bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Responses to Light in a Specimen of Pelagohydra Mirabilis Dendy, 1902 (Coelenterata: Hydrozoa)
Authors: Pilgrim R. L. C.
Published: April 2021

A single specimen of P. mirabilis was subjected to varying degrees of illumination. In constant light occasional spontaneous reactions occurred, the tentacles flexing in an oral direction and moving the animal aborally a very insignificant distance each time. When the level of illumination was reduced suddenly and almost completely there occurred a sequence of such reactions; successive reactions in the sequence occurred with increasing vigour and at diminishing frequency. Readmission of light was shown to act as an inhibitory condition, since it interrupted the reaction sequence. When the illumination was reduced in a series of steps, each step was followed by a sequence of reactions, the sequences showing increase in vigour and decrease in frequency. Each such sequence appeared to be freshly initiated by the stepwise reduction in light.
The Sodium Balance Mechanism in the Fresh-Water Amphipod, Gammarus Lagustris Sars
Authors: Sutcliffe D. W. , Shaw J.
Published: April 2021

The sodium balance mechanism of Gammarus lacustris in fresh water is virtually identical with that found in G. pulex. The sodium transporting system at the body surface has a very high affinity for sodium ions. The system is half-saturated at an external concentration of about 0·14 mM/1. and fully saturated at about 1 mM/1. sodium. The lowest external concentration at which sodium balance was maintained was 0·06 mM/1. Both the total sodium loss rate and the sodium influx rate remained approximately constant in animals acclimatized to the range of external concentrations from 2 to 0·3 mM/1. NaCl. At lower concentrations the loss rate was reduced and the influx increased by a factor of about 1·5. Changes in the sodium influx and loss rates are very closely linked together, and it is shown how these changes are related to the external sodium concentration.
Iodine Accumulation in a Nemertine, Lineus Ruber
Authors: Balfour W. E. , Willmer E. N.
Published: April 2021

Studies with radioactive tracers show that the nemertine Lineus ruber actively accumulates iodide in its pharynx, and stores it mostly as iodide. When the sodium chloride concentration of the ambient sea water is raised, the amount of iodide accumulated is increased, and traces of a ‘thyronine’ can be detected. When the osmotic pressure was raised with sucrose (instead of NaCl) there was no increased uptake of iodine.
Hyperphagia in the Blowfly*
Authors: Dethier V. G. , Gelperin A.
Published: April 2021

The current view of the control feeding in the blowfly Phormia regina Meigen holds that ingestion is initiated by stimulation of oral taste receptors and ultimately terminated by signals from the foregut (Dethier & Bodenstein, 1958). The signals from the foregut originate in stretch receptors which monitor the passage of food from the crop to the mid-gut (Gelperin, 1966b). The recurrent nerve conveys these signals to the brain where they counteract input from peripheral taste receptors. Transection of the recurrent nerve interferes with this inhibitory feed-back system and causes a fly to become hyperphagic (Dethier & Bodenstein, 1958).
Regulation of Heat Production by Large Moths
Authors: Heath James Edward , Adams Phillip A.
Published: April 2021

Moths ‘warm-up’ prior to flight at mean rates of 4·06° C./min. in Celerio lineata and 2·5° C./min. in Rothschildia jacobae. The abdominal temperature rises only 2−3° C. during activity. Oxygen consumption of torpid sphinx moths increases by a factor of 2·27 as temperature changes from 26° to 36° C. Oxygen consumption during ‘warm-up’ increases with duration of ‘warm-up’ from about 1000μl./g. min during the initial 30 sec. to nearly 1600μl./g. min. during the 3rd min. This increase compensates for increasing heat loss from the thorax during ‘warm-up’. When the moths are regulating thoracic temperature, oxygen consumption increases with decreasing air temperature from a mean of about 400 μl./g. min at 31° C. to about 650 μl./g. min. at 26° C Values of O2 consumption calculated from the cooling curve of C. lineata are about 85 % of the measured values of O2 consumption. The giant silk moth, Rothschildia jacobae, regulates thoracic temperature during activity between about 32° and 36°C. at ambient temperature from 17°to 29° C. Moths kept at high temperatures are active longer, have more periods of activity and expend more energy for thermoregulation than moths kept at low temperatures. Large moths increase metabolism during active periods to offset heat loss and thereby maintain a relatively constant internal temperature. In this regard they may be considered endothermic, like birds and mammals. We estimate that male moths use 10% of their stored fat for thermoregulation, while females may use 50 %.
The Effect of Some Anions and Cations Upon the Fluxes and Net Uptake of Chloride in the Larva of Aedes Aegypti (L.), and the Nature of the Uptake Mechanisms for Sodium and Chloride
Authors: Stobbart R. H.
Published: April 2021

The anal papillae of the aquatic larva of Aëdes aegypti are responsible for 90 % of the steady-state exchange of chloride. The relationships between chloride flux and external chloride concentration are approximately described by the Michaelis equation. There is net uptake of chloride, independent of uptake of sodium, from KC1, CaCl2 and NH4C1, probably in exchange for OH’ or , but the rate is much slower than from NaCl. The following ions stimulate influx of chloride from 0·1 mM/1. KC1: H+ = Na+ > K+. The following ions inhibit it: Movements of sodium and chloride ions are explicable in terms of an anionic and a cationic carrier located in an osmotic barrier in the papillae, the carriers being functionally coupled to sodium and chloride pumps located at the inner surface of the barrier. An attempt is made to relate these findings to recent electron microscopical studies of the papillae.
The Jump of the Flea: A Study of the Energetics and a Model of the Mechanism
Authors: Bennet-Clark H. C. , Lucey E. C. A.
Published: April 2021

The energy requirement of a jump of 3·5 cm. height by the rabbit flea, Spilopsyllus cuniadi, is 2·25 ergs. This must be delivered in 0·75−1 ·o msec, over a distance of 0·37−0·5 mm., which is not compatible with direct muscular action. The anatomy of the jumping mechanism has been re-examined and its action studied by high-speed cinematography. The following explanation is offered. The main impulse comes from the depression of the metathoracic femur, whose depressor muscle originates on the notum. In the resting position the attachment of the depressor tendon to the femur is over-centre with respect to the trochanter-femoral joint. When the muscle contracts energy is stored in a resilin pad located between notum and pleuron. This energy is released by a second muscle which pulls the depressor tendon away from the over-centre position, thus enabling it to depress the femur. Operations on live fleas have provided evidence in support of the proposed mechanism. The depressor muscle is capable of providing 1-96 ergs on each side. The resilin pad is capable of storing 4 ergs on each side. Species which are better jumpers have larger resilin pads.
Neuro-Muscular Control of Dipteran Flight
Authors: Nachtigall Werner , Wilson Donald M.
Published: April 2021

Electrical activity from the indirect, myogenic muscles of calliphorid flies was recorded during flight. The animals were suspended from an aerodynamic balance in the laminar air-stream from a wind-tunnel. Muscle action potentials, recorded with 25 μ wire, were 5−7 msec, in duration, up to 10 mV. in amplitude and positive in sign. Frequencies were mostly under 20/sec. Frequencies in all the indirect muscles were similar, but these varied together with changes in aerodynamic power. Frequencies in the indirect muscles of the two sides varied by no more than ±10% during extreme turns to right or left (only left or only right wing beating). Electrical records from the non-myogenic direct muscles were made during tethered flight. The potentials were 2−4 msec, in duration, up to 2 mV. positive and had frequencies up to 180/sec. A nearly linear positive correlation exists between impulse frequency in the musculus latus (pleurostemal muscle), the inward movement of the pleural wall, and the wingbeat frequency, suggesting that this muscle is the basic frequency determiner. Strong turning behaviour is associated with opposed frequency changes in the pairs of antagonistic adductor and abductor muscles of the wings on the two sides of the body. The musculus dorsoventralis IV (tergo-trochanteral) is activated by a short impulse burst at the beginning of flight. It apparently acts as an oscillation starter. Flight initiation normally requires 30−60 msec. Usually activity begins in the musculus latus, which stiffens the thorax. Then simultaneously the myogenic muscles are activated and the ‘starter’ muscle causes a jump and the beginning of oscillation of the thorax. Then the wings are drawn gradually forward and full wingbeat amplitude develops within the first six wingbeats. Flight begins with maximal lift and wingbeat frequency and a nearly synchronous burst discharge in all the indirect muscles. Power production and the transmission and distribution of power are under separate control. The myogenic indirect motor varies only in total power output, this being influenced by its own state of excitation and by a muscle-controlling wingbeat frequency. Steering is accomplished by non-myogenic direct muscles which are capable of differentially engaging the two wings with the motor.
Thermodynamic Aspects of Flagellar Activity
Authors: Holwill M. E. J. , Silvester N. R.
Published: April 2021

The frequencies of the beat of cilia and flagella from various organisms have been determined at temperatures in the range 5–35° C. Values of the activation enthalpy (ΔH‡, kcal./mole) and activation entropy (ΔS‡, e.u.) derived from the thermal dependence of frequency show a linear correlation of the form, ΔS‡ = 3·25 ΔH‡ – 50·75. The corresponding isokinetic activation free energy is 15·6 kcal./mole. The results support a hypothesis that the breakdown of an ATP-ATPase complex could be the common rate-limiting reaction for flagellar activity. Values of AH* and AS* for the decay of length or tension in striated muscles also fall on the same regression line but some smooth muscles show deviations.
Visual Pigments in a Tropical Freshwater Fish Etroplus Maculatus (Teleostei)
Authors: Virabhadrachari V. , Krishnamoorthy R. V. , Parvatheswararao V.
Published: April 2021

In its natural habitat (fresh water) E. maculatus had VP 5152 (porphyropsin) as the predominant visual pigment. On acclimation to 100% sea water VP 495! (rhodopsin) was found to be predominant. On acclimation to 50 % sea water the visual pigment system of the fish presented a transitory phase. The significance and implications of these results in relation to the earlier work is discussed.
Impulse Identification and Axon Mapping of the Nine Neurons in the Cardiac Ganglion of the Lobster Homarus Americanus
Authors: Hartline Daniel K.
Published: April 2021

The isolated cardiac ganglion of the lobster is an autonomous, integrating system containing only nine neurons. Its physiology was first investigated by Welsh & Maynard (1951) and has been reviewed by Hagiwara (1961). Its component cells, when isolated from synaptic input, are usually either quiescent or fire nerve impulses at a uniform low frequency but, when connected normally in the ganglion, they periodically fire short, high-frequency trains of impulses. The periods of activity in all cells are approximately coincident, producing what is collectively termed the ‘burst’, which is followed by a quiescent period in all units (Maynard, 1955). Evidence so far accumulated indicates that the four posteriorly located ‘small cells’ or ‘pacemaker cells ‘control the burst timing, one of them initiating the normal burst. These interact strongly with the five anterior ‘large cells ‘or ‘follower cells ‘, producing firing in them. Output from these goes to the heart muscle, causing heart contraction. Pacemakerpacemaker interactions are presumed but not rigorously demonstrated; followerfollower interactions via impulses are present but weak (Otani & Bullock, 1959); long-lasting potential changes in followers affect pacemaker firing and intracellular potentials of other followers (Watanabe & Bullock, 1960). As a step toward the more exact determination of the means by which the over-all ganglionic behaviour derives from the synaptic interactions of its component cells, the paths of the axons of the large and small cells within the ganglion have been determined physiologically, and a means for identifying the nerve impulses produced by each during a burst has been developed.
Microelectrode Study of the Resting and Action Potentials of the Cockroach Giant Axon with Special Reference to the Role Played by the Nerve Sheath
Authors: Pichon Y. , Boistel J.
Published: April 2021

The use of very fine-tipped and mechanically strong microelectrodes has allowed reliable recordings of resting and action potentials to be made in cockroach giant axons in sheathed and desheathed nerve cords. When the microelectrode was withdrawn from a giant axon in an intact connective the first positive change in the potential from the resting level, was in most cases followed by a negative deflexion to the original zero level, the ‘sheath potential’. The values of this ‘sheath potential ‘together with the resting potential, the action potential, the maximum rate of rise and maximum rate of fall of the action potential have been measured in three different salines. In normal saline, resting potentials were lower in sheathed preparations (58·1 ± 5·4 mV.) than in desheathed ones (67·4 ± 6·2 mV.), whereas action potentials were higher in the former (103 ± 5·9 mV.) than in the latter (85·9 ± 4·6 mV.). Elevation of K+ and Ca2+ concentrations in the saline to the haemolymph level resulted in a decrease of resting and action potentials in desheathed cords, to 57·3 ± 5·3 mV. and 36·5 ± 7·6 mV. respectively. No alterations in the membrane potentials were recorded in intact connectives bathed in this saline, the mean resting potential being 55·6 ± 4·2 mV. and the mean action potential 107·9 ± 6·0mV. Local desheathing of the nerve cord led only to local disturbance of the resting and action potentials, thus indicating that diffusion processes along the extracellular spaces were very slow. The use of a saline in which cation concentrations have been elevated to the extracellular level resulted in normal resting potentials (64·6 ± 3·3 mV.) and action potentials (90·9 ± 7·2 mV.) in desheathed cords, despite the relatively high potassium concentration (17·1 mM./L). Recordings of the maximum rates of rise and rates of fall showed that there was no significant modification in the shape of the action potential in these different experimental conditions. The values of the ‘sheath potential’ were very variable from one impalement to another and it is suggested that this potential might be related to variations of the microelectrode tip potential bathed in different ionic solutions. The low resting potentials and high action potentials of giant axons in intact nerve cords may result from an excess of inorganic cations in the extracellular fluid.
An Electrophysiological Study of the Tentacle-Regulating Potentials in Noctiluca
Authors: Sibaoka Takao , Eckert Roger
Published: April 2021

The duration and frequency of tentacle-regulating potentials (TRPs) recorded from the vacuole of Noctiluca miliaris were modified by both steady and abrupt changes in the vacuolar potential. The spike frequency increased linearly with an increase in the vacuolar negativity over the range of o to −50 mV. A transient decrease of impedance across the soma occurs coincidentally with the negative-going TR spike recorded from the vacuole. Local measurements of impedance changes as well as local surface potential recordings indicate that the TR spike does not propagate over the remainder of the cell from its region of origin near the base of the tentacle. Specimens without visible tentacles exhibited TRPs of normal shape. Concurrent potential recordings from the vacuole and the perinuclear cytoplasm indicate that the vacuolar membrane bordering that portion of the cell is inactive. Except for a relatively more pronounced post-spike hyperpolarization the TRP shape and polarity in the perinuclear cytoplasm, referred to the sea-water bath, are similar to those recorded from the vacuole, but are of smaller amplitude. The TRP appears to consist of a pre-spike pacemaker potential and an action potential having a prolonged post-spike plateau, the pattern recorded from the vacuole being the approximate inverse of that which would be recorded if a microelectrode could be introduced into the cytoplasm adjacent to the electrically active portion of membrane. Several of the findings indicate that the active membrane faces the vacuole and is electrotonically isolated from the perinuclear cytoplasm except through the vacuole.
Sodium and Water Balance in the Cichlid Teleost, Tilapia Mossambica
Authors: Potts W. T. W. , Foster M. A. , Rudy P. P. , Howells G. Parry
Published: April 2021

The total body sodium increases from 45·9 μM/g. fish in fresh water to 59·9 μM/g. fish in 200 % sea water. The rate of exchange of sodium increases from 2 μM/g./hr. in fresh water to 60 μM/g./hr. in 100% sea water. The rate of drinking increases from o·26%/hr. fresh water to 1·6%/hr. in 400% sea water. Even in 200% sea water drinking accounts for only a quarter of the total sodium influx. The permeability to water, as measured by tritiated water, is highest in fresh water and lowest in 200% sea water. The permeabilities to water measured in this way are consistent with the drinking rates determined in sea water and 200% sea water.
Studies on Freshwater Osmoregulation in the Ammocoete Larva of Lampetra Planeri (BLOCH)
Authors: Bull J. M. , Morris R.
Published: April 2021

Measurements have been made of a number of basic parameters related to osmoregulation in the ammocoete larva of the brook lamprey (Lampetra planeri Bloch). There is no significant variation in the water content of whole animals or their tissues between animals analysed during November and July, but the fat content rises in July and the majority of fat storage takes place in the muscles. Analyses have been made of the major osmotically active ions in whole animals, in muscle and in blood. Unlike previous investigators we found no significant seasonal variation in any of these components. The freezing-point depression of ammocoete blood (113–119 mM/1. NaCl) is lower than that of adult river lampreys (140 mM/1. NaCl), but apart from higher potassium values, monovalent ions contribute nearly the same proportion to the total osmotic pressure in both animals. The muscle analyses indicate that the ammocoete has a higher ratio of potassium to sodium (14·8:1) than other vertebrates. Measurements of the fluid and ionic compartments have been made on whole animals and on muscle using isotopic dilution techniques and conventional analyses. The extracellular space of muscle is about half that of whole animals (24·4% body weight) and contains all the chloride and 69 % of the sodium within whole muscle. Potassium almost completely replaces sodium within the cells and part of this may be bound sodium in some tissues. The urine output of the ammocoete amounts to 198 ml. per kg. per day and is similar to the values previously obtained from other lampreys in fresh water. The high potassium to sodium ratio within cells, together with the lack of seasonal variation and low variability in ionic analyses, is taken as an indication of the presence of very efficient controlling mechanisms operating on extracellular fluids and within the cells themselves.
On the Eyespot of the Dinoflagellate, Nematodinium
Authors: Francis David
Published: April 2021

Nematodinium possesses an eyespot which consists of a lens closely apposed to a pigment cup containing a supposedly light-sensitive retinoid. The shape of the lens is described and its refractive index measured. From these data it is concluded that light from sources outside the cell will be brought to focus on the retinoid. The quality of the image formed is assessed. A variety of functions are possible to the organelle. It is suggested that functions involving image formation may be realized, even in the absence of a true retina and nervous system.
The Osmotic Behaviour of a Number of Grapsoid Crabs with Respect to their Differential Penetration of an Estuarine System
Authors: Barnes R. S. K.
Published: April 2021

The effect of salinity upon five Australian grapsoid crabs exhibiting differential penetration of an estuarine system has been investigated. The salinity tolerances over a range of 2–70‰ (approx.) salinity, the acclimation times, and the osmoregulatory capabilities of these species have been determined. It is concluded that for four of the five species salinity is probably a limiting factor in hyposaline conditions; whilst for only one species is salinity probably a limiting factor in hypersaline conditions. The relative abundances of two species in the estuary appears to be a function of their capabilities for osmoregulation. Habitat preferences probably limit the upstream penetration of one species, and may limit the downstream penetration of a second.
The Pedal Neurons of Aplysia punctata
Authors: Dorsett D. A.
Published: April 2021

Three classes of neurons have been identified in the pedal ganglia of Aplysia punctata. The motor neurons, which may be unipolar or bipolar, have the axon passing into one of the pedal nerves and in the case of the bipolars, the other branch entering the pedal commissure. This synapses with neurons on the opposite side, thus providing an integrative link between the ganglia. The interneurons are without axons in the pedal nerves or commissure, although afferent pathways to these cells and the motor neurons occur in the pedal nerves in a variety of combinations. The pathways in the ipsilateral nerves are for the most part excitatory, but inhibitory fibres occur in the posterior pedal nerve. Inhibitory potentials were often obtained in the interneurons by stimulation of the pedal commissure. A second type of coordinative pathway is provided by fibres which enter the CNS in one of the pedal nerves and terminate on neurons in both pedal ganglia.
Urine Formation by the Malpighian Tubules of Calliphora
Authors: Berridge M. J.
Published: April 2021

Rate of urine formation is very sensitive to potassium concentration. Potassium is concentrated in the urine by a mechanism which is independent of other monovalent cations. Rubidium, caesium and sodium are also capable of maintaining a flow of urine. At low external potassium concentrations, sodium stimulates potassium secretion. Rate of urine secretion is stimulated by low osmotic pressures; the osmotic pressure of urine was slightly hypertonic throughout the range of external osmotic pressure employed. Addition of sucrose depresses rate of urine secretion; the potassium concentration of the urine increased by 1 mM/l. for each 2 mM/l. of sucrose added to the bathing medium. Urine formation is insensitive to sulphanilamide, acetazolamide, ouabain and a wide variation of pH. These observations are discussed in relation to the hypothesis that potassium secretion takes place across both surfaces of the cell. The pump on the basal surface may be a coupled sodium-potassium pump, whereas that on the apical surface may be electrogenic. Microvilli at the apical surface or channels formed by a complex infolding of the basal plasma membrane may represent structural devices by which standing osmotic gradients can be established during solute-linked water transport across the cells of Malpighian tubules.
The Influence of Environment and Heredity on Flight Activity in the Milkweed Bug Oncopeltus
Authors: Dingle Hugh
Published: April 2021

Most long flights of Oncopeltus, tested using tethered flight in the laboratory, took place during the middle of the day. This is consistent with field data from other Heteroptera. In bugs reared at 23° C., regardless of length of photoperiod, 20% of males and 30% of females were migrants. Temperatures of 19° and 27° C. reduced these proportions. A short photoperiod of 12 hr. of light failed to increase the proportion of migrants over that present at 16 hr. The period in the life-history during which migration took place, however, was lengthened considerably. In spite of the lengthened flight period and a delay in oviposition, migrants arrive at their destinations with reproductive value high and are therefore colonizers. Food deprivation may increase somewhat the proportion of migrants if it occurs shortly after eclosion, although most of the extra activity seems to be due to additional non-migratory flight. If it occurs after oviposition has begun, food deprivation can result in migration at a time when it would ordinarily have ceased. The proportion of migrants could be significantly increased by appropriate selection and breeding. The basis for migratory behaviour is thus, in part at least, genetic. The data in general support the hypothesis that migration is elicited, enhanced, or suppressed in genotypical migrants by those environmental factors which influence ovary (and corpus allatum) development.
Hearing in Terrestrial Urodeles: A Vibration-sensitive Mechanism in the Ear
Authors: Smith J. J. B.
Published: April 2021

Sinusoidal vibrations delivered to the ventral surface of the urodeles Salamandra salamandra and Triturus cristatus result in sinusoidal displacements of the fluid in the perilymph foramen. The displacing force is transmitted either via the cranial cavity or via the ear capsule. The displacements are of considerably greater amplitude than those of the skull at frequencies between 50 and 400 Hz. These large displacements are explained in terms of a hydraulic system, based on the dimensions of structures associated with the ear. This system, together with a suitably located receptor organ, the amphibian papilla, provides a vibration-detection system of potentially greater sensitivity than one relying on otolith granules. The perilymph duct may act as a shunt pathway, allowing gross low-frequency displacements of the perilymph to bypass the amphibian papilla.
A Simple Electrolytic Respirometer for the Continuous Recording of Oxygen Consumption Under Constant and Natural Conditions
Authors: Chase Ann M. , Unwin D. M. , Brown R. H. J.
Published: April 2021

The principles involved in the design of an electrolytic respirometer are set out. A respirometer is described for air-breathing animals which allows the continuous recording over long periods (up to two weeks) of oxygen consumption at rates of the order of 10-100 μl. per hour. Provision is made for maintaining the temperature, pressure, and carbon dioxide and oxygen levels constant and at atmospheric values. A new design of recorder displays the results directly as rate of oxygen consumption. The features of the apparatus are discussed with reference to specific requirements.
Respiratory Physiology of House Sparrows in Relation to High-Altitude Flight
Authors: Tucker Vance A.
Published: April 2021

Some birds perform the strenuous activity of flapping flight at altitudes in excess of 6100 m. (20,000 ft.), an altitude at which resting, unacclimated man is in a state of incipient hypoxic collapse. This study investigates the respiratory problems associated with avian flight at 6100 m. House sparrows and white mice were exposed to a simulated altitude of 6100 m. for an hour. Their metabolic rates were kept above the basal level by regulating environmental temperature at 5°C. At 6100 m. the sparrows consumed oxygen at 2.2 times the basal rate, used more oxygen and had higher heart and respiratory rates than at sea level. Body temperature decreased 2°C., but the birds were normally active. In contrast, the mice at 6100 m. were moribund and had body temperatures 10°C. below normal after 1 hr. Oxygen consumption and respiratory rates were less than at sea level. At 6100 m. sparrows ventilated the respiratory parts of their lungs 77% more than at sea level. At sea level and 6100 m. respectively, the partial pressure of carbon dioxide in the lungs dropped from 39.5 to 27.2 mm. Hg, and the partial pressure of oxygen in the lungs dropped from 100 to 28 mm. The sparrows removed a greater proportion of the oxygen from the air ventilating the lungs at 6100 m. than they did at sea level. Oxygen dissociation curves were determined for sparrow blood at various pH values. At 6100 m. the arterial blood of sparrows appears to be less than 24% saturated with oxygen. For the cardiovascular system to transport adequate oxygen to the tissues at this low level of saturation house sparrows must have a cardiac output that is at least triple the maximum known for mammals. House sparrows in a hypobaric chamber could fly 2.5 m. and gain altitude at a simulated altitude of 6100 m. but not at 7620 m. (25,000 ft.). Budgerigars trained to fly in a wind tunnel in the hypobaric chamber could fly more than 20 min. at sea level and a maximum of 3 min. at an altitude of 3660 m. (12,000 ft.). A budgerigar trained to wear an oxygen mask while flying in the wind tunnel could fly at an altitude of 6100 m. Calculations based on our present knowledge of avian physiology suggest how birds could be capable of flying at 6100 m. The possible advantages of flight at high altitudes are discussed.
Transpiration Through the Slifer’s Patches of Acrididae (Orthoptera)
Authors: Makings P.
Published: April 2021

Transpiration through the Slifer’s patches of the desert locust (Schistocerca gregaria) was demonstrated experimentally, and was found to be greater than that through the normal cuticle at room temperature (20° C.). The difference increases at higher temperatures. Similar results were obtained with other acridids. Death of the animal appeared to have no effect on the phenomenon. Tentative estimations of the patch transpiration rate gave very high values, probably exaggerated by pinhole diffusion. The surprising figure of 169 ±52 mg./ cm.2/hr. at about 45° C. was obtained with living preparations. With dead ones and a different method, the values were smaller, being near-zero below 40° C but increasing fairly steeply from 45° to 60° C. It is suggested that the patches might show a transition effect at 40° C. Some superficial lipid which appears to melt at 45° C. all over the cuticle may be connected with the high permeability of the patches. The structural peculiarities of the patches can be explained as adaptations to a high transpiration rate. The patches may form an emergency cooling system, but other functions are not excluded.
The Influence of Ephestia Kuehniella on the Development of its Parasite Nemeritis canescens
Authors: Corbet Sarah A.
Published: April 2021

The first larval instar of Nemeritis lasts longer in young caterpillars of Ephestia than it does in older caterpillars. First-instar Nemeritis larvae in young hosts feed and grow very slowly, but they remain capable of fast growth if transferred to older host caterpillars. Measurements of the protein concentration, the amino acid concentration and the freezing-point depression show rapid changes in the composition of the haemolymph of Ephestia caterpillars at that stage of larval development at which they first become capable of supporting the fast development of first-instar larvae of Nemeritis. It is suggested that the rate of development of Nemeritis larvae depends on their rate of feeding, and that their rate of feeding is determined by a behavioural response to the composition of their food, the host’s haemolymph; they feed slowly in young host caterpillars because the concentration of solutes (notably amino acids) in their food is so high. A similar situation may hold when the development of insect parasites is delayed in diapausing hosts.
The Patterns of Renal Electrolyte Excretion in the Duck (Anas platyrhynchos) Maintained on Freshwater and on Hypertonic Saline*
Authors: Holmes W. N. , Fletcher G. L. , Stewart D. J.
Published: April 2021

The renal excretion of water and electrolytes was examined in starved ducks maintained on fresh water and on hypertonic saline containing 284 mM/l. NaCl and 6·0 mM/l. KCI. No significant differences were observed in the urine flow, glomerular filtration rate, renal plasma flow and the excretory rates of K+, NH4+ and inorganic phosphate between these two groups of birds. The excretory rates of Na+, Cl- and Ca2+ were significantly higher in saline-maintained birds than in the freshwater-maintained birds. NH4+ appeared to be a major cationic component which occupied over half of the available osmotic space in the urine of both the freshwater-maintained and saline-maintained birds. In saline-maintained birds the excretion of K+ and inorganic phosphate appeared to be independent of the available osmotic space in the urine whereas the excretion of Na+ and Cl- appeared to be very dependent upon this factor. These observations suggest that the kidneys of the saline-maintained bird constitute the primary pathway for the excretion of K+, NH4+ and inorganic phosphate, and that with respect to the excretion of Na+ they constitute a relatively minor pathway.
Quantitative Analysis of Swimmeret Beating in the Lobster
Authors: Davis W. J.
Published: April 2021

High-speed motion pictures of the metachronous movements of the abdominal swimmerets of the lobster Homarus americanus were analysed. Measurements were made on films produced before and after removing part or all of individual swimmerets. Analysis of the intact swimmeret system provided quantitative constraints for models of the neural mechanisms underlying swimmeret beating. For example, the conduction velocity of the anterior-moving, metachronous wave increases with increasing frequency of swimmeret beating, as does the powerstroke amplitude and velocity of each swimmeret. The phase positions of individual swimmerets in the movement cycle are the same regardless of the frequency of swimmeret beating, and so are the ratios of powerstoke duration to returnstroke duration. The durations of the powerstroke, returnstroke and the short pauses between them decrease as the frequency of swimmeret beating increases. Removal of a swimmeret weakens the movements of ipsilateral swimmerets on adjacent segments, but does not affect the movements of contralateral swimmerets. Control experiments were performed to reduce the possibility that the effects were mechanical. The results suggest that proprioceptive feedback from the movements of individual swimmerets plays a supplemental role in the intersegmental coordination of the swimmerets of one side, but that contralateral proprioceptive influences are weak or absent.
The Mechanism of Burrowing of Some Naticid Gastropods in Comparison with That of Other Molluscs
Authors: Trueman E. R.
Published: April 2021

The burrowing activity of naticid gastropods, described by use of ciné film and electronic recordings, shows four stages, together termed the digging cycle, which are repeated cyclically until burial is complete. In each cycle the retraction and extension of the propodium is integrated with the alternate swelling of two regions of the foot by the movement of blood within the pedal sinus. The shell is pulled into the sand with the propodium dilated by the fluid pressure generated by the columellar and intrinsic pedal muscles. The role of water in the expansion of the foot of Polinices is discussed. In a comparison of the burrowing process of naticids with that of other molluscs a general similarity is observed throughout the phylum and in other soft-bodied invertebrates. The major differences between the burrowing of gastropods and that of bivalves are discussed and indicate that in former burrowing is an adaption of normal surface locomotion, whereas the bivalves are more primitively adapted to an infaunal mode of life.
Effects of Eyestalk Removal On Rhythmic Locomotor Activity in Carcinus
Authors: Naylor E. , Williams Barbara G.
Published: April 2021

Male Carcinus collected in summer and given several days to recover from eyestalk ablation showed a continuously high level of activity. Injection of eyestalk extract inhibited activity. Unlike control animals from which retinae were removed, experimental animals did not show a rhythm after chilling. Chilling the eyestalks alone elicited a rhythm similar to that appearing when the whole animal was chilled. The results are consistent with the view that locomotor rhythmicity is mediated via an inhibitory hormonal mechanism in the neurosecretory cell groups of the eyestalk. There is no direct evidence that the neuroendocrine mechanism alone constitutes an autonomous clock, however, and it is in any case probably co-ordinated by one or more other rhythmic systems within the crab.
The Genesis of Certain Cardiac Arrhythmias in Fish
Authors: Satchell G. H.
Published: April 2021

The hearts of both elasmobranch and teleost fish are known at times to beat at a particular phase of the respiratory cycle and thus to exhibit a regular rhythm locked to that of respiration (Lyon, 1926; Lutz, 1930; Satchell, 1960; Shelton & Randall, 1962). In the laboratory, the hearts of Squalus acanthias and Mustelus antarcticus usually exhibit a 1:2,1:3 or 1:4 rhythm, the P wave of the electrocardiogram occurring as the mouth opens in the appropriate respiratory cycle. Lyon (1926) reported a 1:1 co-ordination in Carcharias sp. In Squalus acanthias it is known that respiration stimulates receptors in the pharynx, the afferent fibres of which pass up the branchial branches of the glossopharyngeal and vagus nerves to the medulla; the efferent limb of the reflex is the cardiac vagus nerve (Satchell, 1960).
Medium and Long-Term Changes in the Behaviour of Visual Neurones in the Tritocerebrum of Locusts
Authors: Horn G. , Fraser Rowell C. H.
Published: April 2021

Extracellular recordings were made from single units in the tritocerebrum of locusts. The units responded to objects moved anywhere in the contralateral visual field. They were relatively insensitive to stationary stimuli and did not respond to auditory or tactile stimulation. Responses to successive movements gradually declined even when an interval of several minutes elapsed between each movement. The number of impulses evoked by a stimulus was strongly influenced by the amount and timing of previous stimulation. Such influences occasionally lasted for several hours. The responses of some cells to the first few groups of stimuli presented at the beginning of an experiment were non-decremental, but the response to subsequent stimulation was always decremental. Many of the units showed directional preferences, discharging more vigorously to movement in one direction than in the reverse direction. In no case was movement inhibitory to the cell. The directional preferences were modified by primacy so that for a number of presentations a unit responded preferentially to the directional characteristics of the first of a group of stimuli. The cells were insensitive to movement of the whole visual field brought about by movement of the whole animal, but still retained their responsiveness to relative movement within the visual field.
A Critical Study of the Evidence for Peripheral Inhibitory Axons in Insects
Authors: Usherwood P. N. R.
Published: April 2021

The metathoracic anterior coxal adductor (a.c.a.) muscle of the locust and the grasshopper is innervated by a peripheral inhibitory axon similar to the inhibitory axon which innervates the metathoracic extensor tibiae muscles of these insects. No evidence was found to justify calling this axon an inhibitory-conditioning axon. Hyperpolarizing inhibitory postsynaptic potentials (IPSPs) are normally recorded from a.c.a. muscle fibres during stimulation of this axon, and if the bathing medium contains a high concentration of potassium ions the tonic fibres of the a.c.a. muscle relax slightly during inhibitory stimulation. The IPSPs are chloride potentials and can be converted to depolarizing responses by changing either the external or internal chloride concentration of the a.c.a. muscle fibres. Depolarizing IPSPs are frequently accompanied by small contractions of a.c.a. muscle fibres innervated by the inhibitory axon. The a.c.a. muscle fibres are permeable to potassium and chloride ions but influx of potassium chloride is much faster than efflux. Therefore when a.c.a. muscle fibres are loaded with chloride by exposing them to high-K saline (20−100 m-equiv. potassium/I.) and are then returned to normal (10 m-equiv. potassium/1.) saline the internal chloride concentration remains elevated for some time and during this period the equilibrium potential for the inhibitory response is less negative than the resting potential and the IPSPs are depolarizing. Depolarizing IPSPs are usually recorded from a.c.a. muscle fibres of locusts and grasshoppers when these fibres are transferred from their normal bathing medium, haemolymph, to 10 K saline. Probably the main reason for this reversal of the IPSPs is the entry of KC1 into the muscle fibres during dissection of the nerve-muscle preparations. Large quantities of KC1 would be released into the environment surrounding these preparations from muscle fibres cut and removed during dissection. Depolarizing IPSPs were more frequently recorded from muscle fibres of grassfed locusts than from fibres of starved locusts. The potassium concentration of haemolymph of grass fed locusts is higher than that of locust saline (10 m-equiv./l.). The potassium concentration of locust haemolymph presumably fluctuates in vivo but these fluctuations are too slow to affect the sign of the IPSP. The IPSPs are therefore always hyperpolarizing in vivo. The effect of changes in the potassium concentration of the bathing medium on the magnitude and polarity of the IPSP could account for the diverse responses recorded previously from a.c.a. muscle fibres of locusts and grasshoppers.
Control of the Circadian Rhythm of Activity in the Cockroach
Authors: Brady John
Published: April 2021

A study was made of the concentration of potassium and sodium in the blood of Periplaneta americana to determine whether daily fluctuations occur which might imply ionic control of the circadian locomotor activity rhythm. Analyses were carried out on 166 blood samples taken at different times of day. A fall of about 10% occurred in the potassium concentration during the first hour of darkness; there was also a gradual decline of 2% in the sodium concentration. However, series of six successive blood samples taken over a period of 3 weeks from ten individual cockroaches revealed no daily change in the level of potassium, sodium or haemocyte density. No conclusions are drawn on the activity control aspect, but the results do suggest that daily changes may occur in cockroach blood ions.
Further Studies On Gradient-Dependent Diversification in the Pupal Cuticle of Galleria Mellonella
Authors: Stumpf Hildegard F.
Published: April 2021

In last instar larvae pieces of integument from different regions of the sixth segment have been transplanted to the fourth segment. The formation by the grafts of a ridge (region 2) and of region-3 cuticle, normally occurring only in the fifth, sixth and seventh abdominal segments, has been studied in the pupa. Grafts containing presumptive regions 1, 2 and 3 developed these regions when transplanted to an equivalent position in the fourth segment. Grafts containing only presumptive region 1 formed also region-2 cuticle and region-3 cuticle when transplanted to the anterior part of the fourth segment. Grafts containing only presumptive region 3 formed also region-2 cuticle and region-1 cuticle when transplanted immediately posterior to the bristle B1 in the fourth segment. The results support the concentration-gradient concept. They reveal that the gradients in the fourth and the sixth segments are of the same nature and that the difference in the cuticular structure of these segments must result from a difference in competence. The concept of determination is discussed in relation to these results. Deceased, October 1967. See editor’s note, p. 59.
The Effect of Ultrasonic Irradiation On the Survival of Daphnia Magna
Authors: Wells P. N. T.
Published: April 2021

Apparatus is described for the irradiation of Daphnia magna by 3 MHz. ultrasound, under controlled temperature conditions. The lethal level for heat exposure was established for Daphnia. It is shown that there was a threshold of irradiation level below which immediate death was due to heat. Above the threshold level for non-thermal damage, streaming in the environment of the animal became considerable. Long-term observations confirmed the existence of a threshold level for nonthermal damage during irradiation.
Thermoacclimatory Variations in the Haematology of the Common Carp, Cyprinus Carpio
Authors: Houston A. H. , Dewilde Mary Anne
Published: April 2021

The haematology of winter, summer, and autumn populations of carp has been investigated as a function of acclimation temperature. Red-cell number, packed-cell volume, and haemoglobin tend to vary directly with temperature. Mean erythrocyte volume is increased at very low temperatures but, like mean erythrocytic haemoglobin and mean haemoglobin/unit erythrocytic volume, tends to be stable at moderate to high temperatures. Although the data suggest a temperature-correlated increase in blood oxygen capacity, it is apparent that the animals must invoke other forms of cardiovascular-respiratory adjustment as well. On a seasonal basis increases in oxygen capacity are seen at low, but not high, acclimation temperatures. It is suggested that this form of response may be related to the pattern of capacity acclimation typical of cyprinid fishes.
Motoneurone Discharges to the Eyecup Muscles of the Crab Carcinus
Authors: Burrows M. , Horridge G. A.
Published: April 2021

During imposed tilt the eyecup of the crab tends to preserve an absolute position which depends upon the tonic activity of eight of the nine eyecup muscles. The detailed activity of all these muscles during imposed tilt in different planes has been recorded intracellularly. The slow- and fast-motoneurone discharges to the eyecup muscles differ in that the former have intervals which are more variable at lower frequencies but the latter are more variable at higher frequencies. The standard deviation of the interval between impulses is 20–30% of the mean interval for a wide range of frequencies of the tonic motoneurones. This large scatter is tolerable because the slow muscle fibres are sluggish and because the eyecup is also visually stabilized by a system of long time-constant. In roll the two eyecups move in opposite directions relative to the midline of the animal. In pitch the two eyecups move in the same direction relative to the body of the animal, but in neither case is there a correlation between individual impulses to the muscles of the right and left eyecups which are active at the same time. Possible mechanisms of linkage between the two eyecups are discussed.