bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupling Mechanisms Between the Contralateral Legs of a Walking Insect (Carausius Morosus)
Authors: Cruse H. , Knauth A.
Published: April 2021

Interactions between contralateral legs of stick insects during walking were examined in the absence of mechanical coupling between the legs by studying animals walking on a horizontal plane covered with a thin film of silicone oil. Investigations of undisturbed walks showed that contralateral coupling is weaker than ipsilateral coupling. Two types of influence were found, (i) For each pair of front, middle and rear legs, when one leg started a retraction movement, the probability for the contralateral leg to start a protraction was increased, (ii) For front- and hind-leg pairs, it was found that the probability of starting a protraction in one leg was also increased, the farther the other leg was moved backwards during retraction. Whether such influences exist between middle legs could not be determined. Both ‘excitatory’ mechanisms very much resemble those influences which have been found to exist between ipsilateral legs. However, in contrast to ipsilateral legs, the interaction between two contralateral legs was found to act in both directions.
Ammonia, Urea and H+ Distribution and the Evolution of Ureotelism in Amphibians
Authors: Wood Chris M. , Munger R. S. , Toews D. P.
Published: April 2021

In theory, the distribution of ammonia across cell membranes (Tammi/Tamme) between intracellular and extracellular fluids (ICF and ECF) may be determined by the transmembrane pH gradient (as in mammals), the transmembrane potential (as in teleost fish), or both, depending on the relative permeability of the membranes to NH3 and NH4+ (pNH3/pNH4+). The resting distributions of H+(via [14C]DMO), ammonia and urea between plasma and skeletal muscle, and the relative excretion rates of ammonia-N and urea-N, were measured in five amphibian species (Bufo marinus, Ambystoma tigrinum, Rana catesbeiana, Necturus maculosus and Xenopus laevis). Although ureai/ureae ratios were uniformly close to 1·0, Tammi/Tamme ratios correlated directly with the degree of ammoniotelism in each species, ranging from 9·1 (Bufo, 10% ammoniotelic) to 16·7 (Xenopus, 79% ammoniotelic). These values are intermediate between ratios of about 30 (low pNH3/pNH4+ ) in ammoniotelic teleost fish and about 3 (high pNH3/pNH4+) in ureotelic mammals. The results indicate that amphibians represent a transitional stage in which ammonia distribution is influenced by both the pHi—pHe gradient and the membrane potential, and that a reduction in cell membrane permeability to NH4+ (i.e. increased pNH3/pNH4+) was associated with the evolution of ureotelism. Hyperosmotic saline exposure increased urea excretion 10-fold in Xenopus, while ammonia excretion remained unchanged. Tammi/Tamme fell, but this response was attributable to an abolition of the pHi—pHe gradient, rather than a physiological change in the cell membrane pNH3/pNH4+.
Entrainment of the Swimmeret Rhythm of the Crayfish to Controlled Movements of Some of the Appendages
Authors: Deller Simon R. T. , Macmillan David L.
Published: April 2021

A machine was used to impose controlled movements, closely resembling natural movements, on some of the swimmerets of crayfish with their ventral nerve cords cut between thorax and abdomen. The rhythm of the unrestrained swimmerets could be entrained to the imposed frequency. Full entrainment occurred most readily when three or four swimmerets were controlled and was uncommon with two. When one was controlled, only partial entrainment was seen. A small proportion of preparations could not be entrained irrespective of the number of swimmerets controlled. Entrainment of the neural rhythm also occurred when movement was imposed on one or more swimmerets attached to an otherwise isolated nerve cord.

This is the first demonstration that sensory input affects the periodicity of the swimmeret rhythm. In the light of this result, the hypothesis that swimmeret rhythm is largely controlled by a central pattern generator should be viewed with caution. It now appears that there is also an influential sensory component responsible for stabilizing and adjusting the timing of the swimmeret rhythm.
Effects of Nicotinic and Muscarinic Agents on an Identified Motoneurone and its Direct Afferent Inputs in Larval Manduca Sexta
Authors: Trimmer Barry A. , Weeks Janis C.
Published: April 2021

The principal locomotory appendages of larval Manduca sexta, the prolegs, bear at their tips an array of mechanosensory hairs (the planta hairs). Each of the single sensory neurones associated with a planta hair sends an axon into the ganglion of the same segment where the afferent terminals make synaptic contact with interneurones and motoneurones. Electrical stimulation of a single afferent elicits a monosynaptic excitatory postsynaptic potential (EPSP) in PPR, one of the motoneurones controlling the prolegs. We have used this synapse to study the pharmacology of sensory transmission in M. sexta. The following observations were made.

The EPSP was reversibly inhibited in a dose-dependent fashion by the cholinergic antagonists d-tubocurarine, atropine and mecamylamine, indicating that the planta hair afferent neurones use acetylcholine (ACh) as a neurotransmitter. α-Bungarotoxin (αBGTX) also suppressed the EPSP but required concentrations above l×10−6moll-1. PPR depolarized in response to ionophoretic or bath application of cholinergic agonists, but compared to motoneurones of a non-nicotine-resistant insect such as the cockroach, PPR was relatively insensitive to nicotine. Application of N-methyl nicotinamide (NMN) to the nerve cord to inhibit putative alkaloid pumps in the central nervous system (CNS) only weakly potentiated PPR’s response to nicotine. This suggests that such pumps do not markedly contribute to PPR’s nicotine resistance. PPR’s responses to nicotinic agents showed several pharmacological differences from those reported for other insects, indicating that the nicotinic ACh receptors of M. sexta may be specifically adapted to accommodate a nicotine-rich diet. During the application of muscarinic agonists to isolated abdominal ganglia, the firing rate of motoneurones, as monitored in the ventral nerve, increased dramatically. PPR responded to muscarinic agents even during synaptic blockade, suggesting that muscarinic receptors may be present on PPR itself. The main effect of muscarine on PPR was to lower its spike threshold. Bath-applied muscarinic agents also affected the afferent-evoked EPSP in a manner consistent with the presence of another group of receptors that, when stimulated, act presynaptically to inhibit the release of ACh from the sensory terminals. These apparent pre- and postsynaptic actions of muscarinic agents are the first reported findings of muscarinic physiology in an identified insect neurone and its synaptic inputs.
Oxygen Transport and Acid-Base Balance in the Haemolymph of the Lobster, Homarus Gammarus, During Aerial Exposure and Resubmersion
Authors: Taylor E. W. , Whiteley N. M.
Published: April 2021

Submerged lobsters at 15°C were normoxaemic ( at a of 6·53 kPa) and normocapnie (; [HCO3-] = 9·3mequivl-1 and pHa = 7·78). After 3h in air the haemolymph was markedly hypoxic and hypercapnic (; ; and pHa = 7·64). Disturbance after 3h in air caused a greater increase in to 1·28 kPa and a fourfold increase in lactate levels to 3·6 mmol l-1. The combined respiratory and metabolic acidosis reduced pHa to 7·39.

After 14 h in air, undisturbed lobsters remained hypoxic and hypercapnic (; ). Lactate levels had increased to 6·2mmoll-1. Despite this clear limit on respiratory gas exchange in air, oxygen transport by the haemolymph was restored. A rise in buffer base ([HCO3-] = 15·8mequivl-1) compensated for the potential respiratory and metabolic acidosis and pH was unchanged at 7·63. The combined effects of the increase in lactate (ΔlogP50/ Δlog[lactate] =–0·175) and calcium (ΔlogP50/Δlog[Ca2+] = — 0·20 at pH7·63) levels contributed to an increase in oxygen affinity of haemocyanin at constant pH. Consequently, mean increased from 0·2 to 0·38 mmol l-1 between 3h and 14 h in air.

Resubmergence after 14 h in air resulted in a transient alkalosis due to retention of bicarbonate; oxygen and CO2 were rapidly restored to submerged levels. The lobster possesses the appropriate respiratory adaptations for survival during the relatively long periods of exposure in air encountered during commercial shipment.
Circadian Change of Photosensiuivity in Paramecium Bursaria
Authors: Nakajima Kaname , Nakaoka Yasuo
Published: April 2021

Circadian changes in behaviour and electrical properties of the membrane were investigated in Paramecium bursaria. Both photoaccumulation and swimming velocity were at a higher level during the day than at night. During the day, swimming velocity decreased as light intensity was increased and the cells almost stopped at the intensity at which they showed the maximum degree of photoaccumulation. When the intensity was increased further, the avoiding reaction was frequently observed. Step increases in the light intensity depolarized the membrane potential. The depolarization was larger in the night cells than in the day cells. The resting potential measured in the dark was about 4 mV more positive in the night cells than in the day cells. Membrane conductance was larger in the day than at night, which can explain the changes in the resting potential and also the photosensitive behaviour.
L-Glutamate Receptors on the Cell Body Membrane of an Identified Insect Motor Neurone
Authors: Wafford K. A. , Sattelle D. B.
Published: April 2021

Current-clamp experiments on an identified neurone have demonstrated the presence of L-glutamate receptors in the insect central nervous system. The cell body of the fast coxal depressor motor neurone (Df) in the metathoracic ganglion of the cockroach Periplaneta americana exhibits a hyperpolarizing response to L-glutamate, accompanied by an increase in membrane conductance. The response is dependent on both intracellular and extracellular chloride concentration, but is not affected by changes in potassium concentration. The hyperpolarization reverses at —82mV (the equilibrium potential for chloride), is mimicked by the action of L-aspartate, blocked by the antagonists picrotoxin and γ-D-glutamylglycine (γ-DGG) at high concentrations (l·0×10−4moll−1), and is enhanced by L-amino phosphonobutyrate (L-APB). The response is insensitive to glutamate diethyl ester (GDEE), cis-2,3-piperazine dicarboxylic acid (cir-2,3-PDA) and D-amino phosphonobutyrate (D-APB). The L-glutamate-activated increase in chloride conductance does not cross-desensitize with the y-aminobu-tyric acid (GABA) response on the same cell. It is less sensitive than the GABA response to block by picrotoxin. In addition, γ-DGG specifically blocks the L-glutamate receptor.

A depolarizing response is elicited by kainate and quisqualate; it is associated with an increase in conductance, and exhibits a much slower time course than the response to L-glutamate, indicating a different underlying mechanism. L-Cysteate produces a small depolarizing response of similar time course to that produced by L-glutamate. L-Homocysteate and N-methyl-D-aspartate (NMDA) are ineffective on the cell body membrane when applied at concentrations up to l·0×10−3moll−1. This first detailed description of the properties of L-glutamate receptors on an identified insect neurone reveals that they are not readily accommodated in the existing classification of receptor subtypes, based on vertebrate pharmacology.
The Tension in a Locust Flight Muscle at Varied Muscle Lengths
Authors: Malamud Jean G.
Published: April 2021

Tension in a resting muscle increases when the muscle is stretched. If the stretch is maintained, the tension decays (stress relaxation). The time course of stress relaxation in the metathoracic second tergocoxal muscle (Tcx2) of the locust Schistocerca americana was found to be adequately described by a multiexponential function with four or more time constants. These constants were independent of strain, and the slowest had a value of more than 60 min. Tension continued to diminish even when stretch was maintained for 2—4h. Tension in a stretched, unstimulated muscle increased with increased length of stretch. Resting tension in the locust Tcx2 at the in vivo length was estimated to be IN cm-2 or less. At 10% strain, resting tension was about 2Ncm-2. The stiffness of the unstimulated locust muscle was similar to that of unstimulated frog muscles. The active tetanic tension was maximal (average = 32·4 Ncm-2) at slightly less than the in vivo muscle length. Tetanic tension was 50% or more of its maximum value over a range of 80–130% of the in vivo muscle length. The active twitch tension was maximal at slightly greater than the in vivo muscle length. The ratio twitch/tetanic force increased with muscle length. Twitch relaxation time increased with muscle length, but the time to peak for twitch force was nearly independent of muscle length in a stretched muscle.
Energy and Communication in Three Species of Hylid Frogs: Power Input, Power Output and Efficiency
Authors: Prestwich Kenneth N. , Brugger Kristin E. , Topping Mary
Published: April 2021

Rates of oxygen consumption for calling, rest and locomotion were measured for three species of treefrogs from the south-east United States: Hyla cinerea (Schneider), H. gratiosa LeConte and H. squirella Bosc. Anaerobic metabolism was slight during calling but large during forced hopping in H. squirella. It is assumed that calling in all three species is primarily aerobic. For all species, oxygen consumption during calling rivalled or exceeded that for locomotion in a closed chamber. Calling apparently is at least as costly as closed-chamber locomotion, if anaerobic contributions to hopping are ignored. The mass-specific costs of producing calls are similar in most species of hylids whose calling energetics have been studied. As in other species of hylids, abdominal trunk muscle masses in male H. squirella and H. gratiosa were large - approximately 10% of the total body mass. Complete sound fields (with measures of variation) were mapped for each species. Each species is an essentially omnidirectional radiator with only a slight flattening of the field behind the head. Efficiencies of sound production (acoustic power/metabolic power) were calculated for each species and compared with values from other frogs, insects and loudspeakers. Efficiencies in hylids vary between 0-8 and 4-9%. Factors that contribute to determining the efficiency of sound production are reviewed. Small animals such as frogs and insects must either use low-efficiency radiators or use high-frequency sounds that do not propagate over great distances. It is possible that low-efficiency transducers maximize the area over which an animal is heard per unit of energy expended.
Processing of Sensory Input From the Femoral Chordotonal Organ by Spiking Interneurones of Stick Insects
Authors: Büschges Ansgar
Published: April 2021

The femoral chordotonal organ (ChO) of the right middle leg of the inactive stick insect Carausius morosus was stimulated by applying movements having a ramp-like time course, while recordings were made from local and interganglionic interneurones in the anterior ventral median part of the ganglion. Position, velocity and acceleration of the movements were varied independently and the interneurones were categorized on the basis of their responses to the changes in these parameters. Position-sensitivity was always accompanied by responses to velocity and/or acceleration. Velocity-sensitive responses were excitatory or inhibitory and were produced by elongation or relaxation, or by both. In some cases, velocity-sensitive neurones were also affected by position and acceleration. Acceleration responses were always excitatory and were often found in neurones that showed no effects of velocity or position. It is inferred that sensory input from different receptors in the ChO is processed by single interneurones. No interneurone in the recording region was found to be directly involved in the resistance reflex of the extensor tibiae motoneurones, elicited by stimulation of the ChO.
H+-Dependent Contraction of the Tritonextracted Tentacle of the Dinoflagellate Noctiluca Miliaris
Authors: Oami Kazunori , Naitoh Yutaka
Published: April 2021

The intracellular conditions required for contraction in the food-gathering tentacle of a marine dinoflagellate Noctiluca miliaris were examined in the isolated tentacle, treated with Triton X-100. The tentacle flexed to its full extent when the pH of the reactivation medium was lowered to 4·0, and extended when it was raised again to its original value. Adenosine triphosphate (ATP) was not needed for the pH-dependent flexion–extension. The flexion was also produced by Ca2+, but in a concentration range more than a thousand times higher than the effective H+ concentration range for producing the flexion. It is concluded that movement of the tentacle in a live specimen of Noctiluca is controlled by membrane potential-regulated cytoplasmic pH.
Rate of Water Admission Through the Madreporite of a Starfish
Authors: Ferguson John C.
Published: April 2021

Time course studies employing the fluorescent, high molecular weight tracer, fluorescein isothiocyanate dextran, confirm that there is a steady entry of sea water through the madreporite of the starfish, Echinaster graminicola, even under constant environmental conditions. This entry serves to supply replacement fluid to both the water vascular system and the perivisceral coelom, with more going to the latter than the former (10·67 vs 6·35 μl h−1 for a 7·25 g animal). Since nearly 2·4 days may be required for an animal to take up 1 ml of sea water through the madreporite, the rate of entry is too low to be easily seen in direct observation, or to have immediate physiological consequences if prevented. Nevertheless, the rate is probably sufficient to make a substantial contribution to fluid volume regulation, functioning along with osmolyte transport and other processes that have been emphasized in recent literature.
Characterization of single non-inactivating potassium channels in primary neuronal cultures of Drosophila
Authors: Yamamoto Daisuke , Suzuki Nobuyuki
Published: April 2021

Permeability and gating properties of single, non-inactivating, K+ channel currents in cultured Drosophila neurons were studied using the gigaohm-seal patch-clamp technique. The non-inactivating K+ currents were activated by depolarizing the membrane to −30 mV or to more positive potentials. The slope conductance of the channel was estimated to be 17·6 ± 3·70 pS when the cytoplasmic side of the inside-out membrane patch was perfused with solutions containing 145 mmol l−1 K+. The single-channel conductance was temperaturesensitive, with a Q10 of 1-44 between 10 and 20°C. Single-channel currents could be recorded when the cytoplasmic K+ was replaced with NH4+, Rb+ or Na+, but not with Cs+. The conductance ratio of the channel for these cations was: K+(l) > NH4+(0·53) > Rb+(0·47) > Na+(0·44). Tetraethylammonium (TEA+) ions applied at a concentration of 10 mmol l−1 to the cytoplasmic side of the membrane increased the frequency of ‘blank’ traces which contained no channel openings during repetitive depolarization. In addition, single-channel amplitude was reduced by about 20%. The open-time distribution was fitted by a single exponential function, whereas the closed-time distribution required a three-exponential fit. Permeability and gating properties of single, non-inactivating K+ channel currents in neurons of eag, a mutant which has defects in the delayed rectifier K+ channel, were indistinguishable from those recorded from wild-type neurons.
Critical Swimming Speeds of Yellow Perch Perca Flavescens: Comparison of Populations from a Naturally Acidic Lake and a Circumneutral Lake in Acid and Neutral Water
Authors: Nelson Jay A.
Published: April 2021

The objectives of this study were to determine if environmental acidity reduces swimming performance in the acid-tolerant yellow perch (Perca flavescens) and to use swimming performance as an indicator of fitness in testing whether fish from naturally acidic environments perform better in acidic water. Perch from a naturally acidic lake (pH 4·4) or a nearby circumneutral lake were swum after either 5–7 months of laboratory acclimation to simulated soft, natural waters or after more than 2 years of acclimation to hard, circumneutral water. The performance test was a critical swimming speed (Ucrit) determination, with 5cms-1 velocity increments at 30 min intervals. Low environmental pH (4·0) produced significant decreases in average swimming performance in each of three experimental series. Acid decreased performance in most but not all fish. The two perch populations had similar mean Ucrit values when swimming in acid water. Pre-acclimation to hard water significantly increased swimming performance. Gravid females acclimated to acid water had very low critical swimming speeds in acid water, whereas Ucrit changed little in acid water when oogenesis occurred in neutral water.
Role of the Telencephalon in the Synchronization of Locomotor and Respiratory Frequencies During Walking in Canada Geese
Authors: Funk Gregory D. , Milsom William , Sholomenko Gerald N. , Steeves John D.
Published: April 2021

To elucidate the importance of telencephalic structures and the effects of metabolic rate in the production of locomotor-respiratory coupling, we examined the relationship between locomotor and ventilatory patterns in: (1) intact trained geese, and (2) brainstem-stimulated (medullary reticular formation) decerebrate geese, that were walking on a treadmill. The decerebrate geese, however, were not completely self supporting. Thus, while the two groups walked with similar stride frequencies (fs), they did so at two different work rates.

While at rest, tidal volume (VT), breathing frequency (fv) and minute ventilation were very similar in the two groups. increased 120% during walking in the intact geese, primarily as a result of increases in fv, while both VT and fv increased to produce a smaller 40 % increase in in the decerebrate birds. Although the magnitude of the increase in was three times greater in the intact geese, the relationships between and oxygen uptake and and CO2 output were similar in the two groups.

Significant coupling between locomotor and respiratory patterns was found in both intact (28·3%) and decerebrate birds (28·9%), suggesting that the telencephalon is not essential for the coupling of locomotor and respiratory rhythms during walking in geese. In addition, the incidence of locomotor-respiratory synchrony was virtually identical in the two groups in spite of a threefold difference in metabolic work rate.
Station-Holding by three Species of Benthic Fishes
Authors: Webb Paul W.
Published: April 2021

Station-holding performance was determined on a smooth substratum and on a grid substratum for three species of benthic fishes differing in body shape, surface texture, density, friction coefficient and behavioural repertoire. The grid was made of wires parallel to the flow, which raised fish into the free stream. Limited observations were also made on the benthopelagic cod. Station-holding performance was evaluated at two speeds. The first was defined as the slip speed, above which activities such as swimming, fin-beating, body arching, body clamping and gripping the substratum were required to hold position on the substratum. The second was defined as the swim speed, when fish began swimming out of ground contact. Cod and lasher started swimming when they began slipping, so that slip and swim speeds were the same, averaging 6cms−1 for cod and 32cms−1 for lasher on the smooth surface. Body postures and fin-beating delayed swimming from a slip speed of about 20 cm s−1 to swim speeds of 47–58 cm s−1 for plaice and rays. The grid had relatively little effect on slip and swim speeds of plaice and rays. Lasher grasped the grid with their pectoral fins, increasing swim speeds to 55cms−1. Amputation of the posterior portion of the median fins of plaice reduced swim speeds on the smooth surface to 36cms−1. Amputation of the pectoral fins of lasher reduced the swim speed on the grid to 38cms−1.

Estimates of drag coefficients for fish were made using published data for blisters. These were used to determine lift coefficients and the effects of grasping the substratum on the friction coefficient. Comparison of lift coefficients of rays on the smooth substratum with those on the grid showed that flow beneath the body reduced lift. Amputation of the posterior of the median fins of plaice and the rarity of body posturing by plaice and rays on the grid showed that the major role of this station-holding behaviour was reduction of lift through induction of flow beneath the body. Lashers were able to hold station at speeds comparable to plaice and rays when they could utilize the small amount of surface structure of the grid to increase friction.

Benthic fishes tend to have either ‘flattened’ plaice-or ray-like forms with low drag coefficients but high lift coefficients, or more fusiform lasher-like forms with high drag coefficients and low lift coefficients. High-lift forms use behaviour to reduce lift coefficients, whereas high-drag forms use behaviour to increase friction.
The neural encoding of the location of targets for saccadic eye movements
Authors: Sparks David L.
Published: April 2021

Current models of the saccadic system imply that there are at least three neural representations of a visual target to which a saccade is made: representations in retinal, spatial (head or body) and motor coordinates. This paper presents the evidence supporting these models and summarizes the available neurophysiological data concerning neural representations of target location. In the superior colliculus, neurones in the superficial layers encode target location in retinal coordinates. Neurones in the deeper layers responsive to auditory and visual stimuli carry motor error signals. Evidence is also accumulating that some neurones in the thalamus and the frontal and parietal cortex convey information about target position with respect to the head or body, but these studies are far from complete.
Coding and processing of electrosensory information in gymnotiform fish
Authors: Heiligenberg W.
Published: April 2021

Studies of the electrosensory system of gymnotiform fish have revealed principles of neuronal coding and processing of information which also character-ize more advanced systems, such as vision and audition in higher vertebrates.

Animals may have different classes of receptors adapted to code different variables within a given modality, and the separation of their central projections provides the basis for independent initial processing of these variables by higher-order neurones. These separate pathways, however, eventually converge at the level of still higher-order neurones which are adapted to ‘recognize’ particular spatial and temporal constellations, or patterns, of the stimulus variables conveyed by these pathways. As different stimulus patterns may control different forms of behavioural responses, corresponding neuronal structures can be identified which are adapted to recognize specific patterns. Neurones at an early level of pattern discrimination may still show very general response properties, whereas neurones closer to the ultimate control of a given behaviour show more specific response properties. These latter are less sensitive to stimulus features which are irrelevant to the control of the behaviour, and they code relevant features more purely and with higher acuity than do lower-level neurones. The acuity of stimulus discrimination displayed by some high-order neurones may rival that observed at the behavioural level. This high sensitivity is achieved through pooling and integration of information supplied by large populations of less-sensitive receptors and lower-order neurones.
The neuroethology of acoustic startle and escape in flying insects
Authors: Hoy R. , Nolen T. , Brodfuehrer P.
Published: April 2021

The acoustic startle/escape response is a phylogenetically widespread be-havioral act, provoked by an intense, unexpected sound. At least six orders of insects have evolved tympanate ears that serve acoustic behavior that ranges from sexual communication to predator detection. Insects that fly at night are vulnerable to predation by insectivorous bats that detect and locate their prey by using biosonar signals. Of the six orders of insects that possess tympanate hearing organs, four contain species that fly at night and, in these, hearing is sensitive to a range of ultrasonic frequencies found in the biosonar signals of bats. Laboratory and field studies have shown that these insects (including some orthopterans, lepidopterans, neuropterans and dictyopterans), when engaged in flight behavior, respond to ultrasound by suddenly altering their flight, showing acoustic startle or negative phonotaxis, which serve as bat-avoidance behavior.

A neural analysis of ultrasound-mediated escape behavior was undertaken in the field cricket Teleogryllus oceanicus. An identified thoracic interneuron, int-1, was shown to trigger the escape response, but only when the cell was driven (synaptically or electrically) at high spike rates, and only when the insect was performing flight behavior; avoidance steering only occurs in the appropriate behavioral context: flight. Thus, significant constraints operate upon the ability of int-1 to trigger the escape response. The integration of auditory input and flight central pattern generator output occurs in the brain. It is found that neural activity descending from the brain in response to stimulation by ultrasound is increased when the insect is flying compared to when it is not. Although the behavioral act of avoidance steering may appear to be a simple reflex act, further analysis shows it to be anything but simple.
A subpopulation of cerebral B cluster neurones ofAplysia californicais involved in defensive head withdrawal but not appetitive head movements
Authors: Teyke T. , Weiss K. R. , Kupfermann I.
Published: April 2021

The cerebral B cluster neurones of Aplysia californica were studied under experimental conditions designed to evoke head movements in a selective fashion: either to approach an appetitive stimulus, or to withdraw from an aversive one. Intracellular recordings indicated the presence of two types of B cluster neurones: Bn cells that had fast (narrow) spikes, and Bb cells that had slow (broad) spikes. Tactile stimulation of the tentacles, rhinophores and lips excited Bn neurones, but inhibited Bb neurones. Intracellular stimulation of Bn cells evoked contractions of body wall muscles. No contractions were observed when Bb cells were fired, indicating that it is unlikely that the Bb neurones are motor neurones. Several lines of evidence indicated that the Bn type neurones are involved in withdrawal responses but not in appetitive head turning. (1) Elimination of the descending axons of the Bn cells by lesioning the cerebropleural connectives (C-Pl connectives) did not affect the head-turning response. This lesion significantly altered the head-withdrawal response by selectively eliminating an initial fast component of the withdrawal movement. (2) In chronic recordings from the C-Pl connective, unit activity was obtained which was correlated with the presentation of an appetitive stimulus rather than with evoked or spontaneous turning movements. A substantial increase in activity also occurred during head withdrawal of the animal. On the basis of these data, we postulate that separate populations of motor neurones are responsible for the aversive withdrawal of the head, and for the directed turning response towards a stimulus.
Errata
Authors: Przysiezniak Jan , Spencer Andrew N.
Published: April 2021

Materials and methods. The fifth line from the bottom of the second paragraph reads ‘digestion in collagenase (…) at 100 units ml−1 …’.

The concentration of collagenase should be 1000 units ml−1
Regulation of Intracellular pH by Toadfish (Opsanus Beta) Hepatocytes
Authors: Walsh Patrick J.
Published: April 2021

The BCECF [2’,7’-bis(carboxyethyl)-5(6)-carboxyfluorescein] method for measurement of intracellular pH (pHi) was successfully applied to toadfish (Opsanus beta Goode and Bean) hepatocytes and used for investigating the pHi regulatory properties of the hepatocytes. As in previous studies of fish hepatocytes, toadfish hepatocyte pHi showed a marked dependence on extracellular pH (pHe) with characteristic values of about 0.15–0.2 units below pHe. Measurement of membrane potential (–33.76±3.07mV, N=3) in toadfish hepatocytes by the S14CN− distribution method allowed calculation of equilibrium pHi values and, despite the close tracking of pHi and pHe, proton equilibration across the membrane was never observed. Furthermore, when toadfish hepatocytes were acidified by the NH4CI prepulse method, recovery to normal pHi values could be inhibited by addition of 0.5 mmol I−1 amiloride or replacement of extracellular Na+, indicating that these cells possessed a Na+/H+ exchanger. These experiments led to the conclusion that pHi is regulated in toadfish hepatocytes. I next exposed toadfish hepatocytes to a physiological range of several extracellular variables that change during exercise (pHe, [lactate], [catecholamine], [glucose]), in the presence and absence of amiloride, in an attempt to determine the importance of Na+/H+ exchange to hepatocyte pHi regulation in a physiological context. The exchanger plays a significant role in post-exercise recovery from acidosis induced by changes in and pHe. Further experiments employing inhibitors of lactate metabolism (3-mercaptopicolinic acid and amino-oxyacetic acid) and amiloride established that the increased lactate metabolism associated with ‘post-exercise’ recovery creates an intracellular acid load, and that Na+/H+ exchange protects the cell from changes in pHi caused by lactate metabolism.
Ion Homeostasis in the Leech: Contribution of Organic Anions
Authors: Hoeger Ulrich , Wenning Angela , Greisinger U. T. E.
Published: April 2021

Organic anion concentrations in the blood of Hirudo medicinalis were determined in samples from individual animals using reverse-phase high-pressure liquid chromatography (HPLC) and ultraviolet detection. Quantitatively important anions were malate, α-ketoglutarate, succinate, lactate and fumarate, constituting about 70% of total blood anions. Malate had the highest concentration, 34–68 mehquiv l−1 blood, which could (depending on metabolic state) exceed the level of blood Cl− (approx. 36mequivl−1). Organic acid concentrations in the blood were considerably higher than in the tissue.

Blood organic acid concentrations changed more with than with temperature. They were unaffected by short periods of aerobic exercise, but stress due to handling and prolonged restraint led to a drastic increase of blood lactate and succinate levels, while malate, fumarate and α-ketoglutarate levels decreased.

After feeding on hypertonic, Cl−-rich meals, the Cl− concentration in leech blood increased far more than the cation concentrations. This was not compensated by a decrease of organic acid levels. The regulatory mechanisms for inorganic and organic ion homeostasis function independently.
The Larval Eclosion Hormone Neurones inManduca Sexta:Identification of the Brain-Proctodeal Neurosecretory System
Authors: Truman James W. , Copenhaver Philip F.
Published: April 2021

Larval and pupal ecdyses of the moth Manduca sexta are triggered by eclosion hormone (EH) released from the ventral nervous system. The major store of EH activity in the latter resides in the proctodeal nerves that extend along the larval hindgut. At pupal ecdysis, the proctodeal nerves show a 90 % depletion of stored activity, suggesting that they are the major release site for the circulating EH that causes ecdysis. Surgical experiments involving the transection of the nerve cord or removal of parts of the brain showed that the proctodeal nerve activity originates from the brain. Retrograde and anterograde cobalt fills and immunocytochemistry using antibodies against EH revealed two pairs of neurons that reside in the ventromedial region of the brain and whose axons travel ipsilaterally along the length of the central nervous system (CNS) and project into the proctodeal nerve, where they show varicose release sites. These neurons constitute a novel neuroendocrine pathway in insects which appears to be dedicated solely to the release of EH.
The Scaling of Aerobic and Anaerobic Muscle Power in Rainbow Trout(Salmo Gairdneri)
Authors: Goolish Edward M.
Published: April 2021

The scaling of anaerobic metabolism and red muscle mass was examined in rainbow trout (Salmo gairdneri) ranging in size from 2 to 1200 g. The initial rate of white muscle lactate production during maximal burst activity was significantly higher in large (28·lcm) than in small (8·0cm) fish. ‘Resting’ lactate concentrations in anesthetized trout (approximately 30 s of stress) increased with fish size, also reflecting higher glycolytic potential for larger fish. Maximum muscle lactate concentrations following 6 min of exhaustive exercise increased from approximately 25 to 45 μmolg−1 with increased fish size (= L0·36, where L is fish length). Total white muscle lactate production, including changes in muscle mass, scaled as L3·52. A scaling comparison of total anaerobic capacity with theoretically predicted power requirements indicated decreased burst swimming performance with increased size. Red muscle mass increased from approximately 1 to 3 % of body mass with increased fish size. The positive allometry in red muscle mass (= L3·62) is greater than the scaling of power requirements during aerobic swimming predicted from hydrodynamic theory, and may provide compensation for decreased mass-specific power output with increased size.
Combined Effects of Environmental PO2 and Temperature on Ventilation and Blood Gases in the Carp Cyprinus Carpio L.
Authors: Glass M. L. , Andersen N. A. , Kruhøffer M. , Williams E. M. , Heisler N.
Published: April 2021

The effects of changes in environmental temperature and oxygen tension on gill ventilation, arterial , pH and [HCO3−] were evaluated in carp (Cyprinus carpio L.). Gill ventilation was measured continuously in specimens acclimated to 10 or 20°C, combining the method of electromagnetic flow determination with the application of a rubber mask technique. After establishing control values in airequilibrated water the environmental water was reduced from about 150 mmHg (20 kPa) during control conditions to 110 or 75 mmHg (14.7 or 10 kPa), respectively. Measurements of blood gases and acid-base parameters were performed repeatedly before, and 1 and 4 h after, initiation of hypoxia. Regardless of temperature, these moderately hypoxic conditions caused considerable and lasting increases in gill ventilation of about 70% or 180% , relative to the respective normoxic control values of about 50ml kg−1 min-1 at 10°C and 230 ml kg−1 min−1 at 20°C. These increases in ventilation reduced substantially, resulting in a rise in pHa by about 0.1 units at of 110 mmHg (14.7 kPa) and by about 0.2 units at of 75mmHg (10 kPa). Arterial was low under normoxic conditions at both temperatures (≈15 mmHg, ≈2kPa). During hypoxia, was marginally reduced, whereas the arterial O2 content and saturation remained at normoxic levels, mainly because of the increase in the blood O2-affinity induced by respiratory alkalosis. This lack of any clear relationship between arterial O2 content and ventilatory response to moderate hypoxia contrasts with previously reported data for trout, and supports the hypothesis that a change in is an adequate stimulus for the adjustment of ventilation in carp.

The considerable ventilatory response, together with small and inconsistent reductions in arterial , may also represent an expression of the action of waterfacing oxygen receptors on the regulation of breathing. A striking feature of the regulation of ventilation in carp compared with that in air-breathing lower vertebrates is that the hypoxic response is maintained at low temperatures, possibly indicating a relatively small safety margin for complete tissue oxygen supply in fish.
Prey capture in the praying mantis Tenodera aridifolia sinensis: coordination of the capture sequence and strike movements
Authors: Corrette B. J.
Published: April 2021

Coordination of the complete capture sequence of the praying mantis has been studied in detail using several specially developed photographic techniques.

The mantis was able to attack prey throughout a large three-dimensional capture zone by changing body orientation relative to its perch. This orientation centred prey on the median plane and brought it within an attack zone relative to the prothorax. Alignment with the median plane simplifies the attack since the prey can then be localized using only two dimensions. The attack comprised several stereotyped components which together formed a single movement sequence of all six legs. Although too rapid for visual feedback, a simple mechanism permits steering of these movements to capture prey at particular locations within the attack zone.

These findings are contrasted with those from studies of mantis visual behaviour and a simple mechanism is suggested for how prey location is encoded to produce steering of the attack.
Are American Homing Pigeons Genetically Different from Italian Ones?
Authors: Benvenuti S. , Brown A. I. , Gagliardo A. , Nozzolini M.
Published: April 2021

The variable results of experiments on anosmic Cornell pigeons, compared with the consistent effect of olfactory deprivation observed in pigeons in Italy, has sometimes been explained by supposing that pigeons in the two countries belong to different genetic strains.

This hypothesis was tested by performing experiments with the progeny of Cornell pigeons transported to Italy as eggs and placed in the nests of Italian foster parents. The homing behaviour of the American birds raised in Italy was compared with that of Italian pigeons hatched and raised in the same loft.

The results of the experiments show that both the American and the Italian pigeons are severely affected by olfactory deprivation in releases at unfamiliar sites, in contrast to the homeward-oriented control groups of both strains. We conclude that there is no major genetic difference in homing mechanism between Cornell and Italian pigeons.

The results of experiments performed in Italy and in the USA have shown that different rearing and training procedures do not induce the development of maps based on different cues. Therefore, the reported differences between the results obtained in the USA and those obtained in Italy may be due to regional differences in the availability of navigational cues.
Neural Control of Heart Beat in the Pteropod Mollusc Clione Limacina: Coordination of Circulatory and Locomotor Systems
Authors: Arshavsky Yu. I. , Deliagina T. G. , Gelfand I. M. , Orlovsky G. N. , Panchin Yu. V. , Pavlova G. A. , Popova L. B.
Published: April 2021

In the intact pteropod mollusc Clione limacina a correlation between heart beat and locomotor activity has been found. In freely swimming Clione, pauses in locomotor activity arose spontaneously with intervals of a few minutes. During these pauses, the heart stopped beating. A link between the heart and locomotor activity was also observed during defensive reactions: mechanical stimulation of the head resulted in the termination of both locomotion and heart beating, while stimulation of the tail accelerated both the locomotor and the heart rhythms. After transection of the medial abdominal nerve supplying the heart, the link between heart rate and locomotor activity disappeared. The heart rhythm accelerated during hunting behaviour of Clione. Four efferent neurones controlling heart beat were found: one heart excitor (HE) in the left pedal ganglion, and three heart inhibitors (HI) in the left abdominal ganglion. The HE exerted an inhibitory action upon the HIs. Spontaneous or reflex activation of the locomotor generator was accompanied by excitation of the HE and by inhibition of the HIs, while spontaneous or reflex inhibition of the locomotor generator was accompanied by inhibition of the HE and by excitation of the HIs. These effects were due, at least partly, to the direct action of the neurones of the locomotor generator upon the HE and HIs.
Fish Hepatocytes Accumulate Hepes: A Potential Source of Error in Studies of Intracellular pH Regulation
Authors: Walsh Patrick J.
Published: April 2021

Since their introduction in 1966, the so-called ‘Good’s’ hydrogen ion buffers (e.g. Hepes, Pipes, etc.; Good et al. 1966; Good and Izawa, 1972) have been used in many experimental systems. Their popularity is widespread because they appear to fit many of the criteria for ideal biological buffers, including appropriate pKa values, high aqueous solubility, minimal complexation with metal ions, and low membrane permeability (Good et al. 1966; Good and Izawa, 1972). More recently, the fit of Good’s buffers to these criteria has come under closer scrutiny. Under some circumstances, particularly in the in vitro study of metal ion-metallo-protein interactions (Nakon and Krishnamoorthy, 1983) and in studies of free-radical production (Grady et al. 1988), their use may lead to spurious results.
Inhibitory Effect of L-Glutamate on the Neuropile Arborizations of Flight Motoneurones In locusts
Authors: Dubas F.
Published: April 2021

In vertebrates, L-glutamate (glutamate) is a major excitatory neurotransmitter in the brain, acting on at least three separate receptors (Fagg, 1985). In insects, there is strong evidence that glutamate is the excitatory neurotransmitter at the neuromuscular synapse (Usherwood, 1981). Since some motoneurones make central synapses (Watson and Burrows, 1982; Burrows et al. 1989), it is probable that glutamate is also released centrally. Indeed, Bicker et al. (1988) found glutamate-like immunoreactivity in the central projections of known glutamatergic motoneurones and in interneurones in the locust, and Watson (1988) has shown it to be localized at central synapses. Furthermore, isolated insect neuronal somata respond to glutamate by activation of a chloride conductance (Usherwood et al. 1980), and ionophoretic applications of glutamate in certain areas of the neuropile cause motoneurones to depolarize and to spike (Sombati and Hoyle, 1984). In cultured embryonic cockroach brain neurones, Horseman et al. (1988) found both excitatory and inhibitory responses to glutamate. Wafford and Sattelle (1989) found only hyperpolarizing responses to glutamate on the fast coxal depressor motoneurone soma in situ, but they recorded depolarizing responses to kainate and quisqualate. These experiments indicate that receptors for glutamate are present on insect neuronal somata. However, since insect neuronal somata play no role in synaptic transmission and are generally not electrically excitable (Gwilliam and Burrows, 1980), the function of somal neurotransmitter receptors is unclear. To study the role of putative neurotransmitters in mediating or modulating normal synaptic inputs it is necessary to apply the substances to the neuropile where the synapses are and to record the effects there. It is also necessary to use an animal preparation where normal synaptic inputs can be recorded. In this study, the effects of topical pressure applications of glutamate were monitored by means of intracellular recordings, in the neuropile, from flight motoneurones (FMNs) during fictive flight behaviour. While this procedure does not ensure that only synaptic receptors are activated, it does enable one to activate synaptic receptors or study the effect that extrasynaptic receptors have on synaptic activity.