bluuebunny/crossref_metadata_2025 huggingface dataset:
Extraretinal Pigmentation and Colour Discrimination
Authors: Volpe P. , Carfagna M. , Lorenzo M. Di
Published: April 2021

The hypothesis that the choice of substrate colour for oviposition may vary preferentially according to the type of eye pigment has been confirmed by experiments on three phenotypes of D. melanogaster, the normal or wild type, the vermilion mutant, having no homochrome, and the brown mutant, lacking pteridine. The results can be summarized thus : (a) no preferential selection on the part of the wild phenotype ; (b) unambiguous preference by vermilion for blue, a preference less clearly marked for yellow, with green rejected ; and (c) clear preference by the brown mutant for green, with rejection of blue. Choice of colour during oviposition was found to be different from that expressed by phototactic response to certain monochromatic lights, as reported some years ago. The probable biological significance of such behaviour in functions which are physiologically distinct is also discussed.
Bioelectric Regulation of Tentacle Movement in a Dinoflagellate
Authors: Eckert Roger , Sibaoka Takao
Published: April 2021

Recurring extensions and flexions of the food-gathering tentacle of Noctiluca miliaris occur spontaneously. Identical movements can be evoked by appropriate electrical stimulation. Spontaneous recurring potential wave forms (TRPs) were recorded from the vacuole of the luminescent form of Noctiluca during movements of the tentacle. The basic TRP wave form consists of a characteristic negative-going spike which arises at −20 to −30 mV. from the slowly redeveloping negativity of a pre-spike depolarization, and is followed by a quasi-stable post-spike d.c. level of relative vacuolar negativity (−45 to −60 mV.). The TRP complex, similar in shape to that which occurs spontaneously, follows an intracellularly applied current pulse of either polarity if the vacuolar potential is at the post-spike level. The duration of the evoked pre-spike wave is related to the current intensity and duration. During the pre-spike state outward current is ineffective, although a TR spike occurs in response to inward current. The TRP is distinct in its behaviour and wave form from the flash-triggering potential, which can be evoked in the same cell, even though both exhibit all-or-none spikes. Simultaneous recordings of intracellular potentials and movements of the tentacle showed a consistent temporal relationship between potential changes and subsequent movement. Extension of the tentacle begins 1–2 sec. after the spike and flexion begins within i sec. after beginning of the pre-spike wave. Tentacle movement ceased in Ca-free sea water even though the cyclic potential changes continued normally. Electron micrographs of the tentacle showed longitudinal aggregations of microtubules near the outer surface of the peripheral cytoplasm. It is proposed that contraction of these microtubules is the immediate cause of tentacle movements.
Sodium, Chloride and Water Balance of the Intertidal Teleost, Xiphister Atropurpureus
Authors: Evans David H.
Published: April 2021

The effluxes of 22Na, 36Cl and tritiated water from the euryhaline teleost, Xiphister atropurpureus were determined in 100% sea water (480 mM-Na/kg.) and 10% sea water. Only the flux of sodium in 100% sea water contained an exchange diffusion component. The relative impermeability of Xiphister is shown by its low fluxes of sodium, chloride and water in both salinities. In 10% sea water the permeability to sodium declined while the permeability to chloride and water remained at sea water levels. In both salinities diffusion and active transport are the major components of the sodium and chloride balance of Xiphister.
Discrimination, Previous Experience and Substrate Selection by the Amphipod Corophium
Authors: Meadows P. S.
Published: April 2021

Populations contain no animals that are consistently less discriminating than others in their choice of substrates. Previous experience in atypical substrates does not alter preferences for typical substrates. Animals live slightly longer in very fine-grained substrates than in coarser ones. Their growth rates do not differ over a range of particle sizes. Animals select the smaller grains in a substrate to build their tubes with.
The Water Repellency and Feather Structure of Cormorants, Phalacrocoracidae
Authors: Rijke A. M.
Published: April 2021

The water-repellency of the feathers of ducks is greatly increased by a structural feature which can be expressed in terms of diameter and spacing of the barbs and barbules. This structural parameter is smaller for cormorant’s feathers and causes a lesser extent of water repellency. The resulting wetness of the feathers is the proximate cause of the cormorant’s characteristic habit of wing-spreading.
A Theoretical Treatment of the Reflexion of Light by Multilayer Structures
Authors: Huxley A. F.
Published: April 2021

A convenient method is presented for calculating the reflectance of a stack of dielectric layers consisting of a series of identical repeats of any particular sequence of layers. The method is closely related to that published by Lord Rayleigh in 1917. In this method, two quadratic equations are formed from the thicknesses and refractive indices of the layers composing a single repeat unit. The reflectance is obtained by substituting the solutions of these equations into an explicit formula. Particularly simple formulae result for the case of a stack of p plates, optical thickness λϕ/2π, uniformly spaced in an infinite medium with spaces of the same optical thickness. If r is the amplitude reflexion coefficient at a single interface, the reflectance of the whole stack is as follows : when cos2ϕ < r2, where when cos2ϕ > r2, where when the number of repeats in the stack is large (p → ∞), reflexion is complete so long as cos2ϕ < r2. Outside this range the reflectance is . These results are extended to cover: (a) unequal optical thicknesses in plates and spaces; (b) oblique incidence; (c) layers of materials of other refractive indices above and below the stack itself; and (d) stacks consisting of repeats of more complex units.
Seasonal Temperature Influence on Vagal Control of Diving Bradycardia in the Frog (Rana pipiens)
Authors: Lund Gordon F. , Dingle Hugh
Published: April 2021

The influences of asphyxia, temperature, and restraint on diving bradycardia in amphibia have been considered. In restrained diving frogs two forms of bradycardia were distinguised on the bases of rate of attainment, control, and degree of hear-rate reduction. A rapidly attained immersion bradycardia could be eliminated by atropine or bilateral vagotomy and was thus similar to that of other vertebrates. A slowly attained asphyxiant bradycardia, independent of vagal influences, also occured but was less pronounced. Electrical stimulation experiments were conducted in September to determine the influence of temperature on vagale inhibition of the heart. With decreasing temperature partial block of vagal inhibition occurred at about 11° C., and complete block occured at 7-8°C.; on rewarming, partial block returned around 11-12°C., and complete vagal inhibition of the heart was re-established at about 14° C. Though both forms of bradycardia may occur in any one dive, the form predominating was dependent on temperature and season. A seasonal variability regarding the temerature at which vagal inhibition of the heart can occur has been suggested. A pronounced diving bradycardia, either slowly or rapidly attained, probably does not occur in unrestrained frogs under normal environmental conditions.
Effect of Adrenergic Drugs on the Lantern of the Larval Photuris Firefly
Authors: Carlson Albert D.
Published: April 2021

A number of adrenergic drugs were tested for their ability to induce luminescence in the extirpated lantern of the firefly larva. The drugs produce sigmoid doseresponse curves characteristic of drug-receptor interactions when drug concentration is plotted against either maximum intensity or maximum rate of intensity rise. Amphetamine and saline of high potassium concentration induce intense luminescence in freshly extirpated lanterns but act only weakly or not at all in lanterns suffering from treatment by reserpine injection 48 hr. previously. No significant difference in response to norepinephrine was observed in lanterns immersed in standard saline, 0.32 M sucrose, 0.16 M choline chloride or 0.16 M-NaCl2 but 0.107 M-CaCl2 considerably slowed the response. Some generalizations concerning structural character and effectiveness in inducing luminescence were made by comparing the drugs tested. It was not possible to describe the mode of action of the drugs. The observation, however, that solutions lacking sodium and potassium did not significantly alter the response was felt to argue against the action of the adrenergic drugs in affecting ion movement across the photocyte membrane.
The Labial Gland: A Salt-Secreting Organ of Saturniid Moths
Authors: Kafatos Fotis C.
Published: April 2021

The labial gland of adult saturniids produces a voluminous liquid at about the time of ecdysis, in response to either confinement of the moth or physostigmine injection. This liquid normally facilitates escape from the cocoon. During secretion the gland accumulates K+ and HCOS−from the blood, and Rb+ if it is available, but excludes rather efficiently Na+, Li+, Sr2+, Ca2+, Mg2+, phosphate and other small molecular weight components of blood. Cl− is approximately equally distributed in blood and secretion. The pH of the secretion is approximately 8·5, as compared with 6·5 for blood. The secretion is in osmotic equilibrium with blood, even after alteration of blood osmotic pressure by injection of hypertonic or hypotonic solutions. For both Cl− and Na+ the rate of entry into the secretion is proportional to concentration in blood; i.e. the efficiency of exclusion is characteristic for each ion, within a wide range of blood concentrations. Secretion is accompanied by a potential difference across the secretory cell (ca. + 25 mV. lumen positive). Secretion is abolished by dinitrophenol, but not by ouabain or acetazoleimide. The results are best explained in terms of a respiration-mediated active accumulation of blood K+, in exchange for H+, in the basal region of the cells; this is presumably followed by release of the K+ into the lumen, with concomitant reabsorption of H+ from the secretion. The alkaline secretion then traps blood CO2 by converting it to HCO3−. Water follows osmotically, and other ions enter passively, at a rate determined by the corresponding permeability of the cells.
Effects of Sub-Lethal High Temperature on An Insect, Rhodnius prolixus (Stål.)
Authors: Okasha A. Y. K.
Published: April 2021

In Rhodnius larvae, when moulting is delayed under normal temperature conditions by exposure to high temperature directly after feeding, the brain is needed for a period longer than normal to complete development, i.e. the critical period is postponed. This is associated with a delay in the activation of the thoracic glands and in the mitotic activity in the epidermis. It is suggested that high temperature may act directly on the brain thus inhibiting the secretion of its hormone, although other possibilities are also discussed. The process of wound heating at normal and high temperatures is compared. Injury of the integument results in the ‘activation’ of the epidermal cells and their migration towards the wound. Consequently, a zone of sparse cells is formed which persists at high temperature, since cell division in the epidermis is inhibited. The bearing of the inhibition of cell division on the cessation of moulting at high temperature, even in the presence of the moulting hormone, is discussed.
The Effect of Enforced Locomotor Activity on Lipid Content in Allatectomized Males of Locusta migratoria migratorioides
Authors: Strong L.
Published: April 2021

Allatectomy has no apparent effects upon feeding activity in males of L. m. migratorioides. If allatectomized locusts are forced to take vigorous exercise, food consumption is increased slightly. Allatectomized males exhibit active sexual behaviour, although they do not develop a mature coloration. The accumulation of lipid in allatectomized males can be limited by forcing the insects to take vigorous exercise. The possibility that hypertrophy of the fat body is due to lethargy in allatectomized male locusts is discussed but considered to be unlikely.
The Wing Mechanism Involved in the Courtship of Drosophila
Authors: Bennet-Clark H. C. , Ewing A. W.
Published: April 2021

The sounds produced during courtship in Drosophila melanogaster are similar to a component of the flight tone. The normal flight wing beat has a rapid upstroke and a slower downstroke. By analysis of the form of the wing beat and its velocity it is shown that the sound that is heard from behind the fly is produced by a rapid increase of thrust in the early part of the upstroke followed by decrease in thrust, or even thrust reversal, during the period which the wing is rotating at the top of the stroke. The downstroke is relatively quiet. The courtship wing vibration consists of a series of single wing beats of about 7-5 msec, duration. Courtship sounds consist of single cycles of pressure change of 3 msec, duration produced at 34 msec, intervals at 25°C. These figures are compatible with the suggestion that courtship sound pulses are produced by one half of an asymmetric wing beat. Drosophila persimilis produces short trains of pure notes of rg msec, period. Here, the wing vibrates at about 250 beats per second and the wing beat is symmetrical. The differences between these two species is discussed in terms of inertial loading of the thorax and the tension in the muscle activating the click mechanism. The courtship wing beat occurs when the extra-coxal depressor of the trochanter of either the mesothoracic or the metathoracic legs is cut. This suggests that this muscle is not responsible for the initiation of flight, but instead, acts as a transmitter of thoracic movement causing the starting jump. Cutting one of the dorso-ventral indirect flight muscles stops courtship vibration, the initiation of flight and jumping, and it is suggested that this muscle is more likely to be involved in flight-starting and courtship vibration.
Spectral Sensitivity of Scorpion Eyes and the Possible Role of Shielding Pigment Effect
Authors: Machan L.
Published: April 2021

The lateral eye shows one maximum in the ultraviolet and another in the blue-green region of the spectrum, probably attributable to two receptor types. Light-adapted lateral eyes show the peculiar effect of a marked drop in ultraviolet sensitivity, irrespective of the colour of the adapting light. Absorption by shielding pigment of the lateral eye is slightly selective in the short wavelengths. The median eye has one maximum in the blue-green, violet sensitivity being apparent only with prolonged dark-adaptation. Absorption by the shielding pigment of the median eye appears to be non-selective.
Respiration in the African Lungfish Protopterus Aethiopicus
Authors: Lenfant Claude , Johansen Kjell
Published: April 2021

Respiratory properties of blood and pattern of aerial and aquatic breathing and gas exchange have been studied in the African lungfish, Protopterus aethiopicus. The mean value for haematocrit was 25%. Haemoglobin concentration was 6·2 g% and O2 capacity 6·8 vol.%. The affinity of haemoglobin for O2 was high. P50 was 10 mm. Hg at , 6 mm. Hg and 25° C. The Bohr effect was smaller than for the Australian lungfish, Neoceratodus, but exceeded that for the South American lungfish, Lepidosiren. The O2 affinity showed a larger temperature shift in Protopterus than Neoceratodus. The CO2 combining power and the over-all buffering capacity of the blood exceeded values for the other lungfishes. Both aerial and aquatic breathing showed a labile frequency. Air exposure elicited a marked increase in the rate of air breathing. When resting in aerated water, air breathing accounted for about 90% of the O2 absorption. Aquatic gas exchange with gills and skin was 2·5 times more effective than pulmonary gas exchange in removing CO2. The low gas-exchange ratio for the lung diminished further in the interval between breaths. Protopterus showed respiratory independence and a maintained O2 uptake until the ambient O2 and CO2 tensions were 85 and 35 mm. Hg respectively. A further reduction in O2 tension caused an abrupt fall in the oxygen uptake. Gas analysis of blood samples drawn from unanaesthetized, free-swimming fishes attested to the important role of the lung in gas exchange and the high degree of functional separation in the circulation of oxygenated and deoxygenated blood.
Electromyography of the Respiratory Muscles and Gill Water Flow in the Dragonet
Authors: Hughes G. M. , Ballintijn C. M.
Published: April 2021

An account is given of the main skeletal elements and muscles involved in the respiratory movements of the dragonet, Callionymus lyra. Using electromyographic techniques it has been shown that the muscles chiefly involved in rapid ejection of water out of the opercular slit are the adductor mandibulae, protractor hyoideus, and hyohyoideus. During the expansion phase of the cycle, which is about six times the duration of the contraction phase, the levator hyomandibulae and sternohyoideus are active, though in some cases the latter only comes in at higher levels of pumping. Changes in volume flow across the gills have been produced by either (a) altering the hydrostatic pressure gradient (Δp) across the system, or (b) altering the oxygen or carbon dioxide content of the water inspired by the fish. With (a), the volume flow decreases linearly at a rate of about 30 ml./min./cm. H2O static pressure head until an inflexion is reached in the curve at which rate of flow decreases and is normally when Δp is zero. That the relative increase in flow rate with negative Δp’s is due to the activity of the fish pumping against the adverse pressure gradient has been confirmed by electromyogram recordings during such experiments. With (b), it was possible to demonstrate a clear relationship between stroke volume and the level of electrical activity as measured by the height of the integrated electromyogram. The integrated EMG increases more than linearly with increasing stroke volume during changes, but this relationship seems to be more nearly linear during changes in CO2 concentration. The respiratory frequency is scarcely affected by changes in flow produced by altering the hydrostatic pressure gradient, but following a decrease in or an increase in CO2 there is a significant fall in frequency which accompanies the increased electromyogram. The time course of these changes during recovery from a decrease in or an increase in suggests that the gas tensions of the inspired water are detected by receptors on the gills and thus influence the electromyogram activity, but the frequency change observed is due to a change in the blood affecting receptors in the brain.
The Developmental Efficiency of the Avian Embryo
Authors: Needham Joseph
Published: April 2021

The “Coefficient d’Utilisation” or Plastic Efficiency Coefficient (P.E.C.) has been calculated for each day during development. It has a trough which is deepest between the eighth and ninth days; development is therefore most expensive at this point. The correlation between this and the point of greatest intensity of protein combustion is exact. The “Rendement Energétique brut” or Apparent Energetic Efficiency has been calculated for each day during development. It rises, changing more rapidly towards the end than at the beginning ; thus it resembles the metabolic rate rather than the growth rate. The “Rendement Energétique réel” or Real Energetic Efficiency cannot at present be calculated for the basal metabolism of the embryo is unknown and it is not certain whether the usual conceptions of basal metabolism can be applied to a rapidly growing and changing organism.
The Mechanism of Cell-Division
Authors: Gray J.
Published: April 2021

The nucleolus in the nucleus of an Echinus oocyte always orientates itself gravitationally on the floor of the nucleus. When the oocyte is disturbed the nucleolus falls through the fluid contents of the nucleus with an average velocity of 0·4 μ per sec. Gravity has no direct action on the direction of the cleavage planes in Echinus eggs, but it orientates the whole egg within the fertilisation membrane. During the first cleavage the mitotic axis can lie in any position in respect to gravity, but if its position deviates appreciably from the horizontal then (as soon as the cell elongates by cleavage) the whole egg moves so as to bring its centre of gravity into equilibrium with gravity and with the frictional forces acting between the egg and the fertilisation membrane. During the second cleavage the mitotic axis must lie in a plane parallel to the first cleavage furrow in conformity with Hertwig’s Law. If its position deviates from the horizontal, then the egg orientates itself to gravity. In this way the second division gives rise to four blastomeres resting as a flat plate on the floor of the fertilisation membrane, independently of whatever position was occupied by the mitotic axis. The third cleavage is also in accord with Hertwig’s Law and no gravitational disturbances occur. The direction of each cleavage plane is determined by the resultant of three factors: (a) the forces underlying Hertwig’s law, (b) gravity, (c) friction between the egg and its fertilisation membrane.
The Senescence of Spermatozoa
Authors: Gray J.
Published: April 2021

There appear to be two main conceptions of the processes of senile decay. According to the first of these, the characters of old age are regarded as the result of inherent decay of the living machine. The theory suggests that the essential organisation of a cell, like that of an atom of radium, can only remain stable for a limited time, after which it undergoes irreversible and unavoidable decay. According to the second theory, senescence is not due to an inherent property of protoplasm itself, but is caused by the adverse effects exerted on the protoplasm by substances which are formed in the cell during its natural life. Thus, by a partial failure of the excretory mechanism an organism is eventually destroyed by its own activities. The analysis of the whole phenomenon is usually complicated by the fact that it is only towards the end of a long and active life that the symptoms of decline are sufficiently obvious to be of use for experimental purposes. Further, in most cases an organism may, during most of its life, throw off old or inefficient cells and replace them by others which are manufactured from the raw materials of its food. It, therefore, seems reasonable to select for experimental investigation a type of cell whose life is short, and which is incapable of absorbing food.
Discharge Patterns of Swimmeret Motoneurones in the Lobster, Stimulated With a Digital Computer
Authors: Davis W. J. , Murphey R. K.
Published: April 2021

The response of a computer-simulated neurone to a sinusoidal excitatory input was studied and compared to the rhythmic discharge patterns of swimmeret motoneurones in the lobster. All of the output parameters of the simulated neurone closely resemble those of the swimmeret motoneurones, suggesting that the excitatory input to the swimmeret motoneurones also varies with time in an approximately sinusoidal fashion. The full range of behaviour exhibited by swimmeret motoneurones was obtained from the simulated neurone by varying the time course of the refractory recovery following each spike, the effective threshold for spike generation, and the rate of accumulation of refractoriness during each burst.
Mechanoreceptors, Photoreceptors and Rapid Conduction Pathways in the Leech, Hirudo Medicinalis
Authors: Laverack M. S.
Published: April 2021

Mechanoreceptors in the body wall of the leech Hirudo are stimulated by deformation of the animal’ s surface. They respond at all frequencies of stimulation up to about 50–60 Hz. Light flashes, from a microscope lamp or an electronic flash source, are also a potent means of peripheral stimulation. After peripheral stimulation impulses can be recorded in a fast central pathway. This pathway conducts equally well in the posterior to anterior and in the opposite directions. Interference with either the right or left connective linking any two segmental ganglia does not interrupt the rapid conduction of these impulses. Severance of the median connective or Faivre’ s nerve interrupts conduction. This seems to implicate at least one, and possibly more, of the nerve fibres of this median connective in the rapid transmission of information from the extremities of the body. A slower conducting pathway also exists in the nerve cord.
Sodium, Chloride and Water Balance of the Intertidal Teleost, Pholis Gunnellus
Authors: Evans David H.
Published: April 2021

Measurements were made of the regulation of the body ionic content, the fluxes of Na, Cl and water and the electrical potential across the intertidal teleost, Pholis gurmellus in 100% (410 mM-Na/1.) and 20% sea water. The rates of the ion flux depended on the method of measurement. The flux of Cl is much below the flux of Na in 100% sea water. In 20% sea water the fluxes of Na and Cl are the same. In 100 % sea water only the Na flux has an exchange-diffusion component. There is no exchange-diffusion component of the flux of either ion in 20 % sea water. The electrical potential across Pholis changes from 18 mV. (inside positive) in 100% sea water to 6 mV (inside negative) in 100% sea water. Comparison with the Nernst potentials indicate that Cl is actively transported in both salinities while Na may possibly be actively transported in 100% sea water. In 20% sea water the permeability to Na decreases to 51 % of the permeability in 100% sea water, while the Cl permeability decreases to 82% and the water permeability remains at the sea-water level. In both salinities the rate of diffusion of Na ions is greater than the rate of diffusion of Cl ions. The osmotic permeability to water is approximately equal to the diffusional permeability to water in both salinities. It is concluded that the passive movements of Na, Cl and water must be independent of each other and not via uncharged, water-filled pores.
Central Control of An Insect Segmental Reflex
Authors: Fraser Rowell C. H.
Published: April 2021

The prothoracic grooming reflex of the locust is normally inhibited by the rest of the C.N.S. This paper examines the effect of removing the most powerful inhibitory source, the metathoracic ganglion, on the signal flow in and out of the prothoracic ganglion. Removal of the metathoracic ganglion decreases the number of action potentials entering the prothoracic ganglion; the number of action potentials leaving the prothoracic ganglion increases. Since the recording samples only about 1 % of the axons in the connective, mainly large ones, and since the sample is probably different in different preparations, it is concluded that removal of the input from the metathoracic ganglion causes a general disinhibition of the prothoracic ganglion. Inhibition of the grooming reflex is probably due to this general inhibition of the ganglion, not to a specific inhibitory connexion with the metathoracic ganglion. It is suggested that the total input to the ganglion may, apart from its specific functions, contribute to a non-specific inhibition, possibly via a ganglionic arousal system.
Sodium Balance in the Eggs of the Atlantic Salmon, Salmo Salar
Authors: Rudy P. P. , W. Potts W. T.
Published: April 2021

Exchanges of sodium ions between the egg of the salmon and the environment have been examined at different stages. In freshly stripped eggs and during the early stages of development exchange is confined to the chorion and perivitelline fluid. The perivitelline fluid can accumulate sodium to several times the ambient concentration probably by a Donnan effect associated with its protein content. At low external concentrations the relative accumulation is lower than the Donnan theory predicts. Sodium accumulation begins during the eyed stage and accelerates after hatching.
The Development of Patterned Activity by implanted Ganglia and their Peripheral Connexions in Periplaneta Americana
Authors: Guthrie D. M. , Banks J. R.
Published: April 2021

The isolation of a thoracic ganglion from the rest of the central nervous system results in a loss of differentiation of the motor output, although repetitive rhythms may appear during the later stages of isolation. Total isolation of the ganglion in vitro results in a further reduction of motor activity to low-frequency, steady-level discharges in a few fibres of some nerves only. Two or three months after implantation a steady low-frequency discharge can be recorded from many of the branches of the implant ganglion, and these may have functional contacts with adjacent muscles. There is little evidence of afferent connexions. Four to seven months after implantation the efferent connexions of the implanted ganglion often show a highly differentiated pattern of spontaneous electrical activity, and the ganglion will respond in a remarkably delayed and progressive manner to the stimulation of adjacent sense organs. The spontaneous rhythms of the long-term implant ganglion may be determined by a balance between central and peripheral input levels similar to those occurring during progressive isolation of the ganglion. The functional relationship between the host and the donor ganglion appears to consist largely of an inhibitory effect exerted by the host ganglion on the donor or implant ganglion. A justification for this in adaptive terms can be found.
The Synaptic Link Between the Sensory and Motoneurones in the Eye-Withdrawal Reflex of the Crab
Authors: Sandeman D. C.
Published: April 2021

The axon of the larger of the two motoneurones in the optic tract of Carcinus which bring about the rapid eye withdrawal is 30–50 µ in diameter and has an unusually thin sheath compared with crab leg neurones of similar diameter. Within the brain the axon of the large eye-withdrawal motoneurone tapers fairly rapidly to 5–10µ. It extends diagonally across one side of the brain and branches in two near the mid line but does not pass the contralateral side of the brain. The axon terminals and the cell body have not been seen. A single stimulus to the afferent inputs of the motoneurone produces a characteristic burst of impulses followed by an irregular train of impulses. The excitatory effects of all tested afferent inputs to the motoneurone are summed before affecting a common spike-initiating locus on the motoneurone. Intracellular recordings from the motoneurone within the brain show two types of subthreshold activity to follow a single pre-synaptic volley : a smooth graded depolarization and small superimposed depolarizations of constant amplitude and duration. The synaptic link between afferents and the eye-withdrawal motor neurone is thought to be via a direct, possibly monosynaptic pathway and also by way of interneurone collaterals.
The Neural Control of Swimmeret Beating in the Lobster
Authors: Davis W. J.
Published: April 2021

The neural basis of swimmeret beating in the lobster Homarus americanus was studied by recording the cyclic motor output to the swimmeret muscles of intact, unrestrained specimens. The force produced by each swimmeret is regulated by changes in the number of impulses within single motoneurones during each movement cycle, and by changes in the number of motoneurones which discharge during each cycle. Both of these parameters increase with the frequency of swimmeret beating. The burst duration of single swimmeret motoneurones is independent of the frequency of swimmeret beating. The duration of the total electrical activity of each muscle nevertheless increases with the cycle duration, owing to changes in the relative timing of the activities of the motoneurones which innervate the muscle. By this method the forces produced by each muscle are presumably distributed evenly throughout cycles of variable duration. As the frequency of swimmeret beating increases, the movement response progressively lags behind the motor nerve activity. At high frequencies of beating powerstroke motoneurones fire during the returnstroke of the preceding movement cycle because of this phase change, thereby actively braking the swimmeret. Tilting the lobster to one side changes the direction of the powerstroke of each swimmeret on the side tilted upward. This change is achieved by an increase in the activity of muscles which rotate the appendage outward on its long axis, by an increase in the activity of a muscle which directs the powerstroke out toward the side, and by a decrease in the activity of a muscle which directs the powerstroke to the rear. The latter decrease is accomplished through the use of a peripheral inhibitor axon. Under some conditions individual swimmeret motoneurones discharge in continuous trains rather than in bursts. This tonic activity is characterized by the occurrence of a disproportionate number of impulse pairs and triplets, a pattern to which the swimmeret muscles may be especially sensitive. During swimmeret beating, all of the swimmeret motoneurones discharge in cyclic bursts. The temporal structure of the bursts suggests that the underlying excitatory input oscillates sinusoidally with time at the same frequency as that of swimmeret beating.
The Physiology of the Antennal Gland of Carcinus Maenas (L.)
Authors: Binns R.
Published: April 2021

U/B ratios for inulin and sorbitol have been measured in 100%, 75% and 50% sea water. When Carcinus is in 100% sea water, a U/B ratio of 1 for both sorbitol and inulin is reached and maintained after 40 and 115 hr. respectively. A reason for this difference is suggested. In dilute media the rate of increase of U/B ratio for both molecules is more rapid than in 100% sea water. For instance, in 50% sea water the inulin U/B ratio is 1 after 50−60 hr. Sorbitol ratios are generally less than 1 in dilute sea water and a possible explanation of this is given. In any particular concentration of sea water blood and urine concentrations of injected solutes fall at approximately the same rate once the maximum urine concentration has been reached. It is concluded that primary urine production in Carcinus is by a filtration mechanism and that reabsorption of water from the urine does not normally occur.
Miniature Excitatory Junction Potentials in the Somatic Muscle of the Earthworm, Pheretima Communissima, in Sodium Free Solution
Authors: Ito Y. , Kuriyama H. , Tashiro N.
Published: April 2021

Miniature excitatory junction potentials (m.e.j.p.s) could be recorded from the longitudinal muscle layer of earthworm in sodium-free solution. The amplitude and frequency of the m.e.j.p.s indicated the diffuse innervation and random release of the chemical transmitter from the nerve terminals. Generation of the m.e.j.p.s was prevented by treatment with D-tubocurarine, but not by atropine and picrotoxin. Hyperpolarizations of the membrane by applications of inward current increased the frequency and amplitude of the m.e.j.p.s in sodium-free solution. The reversal potential level for the m.e.j.p.s in sodium-free solution was −20 mV., and this value was 20 mV. negative to that measured in physiological solution. Low-potassium solution shifted the reversal potential levels in a more negative and high-calcium in a less negative direction. The change of the reversal potential produced by a tenfold change of the external potassium concentration was 24.5 mV., and that by change of the external calcium concentration was 17 mV.
The Physiology of the Antennal Gland of Carcinus Maenas (L.)
Authors: Binns R.
Published: April 2021

The space measured by inulin distribution, the ‘inulin volume’, has been determined, and represents approximately 20% of the body weight in crabs ranging in size from 20·0 to 57·2 g. After the injection of labelled inulin into crabs, the increase in activity of the medium is equal to the fall in blood inulin in all dilutions of sea water. Clearance of inulin from the blood is due only to urine production, and therefore the molecule can be used for quantitative investigations of antennal gland function. Urine production in various concentrations of sea water has been determined by measuring the clearance of inulin from the blood and the rates at which the tracer appeared in the external media. By these methods the mean rate of urine production in 100% sea water was estimated to be 4·4% body weight per day. In dilute sea water the rate of urine production increases ; for example, in 50 % sea water the urine flow is four times greater than in normal sea water.
Innervation Patterns of Fast and Slow Muscle in the Uropods of Crayfish
Authors: Larimer J. L. , Kennedy D.
Published: April 2021

The innervation of 18 uropod and telson muscles in the crayfish has been studied in varying detail. Some muscles display purely phasic properties (short sarcomeres, electrically excitable membrane responses); others are strictly tonic (long sarcomeres, junctional potentials only, spontaneously active motor neurones); a few are mixed, but with anatomical segregation of fibre types. At least 55 efferent neurones are employed to operate these muscles. The tonic muscles all receive peripheral inhibition, and a given inhibitory axon serves only a single tonic muscle. Inhibitory and excitatory axons serving a given muscle discharge reciprocally and often respond to different reflex inputs. The average number of excitatory axons innervating tonic muscles is 2-3. The phasic muscles differ in the richness of excitatory innervation. Some receive as many as five axons per muscle, and as many as four per fibre; others are innervated by only a single motor axon. Many lack inhibitory innervation; where present, peripheral inhibitors may be shared between different phasic muscles. In no case were excitatory axons found to innervate anatomically separate muscles. In ‘mixed’ muscles there is predominantly separate innervation of phasic and tonic fibres; but in at least one case axons were found to serve fibres of both types. The shared axon was phasic in character. Some of the uropod and telson muscles are clearly homologous with axial muscles in more anterior abdominal segments. In a few of the former it was possible to make direct comparisons with the efferent neurones innervating their serial homologues. Differences were found in the size ratios of homologous axons, in their central location, and in their presence or absence.
The Possible Role of the Supra-Oesophageal Ganglion in the Responses of Nephtys (Polychaeta, Annelida) to Changes in Hydrostatic Pressure
Authors: Morgan Elfed
Published: April 2021

The swimming activity of the isolated ‘tail’ region of Nephtys is not affected by changes in hydrostatic pressure. In contrast the responses shown by the isolated anterior third of the body are indistinguishable from those of intact worms. Decerebration, or transection of both circum-oesophageal connectives, also destroys the worms’ ability to respond, whereas transection of the connective on one side only does not. Not one of the sensory structures hitherto described in association with the supra-oesophageal ganglion appears to be the sole mediator of the response.
The Distribution of Po2 and Hydrostatic Pressure Changes Within the Branchial Chambers in Relation to Gill Ventilation of the Shore Crab Carcinus Maenas L
Authors: Hughes G. M. , Knights B. , Scammell C. A.
Published: April 2021

Many studies have been made of the mechanisms which maintain the flow of water across the gills of aquatic animals. In no case, however, has it been possible to formulate a detailed account of the path of the water and blood relative to one another at the exchange surfaces. One of the reasons for this is because the gills are usually contained within enclosed cavities and also they may move during the ventilation cycle. The situation is more complicated as the walls of the branchial cavities may also be involved in the ventilation movements, as, for example, the operculum of teleost fishes. The further detailed analysis of gaseous exchange at gills, which is best known in fishes, has been held up because of the lack of information of this kind. The study of gill ventilation in the Crustacea has distinct advantages from this point of view. The wall of the branchial chamber is rigid and a window can therefore be fixed in it without disrupting the normal hydrodynamic conditions. Furthermore, the rigid exoskeleton allows the animal to be held in a fixed position, and it provides a site for the attachment of recording leads and water-collecting tubing. Another advantage is that the gills of these animals do not move during a normal respiratory cycle. Much work has been carried out on the ventilation of decapod Crustacea but few studies (e.g. Larimer, 1964) have made use of modern pressure recording equipment and oxygen electrodes.
An Acridid Auditory Interneurone
Authors: Rowell C. H. Fraser , McKay J. M.
Published: April 2021

An auditory interneurone (‘alpha neurone’) of Gastrimargus africanus is described. It runs from the mesothoracic ganglion to the brain, and receives summating excitatory inputs from both tympanic nerves. There is no inhibition between the two units or their inputs. The lowest effective frequency is 5−8 kcyc./sec. and response is greatest at the highest frequency tested, 40 kcyc./sec. Threshold at 30 kcyc./sec. is approximately + 50 dB above 0·0002 dynes/cm.2, and response increases with amplitude from 60−90 dB, after which there is no further increase. Increase of amplitude also shortens response latency ; the correlation of latency and response strength is low and very variable. The response is slowly adapting, and mean impulse frequency declines exponentially with increasing length of short sound pulses. Directionality of unilateral sound is signalled by the alpha neurones in only 70% or less of trials, and at least 10% are discriminated ‘wrongly’. The low correlation between response strength and latency improves the signalling of directionality. A second ‘beta’ neurone is described briefly. It signals directionality of a unilateral sound with 100% accuracy, due to mutual inhibition between ipsilateral and contralateral systems, as in some tettigoniid interneurones. Ten or more apparently separate auditory interneurones have now been described in acridids ; this parallels the diversity of receptors described in the ear.
The Physiology of the Antennal Gland of Carcinus Maenas (L.)
Authors: Binns R.
Published: April 2021

It is now well established that the antennal glands of Crustacea, both marine and fresh water, are concerned with regulation of the ionic composition of body fluids (Robertson, 1957; Shaw, 1960; Lockwood, 1962; Potts & Parry, 1964). This activity is considered by some to be the main function of the antennal gland (Webb, 1940; Parry, 1960). Because it produces urine and is undoubtedly concerned with ionic regulation, there is a tendency to discuss antennal gland function in terms of the physiology of the vertebrate kidney. The unqualified inference, often expressed in general zoology texts, that the antennal gland carries out all the functions of the vertebrate kidney is unwarranted, since information concerning antennal gland function, other than ionic regulation, is extremely limited. This is particularly so when considering nitrogen excretion by the antennal gland. A urine-producing ‘excretory organ’ is usually thought of as being concerned with, amongst other things, the elimination of nitrogenous waste products. This function is sometimes ascribed to the antennal gland, despite the fact that there is remarkably little information on this aspect of the physiology of the organ. After a survey of nitrogen excretion by Crustacea and a consideration of analyses of the urine of Maia, Delaunay (1931) concluded that the antennal gland was not concerned with nitrogen excretion and that its importance in this respect has been over-estimated by histo-physiologists. With only a little additional information available, Parry (1960) concluded that the antennal gland was concerned primarily with ionic regulation. Ramsay (1961) was more cautious and considered that because information is so limited, and because little is known of invertebrate biochemistry, the possibility remains that the antennal gland may be concerned with the removal of some excretory products.
Neural Patterns Associated With Ventilatory Movements in Dragonfly Larvae
Authors: Mill P. J.
Published: April 2021

Rhythmic bursts of motor activity associated with the expiratory phase of ventilation have been recorded from the second lateral segmental nerves of posterior abdominal ganglia in Aeshna and Anax larvae. In Aeshna the rhythmic expiratory bursts contain one, or sometimes two, motor units; whereas in Anax there are almost invariably three units. In both animals only one unit is associated with action potentials in the respiratory dorso-ventral muscle. Motor activity synchronized with the expiratory bursts in the second nerves has been recorded from the other lateral nerves and from the last unpaired nerve. In addition the fifth lateral nerves carry inspiratory bursts. It has been confirmed that stimulation of a first segmental nerve can re-set the ventilatory rhythm by initiating an expiratory burst in the second nerves. The original frequency is immediately resumed on cessation of stimulation. The nature of the ventilatory control system in dragonfly larvae is discussed in relation to other rhythmic systems in the arthropods.
Analysis of the Mechanical Responses of Metathoracic Extensor Tibiae Muscles of Free-Walking Locusts
Authors: Usherwood P. N. R. , Runion H. I.
Published: April 2021

Two techniques for indirectly measuring the mechanical responses of metathoracic extensor tibiae muscles (METM’ s) of free-walking locusts are described. First, processed data from neurograms of free-walking (donor) locust preparations were used to stimulate the neurones innervating the METM’s of restrained (recipient) preparations. The mechanical responses of the METM’s of the recipient locusts were recorded isometrically. Second, an electronic model of the METM was designed to give simulated electrical and mechanical responses following activation with processed neurographic data from donor locusts. Both of these techniques give only an indirect estimate of the mechanical responses of the donor METM’s and do not take into account the complex relationships between tension and length in these muscles. The mechanical responses of the METM during a variety of activities, especially walking, kicking and jumping, have been studied using these techniques and further information on the functional role of excitatory and inhibitory motomeurones has been obtained.