bluuebunny/crossref_metadata_2025 huggingface dataset:
Apnoea in Amphibians and Reptiles
Authors: Shelton G. , Boutilier R. G.
Published: April 2021

The amphibian ancestor had two gas exchangers, one working in water and one in air. It also ventilated the aerial exchanger in an intermittent fashion. The functional repercussions of this ancestry can be seen in all amphibians and reptiles. During periods of apnoea, which almost all amphibians and reptiles show in their breathing patterns, there are variable fluctuations in lung and arterial and, . Arterial and pH show only small fluctuations during apnoea induced by voluntary dives, and blood lactate does not build up. More considerable acidoses and lactate accumulations occur in forced dives which the animals can readily survive, even when the dives are prolonged. Anaerobic metabolism plays an important role in their capacity to survive prolonged apnoea. Amphibians ventilate their lungs with a buccal pump whose pattern of activity differs from species to species. Short periods of apnoea characterize the more terrestrial forms. Long dives punctuated by bursts of lung ventilation, or irregular bouts of breathing with no distinctive pattern occur in more aquatic forms. Similar differences in pattern can be seen in terrestrial and aquatic reptiles. The most striking characteristic of ventilation is its extreme variability, even in a single individual. Responses occur to decreasing oxygen tensions and increasing carbon dioxide tensions in inspired air, alveolar air, and arterial blood, the animals almost always increasing lung ventilation and decreasing the duration of apnoea. However, no simple relationship can be seen between the tensions of respiratory gases in lungs or arterial blood and the beginning or end of an apnoeic period. Periods of apnoea are accompanied by vasoconstriction in the lung vasculature. This has the effect of decreasing blood flow to the lung and increasing right to left shunt in the incompletely divided heart.
Peripheral Receptors Affecting Breathing and Cardiovascular Function in Non-Mammalian Vertebrates
Authors: Jones David R. , Milsom William K.
Published: April 2021

Most vertebrates show respiratory and circulatory reflexes which can be traced to stimulation of various extero-or interoceptors. Widely distributed groups of exteroceptors, with a variety of stimulus modalities, are associated with defence reflexes which protect the respiratory passages and gas exchange surfaces. Other exteroceptors are associated only with the gas exchange surfaces. These are either mechanoreceptors or chemoreceptors and have a range of different dynamic characteristics, but are none-the-less amazingly uniform in their role in control of the normal breathing pattern. Intravascular receptors stimulated by the arterial blood pressure are located on all the gills in fishes, yet appear to be restricted to the pulmocutaneous arteries in anuran amphibians and to the truncal region or aortic root in reptiles and birds. On the other hand, the distribution of glomus-sustentacular-nerve cell complexes, associated with intravascular chemoreception, appears to be much more diffuse in higher than lower vertebrates. The wide distribution of these cell complexes may be attributed to their embryological origin from neural crest cells. Even so, the presence of these complexes does not appear to be essential for respiratory responses to environmental hypoxia since they have not been located in teleost fishes.

The role of peripheral receptors in controlling cardiovascular and respiratory functions, under steady state conditions in non-mammalian vertebrates, is not well defined and it may be that they are only modulators of circulatory and respiratory patterns arising from hormonal or humoral effects on the central nervous system.
Thermoregulation and Control of Head Temperature in the Sphinx Moth, Manduca Sexta
Authors: Hegel Jeri R. , Casey Timothy M.
Published: April 2021

Head and thorax temperatures (Th and Tth) were tightly coupled during pre-flight warm-up over a range of ambient temperatures (Ta). A.t Ta= 21 °C, the head reached a significantly higher temperature (Tth= 32 °C) than during exogenous heating of dead moths to the same thoracic temperature (Th = 26 °C). In free-flying moths, slopes of linear regressions for both Tth and Th versus Ta were about 0·4. At any Ta, Th remained only about 7 °C below Tth. Abdominal temperature varied with Ta with a slope of 1·2 and remained 2·5 degrees above Ta. Cooling constants (min−1) for the head, calculated from cooling experiments with the thorax either at Ta or maintained constant at about 40 °C, yielded similar values. During free flight, as Ta increased from 17 to 32 °C, thoracic heat loss decreased from 36 to 20 % of the total heat production, head heat loss decreased from 27 to 8%, and abdominal heat loss increased from 17 to 37%. During warm-up at all Ta’s the largest component of energy expenditure was the heat storage and heat loss that occurred from the thorax, followed by that from the abdomen and then by that from the head. Exogenous heating of some live moths resulted in cyclic temperature fluctuations in which Th and Tth changed simultaneously and in opposite directions. During each cycle, the heart beat pattern changed, becoming irregular when Tth was increasing and returning to a regular pattern when was decreasing. Smaller temperature fluctuations in the head occurred at the same rate as the heart beat. These data suggest that the head temperatures observed during pre-flight warm-up and flight are the result of active heat transfer from the thorax via the blood circulation.
Electrical Coupling Between Supernumerary Motor Neurones in the Locust
Authors: Siegler Melody V. S.
Published: April 2021

While recording from a slow tarsal levator motor neurone of the locust metathoracic ganglion, a second neurone of this type was discovered in the same half of the ganglion. In thirty animals from which recordings were subsequently made, the additional neurone was found in only one. Since two motor neurones could not be found routinely, other tests were made to determine how many motor neurones normally innervated the levator muscle. The tibial nerve containing the motor axons was stimulated whilst intracellular recordings were made from the levator muscle fibres; recordings were made simultaneously from the cell body of a levator motor neurone, from the tibial nerve and from the levator muscle fibres; and the composition of fine nerve branches that terminate on the levator muscle was examined by electron microscopy. It is concluded that normally the levator muscle is innervated by one excitatory motor neurone and two inhibitory ones. The single excitatory motor neurone has the synaptic inputs ascribed in earlier studies to the ‘slow’ motor neurone. It can, however, evoke movements of the tarsus ranging from slow smooth ones, to rapid twitchlike ones. No evidence was found for a second, ‘fast’ motor neurone previously reported (Hoyle & Burrows, 1973). In the two locusts found to possess a supernumerary levator motor neurone, the two motor neurones were electrically coupled by non-rectifying junctions that were strong enough to ensure that the pair invariably spiked in 1 : 1 fashion. The coupled levator motor neurones received different synaptic inputs. One pair of coupled motor neurones was stained intracellularly with cobalt-silver. The cell bodies were some 50 μm apart, but their neurites converged as they entered the neuropil. The neurites and major side branches followed similar courses in the neuropil, and the two neurones shared the major anatomical features of the single levator motor neurones stained in other animals.
Free Amino Acids as Regulators of Osmotic Pressure in Aquatic Insect Larvae
Authors: Edwards H. A.
Published: April 2021

Microanalytical techniques are used to show that organic molecules play an important role is osmoregulation. Changes in the inorganic ion composition of haemolymph from fourth instar larvae of Aedes aegypti are correlated with the changes in the concentration of organic ions. Free amino acids have a significant role in regulating haemolymph osmotic pressure with respect to the osmotic pressure of the water in which the animal lives. Mechanisms by which amino acid levels could respond to changes in salt concentration are discussed.
A Spiking Stretch Receptor with Central Cell Bodies in the Uropod Coxopodite of the Squat Lobster Galathea Strigosa (Crustacea, Anomura)
Authors: Maitland D. P. , Laverack M. S. , Heitler W. J.
Published: April 2021

A proprioceptor located at the base of the uropod coxopodite in the telson of Galathea strigosa is described. The main component of this organ is an elastic strand in which are embedded dendrites from several neurones (approximately 11) whose cell bodies are located within the 5th (last free) abdominal ganglion. A small accessory muscle runs parallel to this strand. Several afferent axons innervating the receptor conduct action potentials in a phasic manner in response to stretch. Information conveyed to the CNS by the receptor causes reflex modulation of the discharge in at least two motoneurones. When afferent spikes from the receptor are blocked by sucrose, reflexive discharges are still recorded in response to stretching the receptor. This suggests that certain reflexes may be mediated by transmission of graded electrotonic potentials from the uropod proprioceptor to the CNS. When sensory hairs on the margins of the uropods are displaced, feedback via the nerves innervating the uropods results in efferent output to the receptor complex (elastic strand and accessory muscle). The receptor also receives bouts of efferent impulses during attempted tail-flips in a restrained animal.
Is the Locust DCMD A Looming Detector?
Authors: Pinter Robert B. , Olberg Robert M. , Abrams Thomas W.
Published: April 2021

To a prey, a salient visual characteristic of an approaching predator is ‘looming’, a figure of average subtended visual angle increasing as some function of time. If the approach is at constant velocity, two important characteristics of the looming figure are an ever increasing velocity (i.e. acceleration) of sideways motion of edges away from the centroid of the figure, and the opposed motion of opposite edges. These characteristics make looming objects distinct from translation of single objects across the visual field, so that the visual looming characteristics may have value in warning of approaching predators. In the locust, a visual neurone, the DCMD (descending contralateral movement detector) in the ventral nerve cord forms an important input to the interneurones triggering the jump response in the locust (Pearson, Heitler & Steeves, 1980; Pearson & Robertson, 1981). Thus it is of considerable interest to determine whether the DCMD responds preferentially to looming visual stimuli.
The Specific Location of Zinc in Insect Mandibles
Authors: Hillerton J. Eric , Vincent Julian F. V.
Published: April 2021

The cutting edges of the mandibles in the locust have been shown to be twice as hard as the rest of the mandible (Hillerton, Reynolds & Vincent, 1982) and this was related to the cutting action employed by the insect. We have investigated the elemental composition of the mandibles of insects from several taxa to see if the hardness is due to ‘mineralization’ as in the ‘teeth’ of several other invertebrates e.g. the radular teeth of Patella, which contain iron and silica (Runham et al. 1969). For the first time we report the specific location, in the cutting edges (incisors) of insect mandibles, of large quantities of two transition elements, zinc and manganese. Metals have been found previously in only a few types of insect cuticle-in exceptional dipteran puparia and some phasmid eggs (Neville, 1975)-but their presence has not been related to any of the mechanical properties of the cuticle.
Simultaneous Measurement of Water Loss and Carbon Dioxide Production in the Cricket, Acheta Domesticus
Authors: Hadley Neil F. , Quinlan Michael
Published: April 2021

The relationship between respiration and its contribution to total water loss in arthropods is based almost entirely on correlations obtained from independent plots of gravimetrically-determined transpiration rates and manometrically-determined gas exchange (Ahearn, 1970; Hadley, 1970). Recently a new system, the ‘transpiration monitor’ has been developed to detect the amount of water released by an arthropod into a moving air stream (Hadley, Stuart & Quinlan, 1982). The transpiration monitor not only permits the continuous recording of very small and sporadic losses of moisture, but can be interfaced with either an oxygen or carbon dioxide analyser to provide a simultaneous measure of the arthropod’s gas exchange. Thus, peaks that correspond to bursts of moisture can be correlated with concurrent increases in respiratory activity. We report here the application of this system to measure water loss and carbon dioxide production in the cricket, Acheta domesticas, under isothermal conditions and at increasing temperatures.
Some In Vivo and In Vitro Characteristics of Aplysia Californica Haemolymph*
Authors: Defur P. L. , Lukowiak Ken
Published: April 2021

The nervous system of the opisthobranch mollusc, Aplysia californica Cooper has been extensively studied and a great deal is known about the electrophysiological properties of a number of identifiable neurones (see Kandel, 1976, 1979). A variety of synaptic and electrical connections have been mapped, permitting identification of the mode in which nervous control is exerted over certain motor functions. Substantially less is known regarding other physiological systems of Aplysia (Kandel, 1979), particularly the respiratory system, and this limits the description of how nervous control is affected by internal physiological state. Chalazonitis & Nahas (1965) reported data for haemolymph pH, CO2 tension and O2 tension in the related species, Aplysia fasciata, and Bevelaqua et al. (1975) identified the respiratory pigment, haemocyanin, in the haemolymph of A. californica. However, there has been no detailed study of in vivo oxygen levels or acid-base status of A. californica. Neither are there any data for the in vitro properties of A. californica haemolymph, such as oxygen carrying capacity, oxygen affinity or buffering properties. Such data are of particular importance in A. californica, for two reasons. Firstly, motor function, such as the often-studied gill withdrawal reflex, may be directly influenced by factors such as pH, or as are the respiratory performances of other marine invertebrates (Mangum & Burnett, 1975; McMahon & Wilkens, 1975; Bayne, 1976; Batterton & Cameron, 1978). Secondly, Chalazonitis (1974) has shown clearly that membrane potential, spike frequency and membrane resistance of many single cells in A. fasciata are directly affected by pH, and of the bathing fluid. Therefore, the present study was undertaken to describe some of the in vivo and in vitro properties of the haemolymph of A. californica with regards to acid-base status and oxygenation characteristics.
Osmoregulation in Salmon and Sea Trout Alevins
Authors: Talbot C. , Eddy F. B. , Johnston J.
Published: April 2021

Changes in survival, body-water content, body electrolyte concentration and Na+ turnover rates were studied in alevins of Atlantic salmon (Salmo salar L.) and sea trout (Salmo trutta L.) at different developmental stages following exposure to various dilutions of sea water. In 100% sea water, salmon alevins at 9 days post-hatch survived approximately 6 h, and sea trout alevins 13 days post-hatch survived approximately 4 h. In both species, survival in hyperosmotic media decreased and rates of dehydration and Na+ turnover increased with age and development. The progressive change in resistance to osmotic stress is associated with a decrease in body surface area occupied by the relatively impermeable vitelline membrane and to the development of functional gills, leading to an increase in permeability to water and salt.
Noninvasive Recording of the Mauthner Neurone Action Potential in Larval Zebrafish
Authors: Prugh John I. P. , Kimmel Charles B. , Metcalfe Walter K.
Published: April 2021

We describe the identification of Mauthner (M –) cell action potentials in an intact zebrafish larva, utilizing recording electrodes located outside the fish: The externally recorded spike occurs at approximately the same time, and its waveform changes with recording site in the same way, as the extracellular M-spike recorded within the central nervous system.The externally recorded M-spike may be readily distinguished from other forms of neural activity.The M-spike can be identified in recordings from unrestrained larvae.

This finding permits the direct study of M-cell function in the freely behaving animal.
Intermittent Gliding in the Hunting Flight of the Kestrel, Falco Tinnunculus L
Authors: Videler J. J. , Weihs D. , Daan S.
Published: April 2021

The hunting flight of the kestrel (Falco tinnunculus) consists of short bouts of flight at wind speed against the wind with the eyes in a fixed position relative to the ground, and of short flights from one such position to the next.

High speed films taken with a camera in a fixed position of a hunting kestrel of known weight and dimensions, allow estimates to be made of the amount of energy required for this behaviour.

A theoretical model shows how a bird could economise by alternating flapping flight with short gliding bouts, without changing the position of the eyes above the ground, by mere displacement of the centre of gravity relative to the head. High speed film data confirm predictions from this model.
Electrophysiological and Morphological Identification of Action Potential Generating Secretory Cell Types Isolated from the Salivary Gland of Ariolimax
Authors: Goldring James M. , Kater Joanne W. , Kater Stanley B.
Published: April 2021

The salivary glands of the terrestrial slug, Ariolimax, are composed of several morphologically distinct cell types which are observable in thin pieces of living glands and in sectioned tissue viewed with the light or electron microscope. ‘Blind’ penetration via microelectrode into the gland reveals different classes of electrical activity including: (1) cells with fast action potentials; (2) cells with slow action potentials; and (3) cells with large resting potentials but which display only delayed rectification. After isolation of cells by enzymatic dissociation we could electrophysiologically characterize individual cell types and relate these to cell types identified morphologically in the living gland and under the light and electron microscopes. Microelectrode recordings from identified cell types have demonstrated: (1) the large granule cell type (granule diameter = 8–12μm) displays a characteristic long duration, slow rise time action potential whose inward current is primarily carried by Ca2+ ; (2) the medium granule cell type (granule diameter = 3–6 μm) displays only delayed rectification and (3) the small granule cell type (granule diameter = 1–2 μm) displays fast rise time, short duration action potentials whose inward current is also carried primarily by Ca2+ ions.

The finding that morphologically distinct cell types display distinct electrical activity may indicate that different secretory products are released only under a specific set of conditions associated with changes in membrane potential.
The Interaction of Environmental Calcium and Low pH on The Physiology of the Rainbow Trout, Salmo Gairdneri
Authors: McDONALD D. G. , Walker R. L. , Wilkes P. R. H.
Published: April 2021

Adult rainbow trout, acclimated to external calcium concentrations ranging from 60–5700 μequiv/1, were exposed to pH 4·0–4·1 for 44 h. Initially, this exposure provoked massive net losses of sodium and chloride across the gills which arose through a combination of an inhibition of active transport and, more importantly, a stimulation in diffusional efflux. Subsequently, ion losses declined substantially, largely due to a rapid decline in passive efflux but also to a slower, partial recovery in sodium transport. External calcium concentration was virtually without effect on ion fluxes either prior to or following acid exposure but had a definite effect during acid exposure. This effect was initially upon the ratio of Cl− to Na+ loss and later upon the degree of inhibition of sodium and chloride transport. Possible mechanisms to explain the complex interactions of calcium and pH are proposed.
The Role of An Identified Brain Neurone in Mediating Optomotor Movements in A Moth
Authors: Rind F. Claire
Published: April 2021

Completely unrestrained moths show an optomotor turning response to horizontal movement during pre-flight warm up or flight. As the moth warms up there is a sequential recruitment of first neck, then abdominal, leg and finally some wing muscles, into the optomotor turning response. Extracellular motoneurone spikes were recorded from neck muscles during optomotor stimulation. As the stimulus is oscillated from side to side, motoneurones on the ipsilateral side are excited. The latency of this response increases greatly in dim light. Flight motoneurones were not observed to spike in response to movements of the optomotor stimulus, but subthreshold oscillations of 5–10 mV, in phase with the response of the identified optomotor interneurone DI, were observed. Three motoneurones, the second pleuroaxillary, the subalar and the dorsal longitudinal to the more medial, ventral fibre bundle, showed depolarizations in phase with the response of the ipsilateral DI interneurone. Synaptic potentials in these motoneurones followed action potentials in DI, suggesting that DI provides a direct, excitatory input to them. An excitatory postsynaptic potential (EPSP) from D1 sums with a steady depolarization of all three directly postsynaptic motoneurones to produce an action potential.
The Transport of Orthovanadate and Similar Oxyanions in Relation to Salt and Water Transport Across the Isolated Intestine of the Common Eel, Anguilla Anguilla
Authors: Bell M. V. , Kelly K. F. , Sargent J. R.
Published: April 2021

An intestinal preparation from the common eel (Anguilla anguilla) was characterized for both mucosal to serosal and serosal to mucosal transport of water, alanine, sodium and chloride. The preparation showed a net outflux of water and a net influx of alanine, and no net fluxes of sodium or chloride. The influxes of all four substances and the outflux of water were inhibited by ouabain, while the outfluxes of alanine, sodium and chloride were increased by ouabain. Influxes and outfluxes of the oxyanions orthovanadate, phosphate, arsenate, sulphate, selenate and chromate were measured over a range of concentrations from 10−8M to 10−4M. The entry of each anion was dependent on the mucosal concentration, not saturable within the concentration range used or competitive with chloride. There were no net fluxes of these anions and pertechnecate from solutions containing equal mucosal and serosal concentrations of the anion.
Adrenergic Control of Oxygen Transfer in Perfused Gills of the Cod, Gadus Morhua
Authors: Pettersson Knut
Published: April 2021

A perfused and ventilated gill preparation is described in which the pO2 of the perfusion medium and the irrigating water is controlled. Dorsal aorta effluent pO2 and flow were measured together with the branchial vascular resistance.

Decreasing pO2 in the perfusion fluid caused increased branchial vascular resistance, probably by constriction of efferent lamellar arterioles, α-adrenoceptor stimulation caused constriction of arteriovenous connections and of efferent lamellar arterioles, and enhanced oxygenation of the perfusion fluid. β-adrenoceptor stimulation also increased O2 transfer, but to a lesser extent.

It is suggested that both hypoxia and α-adrenoceptor stimulation improved O2 transfer via constriction of efferent lamellar arterioles. Both stimuli may also increase systemic blood flow by constriction of the arteriovenous connections, although such an effect of hypoxia has not been clearly shown, β-stimulation probably increased O2 transfer by dilation of afferent lamellar arterioles, thereby causing recruitment of unperfused lamellae.
Copper and Zinc Inhibit Chloride Transport Across the Opercular Epithelium of Seawater-Adapted Killifish Fundulus Heteroclitus
Authors: Crespo Sílvia , Karnaky Karl J.
Published: April 2021

Effects of heavy metals on osmoregulation in aquatic organisms have recently been reviewed by Bouquegneau & Gilles (1979). Whereas most of the data in the literature deal with the toxic effects of mercurials, only a few reports can be found on the toxicity of essential trace elements such as Cu and Zn. Rainbow trout exposed to lethal (Skidmore, 1970) and sublethal (Watson & Beamish, 1980) concentrations of Zn maintain a relatively constant internal ionic environment. On the other hand Lewis & Lewis (1971) showed, in the channel catfish, a decreased osmolarity of blood serum after treatment with either Cu or Zn, and Katz (1979) reported an increased Na efflux in freshwater teleosts exposed to heavy metals. An increased gill Na, K-ATPase activity was described in the Zn-treated rainbow trout (Watson & Beamish, 1980). Shephard & Simkiss (1978) showed, in the same species, an increase in the gill protein content of fish exposed to Cu and Zn. These data agree with reports from Cu-treated winter flounder (Baker, 1969) and from Zn-treated dogfish (Crespo, Soriano, Sam-pera & Balasch, 1981; Crespo, 1982) each of which shows an increase in the number of the gill chloride cells.
Relationship Between Haemoglobin O2 Affinity and the Ventilatory Response to Hypoxia in the Rhea and Pheasant
Authors: Boggs Dona F. , Birchard Geoffrey F.
Published: April 2021

The ventilatory response to hypoxia appears to be controlled largely by carotid body chemoreceptors in birds, as it is in mammals, and the stimulus to these chemoreceptors is probably the partial pressure of oxygen in the arterial blood (Bouverot, 1978; Bouverot, Douguet & Sebert, 1979). There are, however, interspecific differences in the threshold arterial stimulating the hypoxic ventilatory response. Black & Tenney (1980) found that a high-altitude species, the bar-headed goose, initiates an increase in ventilation at a lower arterial than a lowland species, the Pekin duck. The bar-headed goose also has a higher affinity haemoglobin, presumably as an adaptation to its high altitude habitat. Van Nice, Black & Tenney (1980) noted that when the ventilatory response to hypoxia is expressed in terms of the percent saturation of haemoglobin in arterial blood , the bar-headed goose and Pekin duck exhibit a similar threshold . It seems unlikely that the receptors sense haemoglobin O2 saturation directly and experimental reductions in O2 content do not stimulate ventilation in the duck (D. F. Boggs, unpublished observation). Nonetheless a relationship between the threshold of the ventilatory response to hypoxia and the ‘knee’ of the oxyhaemoglobin dissociation curve would be a reasonable evolutionary development in both birds and mammals, as Van Nice et al. (1980) have pointed out. If threshold arterial for the hypoxic ventilatory response were an interspecific constant, then those species with relatively high-affinity haemoglobins would be responding prematurely, and, therefore, ‘wastefully’, whereas those with relatively low-affinity haemoglobins would be in danger of suffering substantial arterial unsaturation before the ventilatory response is initiated. The latter eventuality would be particularly hazardous for tissue oxygen supply in those animals with low affinity haemoglobins, since these animals are in most cases small, with high weightspecific metabolic rates (Lutz, Longmuir & Schmidt-Nielsen, 1974; Schmidt-Nielsen & Larimer, 1958).
Selective Recruitment of Interganglionic Interneurones During Different Motor Patterns in Pleurobranchaea
Authors: Cohan Christopher S. , Mpitsos George J.
Published: April 2021

The buccal and anterior head structures of the mollusc, Pleurobranchaea, participate in several types of behaviour which are generated largely by rhythmic activity produced in the brain and buccal ganglia. This paper examines the neuronal mechanisms (1) by which motor output from these ganglia is coordinated, and, (2) which underlie the generation of different motor patterns. Preliminary experiments indicated that the neuronal circuitry which produces the rhythms is contained in each of the paired buccal ganglia. The timing characteristics of the rhythms arise in the buccal ganglia and the pattern and symmetry of motor output in the brain roots are determined by activity in buccal cerebral interneurones (BCI) within the buccal ganglia.

Intracellular recordings showed that unique properties of individual cells within two pools of interganglionic interneurones, the BCI and paracerebral cells (PCC), determine in part the types of coordinated patterns that are produced. The BCI, which project to the brain, are a heterogeneous population of cells, based on : ( 1 ) the activity they evoke when they are depolarized ; and (2) their activity patterns during rhythms that are evoked by buccal nerve stimulation. Evidence is presented to show that BCI are selectively recruited to produce the distinguishing features of different motor patterns. Similarly, the PCC were found to be a diverse group of cells that exert both excitatory and inhibitory effects on the nervous system. Stimulation of excitatory PCC in isolated nervous systems elicited a variety of activity patterns. These data suggest that the PCC may selectively recruit the BCI to produce different motor patterns and that differences in patterns can be attributed, in part, to the unique properties of individual cells within each pool of interneurones.
Allosteric Interactions Governing Oxygen Equilibria in the Haemoglobin System of the Spiny Dogfish, Squalus Acanthias
Authors: Weber Roy E. , Wells Rufus M. G. , Rossetti John E.
Published: April 2021

The oxygenation-linked, allosteric interactions of erythrocytic organic phosphates and urea with the haemoglobin (Hb), and the functional significance of the Hb multiplicity, were studied in an elasmobranch, Squalus acanthias.

The autochthonous red cell nucleoside triphosphates (NTP) ATP and GTP (guanosine triphosphate) strongly depress O2 affinity of the stripped (cofactor-free) Hb and increase cooperativity in O2 binding. As previously found in teleost Hbs, GTP exerts a greater effect than ATP at the same concentration. Urea, in contrast, increases O2 affinity and depresses cooperativity. It also antagonizes the modulator effectivity of NTP at physiological NTP/Hb concentration ratios.

Deoxygenation of the Hb raises blood pH. This Haldane effect contrasts with earlier findings for Pacific specimens, but accords with the presence of a Bohr effect (Φ = Δlog P50/ΔpH).

S. acanthias Hb resolves into six main components (three pairs) on the basis of isoelectric point. There is no evidence for radical functional differentiation as found in teleosts with electrophoretically anodal and cathodal Hb components.

The physiological implications of the findings and the possible molecular mechanisms basic to the NTP and urea effects are discussed.
The Ionic Basis of the Depolarizing Mechanoreceptor Potential of Paramecium Tetraurelia
Authors: Satow Youko , Murphy A. Don , Kung Ching
Published: April 2021

A depolarizing receptor potential produced by mechanical stimulation was studied in pawn mutants of Paramecium tetraurelia bathed in TEA solution. The potential was dependent upon the strength of the mechanical stimulation until a maximum response was reached. The maximum value was dependent on the concentration of external Ca2+. Discounting the change in resting potential (attributable to change in surface charge), the maximal receptor potential changed by 20 mV per 10-fold change in Ca2+ at the concentrations tested, confirming the result of Ogura & Machemer (1980) that Ca2+ is the major natural cation that carries the receptor current. Mg2+, Sr24-, Ba2+ and Mrr+ can substitute for Ca2+ in the generation of the depolarizing receptor potential. Except for Mn2+, this result is similar to that of de Peyer & Deitmer ( 1980) for Stylonychia. Na+, K+, Li+ and TEA+ cannot effectively substitute for Ca2+.
Ocellar Input to the Flight Motor System of the Locust: Structure and Function
Authors: Rowell C. H. F. , Pearson K. G.
Published: April 2021

This paper deals with the physiology, anatomy and function of the following classes of neurones in the locust Schistocerca : (a) neurones carrying ocellar information to the pterothorax (Descending Ocellar Neurones, DONs), (b) mesothoracic Flight Motor Neurones (FMNs), (c) a heterogenous class of inter- and intraganglionic thoracic interneurones which receive input from the DONs, here called Thoracic Ocellar Interneurones (TONs) without prejudice to their other possible inputs and functions. The thoracic arborizations of five different DONs are characterized. All project unilaterally to the pterothorax, four out of five to the ipsilateral mesothoracic or meso- and metathoracic ganglia. All are phasic OFF units, responding to stimulation either of one lateral ocellus or of the medial ocellus or of both, but none responded to the cephalic wind-hairs. Four of the five DONs showed no response decrement at stimulus frequencies up to 80 Hz. One showed habituation, recovery during a rest interval, and dishabituation in response to mechanical stimulation of a leg. There are more than six DONs, probably more than ten, in each connective. All types of recorded mesothoracic FMNs receive monosynaptic EPSPs from the DONs and/or delayed IPSPs (presumably via TONs) in at least some animals. The pattern of connection is compatible with the hypothesis that a roll or downward pitch deviation induces compensating movements of the wings to correct the deviation. Many of these DON/ FMN connections were, however, only occasionally recorded. None of the ocellar EPSPs recorded in the FMNs elicited spikes. Most TONs receive monosynaptic EPSPs from one or more DONs, sometimes causing them to spike. Two receive delayed IPSPs, presumably via other TONs. At least one third of the recorded TONs spike in phase with either elevator or depressor FMNs during stimulated flight. Intraganglionic TONs in the mesothorax are all unilateral. Their anatomy suggests that they distribute input from DONs to various combinations of ipsilateral FMNs. Interganglionic TONs can be either unilateral or bilateral in the mesothoracic ganglion, and project unilaterally to the metathoracic (or rarely the prothoracic) ganglion, where at least one makes inhibitory synapses with a FMN. Phasic ocellar information reaches the FMNs by two routes. One produces fast subthreshold PSPs in the FMNs directly. The other produces spikes and PSPs in thoracic interneurones, at least some of which are phasic-ally active during flight and are presynaptic to FMNs. The roles of the two pathways are discussed.
Variability in the Structure of an Identified Interneurone in Isogenic Clones of Locusts
Authors: Steeves John D. , Pearson Keir G.
Published: April 2021

Several studies have shown that there can be considerable variability in the morphology of identified neurones. In a recent investigation (Pearson & Goodman, 1979) a great degree of variability was observed in the axon branching patterns of the descending contralateral movement detector (DCMD) interneurones of locusts. Corresponding to the variation in the structure of DCMD was a large variation in the synaptic connections made by this interneuroen; the absence of a monosynaptic connection always correlated with the lack of the appropriate axonal branch of DCMD.

Since this variability could be related to genotypic differences, we investigated the structure and synaptic connections of DCMD in individuals from several different isogenic clones of the locust Schistocerca gregaria. Within a single group of clones the variability in the axonal branching patterns and synaptic connections of DCMD was generally less than that between different clones or in sexually reproduced control animals. More significantly, a few of the clonal groups had consistently unique branching patterns and concomitant synaptic connections. Nevertheless, there was still some variability in the structure of DCMD within each clone. We conclude from these observations that differences in genotype can influence the morphology of individual neurones at the relatively refined level of axonal branching patterns and consequently the neurone’s synaptic connections. However, due to the variability of DCMD structure within a single clone, epigenetic factors must also determine the pattern of axonal branching.
Oxygenational Properties and Phosphorylated Metabolic Intermediates in Blood and Erythrocytes of the Dogfish, Squalus Acanthias
Authors: Wells Rufus M. G. , Weber Roy E.
Published: April 2021

A typical whole blood Oz-equilibrium curve from Squalus acanthias had a P50 of 13·2 mmHg and was slightly sigmoidal, having an n value of 1·6 at 15°C, (pH = 7·85). A small Bohr effect was present (ϕ= −0·28) together with a weak Haldane effect and no Root shift.

The predominant trinucleotide, determined by thin layer chromatography, was ATP (0·44 ±0·13 S.D. mmol l−1 blood) with smaller amounts of GTP present (0·07 ± 0·02S.D. mmol 1−1). Total nucleotide concentrations, determined enzymatically, were low by comparison with teleosts. Incubation of erythrocytes with or without oxygen, or in the presence of a metabolite-enriched ‘cocktail’ showed limited potential for phosphate cofactor regulation of blood oxygen affinity.
Physiological and Behavioural Aspects of Water Balance and Respiratory Function in the Terrestrial Slug, Limax Maximus
Authors: Prior David J. , Hume Mary , Varga Dan , Hess Stephen D.
Published: April 2021

A method is described for establishing a stable relationship between body weight and hydration (i.e. 100% hydrated) in terrestrial slugs. This allows the use of ‘% initial body weight’ as an indicator of relative body hydration. During progressive dehydration in the slug, Umax maximus (L.), the haemolymph osmolality increases exponentially. This, together with measurements of wet weight/dry weight ratios of various tissues, indicates that the water loss during the initial stages of dehydration is from the haemolymph. Although long-term (days) cyclical changes in body hydration were not observed, a daily cycle is described with highs at 12.00 midnight and lows at 12.00 noon. It is shown that the huddling behaviour of slugs can reduce evaporative water loss from individual slugs. Dehydration of a slug to about 90 % of its initial body weight initiates a rhythmic cycle of pneumostome closures. Further dehydration results in an increase in the duration of the closures and reduction of the diameter of the pneumostome when open. The absolute and relative O2 uptake by the integument and lung are presented. In quiet slugs, the lung is responsible for about 20 % of the total O2 uptake, while in active slugs it is responsible for 50 % of the total. During activity there is a greater increase of O2 uptake across the lung than across the integument.
Insects are Both Impeded and Propelled by Their Legs During Walking
Authors: Graham D.
Published: April 2021

The kinetics of walking behaviour in stick insects differ from vertebrate walking behaviour. The differences suggest that insect locomotion consists of a hold-push-recover sequence similar to that used by a climber. This is supported by evidence from force platform measurements on free-walking insects and motor output recordings from animals walking on a treadwheel.
The Exchange of Calcium in Larvae of the Mosquito Aedes Aegypti
Authors: Barkai Amiram I. , Williams Roger W.
Published: April 2021

The exchange of labelled calcium between the external medium and the whole body was investigated in the larva of Aedes aegypti (L.) using a closed, two-compartmental model. The transport system for the uptake of Ca2+ was found to be saturable and obeyed Michaelis-Menten kinetics. The efficiency of the inward transport of calcium from dilute solutions was markedly reduced by starvation or by ruthenium-red, a selective inhibitor of Ca2+ activated ATPase, indicating that this transport system is energy dependent. Unlike transport systems for the major monovalent ions, the Ca2+ transport system is not located in the anal papillae, since removal of these organs resulted in enhanced Ca2+ fluxes. While over 95 % of the calcium in the larva appeared to be distributed in the extracellular haemolymph, only 16 % of the total calcium was readily exchangeable with the external medium; thus the majority of the calcium is apparently bound to haemolymph constituents. The results suggest that calcium pumps consisting of Ca2+ activated ATPases play an important role in the absorption of Ca2+ from dilute solutions in the gut and its reabsorption from the urine in the rectum.
The Role of Low Molecular Weight Antifreeze Glycopeptides in the Bile and Intestinal Fluid of Antarctic Fish
Authors: O’grady S. M. , Ellory J. C. , Devries A. L.
Published: April 2021

The role that low molecular weight antifreeze glycopeptides play in the physiology of polar fishes has been an open question. In this study, we demonstrate that antifreeze glycopeptides are present in the bile as well as the intestinal fluid of antarctic fishes. Isolation of antifreeze glycopeptides from these fluids by DEAE ion exchange chromatography followed by polyacrylamide gel electrophoresis revealed the presence of only low molecular weight glycopeptides (6, 7 and 8). Removal of the gall bladder with subsequent occlusion of the common bile duct eliminated the transport of antifreezes into the intestine. This suggests that antifreeze glycopeptides enter the intestinal lumen by biliary secretion. Measurements of reabsorption, both in vivo and in vitro, indicate that antifreeze glycopeptides are not reabsorbed as intact molecules. Our results suggest that these glycopeptides are excreted. We conclude that low molecular weight antifreeze glycopeptides are necessary to prevent the intestinal fluid from freezing and provide the first clear evidence that low molecular weight antifreeze glycopeptides have a specific biological function in polar fishes.
Motor Programme Switching in the Ventilatory System of Carcinus Maenas: the Neuronal Basis of Bimodal Scaphognathite Beating
Authors: Simmers A. John , Bush Brian M. H.
Published: April 2021

Intracellular recordings have been made from ventilatory neurones in semi-isolated and isolated thoracic ganglia of the crab Carcinus during spontaneous switching between the two motor programmes underlying forward and reversed beating of the scaphognathites (SGs).

Ventilatory reversals are dependent upon the central activation of two subgroups of motoneurones which are normally silent, and different from those driving the same SG muscles during the forward rhythm. Two further subgroups of motoneurones remain active throughout both rhythm modes.

The results suggest that both motor output patterns are produced mainly by periodic inhibitory synaptic input from the same oscillator network, and that neural switching between the rhythm modes occurs directly at the level of the motoneurones themselves.

It appears that both sets of ‘forward’ and ‘reversal’ motoneurones are driven continuously throughout oscillator activity, and that bursting activity in these sets is gated by the selective application or removal of additional, tonic inhibition.
Cardiovascular Changes in the Exercising Emu
Authors: Grubb Barbara , Jorgensen Darwin D. , Conner Melinda
Published: April 2021

Cardiovascular variables were studied as a function of oxygen consumption in the emu, a large, flightless ratite bird well suited to treadmill exercise. At the highest level of exercise, the birds’ rate of oxygen consumption was approximately 11·4 times the resting level (4·2 ml kg−1 min−1). Cardiac output was linearly related to , increasing 9·5 ml for each 1 ml increase in oxygen consumption. The increase in cardiac output is similar to that in other birds, but appears to be larger than in mammals. The venous oxygen content dropped during exercise, thus increasing the arteriovenous oxygen content difference. At the highest levels of exercise, heart rate showed a 3·9-fold increase over the resting rate (45·8 beats min−1). The mean resting specific stroke volume was 1·5 ml per kg body mass, which is larger than shown by most mammals. However, birds have larger hearts relative to body mass than do mammals, and stroke volume expressed per gram of heart (0·18 mlg−1) is similar to that for mammals. Stroke volume showed a 1·8-fold increase as a result of exercise in the emus, but a change in heart rate plays a greater role in increasing cardiac output during exercise.
Suppression of a Locust Visual Interneurone (DMCD) During Defensive Kicking
Authors: Heitler W. J.
Published: April 2021

Visual stimuli presented to a locust during performance of a defensive kick fail to elicit a response from the descending contralateral movement detector (DCMD) visual interneurone. Similar control stimuli presented before the initial flexion and at least 1 s after the movement elicit a normal DCMD response (10–15 spikes). External stimuli used to elicit defensive kicking can sometimes cause suppression of the DCMD without the occurrence of kicking, but only when there is an increase in central nervous activity, or associated behavioural response. Proprioceptive stimulation similar to that occurring in a kick does not cause suppression of the DCMD unless there is an increase in central nervous activity or associated behavioural response. Extensive dorsal dissection abolishes the suppression of the DCMD.
Short Communications Initiation of Flight By an Identified Wind Sensitive Neurone (Tcg) in The Locust
Authors: Bicker Gerd , Pearson Keir G.
Published: April 2021

When the tarsi are not in contact with the ground, brief wind stimuli applied to the wind sensitive hairs on the head elicit flight in the locust (Weis-Fogh, 1949; Camhi, 1969). The descending interneurones mediating this reaction have not been identified but some likely candidates have been reported (Bacon & Tyrer, 1978; Simmons, 1980, 1981). The most extensively studied is the tritocerebral commissure giant (TCG) (Bacon & Tyrer, 1978; Bacon & Möhl, 1979). This large wind sensitive interneurone descends from the brain, crosses to the contralateral side of the nerve cord via the tritocerebral commissure, and makes excitatory connections with some flight motor neurones in the thoracic ganglia (Bacon & Tyrer, 1979). The location of the TCG’s axon in the tritocerebral commissure makes this neurone easily accessible for recording and stimulation in almost intact, freely moving animals. Recordings during flight, for example, have shown that the TCG discharges one or two spikes during each cycle (Bacon & Möhl, 1979). The spike activity results from rhythmic air turbulences caused by flapping of the wings and head movements during flight. This rhythmic activity may play a role in regulating motor output during flight manoeuvres, such as yaw (B. Möhl & J. Bacon, in preparation). It seems unlikely however that this is the only function for the TCG since it is capable of discharging in very high frequency bursts quite unlike those occurring in flying animals. Here we present evidence that the TCG also functions to facilitate the initiation of flight following a jump.
VAMP: A Video Activity Monitoring Processor for the Registration of Animal Locomotor Activity
Authors: Kaufmann Ruediger
Published: April 2021

In many bioenergetic investigations, the discrimination of resting and activity metabolism represents an important problem. Personal observation, a possible solution to this problem, becomes very impractical in highly automated long-term experiments. An adequate method of measuring activity should meet the following demands : it should be able to quantify the movement of several objects simultaneously, it should be usable with animals of different shapes and sizes, and it should cause minimal disturbance to the animals.