bluuebunny/crossref_metadata_2025 huggingface dataset:
The Growth of Blackbeetles and of Cockroaches on Artificial and on Incomplete Diets. Part I
Authors: Żabiński Jan
Published: April 2021

The normal development cycle at 25 ° of the blackbeetle lasts about 12 months, that of the cockroach about 3 months, so that in comparing the velocity of growth of these insects the ratio 4 : 1 may be taken (1 month is equivalent to 1 week). During approximately one-third of these periods the insects grow equally rapidly on synthetic as on normal diets. The entire development cycle of the blackbeetle could not be completed on a synthetic diet. The larvae attain barely one-third of the normal weight during the normal post-embryonic development period, after which they die, without, however, losing weight to any great extent. Blackbeetle larvae put on synthetic diets half-way through the growth period can attain sexual maturity. The cockroach is able to complete its entire development cycle on a synthetic diet, even when the only nitrogenous constituent is glycine. The symptoms of avitaminosis, which appear after the above-stated time, are lack of mobility, the appearance of a matt surface of the chitin envelope; should sexual maturity be attained, small dimensions and infertility are characteristic symptoms. Ovalbumin may be replaced by biologically deficient proteins such as gelatin, or even by glycine, without in any way affecting the character of growth. By diminishing the percentage nitrogen content in diets the rate of growth is distinctly diminished, but at the same time the period of its duration is prolonged. Blackbeetles and cockroaches are exceptionally resistant to the absence of nitrogenous constituents in their food, being able to maintain their body-weight over periods of time equal in length to that of the entire normal post-embryonic cycle. Even after prolonged inhibition of growth, the administration of a normal diet allows these animals to resume growth and attain sexual maturity, including the production of normal young. The rate of growth of insects which have been given normal food after long periods of inhibition of growth is independent of the actual age of the inSect, and corresponds to that which the animal possessed at the commencement of the period of inhibition. These insects do not survive long if fed upon exclusively protein diets, in the absence of carbohydrates. The addition of small quantities of butter, yeast, or vitamin B extracts to synthetic and complete diets does not lead to any enhancement of growth.
A Study of the Afferent Pathways of the Dragonfly Lateral Ocellus From Extracellularly Recorded Spike Discharges
Authors: Rosser B. L.
Published: April 2021

The lateral ocellar nerve of adult dragonflies contains at least two kinds of afferent nerve fibres: the ‘giant’ afferent and small afferents. Efferent fibres are also present, but are not described here. The afferent fibres and receptor axons were studied by extracellular recording of their spike discharges. Experiments using light and electrical (D.C.) stimulation and the application of magnesium were performed. Responses of the giant afferent were analysed into a number of exponential components. The number could be altered experimentally. The giant afferent shows the phenomenon of ‘delayed response’, a delayed onset of the off-response to brief light stimuli. A qualitative model for delayed responses, incorporating the exponential components, is described. It is concluded that the small afferents behave in accordance with Ruck ‘s model of ocellar of functioning but that the giant afferent does not. It is proposed that inhibion in the giant afferent fibre is produced electrotonically, but there may be a synaptic contribution also."
Quantitative Analysis of the Speed of Snakes as A Function of Peg Spacing
Authors: Bennet S. , McConnell T. , Trubatch S. L.
Published: April 2021

The speed of snakes moving by lateral undulation was measured on a smooth board studded with equally spaced pegs arranged in a hexagonal pattern. For some snakes speed was drastically reduced (by as much as 50%) as the ratio of body length to peg spacing was reduced from values as high as twelve to values near or below three. Speed is also influenced by the relative orientation of the pegs contacted by the moving snake. Snakes which can sidewind use this ability to maintain a constant speed when the number of contact points available is insufficient for continuous lateral undulation."
Urinary Bladder Volume and the Reabsorption of Water from the Urine of Crabs
Authors: Riegel J. A. , Lockwood A. P. M. , Norfolk J. R. W. , Bulleid N. C. , Taylor P. A.
Published: April 2021

Measurements have been made to determine the blood volume, bladder volume, clearance of 131I-sodium diatrizoate and U/H for diatrizoate in the crabs Carcinus maenas and Macropipus (Portunus) depurator. Observed values of clearance blood volume and bladder volume in the two species at 18 °C were: Clearance (as % blood volume per day), Macropipus 56.1±14.5; Carcinus 27.1±5.8; Blood volume (as % body weight), Macropipus 21.0±4.0; Carcinus 19.2±3.0; Bladder volume (as % blood volume), Macropipus 12.1 ±5.0; Carcinus 11.0±8.0. It is shown that the measured U/H differs from that to be expected if no reabsorption of water or secretion of diatrizoate occurs. 14C-inulin and 51Cr-EDTA are excreted in an essentially similar manner to 131I-diatrizoate by Carcinus, implying that any active secretion of diatrizoate must be small in magnitude. Injections of ethacrynic acid decrease the U/H ratio for diatrizoate relative to that in control Carcinus injected with sea water. In some Carcinus the concentration of diatrizoate in the urine comes to exceed that initially present in the blood. Both these points are taken, with 3, as support for the conclusion that water can be withdrawn from the primary urine of Carcinus.
Attachment of Giardia - A Hydrodynamic Model Based on Flagellar Activity
Authors: Holberton D. V.
Published: April 2021

The attachment of Giardia trophozoites can be modelled by viscous-flow equations demonstrating that a suction pressure arises from the viscous stress of a fluid flow led beneath the cell by flagellar activity. Changing fluid velocity is less significant in generating suction. Over the range of flagellar wave parameters observed from cells attached to glass, suction pressure may reach io2 dynes cm-2. Expressions for the bending of a thick disc under normal load allow an estimate of suction pressure in situ from its deforming effect on the gut-cell cortex. Allowing for alternative boundary states, calculations suggest that suction pressures close to 102 dynes cm-2 account for the deformations measured from electron micrographs. The shape assumed by a ventro-lateral flange determines the magnitude of the developed suction pressure and may constitute a control mechanism of attachment and detachment.
A Critical Examination of the Physical and Adrenergic Factors Affecting Blood Flow Through the Gills of the Rainbow Trout
Authors: Wood Chris M.
Published: April 2021

Perfusion of the whole gill of Salmo gairdneri with a Newtonian medium under different afferent and efferent pressures has revealed considerable passive distensibility in the branchial vasculature. A capacity for autoregulation may exist. Changes in dorsal aortic pressure are relatively more effective than changes in ventral aortic pressure in altering branchial vascular resistance. Measurements of changes in vascular tone in the gills determined as the ratio of resistances in the experimental and the control states at one point on the pressure differential/flow profile can be extrapolated to the rest of the profile when the comparisons have been made at the same flow. True catecholamines cause a maximum 60 % decrease in vascular resistance (at the same flow) by stimulation of β1-adrenergic receptors in the gills. Branchial dimensions and perfusate viscosities have been measured and, together with the pressure differential/flow data, have been used to evaluate the Muir-Brown model of vascular resistance in the teleost gill. The model, with some limitations, fits the present data and suggests that both active and passive resistance changes are best explained by alterations in the number of secondary lamellae perfused.
A Study of the Malpighian Tubules of the Pill Millipede, Glomeris Marginata (Villers)
Authors: Farquharson Patricia Anne
Published: April 2021

Isolated Malpighian tubules of Glomeris produce fluid which is identical to the bathing media with respect to ion concentrations and osmotic pressure. The tubules secrete normally in a potassium-free Ringer, but they cease to function in a sodium-free Ringer. The rate of fluid production is dependent on the availability of sodium ions, but it is also inhibited by higher concentrations (25 mM/1) of potassium ions. Throughout a wide variation in concentrations of sodium and potassium ions in the bathing Ringer, the concentrations of these ions in the tubule fluid are the same as their concentrations in the Ringer. Fluid production by the tubules of Glomeris is inhibited by ouabain at a concentration of 5 × 10−6 M/1 or greater. The rate of fluid production varies inversely with the osmotic pressure, and the secreted fluid remains approximately isosmotic to the bathing media. No electrical potential difference could be recorded across the tubule wall.
A Study of the Malpighian Tubules of the Pill Millipede, Glomeris Marginata (Villers)
Authors: Farquharson Patricia Anne
Published: April 2021

Tubule fluid:medium ratios (TF/M) have been measured for inulin, glucose, LMWD and HMWD. These TF/M ratios were surprisingly high. The tubule appears to act as a molecular filter; that is to say, molecules move through the tubule wall in inverse relation to their size. This is best illustrated using polyvinyl pyrrolidone as a tracer. The molecular size distribution of PVP fractions present in tubule fluid differs markedly from the molecular size distribution of PVP in the bathing Ringer. No correlation can be made between the inulin and glucose TF/M and the rate of fluid production. However, the inverse relationship between TF/M and rate of fluid production for dextrans indicates a molecular sieving effect. The significance of these results is discussed with reference to models of fluid transport.
The Effect of Low-Calcium Sea Water and Actinomycin-D on the Sodium Metabolism of Fundulus Kansae*
Authors: Fleming Warren R. , Nichols James , Potts W. T. W.
Published: April 2021

Transfer of Fundulus kansae from 80% sea water to a low-calcium water containing 0·4 mm/1 Ca2+ caused a sharp rise in sodium efflux and a change in the kinetic pattern of efflux. A transient drop in whole-body sodium levels occurred within 1·2 days after transfer. Both sodium and potassium levels were normal after 9 days exposure to low-calcium saline. Transfer into low-calcium sea water increased the rate of incorporation of radio-phosphorus into gill RNA. Actinomycin-D blocked the stimulation of sodium turnover after transfer into low-calcium sea water. It did not affect the whole-body sodium or potassium levels of long-term sea-water adapted animals. Actinomycin-D reduced the sodium efflux of short-term sea-water adapted animals regardless of the environmental calcium concentration. The antibiotic also upset the balance of sodium fluxes in those animals held in low-calcium sea water. It is suggested that in addition to the generalized effect of calcium on perme-ability to monovalent ions and water, calcium serves to inhibit some of the synthetic processes involved in regulating sodium metabolism, and also serves to stabilize the metabolic machinery already present.
The Water Balance of a Serpulid Polychaete, Mercierella Enigmatica (Fauvel)
Authors: Skaer Helen Le B.
Published: April 2021

The serpulid polychaete Mercierella enigmática is found naturally in a wide range of salinities – from fresh water to 150% sea water (< 1–55‰, < 25·8–1421 mOsm). Changes in body weight, blood volume and blood osmolality have been measured both during and after equilibration of animals with media of altered salinity. The blood remains similar in osmolality to the external medium over a very wide range of salinity (43–1620 mOsm); osmoregulation occurs only at the lowest limit of the natural range. Mercierella enigmática shows volume regulation; after 4 days of equilibration with a medium of altered salinity the blood volume shows much less change than the blood concentration. During equilibration there appear to be passive movements of both water and salts between the animals and their environment.
The Water Balance of a Serpulid Polychaete, Mercierella Enigmatica (Fauvel)
Authors: Skaer Helen Le B.
Published: April 2021

Mercierella enigmatica, a serpulid polychaete, lives in water ranging in concentration from fresh water to 150% sea water (< 1–55 ‰). The concentrations of five inorganic ions (Na+, K+, Ca2+, Mg2+ and Cl−) in the blood have been measured both during and after equilibration of the animals with media of altered salinity. The concentrations of calcium and potassium have also been measured in filtrates of the blood from animals equilibrated in three media of differing salinity. Concentrations of all the ions measured vary linearly with the concentration of the external medium. The levels of sodium, calcium (in filtered blood) and chloride are near the isionic line, while those of magnesium and potassium (even in filtered blood) are slightly higher in the blood over the whole range.
Physiology of Insect Rhythms
Authors: Truman James W. , Riddiford Lynn M.
Published: April 2021

The moulting process of insects is governed by the interaction of three hormones: prothoracicotropic hormone (PTTH), juvenile hormone, and ecdysone (see Doane, 1973; Wyatt, 1972; Wigglesworth, 1971 for recent reviews). To initiate the moult the brain releases PTTH which causes the secretion of ecdysone from the prothoracic glands. Ecdysone in turn triggers the detachment of the epidermis from the old cuticle and the subsequent secretion of the new cuticle. Whether this new cuticle is larval, pupal, or adult depends on the titre of juvenile hormone at the time of ecdysone secretion.
The Nervous Control of Autotomy in Carcinus Maenas
Authors: McVean Alistair
Published: April 2021

The musculature which operates the coxopodite and basi-ischiopodite of the fifth limbs of the common shore crab has been described. A comparison between the basi-ischiopodite depressor and anterior levator has shown that the levator muscle has a large reserve with which it effects limb severance at autotomy. Recordings from the nerve to the anterior levator muscle show that it is innervated by a tonic and phasic unit together with another, large spiking unit, which is activated at autotomy. Transverse sections of the nerve to the anterior levator show that it contains giant axons. Intracellular recordings from the anterior levator together with whole muscle tension confirm that there are three motor neurones, which produce a slow, fast and ‘giant twitch ‘response in the muscle.
Response Modification by the Central Flight Oscillator of Locusts
Authors: Camhi Jeffrey M. , Hinkle Maija
Published: April 2021

Flying locusts respond to changes in wind-velocity or wind-angle with abdomen posturing in the vertical or horizontal plane, respectively. Receptor hairs on the head sense these wind parameters and evoke the responses in specific abdominal muscles. Records were made from individually identifiable motoneurones to these muscles during the performance of wind-evoked behaviour. During flight these motoneurones are excited by the central flight oscillator and show a burst rhythm at flight frequency. Wind stimuli modulate the number of spikes per burst in this rhythm, but do not affect its frequency or phase with respect to the wingbeat. Changes in wind-velocity and wind-angle evoke different relationships of muscle synergy and antagonism, resulting in the two different patterns of behaviour performed by the same group of muscles. During flightless periods the motoneurones show no flight rhythm, but only the much lower frequency ventilatory rhythm. At these times they are unresponsive to wind stimuli.
Effects of Pressure and Temperature Changes On the Flagellar Movement of Crithidia Oncopelti
Authors: Coakley C. J. , Holwill M. E. J.
Published: April 2021

The combined effects of hydrostatic pressure and temperature on the flagellar movements of Crithidia oncopelti were studied. Provided that a critical pressure, which depended on the temperature, was not exceeded, the application of pressure produced an initial increase in flagellar frequency ; the frequency then fell to a steady level which was below the value obtaining before the application of pressure. The compression also caused a transient increase in the number of organisms propagating coherent waves, an increase in the average wave amplitude, and asymmetric waveforms with decreasing wavelength and amplitude towards the flagellum tip. The results are consistent with the hypotheses that the observed flagellar response is due to (a) changes in the equilibrium of a reversible enzyme denaturation process, and (b) changes in the rate of decomposition of an enzyme–substrate complex. Values of the volume, enthalpy and entropy changes associated with each process are derived and their significance for mechanism is discussed.
Electrophysiology of the Giant Nerve Cell Bodies of Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)
Authors: Sattelle D. B.
Published: April 2021

A mean resting potential of − 53·3 (S.D.± 2·7) mV has been obtained for 23 neurones of the parietal and visceral ganglia of Limnaea stagnalis (L.). Changes in the resting potential of between 28 and 43 mV accompany tenfold changes in [K+0]. A modified constant-field equation accounts for the behaviour of most cells over the range of external potassium concentrations from 0·5 to 10·0 mM/1. Mean values have been estimated for [K+1], 56·2 (S.D.±9·O) mM/1 and PNa/PK, 0·117 (S.D. ±0·028). Investigations on the ionic basis of action potential generation have revealed two cell types which can be distinguished according to the behaviour of their action potentials in sodium-free Ringer. Sodium-sensitive cells are unable to support action potentials for more than 8−10 min in the absence of sodium. Sodium slopes of between 29 and 37 mV per decade change in [Na+0] have been found for these cells. Tetro-dotoxin (5 × 10−5 M) usually blocks action potentials in these neurones. Calcium-free Ringer produces a marked reduction in the overshoot potential and calcium slopes of about 18 mV per decade change in [Ca2+0] are found. Manganous chloride only partially reduces the action potential overshoot in these cells at concentrations of 10 HIM/I. Sodium-insensitive neurones maintain action potentials in the absence of external sodium. Stimulation only slightly reduces the amplitude of the action potential under these conditions and such cells are readily accessible to potassium ions in the bathing medium. A calcium-slope of 29 mV per decade change in [Ca2+0] has been observed in these cells in the absence of external sodium. It is concluded that both sodium and calcium ions can be involved in the generation of the action potential in neurones of Limnaea stagnalis, their relative contribution varying in different cells.
The Initiation and Conduction of Action Potentials in the Optic Nerve of Tritonia
Authors: Chase Ronald
Published: April 2021

As noted in the preceding article (Chase, 1974), an optic nerve origin for photoreceptor spikes in the mollusc Tritonia diomedia is indicated by the small size and frequent absence of somatic action potentials. Axonal trigger sites are the rule for invertebrate ganglion cells (Tauc, 1962) and most peripheral sensory neurones (Edwards & Ottoson, 1958), but there are exceptions (Mellon & Kennedy, 1964) and the issue has not been well investigated in molluscan sensory neurones. Recently Alkon & Fuortes (1972) found evidence for axonal spike initiation in photoreceptors of the nudibranch Hermissenda. In Tritonia, also a nudibranch, the receptor fibres are several millimetres longer than in Hermissenda, and the optic nerve itself, apparently composed exclusively of these fibres, measures about 2·0 mm. These experiments take advantage of the long optic nerve in Tritonia to examine in detail the origin of photoreceptor spikes.
L-Glutamate in Arthropod Blood Plasma: Physiological Implications
Authors: Murdock Larry L. , Chapman Grace Y.
Published: April 2021

The L-glutamate concentration in blood plasma of the crayfish, Astacus lepto-dactylus and A. astacus, was found to be about 1·5 ×10−6M, as measured by a specific enzymatic method. Even 10 times this concentration of L-glutamate in saline failed to significantly affect neuromuscular transmission in the dactyl abductor muscle, although higher concentrations caused depression. L-Glutamate in the blood plasma of the spider, Dugesiella hentzii, amounted to 7 × 10−6M. As in the crayfish, even 10 times this concentration of L-glutamate in saline failed to affect neuromuscular transmission in the promotor tibiae muscle, while higher concentrations caused depression. The concentration of L-glutamate in Locusta migratoria blood plasma, ca. 7 ×10−6M, would appear to be sufficient to cause depression of neuromuscular transmission in vivo. Perfusion of the extensor tibiae preparation with 15 ×10−6ML-gluta-mate caused marked depolarization and decreases in the size of e.j.p.s. It appears that in the tarantula and the crayfish, blood plasma L-glutamate does not pose difficulties for neuromuscular transmission. In the locust, additional protective mechanisms which are not able to function in the saline-perfused in vitro preparation must be at work in the living animal.
The Physiology of the Tettigoniid Ear
Authors: Lewis D. B.
Published: April 2021

The acoustic opening of the large, double prothoracic spiracle gives rise to a vesicula and a trachea which descends into the leg and divides to form the anterior and posterior tympanal air spaces, their apposed walls forming the secondary tympanal membrane. This trachea is independent of the respiratory system. The trachea is exponential or catenoidal in form in the Tettigoniids investigated, and the physics of horns is discussed in relation to the tracheal system. Bilateral recordings from the tympanal nerves have shown that blocking the spiracular opening eliminates the response to a sound signal at an intensity of 45 dB. Unilateral recordings during the blocking and reopening of both the spiracle and the tympanal slits has shown that at a sound intensity of 47·5 dB a response is obtained from the tympanal organ only when the sound is directed at an open spiracle; blocking the spiracle eliminates the response. Threshold curves for the ‘spiracle’ and for the ‘tympanal slits’ show a sensitivity difference of between 2 dB and 25 dB, the difference varying with frequency. The implications of this finding are discussed.
GAS EXCHANGES AND BLOOD GAS CONCENTRATIONS IN THE FORG RANA RIDIBUNDA
Authors: Emílio M. G.
Published: April 2021

The respiratory exchanges through the lungs and skin of frogs and the time courses of blood gas concentrations were studied during emergence and diving periods. Most of the total oxygen uptake is carried out through the lungs. The partial pressure of oxygen in arterial blood falls to very low levels a few minutes after diving, showing that the cutaneous respiratory surface cannot compensate for the lack of lung respiration. Most of the metabolic carbon dioxide is disposed of through the skin. Although the skin output is maintained through diving periods, there is an important rise in the partial pressure of carbon dioxide in blood following submergence. However, the total concentration of CO2 in the blood decreases, as does the blood pH value. This phenomenon is probably the result of a metabolic acidosis due to the switching on of anaerobic processes during diving periods.
Directional Differences in the Colour Sensitivity of Daphnia Magna
Authors: Young Stephen
Published: April 2021

The Daphnia compound eye movements can be driven by a flashing light. The action spectrum for the threshold light intensity required to evoke this response depends on the orientation of the stimulus light beam with respect to the animal. If the light falls on the eye through the top of the animal’s head the action spectrum peaks at the low wavelength end of the spectrum, while if it falls on the eye through the side of the head the peak is in the yellow-green. Eye movements cannot be evoked by illuminating any part of the animal except the compound eye so neither of these action spectra is due to a light receptor other than the compound eye. Some anomalous action spectra in the literature on the behaviour of free-swimming Daphnia are accounted for.
Calcium Balance at the Postmoult Stage of the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Greenaway Peter
Published: April 2021

Net uptake of calcium by Austropotamobius begins 15–30 min after the moult and rapidly reaches a maximum level (2 μmoles/g/h at 10°C) which is maintained throughout stages A and B. At stage C1 the rate of net uptake falls sharply to a lower level which is gradually reduced until equilibrium is reached at C4. The uptake mechanism is near-saturated at 0·4 mm-Ca/l and half-saturated at 0·13 mm-Ca/1. In the absence of external HCO3− net uptake is reduced. Calcium uptake is against an electrochemical gradient. The concentration of ionised calcium in the haemolymph remains unchanged during the intermoult cycle.
Functional Aspects of Anuran Middle Ear Structures
Authors: Lombard R. Eric , Straughan Ian R.
Published: April 2021

The opercular complex of amphibians functions to enhance perception of airborne environmental sounds below 1 KHz. The columella and tympanum of frogs function in the perception of acoustic information above 1 KHz. The opercular complex and amphibian papilla comprise the general hearing mechanism in amphibians. The tympanum, columella and basilar papilla, present in totality only in frogs, are concerned with reproductive communication. Interaction of the two systems in frogs provides a mechanism for enhancing input signal to noise ratio during chorusing. Experimental determinations of acoustic perception in amphibians must be controlled for anaesthesia and forelimb disposition. The presence of anaesthesia or unnatural limb position can affect the animal’s ability to perceive low frequency sounds by preventing normal opercularis function.
An Electrolytic, Digital Recording, Multichannel Micro-Respirometer
Authors: Turner B. D. , Stevenson R. A.
Published: April 2021

A 20-channel micro-respirometer is described which replaces oxygen consumed by the respiring organism by that generated by the electrolysis of saturated copper sulphate solution. Electronic circuitry checks each respirometer once every second and provides a square-wave pulse 0·1 sec long and 1·0 mA in amplitude if oxygen is required. A single pulse produces 5·7 nl of oxygen at S.T.P. Electromechanical counters record when a pulse is required for oxygen generation. Total errors introduced by the electronics amount to less than 0·1%.
Muscular Activity of the Mantle of Sepia and Loligo (Cephalopoda) During Respiratory Movements and Jetting, and Its Physiological Interpretation
Authors: Packard A. , Trueman E. R.
Published: April 2021

The action of the mantle of Sepia and Loligo has been monitored under nearly natural conditions. Respiratory movements are confined to the anterior mantle whilst during jet cycles the circular muscles contract powerfully throughout the mantle. Contraction of circular muscle results in thickening of the mantle and expulsion of water from the mantle cavity. Activity of radial muscles causes the mantle to become thinner and to expand in surface area so as to inhale water. During such movements these two groups of muscles antagonize each other directly without the participation of a discrete skeleton.
Free Amino Acids in the Haemocytes and Plasma of the Larva of Calliphora Vicina
Authors: Evans P. D. , Crossley A. C.
Published: April 2021

Free amino acid concentrations have been measured in haemolymph samples taken from 3rd instar larvae of the blowfly, Calliphora vicina, at various stages prior to pupariation. The amino acids found in the haemocyte fraction only accounted for 6% of the total free amino acid concentration of the haemolymph. However, a high percentage of the dicarboxylic amino acids, glutamate and aspartate, 62% and 69% respectively, appeared to be sequestered in the haemocyte fraction at 72 h prior to pupariation. The percentage of the other individual amino acids found in the haemocyte fraction represented less than 10% of their amount in whole haemolymph. It is proposed that these results, together with the increase in the haemocyte levels of glutamate observed after injecting larvae with saline containing glutamate, are one of the first indications of a homeostatic function of insect haemocytes with respect to haemolypmh amino acids.
Control of Moulting and Metamorphosis in the Tobacco Hornworm, Manduca Sexta (L.): Cessation of Juvenile Hormone Secretion as A Trigger for Pupation
Authors: Nijhout H. Frederik , Williams Carroll M.
Published: April 2021

During the final larval instar of the tobacco hornworm the presence of juvenile hormone (JH) inhibits the secretion of the brain ‘s prothoracicotropic hormone (PTTH). The corpora allata cease to secrete JH when the larvae attain a weight of approximately 5 g. The JH is cleared from the haemolymph in about 24 h. This process in itself renders the brain competent to release PTTH. The actual release of PTTH occurs at the very first photoperiodic gate after the JH has disappeared from the haemolymph. A functional failure of this normal mechanism is apparently responsible for the developmental standstill of Lepidoptera which diapause as mature larvae.
Effects of 5-Hydroxytryptamine On Action Potentials and On Contractile Force in the Ventricle of Dolabella Auricularia
Authors: Hill Robert B.
Published: April 2021

Concentrations of 5-hydroxytryptamine from 10−8 10−5 M had the effect of starting quiescent ventricles, with a slow slight depolarization followed by the onset of beating, with hyperpolarization between beats. Concentrations of 5-hydroxytryptamine from 10−7 to 10−3 M had the effect of prolonging the cardiac action potential and increasing force. Over the entire range, an increase in concentration led to an increase in the duration and amplitude of the plateau phase of the action potential, and an increase in force of contraction.
Diffusion and Permeation of Water in the Frog Egg: the Effect of Tension and Tonicity
Authors: Mild Kjell Hansson , Løvtrup Søren
Published: April 2021

The isotopic water permeability coefficient, P, of the plasma membrane of frog body cavity eggs has been determined as a function of the incubation time in media of different tonicity. It was found that the permeability decreases with the incubation time in hypotonic solutions. The observed changes may be correlated with an increase of the tension in the vitelline membrane. In the evaluation of the experimental results the diffusion of water in the external medium (‘unstirred layers’) is taken into account.
Sodium Regulation and Adaptation to Fresh Water in the Isopod Genus Asellus
Authors: Sutcliffe D. W.
Published: April 2021

The principal features of the sodium regulatory mechanism are compared in Asellus communis Say, A. aquaticus (L.) and A. meridianas Rae. Water content and total concentrations of sodium and chloride are similar in the three species, but they differ with respect to values for Kmax, Km, the loss rate, and the minimum sodium balance concentration. It is suggested that A. meridianas, A. aquaticus and A. communis represent a natural series of increasing adaptation to fresh water. A. communis from North America is completely adapted to fresh water. It has the lowest loss rate, the lowest maximum saturation level (Kmax) for sodium influx, and the highest affinity (low Km value) for sodium ions in the transporting system at the body surface. In many respects A. meridianus resembles freshwater populations of Mesidotea entomon and Gammarus duebeni, and may therefore have had a relatively short history in fresh water.
Some Factors Regulating Water Intake by the Eel, Anguilla Japonica
Authors: Hirano Tetsuya
Published: April 2021

Internal as well as external factors affecting water ingestion in the eel were analysed using oesophagus-cannulated eels. Acute withdrawal of the blood induced an immediate drinking response in the freshwater eel, whereas infusion of a large amount of hypertonic saline interrupted the copious drinking observed in the seawater eel. The freshwater eel responded to slow infusion of hypertonic NaCl solution by constant drinking. Inhibition of drinking was observed in the seawater eel by distension of the stomach or intestine with isotonic mannitol solution. The freshwater eel started drinking immediately after transfer to sea water, and stopped drinking immediately after return to fresh water. Application of various salt solutions revealed that chloride ions are responsible for the induction of drinking in sea water. Stimulation of drinking by chloride ions and inhibition by fresh water may be an anticipatory drinking behaviour, which facilitates adaptation of eels to both sea water and fresh water.
Active Transport of Magnesium by the Malpighian Tubules of the Larvae of the Mosquito, Aedes Campestris
Authors: Phillips J. E. , Maddrell S. H. P.
Published: April 2021

Larvae of Aedes campestris can survive in water containing up to 100 MM Mg even though they ingest and absorb into the haemolymph considerable amounts of magnesium-rich fluid. Isolated Malpighian tubules, unlike those of Rhodnius and Carausius secreted fluid containing elevated concentrations of magnesium. This transport displayed saturation kinetics, the half-maximal rate hieing at approximately 2·5 mm Mg. Active transport of magnesium was demonstrated by the secretion of this cation against a tenfold concentration gradient and an electrical potential difference of 15 mV. Magnesium ions are not required for fluid transport, which proceeds independently of magnesium transport. As a result fluid which is secreted slowly contains higher concentrations of magnesium than that which is secreted more rapidly. Magnesium is transported by isolated Malpighian tubules fast enough to account for the observed excretion of magnesium in living mosquito larvae.
The effect of temperature on the outward currents in the soma of molluscan neurones in voltage-clamp conditions
Authors: Magura I. S. , Valeyev A. E. , Zamekhovsky I. Z.
Published: April 2021

The delayed outward current in snail neurones was separated into two components with different temperature sensitivity: (i) a persistent component and (ii) a transient (inactivating) component. The effect of cooling on the value of the transient current is strongly dependent upon the value of the conditioning potential. It was supposed that cooling causes a decrease in the negative surface potential in the vicinity of the potassium pathways and removes their inactivaton. Simultaneously cooling depresses the potassium conductance. The effect on surface potential is more distinct with conditioning potentials at which a significant fraction of the transient outward current is inactivated. The effect of cooling on the transient component of the fast outward current was similar to that on the transient component of the delayed outward current.
Peripheral control of acoustic signals in the auditory system of echolocating bats
Authors: Suga N. , Jen P. H.
Published: April 2021

Many species of echolocating bats emit intense orientation sounds. If such intense sounds directly stimulated their ears, detection of faint echoes would be impaired. Therefore, possible mechanisms for the attenuation of self-stimulation were studied with Myotis lucifugus. The acoustic middle-ear-muscle reflex could perfectly and transiently regulate the amplitude of an incoming signal only at its beginning. However, its shortest latency in terms of electromyograms and of the attenuation of the cochlear microphonie was 3·4 and 4·8 msec, respectively, so that these muscles failed to attenuate orientation signals by the reflex. The muscles, however, received a message from the vocalization system when the bat vocalized, and contracted synchronously with vocalization. The duration of the contraction-relaxation was so short that the self-stimulation was attenuated, but the echoes were not. The tetanus-fusion frequency of the stapedius muscle ranged between 260 and 320/sec. Unlike the efferent fibres in the lateral-line and vestibular systems, the olivo-cochlear bundle showed no sign of attenuation of self-stimulation.
Electrophysiology of the peripheral nerve net in the polyclad flatworm Freemania litoricola
Authors: Koopowitz H.
Published: April 2021

A diffuse-conducting system close to the dorsal epithelium of the polyclad flatworm Freemania litoricola is described. Tactile stimuli elicit small action potentials which can be conducted around lesions through the body wall. The potentials can occur in bursts or barrages. This conducting system appears to be insensitive to Mg2+ ions. Conduction velocities (0·26–71 m/sec) vary over the animal. Conduction spread in the anterior half of the animal appears to be greater than that in the posterior portion. Response decrement to repeated stimulation can be recorded in the peripheral system but it is not clear if this is due to habituation or fatigue. Conduction from the peripheral net to the brain occurs. Some central units appear to pick up information only, or mainly, through the anterior nerves, while other units can respond to information conducted through the network to nerves of the contralateral side. Different possibilities to account for this system are discussed, and it is suggested that the animals either possess a unique Mg2+ insensitive synaptic nerve-net or else the network is electrically coupled.
The Control of Eyestalk Movements in the Mysid Shrimp Praunus Flexuosus
Authors: Neil D. M.
Published: April 2021

The compensatory eyestalk movements of intact and statocystless mysid shrimps Praunus flexuosus have been measured under a variety of light conditions. The results indicate that the statocyst organs in the urppods are the major gravity receptors, and that they are both necessary and sufficient to produce sinusoidal compensatory eyestalk movements. The addition of visual cues (vertical light beam, optokinetic stimuli) modifies the eyestalk response to some extent, but does not alter its general form. When the statocysts are removed, however, light stimuli become important orientational cues, and the eyestalks perform a tracking response which is considered to be the experimental counterpart of the dorsal light reaction of the free-swimming animal.
Nervous control of respiration: oxygen-sensitive elements in the prosoma of Limulus polyphemus
Authors: Thompson C. , Page C. H.
Published: April 2021

Responses of oxygen-sensitive units in the prosomal haemal nerve of Limulus polyphemus were examined while varying the oxygen content of sea water bathmg the intercoxal cuticle. When exposed to high oxygen levels these units maintained a continuous background discharge of spikes. Unit activity was inhibited when oxygen content decreased. Upon réintroduction of oxygen tonic spike discharge resumed. Mechanosensitive units with receptive fields on the prosomal shield or intercoxal cuticle were also present in the haemal nerve. Neither the mechanosensitivity nor the background discharge of these units was affected by changes in oxygen content. It is proposed that the oxygen-sensitive respiratory reflexes of Limulus are an adaptation to existence in the intertidal zone. Published observations of the respiratory stress responses of many intertidal animals support this hypothesis.
Behavioural and electrophysiological studies of taste discrimination by the maxillary palps of larvae of Locusta Migratoria (L.)
Authors: Blaney W. M.
Published: April 2021

Behavioural studies show that larvae of Locusta migratoria (L.) can discriminate between certain simple chemicals and between chemicals obtained from plant sources. Electrophysiological tests show that within each sensillum the same neurones respond to different chemicals. The frequency of occurrence of sensilla with enhanced specificity to certain chemicals is investigated. Statistical tests confirm that, despite the variability of response, across-fibre analysis could allow discrimination between chemicals pro-vided an adequate number of sensilla are used. The conclusions are discussed in relation to current theories of chemo-receptor functioning.
Colonial conduction systems in the Anthozoa: Octocorallia
Authors: Shelton G. A. B.
Published: April 2021

The octocorals Alcyonium digitatum, Pennatula phosphorea and Virgularía mirabilis each have a through-conducting nerve net. The nerve net demonstrated electrophysiologically may well be the same as that previously shown by the use of histological techniques. It exhibits both facilitation and defacilitation in the rate of conduction of pulses. The distance of spread of nerve net activity is not limited by the number of stimuli applied. The nerve net controls fast muscle contractions; the frequency of pulses is important in determining which muscles contract and in which sequence. The nerve net is ‘spontaneously’ active. A previously undescribed slow system has been identified in Pennatula. It has many of the properties of slow systems in sea anemones and may well be ectodermal. It is suggested that multiple conduction systems are of common occurrence in the Anthozoa.
Respiratory and Circulatory Responses to Hypoxia in the Lobster Homarus Americanus
Authors: McMahon B. R. , Wilkens J. L.
Published: April 2021

Contrary to previous reports, oxygen consumption is maintained over a wide range of external oxygen tensions in the lobster Homarus americanus. In animals acclimated to the experimental conditions this response is mediated by increased branchial pumping, increased effectiveness of oxygen uptake by the gills and an increased contribution by the respiratory pigment to the oxygen delivered to the tissues. Circulatory blood oxygen levels are generally high in lobsters resting in well-aerated water. Mechanisms for detection of hypoxia and possible control mechanisms are discussed.
Reversible Arrest of Uptake of Water from Subsaturated Atmospheres by the Firebrat, Thermobia Domestica (Packard)
Authors: Noble-Nesbitt J.
Published: April 2021

A novel experimental technique incorporating a double-chambered array, which allows the independent and reversible exposure of head and tail ends of the insect to the surrounding atmosphere, without otherwise altering the constraints on the insect, is described. Using this technique, it has been possible to demonstrate that rapid uptake of water from subsaturated atmospheres occurs in Thermobia only when the tail-end is exposed. This effect is immediately and completely reversed when the tail-end is shielded from the atmosphere, and can be restored again on re-exposure of the tail-end, as shown repeatedly during electrobalance recordings. The relative humidity within the closed head-end chamber slowly rises, but within the closed tail-end chamber it falls, to approximately 50 % (the critical equilibrium humidity) with the desiccated insects and to 60-65% with hydrated insects, whilst the anal valves show movements indicating the operation of the rectal uptake mechanism. These findings are compatible with the anus being the avenue for the passage of water into the insect from the atmosphere.
Secretion of Hypo-osmotic Fluid by the Lower Malpighian Tubules of Rhodnius Prolixus
Authors: Maddrell S. H. P. , Phillips J. E.
Published: April 2021

The ability of Rhodnius to excrete an hypo-osmotic fluid at high rates can be attributed to the activity of the lower lengths of the Malpighian tubules. In the presence of a stimulant (such as 10−8 M 5-HT) they can absorb KC1 from fluid in the lumen at rates as high as 0·5 /μ mol.min−1 cm−2. The solution absorbed is strongly hyperosmotic (900 mM KC1) so that the fluid in the lumen becomes hypo-osmotic (as low as 75 mOsm) and its flow is not much slowed. The rate of absorption of KC1 from the lumen depends on the potassium content of fluid there; the highest rates are achieved when K-rich fluid is run through the tubule at high speed from a cannula. Rubidium ions are partly effective substitutes for potassium ions in the system, but sodium ions are not absorbed at measurable rates. The wall of the lower tubule has a much lower permeability top-amino-hippuric acid, xylose, sucrose and inulin than has the upper tubule - as expected in a system able to maintain a large osmotic concentration difference.
Integumentary Amino Acid Transport and Metabolism in the Apodous Sea Cucumber, Chiridota Rigida
Authors: Ahearn Gregory A. , Townsley Sidney J.
Published: April 2021

The apodous sea cucumber, Chiridota rigida, was found to transport exogenous amino acids to intracellular free amino acid pools in the integument, the gastrointestinal epithelium making only a minimal contribution to total animal uptake. Amino acids entering the integumentary free amino acid pool were either completely catabolized to CO2, incorporated into large molecular weight compounds, such as proteins, or left unchanged. The latter fraction was available for efflux through both apical and basal cellular membranes through saturable or non-saturable transport processes. Influx of natural (glycine) and analog (AIB) amino acids into the integumentary epithelium was achieved by a combination of saturable and non-saturable transport mechanisms: the former displaying Michaelis-Menten kinetics, being Na+-dependent, and transporting both glycine and AIB; the latter involving a simple diffusion of amino acid across the apical cell membranes and/or through the intercellular septate desmosomes. Preloaded AIB exhibited both homo-and hetero-exchange diffusion with exogenous amino acids when a relatively large internal analog pool had been established. With a small internal pool of AIB, homo-exchange diffusion persisted, but high external concentrations of glycine inhibited the washout of the analog. Transintegumentary influx of AIB to the coelomic fluid was a linear function of the exogenous amino acid concentration and was unchanged when choline chloride was used as a substitute saline. At steady-state the coelomic fluid analog concentration was maintained at a much lower level than the incubation medium or the epithelial free amino acid pool, due to apparent absorptive processes of the dermis and muscle layers of the integument, as well as by possible carrier-mediated re-uptake mechanisms on the basal membranes of the epithelial cells. A tentative model of integumentary amino acid transport and metabolism in C. rigida is presented.
Potassium-induced motion increase in a central nervous ganglion
Authors: Sattelle D. B. , Piddington R. W.
Published: April 2021

By means of light-beating spectroscopy, a four-fold increase in the modulation of laser light scattered at right angles by a locust (Schistocerca gregaria, Forskâl) ganglion is detected when potassium ions replace sodium ions in the Ringer solution. This is interpreted as an increased level of motion of the scattering particles (size 0·3–3·0 μm, if viscosity is taken to be o-oi poises). The amplitude of the potassium-response is similar at all frequencies in the range 6·3-150 Hz and is reversible on return to normal (Na+) Ringer. Desheathing the ganglion reduces the half-time of the potassium-response by 3-4 times. By means of photon-correlation spectroscopy it was estimated that less than 10% of the tissue contributes to the motion detected. Cyanide (1-2 HIM) typically enhances the potassium-response and renders it irreversible, suggesting that the response is thermally rather than metabolically-driven. In addition, the dependence of both the correlation function and the power spectrum on the scattering angle is in the direction predicted for a diffusive process. Cobaltous ions (2-10 HIM), which block calcium entry into nerve cells, depress the potassium-response. It is proposed that potassium-depolarization and the resultant calcium entry into the cells causes a partial liquefaction of the cytoplasm which is detected as an increase in the level of Brownian motion. This mechanism could be used in vesicular release or in growth.