bluuebunny/crossref_metadata_2025 huggingface dataset:
Interneuronal Control of Feeding in the Pond Snail Lymnaea Stagnalis
Authors: Rose R. M. , Benjamin P. R.
Published: April 2021

The Lymnaea buccal ganglion is organized such that the basic feeding rhythm is generated by an interneuronal network which imposes its activity on a set of follower cells. In this paper we extend our earlier observations (Benjamin & Rose, 1979) on the follower cells to show that they receive four consecutive synaptic inputs. The main objective of the paper is to describe the properties of an interneurone called the ‘slow oscillator’ which is capable of initiating feeding cycles. This interneurone will be used in the following paper (Rose & Benjamin, 1981) to drive other members of the interneuronal network in order to determine how it is organized, and to understand the origin and timing of the four synaptic inputs to the follower cells.
Interneuronal Control of Feeding in the Pond Snail Lymnaea Stagnalis: II. The Interneuronal Mechanism Generating Feeding Cycles
Authors: ROSE R. M. , BENJAMIN P. R.
Published: April 2021

The feeding cycle of Lymnaea is generated by a network of three types of interneurone, N1, N2 and N3. This network is driven by the slow oscillator (SO) interneurone described in the previous paper. Interaction between the different interneurones is dependent on both connectivity and endogenous properties, and utilizes such properties as post-inhibitory rebound and self-feedback within electrically-coupled populations. Each of the four components of the interneuronal network (SO, N1, N2 and N3) is responsible for a different phase of synaptic input to the follower cell population which was previously shown to directly control feeding movements.
Crab Gill Intra-Epithelial Carbonic Anhydrase Plays a Major Role in Haemolymph CO2 and Chloride Ion Regulation
Authors: Burnett Louis E. , Woodson Paul B. J. , Rietow Martha G. , Vilicich Victoria C.
Published: April 2021

The distribution and function of the enzyme carbonic anhydrase in the crab Pachygrapsus crassipes was investigated. Carbonic anhydrase was found in gill epithelial tissue but not in the haemolymph, muscle, heart, hepatopancreas or gonads of male crabs.

Enzyme activity was completely inhibited in vitro by 2 × 10 −4M sodium acetazolamide (Diamox). Radiolabelled Diamox (2 ×10−4M) in sea water was found to equilibrate with the intact crab’s haemolymph within one hour.

Haemolymph CO2 content, pH and chloride ion concentration were measured in crabs acclimated to different salinities and exposed to 2 × 10−4M Diamox. Haemolymph CO2 content increased at all salinities, especially low salinities, while pH remained unchanged, except at low salinities where it increased. Diamox impaired the regulation of haemolymph chloride at low salinities, but had no effect on chloride regulation at high salinities. Measurement of O2 uptake (estimating CO2 production) in crabs before and after Diamox exposure confirmed that elevated haemolymph CO2 was not due to increases in tissue CO2 production.
Short Communications: The Egg Case of the Oviparous Elasmobranch, Raja Erinacea, Does Osmoregulate
Authors: Evans David H.
Published: April 2021

Like many other elasmobranchs (Wourms, 1977), the little skate, Raja erinacea, lays individual eggs covered with a specialized structure termed the egg case or ‘Mermaid’s Purse’. Collagen is the major component of the egg case, which is secreted by the shell gland in the anterior region of the oviduct (Wourms, 1977). Smith (1936) and Price & Daiber (1967) suggested that the egg case provided an osmotically isolated environment until the embryo was capable of urea retention and osmoregulation. However, Reed (1968a) showed that the encapsulated embryos of the skate, Raja binoculata, possess the enzymes of the Krebs omithine-urea cycle and are able to retain near-adult levels of both urea and trimethylamine oxide, even at very early stages (Reed, 1968b). The retention of urea seems to be secondary to a urea-impermeable embryonic membrane since Needham & Needham (1930) found that the egg cases of Syllium (= Scyliorhinus) canicula are permeable to urea, and this has been substantiated by recent work on the egg cases of the same species (Hornsey, 1978; Foulley & Melinger, 1980). Despite the ability to maintain high urea levels, it appears that the full complement of elasmobranch osmoregulatory mechanisms is not present in at least the early stages of encapsulated elasmobranch development since Libby (1959) found that R. eglanteria cannot survive in sea water if it is removed from the egg case before day 20 of the 64-day developmental period. In this species, at day 20 a mucous plug in the egg case is dissolved and sea water enters. This opening of the egg case to sea water during the later stages of development is also found in other oviparous elasmobranch species (Wourms, 1977).
Short Communications: The Association of Uropod Steering with Postural Movement of the Abdomen in Crayfish
Authors: Takahata Masakazu , Yoshino Masami , Hisada Mituhiko
Published: April 2021

Decapod crustaceans have elaborate statocysts to detect changes in the body position. They utilize these organs to initiate and control various equilibrium reactions so that they can always maintain an upright posture. In macrurans, these reactions consist of asymmetrical movements of walking legs, swimmerets and uropods, as well as compensatory movements of the eyestalks and antennae. They have been previously described in terms of a simple input (i.e. the tilt angle)-and-output (i.e. the magnitude of the resultant reaction) relationship (e.g. Schöne, 1954). But do these equilibrium reactions occur whenever the animal tilts? We report here that one of them, the uropod steering movement, does not occur by itself and always occurs together with the abdominal movement which is unrelated to the equilibrium reaction. It is shown that this association of two independent movements is not mediated by any peripheral sense organ. Quantitative aspects of the uropod steering movement were described elsewhere (Yoshino, Takahata & Hisada, 1980).
Is the Position of the Femur-Tibia Joint Under Feedback Control in the Walking Stick Insect?: I. Force Measurements
Authors: Cruse H.
Published: April 2021

It is known that a feedback system is involved in the position control of the femur-tibia joint of a fixed stick insect. Force measurements indicate that the control system also mediates negative feedback in the walking animal, the gain of the reflex loop and the half-time value of the reflex response being decreased. The biological significance of this effect is discussed. The results agree with similar experiments on man by other authors.
Symmetrically Organized Dorsal Unpaired Median (Dum) Neurones and Flash Control in the Male Firefly, Photuris Versicolor
Authors: Christensen Thomas A. , Carlson Albert D.
Published: April 2021

Male fireflies of the species Photuris versicolor produce a species-typical triple-pulsed flash which is used as a courtship signal. The neural anatomy was examined to determine if this complex behaviour could be attributed to the organization within the central nervous system. The lantern is innervated primarily by the two most posterior abdominal ganglia. Bilateral roots from these ganglia form a symmetrical pattern of innervation to both sides of the lantern tissue. With minor exceptions, this pattern is similar to that described for other firefly species. The neural organization within the lantern ganglia was determined by back-filling the roots with cobalt or Lucifer Yellow CH, and then examining the ganglia in whole mount. Clusters of three or four large dorsal unpaired median (DUM) neurone somata, each sending bilateral processes out of the lantern roots, were found in both lantern ganglia. The DUM neurone axons bifurcate several times and ramify throughout the dorsal surface of the lantern tissue. More than one DUM neurone may innervate a particular region of photogenic tissue. When dye was back-filled into peripheral branches of the lantern roots that do not innervate photogenic tissue, no DUM somata were stained. Instead, the fibres that filled carried the dye anteriorly up the nerve cord through the ipsilateral connective. No fibres were observed to cross the gang-lion midline or exit from the contralateral root, nor were any fibres stained in the contralateral connectives. DUM neurones within the lantern ganglia have resting potentials between 30 and 45 mv and they exhibit multiple, as well as single-peaked spontaneous action potentials. The presence of multiple spikes might reflect the special bilateral morphology of these neurones. The lantern nervous system is organized in an arrangement capable of synchronizing the excitation of all the lantern photocytes. This neural organization could aid in the control of the complex flash pattern displayed by male Photuris versicolor fireflies.
Post-Metamorphic Development of the Frequency Selectivities and Sensitivities of the Peripheral Auditory System of the Bullfrog, Rana Catesbeiana
Authors: Shofner William P. , Feng Albert S.
Published: April 2021

Acoustic response characteristics of single fibres were studied in the VIIIth cranial nerve of adult and early post-metamorphic bullfrogs (Rana catesbeiana). Based on the distribution of units’ best excitatory frequencies, three populations of auditory fibres were found in each group of frogs. The sharpness of the tuning curves and temporal firing patterns of primary fibres were similar in both adults and froglets. However, the distributions of the populations were different between the two groups, and it was found that froglets responded to higher frequencies than did adults. There were also differences in the distributions of thresholds of excitation between the froglets and adults. The excitation thresholds of low-frequency selective and high-frequency selective fibres tended to be higher in froglets. Low-frequency selective fibres in both groups of frogs exhibited two-tone inhibition, and the best inhibitory frequencies were higher in froglets than in adults. These results demonstrate that changes in the response properties of primary auditory fibres occur during the development of the bullfrog. These functional changes presumably reflect morphological changes which may occur in the peripheral auditory system.
Contribution of Compound Eyes and Ocelli to Steering of Locusts in Flight
Authors: Taylor Charles P.
Published: April 2021

Locusts (Orthoptera, Acrididae) were induced to fly while tethered within a simulated horizon display. Rotation of the horizon about the animal’s long axis caused changes in the relative timing of the spikes of homologous flight muscles of either side. Changes in relative timing paralleled the pattern of head motions (Taylor, 1981) elicited by horizon rotation. Systematic changes in relative spike timing were also seen after the compound eyes were surgically disconnected and in response to forced head rotation. These results are discussed in relation to the functions of the compound eyes, the ocelli, and the cervical proprioceptive hairs for visual flight stabilization.
Respiration in the Land Crab, Gecarcinus Lateralis
Authors: Taylor A. C. , Davies P. Spencer
Published: April 2021

The oxygen consumption, ventilation and blood gas transport were investigated in the tropical land crab Gecarcinus lateralis to determine the adaptations of the respiratory system for aerial respiration. The gills of Gecarcinus are reduced in size and specialized, in part, for salt and water uptake. The epibranchial space of the branchial chamber is very much enlarged and lined with what is probably a respiratory epithelium. There is a high ventilatory air-flow, produced by the beating of the scaphognathites, but the percentage extraction of oxygen is extremely low. This may be the result of ventilatory ‘shunts’, whereby a proportion of the air does not come into contact with the respiratory surfaces. The energetic cost of a high ventilation rate need not be high, because of the low inertial mass of air in comparison with water. A high oxygen tension gradient of 103 torr is maintained across the respiratory surfaces. This is interpreted as an adaptation to achieve a high oxygen diffusion rate through the reduced surface area of the gills. The blood has a relatively high oxygen capacity which is again thought to be an adaptation to compensate for the reduced gill surface area. Carbon dioxide tensions and content were high as in other terrestrial animals. Overall, the respiratory adaptations are thought to be related primarily to the reduction in the respiratory surface area which has evolved to deal with the problems of water conservation in these terrestrial animals.
Respiration in Exercising Fowl
Authors: Brackenbury J. H. , Avery P. , Gleeson M.
Published: April 2021

Oxygen consumption, respiratory frequency, and the of expiratory and interclavicular air sac gases were continuously monitored in six female domestic fowl trained to exercise on a treadmill for 10 min periods at normal or elevated air temperatures. At normal temperatures (20 ± 2 °C) the cost of locomotion rose from 0·46 ml O2 kg-1 m-1 at 0−3 km h-1 to 0·77 ml O2 kg-1 m-1 at the maximum speed of 4·3 km h-1. At 32 ± 2°C, increased by as much as 20% compared to normal temperatures. Hyperventilation occurred at all speeds and at both normal and elevated temperatures. End-tidal and interclavicular increased in a parallel manner with speed, the latter remaining consistently 6−7 Torr less than the former both at rest and during exercise.
The Parameters and Properties of A Group of Electrically Coupled Neurones in the Central Nervous System of A Hydrozoan Jellyfish
Authors: Spencer A. N.
Published: April 2021

Swimming of the jellyfish Polyorchis penicillatus is controlled by a network of large, electrically coupled, motor neurones in the inner nervering (Fig. 3). Recordings from pairs of neurones, even at widely separated positions, display essentially the same electrical activity (Fig. 1). Electrical coupling between neurones is via gap-junctions and is very strong, giving the network a space constant of approximately 7·1 mm (Figs. 2, 4, 5). The network acts as a low-pass filter progressively attenuating signals with frequencies greater than 1 Hz (Figs. 4, b). I/V experiments demonstrate that the neurones show rectifying properties since membrane resistance decreases noticeably with depolarizations greater than about 25 mV (Figs. 7, 8). A number of electrical constants of the network were measured or calculated: rm = 3·55 MΩ cm-1, Rm = 98 kΩ cm2, ri = 7 MΩ) cm-1, input = 2·5 MΩ, Cm = I·52µF cm-2. Stimulated action potentials are conducted in the network at approximately 112 cm s-1 while spontaneous action potentials have velocities up to 200 cm s-1. As an action potential propagates from its initiation site its duration decreases from about 30 ms to 8 ms when it reaches the opposite side of the margin. Epithelial impulses, which mediate crumpling, cause large i.p.s.p.s in the motor network that can inhibit swimming for several seconds.
A Simple Design for A Force-Plate to Measure Ground Reaction Forces
Authors: Heglund Norman C.
Published: April 2021

This paper describes an inexpensive force-plate that can measure ground reaction forces in two planes and can be built to a size or sensitivity suitable for nearly any biological application.
Acid-Base and Electrolyte Status in Carp (Cyprinus Carpio) Exposed to Low Environmental pH
Authors: Ultsch G. R. , Ott M. E. , Heisler N.
Published: April 2021

Carp (Cyprinus carpio) were exposed to environmental water pH (pHw) step changes from 7·4 to 5·1, 5·1 to 4·0 and 4·0 to 3·5. pH, , and lactate in dorsal aortic blood, [Na+], [K+] and [Cl−] in dorsal aortic plasma, base loss, and ammonia excretion were determined as a function of time after each pHw step change.

At pHw 5·1 the measured blood acid-base and electrolyte parameters remained essentially unchanged; the base loss, however, was increased by a factor of 2. When pHw was lowered to 4·0 an additional severe increase in the ‘net base loss’, expressed as the difference between base loss and ammonia excretion, resulted in progressive reduction of arterial pH and [HCO3−]. The electrolyte status was also severely disturbed by progressively falling plasma [Na+] and [Cl−], which is attributed to failure of the active H+/Na+ and HCO3− /C1− exchange mechanisms in the gills.

At pHw 4·0 the acid-exposure syndrome is characterized by acid-base and electrolyte disturbances apparently not related to hypoxia. However, at pHw 3·5, tissue hypoxia, due to disturbances of gill gas exchange and to Bohr and Root effects, appears to be an additional important factor aggravating the disturbances of acid-base and electrolyte status.
Physiology and Energetics of Pre-Flight Warm-Up in the Eastern Tent Caterpillar Moth Malacosoma Americanum
Authors: Casey Timothy M. , Hegel Jeri R. , Buser Charlene S.
Published: April 2021

Thoracic temperature (Tth) during pre-flight warm-up increased linearly with time at all air temperatures (Ta). The rate of pre-flight warm-up increased from 3·3 to 12·7 °C/min between Ta’s of 14 and 28 °C. Head temperature remained within a few °C of Tth during warm-up, while ventral abdominal temperature remained within a few °C of Ta. Pulsation rate of the dorsal vessel in the thorax increased directly with thoracic temperature. Wing-stroke frequency (n) varied from 15 s−1 at Tth = 16 °C to 58 s−1 at Tth= 40 °C and was similar at any given Tth between Ta’s of 14 and 28 °C. While stroke amplitude varied significantly between warmup and tethered flight, stroke frequency was similar for the two activities in the same Tth range. Calculated rates of heat production were tightly coupled to Tth and did not vary with Ta. The change in heat production during warm-up was dependent entirely on changes in frequency of muscle contraction. Stroke work was constant at 0·68 mW between Tth of 15 and 40 °C.
Morphology of the Giant Dopamine-Containing Neurone, R.Pe.D.1, in Lymnaea Stagnalis Revealed by Lucifer Yellow CH
Authors: Haydon P. G. , Winlow W.
Published: April 2021

The morphology of the giant dopamine-containing neurone of Lymnaea stagnalis, R.Pe.D.1, was studied by injection of Lucifer Yellow CH and by electrophysiological, techniques.

R.Pe.D.1 was found to project to the periphery via the nerve trunks of the right parietal and visceral ganglia. Neurites bearing varicosities were found in each ganglion through which the axon passed. The neurites consistently arose from the same regions of the axon and the neuritic fields were similar in each preparation.
Temperature Effects On Neuromuscular Transmission (Opener Muscle of Crayfish, Astacus Leptodactylus)
Authors: Fischer Ludwig , Florey Ernst
Published: April 2021

In experiments on the opener muscle of the third walking legs of crayfish (Astacus leptodactylus) it was found that the mechanical tension developed in response to repetitive stimulation of the single motor axon increases over the entire temperature range from 30 down to 0 °C. In contrast to this, the tension elicited by depolarizing single muscle fibres decreases with decreasing temperature ; the threshold for excitation-contraction coupling is not significantly altered.

With decreasing temperature the resting potential decreases (up to 2 mV/°C) but the amplitude and decay time of the e.p.s.p.’s increase. The time constant, τ, of e.p.s.p. decay has a Q10 of less than – 2 in the range above 15 °C but reaches a value of –7 between 10 and 0 °C. This pattern of temperature dependence is fully accounted for by a parallel change of membrane resistance and its reciprocal, the membrane conductance. The corresponding activation energies computed from τ-values approximate 3 kcal/mol at high temperature and 46 kcal/mol in the low temperature range.

The combined effects of a lowered resting potential, an increased amplitude, and especially an increased decay time of e.p.s.p.s result in a drastic enhancement of the depolarization reached during summation of e.p.s.p.s as the temperature is decreased. These effects overcompensate the declining effectiveness of excitation-contraction coupling so that the entire process of neuromuscular transmission becomes more and more effective as the temperature declines. In order to reach the same tension lower frequencies of nerve stimulation are needed at lower temperatures.
Absorption of Fluid by the Midgut of Rhodnius
Authors: Farmer J. , Maddrell S. H. P. , Spring J. H.
Published: April 2021

Isolated midguts of 5th-instar Rhodnius prolixus will transport fluid from the lumen that is close to iso-osmotic with the luminal contents. The transported fluid contains sodium and chloride ions as its major constituents. Fluid transport can be attributed to active transport of sodium ions from the lumen. The haemolymph side of the epithelium, towards which transport is directed, is at a potential positive with respect to the lumen; this potential difference is greatly increased if the lumen contains only impermeant anions, and the rate of fluid transport is strongly dependent on the concentration of sodium ions in the luminal fluid. The rate of fluid transport is increased approximately six times by treatment with 5-hydroxytryptamine (2 × 10−7 M) or cyclic AMP (2 × 10−3 M). The transepithelial potential is increased by such treatment but the major effects are on the short-circuit current, which increases by about five times, and on the electrical resistance of the epithelium, which falls to about a quarter of its earlier value.
Light and High Potassium Cause Similar Phase Shifts of the Aplysia Eye Circadian Rhythm
Authors: Jacklet Jon W. , Lotshaw David P.
Published: April 2021

The eye of Aplysia, with its circadian rhythm of spontaneous optic nerve impulses (Jacklet, 1969a), is a model system for studying the cellular mechanisms of circadian rhythms generated by nervous tissue (Jacklet, 1981). An approach to determine the mechanisms of rhythms is to apply pulses of experimental agents and then observe the shifts in phase of subsequent cycles of the rhythm. If the size and direction of the phaseshifts are dependent upon the phase of the cycle when the pulse was given (phasedependent phase shifts), it is evidence that the rhythm timing mechanism has been perturbed. The specific cellular process acted on is then believed to be important in the cellular clock mechanism. Some agents cause phase-dependent phase shifts and the shifts are plotted in phase response curves (PRCs). It is useful to compare the PRCs produced by different agents in order to identify similar or dissimilar actions on the cellular clock (Jacklet, 1978).
The Exoskeleton and Insect Proprioception
Authors: Zill Sasha N. , Moran David T. , Varela Francisco G.
Published: April 2021

Mechanical stimulation of individual tibial campaniform sensilla produces specific reflex effects upon motoneurones to leg muscles. The reflex effects of a campaniform sensillum depend upon the orientation of its cuticular cap. The proximal sensilla, oriented perpendicular to the long axis of the tibia, excite slow motoneurones to the extensor tibiae and extensor trochanteris muscles and inhibit slow motoneurones to the flexor tibiae and flexor trochanteris muscles. The distal sensilla, oriented parallel to the tibia, exhibit reflexes of opposite sign, inhibiting the extensors and exciting the flexors. These reflexes constitute a negative feedback system. Individual sensilla specifically excite motoneurones which innervate muscles whose resultant tensions decrease the firing of those sensilla. It is postulated that individual campaniform sensilla can detect loading of the leg in various postures and can excite appropriate motoneurones in compensation. These receptors can also detect strains caused by large, resisted contractions of the antagonist muscles and inhibit the corresponding motoneurones.
Synaptic Actions of Oesophageal Proprioceptors in the Mollusc, Philine
Authors: Sigger J. N. , Dorsett D. A.
Published: April 2021

The buccal ganglia of Philine each contain a group of mechanoreceptors, consisting of 1 large and 3 small cells, with receptive fields in the oesophagus. Synaptic contacts occur between the receptors; the large cell providing an EIPSP input to its contralateral partner and to the two groups of smaller receptors. The small receptors make weak excitatory contacts with both the large receptors.

The sensory cells synapse with other buccal motoneurones and interneurones, some of which show periodic activity associated with the feeding movements.

Protraction phase neurones are divisible into two groups, one of which receives EPSPs from the receptors, while the other group receives IPSPs. Retraction phase neurones receive a biphasic EIPSP.

The receptors provide excitatory synaptic input to a pair of interneurons which ‘gate’ the feeding cycle. A third class of neurones which are not rhythmically active during feeding receive a predominantly inhibitory EIPSP.
Membrane Structure in Mammalian Astrocytes: A Review of Freeze-Fracture Studies on Adult, Developing, Reactive and Cultured Astrocytes
Authors: Landis Dennis M. D. , Reese Thomas S.
Published: April 2021

The application of freeze-fracture techniques to studies of brain structure has led to the recognition of two unsuspected specializations of membrane structure, each distributed in a specific pattern across the surface of astrocytes. ‘Assemblies’ (aggregates of uniform, small particles packed in orthogonal array into rectangular or square aggregates) are found to characterize astrocytic plasma membranes apposed to blood vessels or to the cerebrospinal fluid at the surface of the brain. These particle aggregates are much less densely packed in astrocytic processes in brain parenchyma. Assemblies are not fixation artifacts, have been shown to extend to the true outer surface of the membrane, are remarkably labile in the setting of anoxia, and are at least in part protein. The function of assemblies is unknown, but their positioning suggests that they may have a role in the transport of some material into or out of the blood and cerebrospinal fluid compartments. A second specialization of intramembrane particle distribution, the polygonal particle junction, links astrocytic processes at the surface of the brain, and also links proximal, large caliber astrocytic processes in brain parenchyma. The function of this membrane specialization also is unknown, but it may subserve a mechanical role.
A Study of the Deformability of Red Blood Cells of A Teleost Fish, the Yellowtail (Seriola Quinqueradiata), and A Comparison with Human Erythrocytes
Authors: Hughes G. M. , Kikuchi Y. , Watari H.
Published: April 2021

The blood of a carangid fish, the yellowtail (Seriola quinqueradiata) has been studied with particular reference to the deformability properties of the red blood cells. The rate at which blood flows through a Nuclepore filter containing 5 μm pores has been determined under the same conditions that have been used with human blood. Marked differences were found in the flow of yellowtail blood which depended on the particular way in which the blood had been sampled. Such differences seem to be due to a sensitivity of fish red blood cells to their environmental conditions. Blood flow through filters is temperature-dependent, the rate increasing with a rise in temperature. Measurements made at 37 °C gave values which were similar to those normally obtained for human red blood cells, in spite of their greater dimensions (10·4 × 6·8 × 3·4μm), and nucleated nature. It was also found that the blood flow rate of human blood was slower than that of yellowtail blood when measured at the normal environmental temperatures (15 °C) for these fish.
The Effects of Tetraethylammonium and Other Agents On the Potassium Mechanoreceptor Current in the Ciliate Stylonychia
Authors: Deitmer Joachim W.
Published: April 2021

The membrane response to mechanical stimulation was investigated under voltage-clamp conditions in the hypotrich ciliate Stylonychia mytilus (Protozoa). The mechanoreceptor current shows high ionic selectivity, unlike that in metazoans. It is exclusively carried by potassium ions and is selectively inhibited by tetraethylammonium and 4-aminopyridine. Procaine, tetramethylammonium, caesium and divalent cations have no or little effect on this receptor current. The ionic channels mediating the currents differ from voltage-dependent channels in the ciliate membrane in their low sensitivity to divalent cations, and their relatively high sensitivity to tetra-ethylammonium and 4-aminopyridine.
Respiration and Acid-Base Physiology of the Spotted Gar, A Bimodal Breather
Authors: Smatresk Neal J. , Cameron J. N.
Published: April 2021

Elevation of temperature from 20 to 30 °C, increased the pulmonary ventilation and pulmonary oxygen consumption (from 0·18 to 0·43 ml O2.kg−1. min−1). The total CO2 excretion also rose, but branchial ventilation and branchial oxygen consumption did not change significantly.

The blood pH dropped quickly when temperature was elevated, with a slope (dpH/dT°) of −0·015, but the OH−/H+ ratio did not change significantly. This change in pH resulted from an elevation in arterial , without any concomitant change in plasma HCO3−. Arterial per se was probably not actively regulated, but rose passively as a consequence of the gar’s utilization of the lung for increased oxygen uptake, and the inefficiency of the lung in CO2 exchange. The lung had an exchange ratio (R) of about 0·1.

Temperature change produced no significant alteration in the net acid excretion from either the kidney or the gills, despite an increased ammonia excretion rate at 30 °C. The urine formation rate was very low (74 μl. 100 −1.h− 1) which imposed a limitation on the importance of the kidney in acid-base regulation.

Hypercapnia produced a respiratory acidosis which was partially compensated by an elevation in blood HCO3− after 24 h of exposure. The gill ventilation rose only slightly, and later fell as compensation proceeded. Air-breathing frequencies were not greatly affected by hypercapnia.
The Physiology and Morphology of Median Nerve Motor Neurones in the Thoracic Ganglia of the Locust
Authors: Burrows Malcolm
Published: April 2021

Simultaneous intracellular recordings have been made from the two expiratory, and from the two inspiratory motor neurones which have their axons in the unpaired median nerves of the thoracic ganglia. Each motor neurone has an axon that branches to innervate muscles on the left and on the right side of one segment.

The expiratory neurones studied were those in the meso-and metathoracic ganglia which innervate spiracular closer muscles. The depolarizing synaptic potentials underlying the spikes during expiration are common to the two closer motor neurones in a particular segment. Similarly, during inspiration when there are usually no spikes, the hyperpolarizing, inhibitory potentials are also common to both motor neurones. The synaptic input to the neurones can be derived from four interneurones; two responsible for the depolarizing potentials during expiration and two for the inhibitory potentials during inspiration.

The inspiratory neurones studied were those in the abdominal ganglia fused to the metathoracic ganglion which innervate dorso-ventral abdominal muscles. During inspiration the two motor neurones of one segment spike at a similar and steady frequency. The underlying synaptic input to the two is common. During expiration, when there are usually no spikes, the hyperpolarizing synaptic potentials are also common to both neurones. In addition they match exactly the depolarizing potentials occurring at the same time in the closer motor neurones. The same set of interneurones could be responsible.

No evidence has been revealed to indicate that the two closer, or the two inspiratory motor neurones of one segment are directly coupled by electrical or chemical synapses.

The morphology of both types of motor neurone is distinct from that of other motor neurones in these ganglia. Both types branch extensively in both the left and in the right areas of the neuropile.
Auditory Acuity in the Sea Catfish (Arius Felis)
Authors: Tavolga William N.
Published: April 2021

Frequency discrimination limens and signal-to-noise ratios were determined for the sea catfish, Arius felis, using avoidance-conditioning techniques. The lowest frequency discrimination limens had values of about 2·5 % at 100 Hz. Other determinations were 3·5 % at 200 Hz, and 5 % at 400 Hz, but these values were significantly greater if the test frequencies were higher than the reference. Signal-to-noise ratios were 14 dB at 100 Hz, 18 dB at 200 Hz, and 24 dB at 400 Hz, with reference to the spectrum level of broad-band noise. These findings, and previous measurements of acuity, are discussed in relation to echolocation in Arius, which is known to involve sounds in the 100-200 Hz range.
Resting Tension and Posture in Arthropods
Authors: Yox Daniel P. , Dicaprio Ralph A. , Fourtner Charles R.
Published: April 2021

This study was prompted by reports of resting tension in muscles of various arthropods (Machin & Pringle, 1959; Hoyle, 1968; Burns & Usherwood, 1978; Hoyle, 1978; Hawkins & Bruner, 1979) and our observation that when the legs of the cockroach and crab are severed from the thorax, the joints appear to assume rather fixed angles. Recently Chesler & Fourtner (1981) have shown that significant resting tension exists in one of the femoral extensors of the cockroach (muscle 177 d) (Carbonell, 1947). The purpose of this study was to determine if resting tension is characteristic of all the limb muscles and if it could account for the fixed angle of the joint. We present evidence in this report that resting tension in the leg muscles of the cockroach, Periplaneta americana, and the crab, Carcinus maenas, is responsible for maintaining a relatively fixed angle in the joints of the limbs. These data, along with other evidence, provide a good argument for a system in which posture is partially maintained in these arthropods by resting tension which appears to be passive in nature. The maintenance of posture by this passive mechanism could result in an energetic savings in a quiescent arthropod.
The Effects of Calcium On Sodium Fluxes in the Brown Trout, Salmo Trutta, in Neutral and Acid Water
Authors: McWILLIAMS P. G.
Published: April 2021

It is well established that external calcium can have a marked effect on sodium fluxes in both marine and freshwater organisms (Potts & Fleming, 1971; Cuthbert & Maetz, 1972; Fleming, Nichols & Potts, 1974; Eddy, 1975; Carrier & Evans, 1976; Isaia & Masoni, 1976). In the few fish species which have so far been examined the effects of external calcium appear to be primarily on sodium efflux, which is reduced in the presence of calcium (Fleming et al. 1974; Eddy, 1975; Isaia & Masoni, 1976). The influence of calcium on sodium influx shows considerably more variation between species (Shaw, 1960; Sutcliffe, 1971; Eddy, 1975) making it difficult to propose a suitable mechanism to account for the observed effects.
Skylight Polarization Patterns and Animal Orientation
Authors: Brines Michael L. , Gould James L.
Published: April 2021

Although many invertebrate animals orient by means of ultraviolet sky-light polarization patterns, existing measurements of these patterns are inadequate for full analysis of the biologically relevant information available from the sky. To fill this gap we have used a precision scanning polarimeter to measure simultaneously the intensity, degree, and direction of vibration (E-vector orientation) of polarized light at 5° intervals over the sky. The resulting sky maps were constructed for u.v. (350 nm) and visible wavelengths (500 and 650 nm) under a variety of atmospheric conditions. Our measurements confirmed that the patterns of radiance and degree of polarization of skylight are highly variable and hence unreliable as orientation cues; but patterns of E-vector orientation are relatively stable and predictable over most of the sky under all but very hazy or overcast conditions. The observed E-vector patterns correspond more closely to predictions based on first order (Rayleigh) scattering at 650 and 500 nm than at 350 nm. This is true both in terms of absolute accuracy and the proportion of the sky with relatively ‘correct’ information. Yet most insects respond to polarization patterns only at u.v. wavelengths. This apparent paradox can perhaps be resolved by assuming that there is no great selective advantage for any particular wavelength when large areas of blue sky are visible, but that under special and difficult conditions ultraviolet has advantages over longer wave-lengths. Measurements under partially cloud-covered sky, for instance, or under extensive vegetation, show that both spuriously polarized and un-polarized light resulting from reflexions present more troublesome interference at longer wavelengths than in the u.v. The accuracy of orientation achieved by dancing honey bees appears to be greater than can readily be accounted for by assuming that they use a strictly geometrical or analytical processing system for their orientation to polarized light.
Energetic advantages of burst-and-coast swimming of fish at high speeds
Authors: Videler J. J. , Weihs D.
Published: April 2021

A theoretical model describes how an intermittent swimming style can be energetically advantageous over continuous swimming at high average velocities. Kinematic data are collected from high-speed ciné pictures of free swimming cod and saithe at high velocities in a burst-and-coast style. These data suggest that fish make use of the advantages shown by choosing initial and final burst velocities close to predicted optimal values. The limiting role of rapid glycogen depletion in fast white anaerobic muscle fibres is discussed.
Oxygen uptake in air and water in the air-breathing reedfish Calamoichthys calabaricus: role of skin, gills and lungs
Authors: Sacca R. , Burggren W.
Published: April 2021

The reedfish Calamoichthys calabaricus (Smith) is amphibious, making voluntary excursions on to land (in a simulated natural environment) an average of 6 + 4 times/day for an average duration of 2·3 ± 1·3 min.

Oxygen uptake is achieved by the gills, skin and large, paired lungs. In water at 27 °C, total oxygen uptake is 0·088 ml O2/g. h. The lungs account for 40%, the gills 28%, and the skin 32% of total .

Total oxygen uptake during 2 h of air exposure increases from 0·117 ml O2/g.h to 0·286 ml O2/g.h, due largely to an enhanced lung and a small increase in skin .

Calamoichthys is both capable of aerial gas exchange and adapted to maintain O2 uptake during brief terrestrial excursions.
Structure and Function of the Auditory System in the Clown Knifefish,Notopterus Chitala
Authors: Coombs Sheryl , Popper Arthur N.
Published: April 2021

Hearing sensitivity and the anatomy of the auditory system in the clown knifefish, Notopterus chitala, were studied using behavioural techniques and scanning electron microscopy. While many structural features of the inner ear were similar to those found in other teleost species, the saccular endorgan in Notopterus was unusual in having three discrete epithelial regions. These regions could be distinguished from one another by regional differences in portions of the otolith overlaying them, by hair-cell orientation patterns, and by their position relative to the swimbladder. Notopterus was found to be able to detect sounds from 100 to 1000 Hz and best sensitivity occurred at 500 Hz, where the mean threshold was – 30 dB (re : 1 microbar). For frequencies from 300 to 700 Hz there was substantial variation in threshold values and indications of a bimodal distribution of thresholds. One hypothesis that may tie the ultrastructural and behavioural results together is that the ear in Notopterus is anatomically and functionally differentiated to mediate independent detection of two sound properties: changes in pressure and particle motion.
The effect of temperature on the oxygen dissociation curves of whole blood of larval and adult lampreys (Geotria australis)
Authors: Macey D. J. , Potter I. C.
Published: April 2021

Oxygen dissociation curves of the whole blood of larvae and adults of the Southern Hemisphere lamprey Geotria australis have been determined between pH 6·8 and 8·2 at 5, 15 and 25 °C. The P50’s at temperatures of 5, 15 and 25 °C and a pH of 7·75 were respectively 0·57,0·92 and 1·19 mmHg in larvae and 6·9,10·3 and 19·0 mmHg in adults. The relatively very high affinity of larval blood for oxygen may reflect an adaptation to low environmental oxygen tensions. The Bohr shift was not significantly affected by either temperature or life-cycle stage. The slope (n) in Hill plots increased with temperature and oxygen saturation, and was greater in adults than in larvae.
Cardiovascular changes associated with treadmill running in the Pekin duck
Authors: Bech Claus , Nomoto Shigekt
Published: April 2021

Six adult white Pekin ducks were trained to run on a treadmill for 10 min at a speed of 1·43 km h−1. O2 consumption, CO2 production, breathing rate, blood gas tension and pH, sciatic and carotid blood flows and colonic and skin temperatures were measured in the experiments.

A 2·6 times increase in oxygen consumption was observed when going from resting on the treadmill to exercise. The increased oxygen delivery was achieved by a 61% increase in cardiac output and a 51% increase in the arterio-venous oxygen content difference. Probably the reported resting oxygen consumption was higher than a true resting level causing the increment in oxygen consumption to be more correctly 3·6 times the resting level.

Sciatic and carotid blood flow increased by 3·7 times and 2·3 times, respectively, during exercise. At cessation of exercise, the carotid blood flow decreased very rapidly, while the sciatic blood flow decreased more slowly. An increased web temperature above the exercise level was seen in the post-exercise period.

The results suggest that the ducks prefer to use non-evaporative heat loss in the post-exercise period, respiratory evaporative cooling being of minor importance. This strategy may be correlated to the small internal heat load induced by the running (body temperature increased by only 0·3 °C).
Interneurones Co-Ordinating the Ventilatory Movements of the Thoracic Spiracles in the Locust
Authors: Burrows Malcolm
Published: April 2021

A pair of interneurones has been identified by intracellular recording and staining which co-ordinates the movements of the thoracic spiracles in the ventilatory rhythm.

An interneurone has its cell body on the left or on the right side of the metathoracic ganglion and an axon which ascends to the other thoracic ganglia in the contralateral connective. Each interneurone produces bursts of spikes in time with the inspiratory phase of ventilation. These spikes evoke inhibitory post-synaptic potentials (IPSPs) in thoracic spiracular closer motor neurones. Both interneurones synapse upon the closer motor neurones in each thoracic segment. These connexions, which may be direct, inhibit the spiking of the closer motor neurones during inspiration.

The interneurones do not appear to have an innate rhythmicity but instead receive a periodic synaptic input which inhibits their spikes during expiration. The underlying cause of the spikes is less clear. Apart from brief periods at the start and end of a burst, the spikes occur at a constant frequency that is independent of the ventilatory rate.

The pattern of the spiracular motor output could be altered by manipulating the frequency and number of spikes in an interneurone. When the frequency of spikes in the interneurone was raised, the motor bursts had a higher initial frequency and were of briefer duration ; when the frequency was lowered, the motor bursts were of lower initial frequency and of longer overall duration. Altering the spikes in one interneurone, however, could not affect the frequency of the ventilatory rhythm, or reset the rhythm.
The Distances at Which a Primitive Jumping Spider,Portia Fimbriata, Makes Visual Discriminations
Authors: Jackson R. R. , Blest A. D.
Published: April 2021

The anterior median (AM) or principal eyes of the primitive jumping spider, Portia fimbriata (Doleschall), are miniature telephoto systems (Williams & McIntyre, 1980). Another study on the AM eyes of Plexippus suggests that most salticid principal eyes may be of similar design (Blest, Hardie, McIntyre and Williams, 1982). Both studies assumed, from anecdotal evidence (e.g. Forster, 1979), that jumping spiders can make visual discriminations between prey and mates at distances of ca. 20 cm. This estimate is necessary to the functional analyses that were essayed; because it is impossible to make sufficiently accurate direct measurements of some of the parameters of these small eyes, their optics can only be modelled with confidence when something is known about what they are designed to see. Land (1969 a, b), in an elegant optical study, followed Drees (1952) in stating that jumping spiders respond to significant objects some 5-10 body-lengths in front of them. In the case of Portia, this would be a distance of no more than 10 cm at most. Recognition of objects is mediated through the AM eyes (Drees, 1952).
The effects of hypercapnia on intracellular and extracellular acid-base status in the toadBufo marinus
Authors: Toews D. P. , Heisler N.
Published: April 2021

Toads (Bufo marinus) were exposed to environmental hypercapnia of 5 % CO2 in air, and extracellular and intracellular acid-base parameters were determined 1 and 24 h after the onset of hypercapnia.

The initial drop in pH was compensated by the elevation of extracellular and intracellular bicarbonate. Relating the pH compensation to the pH drop that is expected to occur by increased at constant bicarbonate concentration, the pH compensation in the extracellular space was 30 % and reached the following values for intracellular body compartments : 65 % in skeletal muscle, 77 % in heart muscle and 44 % in skin. The additional bicarbonate was partly produced by blood and intracellular non-bicarbonate buffers; the major portion of the remainder was related to the excretion of ammonia into the environmental water.

The hypercapnia-induced changes of pH were considerably smaller in all tissue cells than in the extracellular space. Thus Bufo marinus exhibits the relative preference of intracellular over extracellular acid-base regulation that has been observed in other vertebrates.
Physiological Evidence for the Occurrence of Pathways Shunting Blood Away from the Secondary Lamellae of Eel Gills
Authors: Hughes G. M. , Peyraud C. , Peyraud-Waitzenegger M. , Soulier P.
Published: April 2021

Several cardiovascular and respiratory measurements have been performed in eels before and after intravenous injections of adrenaline. These experiments have allowed a comparison to be made of values for the cardiac output determined directly () and using the Fick principle () on individual fish under these two conditions. Under control conditions it was shown that = 0·72, indicating that about 30% of the mixed venous blood afferent to the gills is returned directly to the heart and bypasses the lamellar circulation via veno-venous anastomoses between the afferent filament arteries and the central venous space of the gill filaments. Adrenaline, which during winter only has its action due to stimulation of α-adrenoreceptors, induced a hypoventilation but no changes in cardiac output in spite of a bradycardia. The oxygen content of the mixed venous blood was markedly increased whereas remained unchanged as did the percentage utilization of oxygen from the water as it passed over the gills. The efferent blood flow from the gills after injection of adrenaline was almost equal to the total cardiac output.

It is suggested that such a circulatory change was due to adrenaline-mediated constriction of veno-venous anastomoses in the gills of the eel.