bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neural Mechanism of Hearing in Insects
Authors: Katsuki Yasuji , Suga Nobuo 
Published: April 2021

ABSTRACT
The frequency response ranges of the tympanal and cereal nerve were measured in ten species belonging to four families, Cicadidae, Acridiidae, Tettigoniidae and Gryllidae. The tympanal organs of Acridiidae and Tettigoniidae responded to ultrasonic waves and the most effective frequency was very high (&gt; 10 kc./s.), while the response ranges of the other two families, Cicadidae and Gryllidae, were within that of man. The response ranges of the cereal nerves (lower) and tympanal nerves (higher) were partly overlapping. Stridulation consisted of pulsatory sounds and had species-specific rhythms, to which the tympanal nerves responded with synchronous discharge. The dominant frequency range involved in stridulation agreed well with the frequency range to which the tympanal organ of the same insect was most sensitive. The threshold of the tympanal nerve varied with different directions of incident sound, especially for ultrasonic waves, indicating the possibility of directional sense. Tympanal neurons of Gampsocleis buergeri were referable to two types having different response ranges. The curves relating number of spikes per second to intensity of stimulus were sigmoid and almost parallel for different frequencies. In Discussion it is pointed out that although no single receptor organ is able to discriminate stimulus frequency, an insect which has different sound receptors on various parts of its body may have some power of discrimination.
Neuronal Pathways and Synaptic Connexions in the Abdominal Cord of the Crayfish*
Authors: Hughes G. M. , Wiersma C. A. G. 
Published: April 2021

ABSTRACT
As material for the study of functional connexions within a central nervous system, invertebrates with ganglionated nerve cords appear to offer advantages absent elsewhere. In such animals it should be possible to lead off from the axons which transmit the information from one synaptic region to another at all levels in the connectives, provided there are no cells or synapses in these connectives. In the crayfish, it has been previously shown that such an analysis is indeed possible, at the level between the ‘brain ‘and the remainder of the ventral cord. It was found (Wiersma, Ripley & Christensen, 1955) that many interneurones respond to stimulation of several segments of the body, usually to stimulation of homologous areas of the individual segments. Three fundamentally different ways in which the inflow to different ganglia may become integrated in this way were suggested by Wiersma (1958), and are illustrated diagrammatically in Fig. 1. To gain further information about the occurrence of these different types, it was desirable to obtain recordings from interneurones at a lower level in the cord where the actual integration takes place. The isolated abdomen preparation proved highly suitable for this purpose. The number of fibres in each connective here is still smaller than that in each circumoesophageal commissure (about 1200 as against about 2000), and it was found possible to obtain from the cord preparations in which unit responses were clearly recognizable with not much more difficulty than from the commissure. Altogether it was possible to account for some 75 definite entities as against 100 in the commissure. In both places some of these are not single fibres but bundles of primary sensory fibres with similar properties. In the cord such bundles are more frequent than in the commissure. The nature and distribution of these entities will be described elsewhere; in the present paper their physiological properties will be discussed with special reference to the evidence they provide for the existence of these three possible types of integration. The results will show that the one in which a single interneurone collects impulses from different ganglia (scheme C of Fig. 1) is certainly realized in many of these interneurones.
The Thickness of Some Insect Epicuticular Wax Layers
Authors: Lockey Kenneth H. 
Published: April 2021

ABSTRACT
The average thickness of the epicuticular wax layers on the wing membranes and elytra of a number of different insects has been measured by relating the volume of extracted wax to the area of cuticle over which it was spread. The true surface area of the epicuticle was measured by krypton adsorption. The ratio of absorption area to apparent projected area was found to be 1·6 for the wing membranes, and 6·7–8·2 for the elytra, with an average value of 4·1. The wax layers were found to be remarkably similar in thickness on the wing membranes, ranging from 0·11 to 0·13 μ but to vary from 0·11 to 1 ·26 μ in the case of elytra, where the wax thickness appears to be related to extent of modification.
The Development of Salinity Tolerance in the Salmon, Salmo Salar (L.) and Some Related Species
Authors: Parry Gwyneth 
Published: April 2021

ABSTRACT
A study has been made of the survival and osmotic regulation of young salmonid fishes following transfer from fresh water to various dilutions of sea water Survival is in the order: and is generally better the larger the fish. The survival pattern of alevins differs from that of the older stages. Hypo-osmotic regulation is first seen in parr and becomes fully effective in smolts.
The Determination of Total Carbon Dioxide in Water
Authors: Milburn T. R. , Beadle L. C. 
Published: April 2021

ABSTRACT
The method described involves extraction of the dissolved gas from an acidified sample in a modified van Slyke apparatus, and measurement of the electrical. resistance of a standard sodium hydroxide solution before and after equilibration with the extracted gas. The original sample must be not less than about 30 ml. for which a 10 ml., sample is drawn into the extraction apparatus. There is a linear relation between the resistance finally measured and the total carbon dioxide content of the original sample up to a maximum determined by the strength of the standard hydroxide solution, which is thus adjusted to the desired range of carbon dioxide concentration, e.g. 0 ·005 N-NaOH for 0 –50 mg./L and 0 ·02 N for 0 –200 mg./l. CO2. The method is easily sensitive to 0 ·3 mg./l. in the range 0 –50 mg./l. total carbon dioxide and about 1 mg./l. in the range 0 –200 mg./l. With a rigidly standardized procedure increased accuracy was obtained so that replicate determinations, on standard solutions in the 0 –50 mg./l. range did not differ by more than 0 ·16 mg./l. Precautions for handling samples containing carbon dioxide in solution prior to determination have been suggested. About 15 –20 min. are required for each determination and to Mrs D. E..
A Cineradiographic Study of Respiration inMyxine GlutinosaL
Authors: Johansen Kjell , Hol Ragnar 
Published: April 2021

ABSTRACTThe anatomy of the respiratory organs, as well as the mechanism of breathing in myxinoids, is distinctly different from that in all other fish-type craniotes even including the petromyzonts. In Myxine the branchial gill lamellae are enclosed in rounded sac-like pouches, with ducts conveying the water from the oesophagus to the gills from which it travels through efferent ducts uniting on each side, finally leaving the animal through paired branchial apertures. In addition to the paired gill pouches there exists an oesophago-cutaneous duct connecting the pharynx to the exterior behind the left, last gill sac. The exterior opening is confluent with the left gill pore. Regarding the course of the respiratory current in this system contradictory explanations have been presented. More recent authors seem, however, to agree upon the concept that the water current is solely dependent upon the pulsating activity of the velum and is not influenced actively by either the gill pouches or their ducts (Gustafson, 1935; Strahan, 1958; Marinelli, 1956). The velum and its connected muscles, which is a unique structure in myxinoids, was already anatomically described by Müller in his Myxine monograph (1835) and later by Fürbringer (1875) and Cole (1907). The first two authors, however, did not contemplate the velum as being of any functional value for respiration. Cole, on the other hand, suggested a role for this structure in the maintenance of the respiratory current. Goodrich (1930) has advocated that breathing in Myxine takes place by expansion and contraction of the muscular elements in the gill sacs. That the gill sacs in Myxine contain distinctly striated muscular elements has been described by Cole (1912) and later by Goodrich (1930) and Hofbauer (1937). It seems obvious, upon reviewing the literature, that the physiological interpretations of this problem in earlier works are mostly founded on anatomical studies with little or no physiological experimentation. The excellent works of Gustafson (1935) and Strahan (1958) base their functional interpretations entirely upon external observations of the living animal or upon dropping coloured solution in the respiratory water and following its course into the nostril and out of the branchial apertures. The present study attempts to analyse the mechanics of respiration in Myxine by utilizing modern cineradiographic equipment which allows fluoroscopic examination of all events inside the respiratory passages; these may be recorded on a camera at 26 frames per second. The method has been used earlier for the study of the circulation in snakes (Johansen & Hol, 1960) and of the central circulation in Myxine (Hol & Johansen, 1960).
Proprioception and Visual Discrimination of Orientation in Octopus
Authors: Wells M. J. 
Published: April 2021

ABSTRACT
Twenty-two small octopuses were trained to make visual discriminations before and after removal of the statocysts. Removal of one statocyst (left or right) did not affect performance in a visual discrimination of rectangles shown horizontally and vertically (8 experiments), nor did it determine which eye was used to guide attacks upon things seen (a record of this was kept in four of the experiments). Removal of both statocysts did not affect performance in a discrimination between black and white circles (7 animals) but did destroy the capacity to discriminate successfully between rectangles shown horizontally and vertically (11 animals). After removal of both statocysts the orientation of the retina (as indicated by the slit-like pupils) is no longer constant over the normal wide range of bodily positions, but depends upon how the animal is sitting on the side or bottom of its tank. An analysis of the postoperational responses of animals trained to make the orientation discrimination showed that nearly all of them were biased in favour of one or other of the test figures, not always that used as ‘positive’ figure during preoperational training. The postoperational scores of these trained animals depended mainly upon the positions in which they habitually sat in their tanks; ndividuals in positions such that the retina of the eye used to observe the test figures lay at right angles to the position held during pretraining tended to behave perversely. These results indicate that orientation discrimination is dependent upon correct orientation of the retina, rather than upon central integration of proprioceptive and visual information. This is discussed in relation to a possible mechanism of visual discrimination proposed by Sutherland (1957), and in relation to what is already known about the role of proprioceptive information in learning.
The Nutrition of the Central Nervous System in the Cockroach Periplaneta Americana L
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
The organs and tissues of insects are mostly composed of single layers of cells separated from the circulating blood by thin connective tissue membranes (Wigglesworth, 1956a; Pipa & Cook, 1958). The supply of nutrients to such organs presents no problem. But the central nervous system is an exception. The ganglia are the only solid organs in the insect body. They consist of densely packed peripheral cells surrounding a central neuropile, the whole ganglion being covered by a tough fibrous sheath or neural lamella continuous with the connective tissue membranes elsewhere. The total thickness of the ganglion may be 1 mm. or more.
The Physical Basis of Astro-Navigation in Birds: Theoretical Considerations
Authors: Pennycuick C. J. 
Published: April 2021

ABSTRACT
Matthews’s hypothesis of sun navigation in its original form is rejected on the grounds of physical impossibility of making one of the measurements, and an invalid assumption in the reasoning. It is suggested that the bird should measure the sun’s altitude and rate of change of altitude. The position lines corresponding to these quantities are discussed, and the way in which birds might make and use such observations is considered. The sensory performance required is shown to be reasonable. The magnitude and direction of the errors of position resulting from various sorts of errors of observation are discussed in relation to the experimental evidence. Suggestions are put forward for future experiments.
Studies on the Exchange and Regulation of Sodium in the Larva of Aedes Aegypti (L.)
Authors: Stobbart R. H. 
Published: April 2021

ABSTRACT
The net transport of sodium into the haemolymph by sodium-deficient 4th-instar larvae of Aëdes aegypti (L.) has been studied by means of flame photometry. The fluxes associated with this net transport have been studied by means of 22Na. The net transport is much more rapid in fed larvae (rate about 50 mM./l./hr.) than in starved larvae (rate about 10 mM./l./hr.). The fluxes are also much greater in the fed larvae. The fluxes associated with net transport in fed and starved larvae are much greater (initially at any rate) than the fluxes occurring in normal fed and starved larvae during steady-state exchange. In both fed and starved larvae almost all the net transport and the fluxes associated with it occur through the anal papillae, so these organs must be responsible for almost all the difference between fed and starved larvae in the rate of net transport and fluxes. Cytological changes in the anal papillae following upon feeding and starvation are described. The results are discussed in terms of possible carrier mechanisms in the anal papillae.
Aspects of Flight Mechanics in Anisopterous Dragonflies
Authors: Neville A. C. 
Published: April 2021

ABSTRACT
Movements of the wings and pterothorax of Aeshna spp. have been studied by stroboscopic observation combined with the cutting of certain muscles. There is a constant phase difference between the contractions of the mesothoracic and metathoracic flight muscles, and a resulting phase difference between the movements of the wing-base sclerites and wings in the two pterothoracic segments. As the wings in each segment move upwards and backwards, the respective notal sclerites are moving forwards and downwards. Conversely, as the wings beat forwards and downwards, the nota move backwards and upwards. The anterior coxoalar elevator muscle pulls on the anterior lobe of the lateroprescutum and so, via the membrane on the posterior edge of the humeral complex. This causes extensive supination of the wing, important in hovering and backward flight, and is due to a sudden snap-like separation of the humeral and axillary complexes about a fine of weakness between them when the descending wing is at io° from its lowest position. Both remotion at the end of the downstroke, and the complex propeller-like supinated wing section which develops during the last 10° of the downstroke and most of the upstroke, are made possible by the line of weakness running along the membrane between the two complexes. Comparison of manipulated wingstrokes with normal wingstrokes showed that supination is actively controlled in the flying insect by muscular contraction. Scutal ascension, described in the paper, was detected. At any point on the downstroke, the scuta occupy higher and more posterior positions than they do at the corresponding point on the upstroke. Fore and aft movements of the nota are greater during flapping flight at low wingbeat frequency, than during full flight at higher wingbeat frequency. The prescutum, scutum and scutellum move together as a unit up and down and fore and aft, throughout the wingstroke cycle. Supination during the last 10° of the downstroke and the first half of the upstroke is due to the anterior coxoalar muscle, and during the second half of the upstroke to the third subalar muscle. Downstroke pronation/supination balance is controlled by the basalars and second subalar. A detailed summary of these rotation balances is given in the discussion. The oblique intersegmental muscle of the metathorax is shown to be an abdomen elevator and not a wing depressor. The functions of the various flight muscles are demonstrated experimentally for the first time. The anterior coxoalar muscle is shown to be specialized, functioning in elevation and supination and assisting remotion.
The Effects of Ions and Drugs on Neuromuscular Preparations of Sea Anemones
Authors: Ross D. M. 
Published: April 2021

ABSTRACT
Isolated preparations of the columns of Calliactis and Metridium take up a basic extended length and show repeated contractions at intervals of a few minutes to half an hour. The preparations respond to stimuli with slow movements whose latencies range from about 20 sec. to 2 min. Direct contractions and higher tonus of the preparations are caused by excess K.+ and by Mg2+-free sea water; excess-Ca2+ raises tone slightly. Activity is greatly enhanced by Mg2+-free water, and moderately enhanced by excess K+ and excess Ca2+. It is abolished by excess Mg2+ and Ca2+-free sea water, but not by sea water free of both Ca2+ and Mg2+. In K+-free sea water and in Na+-free sea water activity declines slowly and responses to stimuli still occur for at least 1 hr. Except for some enhancement by excess Ca2+ and the depression with excess Mg2+ and Ca2+-free sea water, responses to stimuli are not much affected by ions. Acetylcholine and associated drugs, and also histamine, 5-hydroxytryptamine, and many other substances, have no significant effects on the tone, activity, or responses of column preparations. Adrenaline raises tonus at a concentration of 1 × 10-6; at 1 × 10-5 and above; it causes direct contractions, enhanced activity and high tonus, but it has no effect on responses to stimuli. Noradrenaline, dopamine, tyramine, and other related compounds, as well as various adrenergic blocking agents, are totally inactive. Tryptamine, at concentrations of 1 × 10-4, causes direct contractions, high tonus and enhanced responses to stimulation. 5-Methoxytryptamine has similar effects. To be effective, treatments must be applied directly to the contractile part of the preparation. Applying the active ions and drugs to attached strips of column has no effect. Some comparative and functional aspects of the results are discussed.
The Distribution and Exchange of Some Ions and Molecules in the Central Nervous System ofPeriplaneta AmericanaL.
Authors: Treherne J. E. 
Published: April 2021

ABSTRACTThe rapidly exchanging 24Na fraction was found to account for approximately a third of the sodium contained in desheathed terminal abdominal ganglia which had been previously made radioactive by the injection of labelled ions into the haemolymph. This rapidly exchanging sodium was associated with the extracellular spaces which, with the aid of 14C-inulin, were shown to contain 18·2 % of the ganglion water. Using this figure it was possible to calculate that the extracellular sodium concentration exceeded that in the haemolymph by a factor of 1·8 and was 2·5 times greater than that in the cellular fraction of the ganglion. Experiments using 22Na, 42K, 45Ca, 36Cl and 3H0H showed that the concentrations of the ions in the rapidly exchanging extracellular fractions of isolated abdominal nerve cords were different from those of the external medium. The three cations were maintained at considerably higher concentrations in the extracellular spaces, chloride ions being present at a much lower concentration than in the external solution. It was concluded that the ions were distributed between the extracellular spaces and the external solution according to a Donnan equilibrium. The evidence would seem to indicate that a significant proportion of the free anion groups in the extracellular spaces may be those of protein molecules in solution. An appreciable portion of the cations may also, however, be associated with the free anion groups of structural elements such as collagen and mucopolysaccharides. It is suggested that the relatively rapid depolarization observed in desheathed preparations, as compared with intact nerves, in conditions of high external potassium concentration may result from the effects of the disruption of the Donnan equilibrium as well as to any properties of the nerve sheath as a diffusion barrier. It was shown that because of their positive charges the diffusion of the cations in the extracellular spaces occurred more slowly than would be expected on the basis of their free-diffusion constants. The efflux of 14C-inulin also occurred more slowly than would be expected from its free diffusion, an effect probably caused by the passage of the polysaccharide molecules through relatively small spaces in the extracellular system.
Pharyngeal Proprioceptors in the Dogfish Squalus Acanthias L.
Authors: Satchell G. H. , Way H. K. 
Published: April 2021

ABSTRACT
Hughes (1960) described the respiratory cycle of Scyliorhinus as commencing with a contraction of the oro-and para-branchial cavities; this phase occupies about one quarter of a cycle and is succeeded by an expansion of these cavities which is rapid at first and terminates in a pause before the next respiration. A similar series of events occurs in the dogfish Squalus acanthias L.