J. , Bullock T. H. 
Published: April 2021

ABSTRACTExperiments were carried out on the isolated ganglia of Aplysia californica to discover whether the precise timing (i.e. the interspike interval distribution and sequence) of a group of spikes entering a neuronal system at a given mean frequency constitutes a variable that is significant in the control of its output. The input consisted of stimulation bursts with different timings but identical mean frequencies applied to one or more afferent trunks. The output (EPSPs or spikes) was monitored with an intracellular micro-electrode placed in the giant cell. Changes in the timing of the input produce definite changes in the magnitude of the output, both in terms of depolarization induced and of spikes evoked. Because of the critical nature of the spike firing threshold, a consistent small increment in depolarization due to favourable timing can be functionally important in the vicinity of the firing level. The following properties contribute to timing-dependence : (i) Temporal summation of successive EPSPs. (ii) Interaction. Each EPSP is characteristically augmented or, more frequently, decreased by those preceding it; linear summation is a special case. The modification in general cannot be predicted from the excitability cycle after one EPSP; interactions between EPSPs of different origins are often irreciprocal; sequence of heterologous inputs is influential, (iii) Post-spike excitability. Responsiveness changes which follow a post-synaptic spike depend on whether it is preceded by others, on their number and timing. Nerve cells were thus found to exhibit a sensitivity to timing that issued from elementary functional attributes. Such sensitivity to timing would be biologically advantageous, especially in areas of sensory convergence, for it provides an additional coding parameter complementing mean frequency modulation. It is still too early to decide whether or not this mechanism is actually important in natural operation, though it appears likely.
Temperature Relationships of the Locomotor Rhythm ofCarcinus
Authors: Naylor E. 
Published: April 2021

ABSTRACTThe locomotor rhythm of Carcinus maenas was shown to be relatively similar at 10°, 15°, 20° and 25° C., but it was shown to be modified by changes in temperature. A fall of about 5 − 10° C. just before the onset of activity usually advanced and enhanced the initial peak of activity, whilst a rise of the same magnitude usually delayed and partly suppressed the initial peak, each without affecting the basic rhythm. A fall in temperature of about 10° C. or more between activity peaks usually initiated transient outbursts of activity, again without affecting the normal rhythm. Chilling to 4° C. for more than 6 hr., irrespective of the time of onset of chilling, resulted in a rephasing of the rhythm with the initial outburst occurring immediately on return to room temperature. In Carcinus from non-tidal docks chilling resulted in a change from the normal approximately nocturnal rhythm to an overt tidal rhythm, but in Carcinus from the virtually tideless Mediterranean the character of the normal nocturnal rhythm was unaffected by chilling.
Transpiration inPodura AquaticaL. (Collembola, Isotomidae) and the Wetting Properties of Its Cuticle
Authors: Noble-Nesbitt J. 
Published: April 2021

ABSTRACTIn the collembolan, Podura aquatica, transpiration through the cuticle is high at all relative humidities. Above 90% relative humidity, cuticular permeability is abnormally high but no adequate explanation of this can be given. Transpiration through the cuticle is high at all temperatures and there is no evidence of a critical temperature over the range 17-29° C. Abrasion increases the transpiration rate, and at least partial recovery occurs within the instar. Moulting fully restores the transpiration rate to the normal level. The hydrofuge nature of the cuticle strongly suggests the presence of an orientated lipid monolayer on its surface. Strong wax solvents render the cuticle wettable, whereas treatment with water under reduced pressure does not. Consideration of the fine structure suggests that the hydrofuge layer is discontinuous and that it occurs on the tips of the minor tubercles. This is compatible with an overall high transpiration rate. The occurrence of hydrophil areas of cuticle is correlated with a smooth cuticular surface. The biological effects of the hydrofuge and hydrophil areas in the life of the insect are discussed.
A Site of Water and Ionic Exchange with the Medium inPodura AquaticaL. (Collembola, Isotomidae)
Authors: Noble-Nesbitt J. 
Published: April 2021

ABSTRACTIn the collembolan Podura aquatica L., uptake of water occurs both via the mouth and across the ventral tube vesicles. Drinking is important in water-stress situations and when the haemolymph pressure is too low for eversion of the vesicles. Everted vesicles alone are sufficient for recovery from partial desiccation. Experiments in which insects with their mouths or ventral tubes blocked were exposed to a medium containing 24Na indicated that most of the exchange of sodium between insect and medium occurred over the ventral tube vesicles, and that this exchange was rapid. In experiments using 42K, no measurable exchange occurred between the insect and the medium.
Studies On the Myoneural Physiology of Echinodermata
Authors: Boltt R. E. , Ewer D. W. 
Published: April 2021

ABSTRACTThe lantern retractor muscle of Parechinus angulosus responds to light stimulation by a rapid contraction which is followed by a slower increase in tension. The details of these contractions vary from preparation to preparation. With very brief light exposures only the quick response is shown, while with prolonged light stimulation rhythmical activity develops after a minute or more. Exposure of a contracting preparation to the light of a mercury vapour lamp causes a slight fall in tone. This is not due to the ultra-violet component of this light. Responses to repeated light pulses may result in simple summation or the response to the first pulse may be markedly greater than those which follow. In preparations which show this latter effect, there is evidence for an inhibitory phenomenon which persists for about 30 sec. With paired stimuli the response to the second stimulus may show an initial depression which reaches a maximum at an interval of about 10 sec., then a recovery and finally a second depression of response which is maximal when the interval between stimuli is about 5 min. There is evidence that stimulation of the comminator muscles may result in loss of tone of the lantern retractor muscles. A provisional hypothesis to explain these effects is presented.
Studies On Crop Function in the Cockroach (Periplaneta AmericanaL.)
Authors: Davey K. G. , Treherne J. E. 
Published: April 2021

ABSTRACTThe structure and mode of action of the proventriculus are described. X-ray photographs have shown that as the crop empties the decrease in volume of the fluid is partially compensated for by the swallowing of air. The effects of various factors upon the rate of crop-emptying have been studied using solutions of different osmotic pressures. Changes in viscosity, effected by the addition of methyl cellulose, produce only a minor reduction in crop-emptying. The frequency of opening of the proventricular valve is not proportional to the rate of crop-emptying over the whole range of concentrations used, and it is assumed that changes in other parameters must affect the process.
Rectal Absorption in the Desert Locust, Schistocerca Gregaria Forskål
Authors: Water I. , Phillips J. E. 
Published: April 2021

ABSTRACT
The histology of the rectum of Schistocerca gregaria is described. A method is described whereby net absorption of water from the rectum (in situ, isolated by ligation) can be measured. Water is actively absorbed from the lumen of the rectum against an osmotic gradient and in the absence of a significant net flux of solute. The maximum osmotic gradient developed is 2-3 times greater in locusts supplied with hypertonic saline than in locusts supplied with tap water. This indicates some ability to regulate water absorption in relation to requirement. The ionic concentration of rectal fluid and the rate of salt absorption from the lumen have little effect on the maximum osmotic gradient developed across the rectal wall. Possible mechanisms of active absorption of water are discussed.
Excretion in the Blood-Sucking Bug, Rhodnius Prolixus Stål: II. The Normal Course of Diuresis and the Effect of Temperature
Authors: Maddrell S. H. P. 
Published: April 2021

ABSTRACT
The course of diuresis in Rhodnius is described and interpreted in terms of the underlying mechanism. The rapid onset of diuresis is attributable to the prompt release of the diuretic hormone into the haemolymph and to an acceleration of the circulation of the haemolymph caused by peristaltic movements of the mid-gut. Diuresis proceeds at a surprisingly constant rate. This is shown to be a reflexion of the fact that the concentration of the diuretic hormone in the haemolymph at this time is always higher than that which causes the maximum response by the Malpighian tubules. The diuretic hormone is quickly destroyed by the activity of the Malpighian tubules and possibly other tissues. Consequently, the extent of diuresis is controlled by the length of time during which diuretic hormone is released into the haemolymph. Excretion is very sensitive to changes in temperature; both the rate of excretion and the composition of the urine are affected.
The Lift-Control Reaction of Flying Locusts
Authors: Gettrup Erik , Wilson Donald Melvin 
Published: April 2021

ABSTRACT
Angle of attack of a distal wing segment was estimated for forewings and hind-wings of locusts during constant lift at different body angles. At the middle of the downstroke the forewing angle of attack remained nearly constant, but the hindwing angle varied with the body angle. The results are consistent with earlier electro-physiological findings and emphasize that the twist parameter does not contribute by equal amounts to the mean wing twisting of the two pairs of wings. A qualitative model of the constant-lift reaction includes a factor for simultaneous correction of body pitch.
Rectal Absorption in the Desert Locust,Schistocerca GregariaForskål: III. The Nature of the Excretory Process*
Authors: Phillips J. E. 
Published: April 2021

ABSTRACTThe physiology of the excretory system and its role in salt and water balance have been studied in the desert locust, Schistocerca gregaria. Collections and analyses were made of hindgut fluid (derived from the Malpighian tubules) and rectal fluid from locusts kept under various dietary régimes. In starved locusts supplied with tap water very little fluid accumulates in the rectum, the output of the Malpighian tubules being almost completely reabsorbed. Relatively more salt than water is reabsorbed with the result that the rectal fluid, attains a lower ionic concentration but higher osmotic pressure than the haemolymph. No fluid is voided. In starved locusts supplied with hypertonic saline the rectum is distended with fluid which has an osmotic pressure and ionic concentration considerably above that of the haemolymph. Very little fluid is voided. Substantial elimination of fluid from the rectum occurs only in fed locusts, in association with the voiding of faeces. These results are discussed in relation to the mechanism of osmotic and ionic regulation.
Some Aspects of Electrolyte Excretion in the Green Turtle, Chelonia Mydas Mydas
Authors: Holmes W. N. , McBean R. L. 
Published: April 2021

ABSTRACT
The ‘salt gland’ appears to be the predominant route of sodium and potassium excretion in the marine turtle Chelonia mydas mydas. The kidney of the marine turtle is probably not capable of maintaining a positive water balance in the face of the electrolyte loads presented by sea water and food. Treatment with amphenone reduced the sodium and potassium excretion of fed and saline-loaded marine turtles. The administration of corticosterone partially corrected this reduction. Thus the excretion of electrolytes by the ‘salt gland ‘appears to be, at least partly, dependent upon a fully functional adrenal cortex. The significance of the ingestion of sea water by marine turtles is discussed in relation to the excretion of the large amount of potassium contained in their food.
Diffusion in Insect Wing Muscle, the Most Active Tissue Known
Authors: Weis-Fogh Torkel 
Published: April 2021

ABSTRACTThe tracheal system of insect wing muscle is so dense that between 10−1 and 10−3 of any cut area is occupied by air tubes. In most cases, air tube diffusion of O2 and CO2 through the muscle is therefore several thousand times quicker than diffusion in the liquid phase. In large insects the primary tracheal supply must be strongly ventilated while diffusion is sufficient in the remaining part of the air tubes, even at the highest metabolic rates encountered in any insect. The tracheoles represent the main site of exchange between the gaseous and the liquid phase while the tracheae are of little significance in this respect. The fibres cannot exceed about 20 μ in diameter unless the tracheoles indent the surface and become ‘internal’. Muscular pumping of air and blood due to shortening is of little importance for the exchange of gases but of major importance for the supply with fuel for combustion. However, the large fibre diameters and the tidal nature of the pumping necessitates a very high concentration of fuel in the haemolymph. The high concentration of trehalose in insect blood is considered to be an essential adaptation to flapping flight. The transport by diffusion of O2 and CO2 was followed in detail in a number of concrete examples in the gaseous as well as in the liquid phase. Within a safety factor of 2–3, the rate of transport was always found to be adequate. There is no reason to suggest other mechanisms than a simple, normal diflfusion.
Locomotory Movements of the Hind Limbs in Rabbits After Isolation of the Lumbosacral Cord
Authors: Cate J. Ten 
Published: April 2021

ABSTRACT
In my earlier experiments with spinal cats (1962) I established that the isolated lumbosacral cord is able to co-ordinate walking movements of the hind limbs. In cats this part of the cord possesses a high degree of autonomy. It seemed interesting to know whether in rabbits the isolated lumbosacral cord is also able to maintain these functions. It was especially important to establish whether the spinal rabbit can carry out the typical jumping movements with hind limbs, which serve, as is well known, in the act of progression in normal conditions.
The Reproductive Biology of the Rabbit Flea Spilopsyllus Cuniculi (Dale) and the Dependence of this Species Upon the Breeding of Its Host
Authors: Mead-Briggs A. R. 
Published: April 2021

ABSTRACT
Unlike any other species of flea which has been cultured successfully Spilopsyllus cuniculi (Dale) is entirely dependent for its own reproduction upon its host becoming pregnant. The ovaries of fleas kept on male or non-pregnant female rabbits remain immature whereas those on a pregnant host are mature at the time of parturition. Vitellogenesis commences at a critical point approximately 7 days pre-partum, irrespective of how long the fleas have been on the host. It is postulated that a factor required by the flea for ovarian development is only available during the final week of pregnancy, and not at all in male or non-pregnant rabbits. The factor disappears from the adult after parturition but is present in her nestlings for at least 7 days. Most fleas desert the adult doe shortly after the young are born and enter her nest, where copulation and oviposition occur. The factor does not act solely as a trigger initiating in the flea developmental processes which then continue in its absence; ovarian regression occurs among maturing fleas transferred to hosts that do not supply the factor. The processes of vitellogenesis, not those of oogenesis, fail in the absence of the factor. It is suggested that the ‘yolk-forming hormone’ normally secreted by the corpus allatum of the adult insect may only be produced by rabbit fleas when they can obtain the postulated factor. Variations in the quantity of this factor available to fleas on different hosts could explain the observed variations in ovarian activity. Some parallels between the factor and steroid hormone levels in the host’s blood are discussed.
Factors Influencing Submergence and the Heart Rate in the Frog
Authors: Jones D. R. , Shelton G. 
Published: April 2021

ABSTRACTThe ability of the frog to remain submerged declines as the oxygen concentration in the water falls or the carbon dioxide content rises. The critical oxygen concentration appears to be about 5 mg./l. and the critical carbon dioxide concentration 100 mg./l. at temperatures around 10° C. Submergence results in a decrease in heart rate which develops over a period of 15-30 min. but which disappears immediately the animal surfaces and breathes. The bradycardia is accentuated by oxygen lack or carbon dioxide excess. During submergence the heart is influenced by two main factors, the shortage of oxygen and the cessation of breathing movements, both of which contribute to the decrease in rate. The former can still affect rate after vagotomy. The connexion between breathing and heart rate is dependent on the nervous system, though the detailed pathway is not worked out.
The Role of Lipid in Adult Development and Flight-Muscle Metabolism in Hyalophora Cecropia*
Authors: Domroese Kenneth A. , Gilbert Lawrence I. 
Published: April 2021

ABSTRACT
Changes in total lipid and R.Q. show that female pupae of H. cecropia begin to catabolize lipid early in adult development. In males there is a conservation of lipid during adult development resulting in the male moth having about three times the lipid content of the female. In the adult moth both sexes utilize lipid as the major energy source. Lipid is the available substrate as well as the preferred substrate in flight-muscle metabolism in male moths. Flight-muscle homogenates show greater oxidative activity with fatty acids and citric acid cycle intermediates than with glucose or glycolytic intermediates, indicating that carbohydrate pathways are not prominent. A fatty acid oxidizing system has been identified in flight muscle which requires ATP, magnesium and a citric acid cycle intermediate for optimum activity. Experiments with radiotracers and metabolic inhibitors reveal that fatty acid oxidation in flight muscle proceeds via the citric acid cycle and the cytochrome chain. Active fatty acid activating enzymes are present in flight muscle, and fatty acid oxidation in H. cecropia is discussed in relation to vertebrate and other invertebrate systems.
Sodium and Chloride Balance in the Prawn, Palaemonetes Varians
Authors: Potts W. T. W. , Parry Gwyneth 
Published: April 2021

ABSTRACT
The exchanges of sodium and bromide (for chloride) ions between the brackish-water prawn Palaemonetes varians and its environment are described. In an isosmotic medium the exchange of sodium and chloride ions takes place by passive diffusion. In full-strength sea water sodium ions are actively removed extrarenally, the potential difference produced by the active extrusion of sodium ions maintaining the chloride ions in passive equilibrium. There is some evidence of an increased flux of ions in hyperosmotic sea water associated with water-swallowing to obtain water for water balance. In 2 % sea water chloride ions are actively absorbed, the potential produced by this active uptake helping to maintain sodium balance ; but some active sodium uptake also occurs. In salinities below 2% uptake of ions declines and the animals can no longer maintain equilibrium.