bluuebunny/crossref_metadata_2025 huggingface dataset:
The Roles of Endogenous Membrane Properties and Synaptic Interaction in Generating the Heartbeat Rhythm of the Leech, Hirudo Medicinalis
Authors: Calabrese Ronald L.
Published: April 2021

Inhibitory synapses among the central neurones involved in the genera- tion of the heartbeat rhythm of the leech were blocked by either low Cl− physiological saline or presynaptic hyperpolarizing current. Low Cl− saline reversibly blocked inhibitory postsynaptic potentials (IPSPs) from the HN cells onto both other HN cells and HE cells but did not block electrical coupling among HN cells. The rhythmic bursts of impulses in HE cells were abolished when IPSPs were blocked by either low Cl− saline or hyperpolarization of HN cells. The rhythmic bursts of impulses in HN cells were not abolished (except in cell HN(5)) when IPSPs were blocked by low Cl− saline, but phase relations became unfixed (unless the cells were electrically coupled). Both brief depolarizing and hyperpolarizing current pulses reset the rhythm of HN cells whose IPSPs were blocked by low Cl− saline. The results indicate that the motor neurones to the heart (HE cells) produce rhythmic impulse bursts because their steady discharge is period- ically inhibited by the HN interneurones. The pattern generated by die HN cells originates from an endogenous rhythm co-ordinated by the inhibitory interactions and electrical coupling between these cells.
Biomodal Gas Exchange During Variation in Environmental Oxygen and Carbon Dioxide in the Air Breathing Fish Trichogaster Trichopterus
Authors: Burggren Warren W.
Published: April 2021

Gas exchange in the gourami, Trichogaster trichopterus, an obligate air breather, is achieved both by branchial exchange with water and aerial exchange via labyrinth organs lying within the suprabranchial chamber.

Ventilation of the suprabranchial chamber, , gas exchange ratios of both gills and labyrinth organs, and air convection requirements have been measured under conditions of hypoxia, hyperoxia or hypercapnia in either water or air.

In undisturbed fish in control conditions (27 °C), air breathing frequency was 12 breaths/h, gas tidal volume 30 μl /g, total oxygen uptake 5· 2 μ/g/h and total carbon dioxide excretion 4·1 μ/g/h, indicating a total gas exchange ratio of approximately 0·8. The aerial labyrinth organs accounted for 40% of oxygen uptake but only 15% of carbon dioxide elimination.

Hypoxia, in either inspired water or air, stimulated air breathing. Total was continuously maintained at or above control levels by an augmentation of oxygen uptake by the labyrinth during aquatic hypoxia or by the gills during aerial hypoxia. Hypoxia had no effect on partitioning between air and water. Hypercapnia in water greatly stimulated air breathing. About 60 % of total then occurred via aerial excretion, a situation unusual among air breathing fish, enabling the overall gas exchange to remain at control levels. Aerial hypercapnia had no effect on air breathing or O2 partitioning, but resulted in a net aerial CO2 uptake and a decrease in overall gas exchange ratio.

Trichogaster is thus an air breathing fish which is able to maintain a respiratory homeostasis under varying environmental conditions by exploiting whichever respiratory medium at a particular time is the most effective for O2 uptake and CO2 elimination.
Interaction Between Abdominal Ganglia During the Performance of Hormonally Triggered Behavioural Programmes In Moths
Authors: Truman James W.
Published: April 2021

The isolated chain of four abdominal ganglia of Hyalophora cecropia has previously been shown to respond to the eclosion hormone by generating a pre-eclosion motor programme followed by the eclosion programme. Abdominal nervous systems reduced at any two ganglia could still generate both programmes. Selective addition of hormone to individual ganglia of the intact abdominal CNS resulted in the coordinated performance of both programmes by the entire CNS. In the eclosion programme, burst frequency was little influenced by which ganglion was exposed to hormone but in many cases the eclosion waves were initiated by the neurones in the treated ganglion rather than at the normal site in the terminal ganglion. When ganglia were removed from hormone-treated preparations during eclosion, the remainder of the chain showed a transient disruption in the bursting frequency but the frequency often eventually returned to pre-cut levels. Removal of anterior ganglia had no effect on the patterning of posterior bursts but removal of posterior ganglia resulted in a permanent reduction in the length of eclosion bursts in anterior ganglia. It was concluded that the information for both the pre-eclosion and eclosion programmes is patterned into each ganglion of the abdominal chain. For the pre-eclosion behaviour, the endogenous programme becomes pro-gressively longer in more posterior ganglia and each ganglion appears to have mutually exciting interactions with the other ganglia in the chain. In the intact animal the most anterior ganglion appears to drive the behaviour. By contrast, the eclosion behaviour also has segmental burst generators but they appear very similar in their properties. Each burst generator has an excitatory input on to the next anterior ganglion and inhibitory influences on posterior ganglia. Normally, the most posterior ganglion serves as driver for the eclo-sion behaviour.
Electrophysiology of Acanthocephalan Body Wall Muscles
Authors: Wong B. S. , Miller Donald M. , Dunagan T. T.
Published: April 2021

Body wall muscles of an acanthocephalan Macracanthorhynchus hirudi- naceus were studied by means of scanning and light microscopy and intracellular recording of potentials. Three types of spontaneous potential changes were found: larger (L) potentials which usually exhibited overshoot and were as large as 65 mV; smaller symmetric (A) potentials approximately 15 mV in amplitude; and even smaller asymmetric (S) potentials which sometimes reached 10 mV. The potentials recorded depended upon the Position of the electrode in the anterior-posterior, as well as the medialateral, axis. Tetrodotoxin eliminated L but not S potentials. Ouabain lengthened the time for depolarization of L potentials and depolarized the membrane potentials. It is suggested that the rete system activates the body wall muscles in Acanthocephala.
Intrasegmental Proprioceptive Influences on the Period of the Swimmeret Rhythm in Crayfish
Authors: West Lani , Jacobs Gwen , Mulloney Brian
Published: April 2021

When the swimmerets of decapods beat, they do so because the muscles of each swimmeret are driven by a series of periodic bursts of impulses in its motor neurones. We investigated the effects of proprioceptive feedback on the period of this motor pattern by interfering with the movement of particular swimmerets. In different experiments, we observed three different kinds of results during interference with a swimmeret. Either the period decreased, or it did not change, or bursting was inhibited altogether. These different results are discussed in terms of the connectivity of different command fibres.
Metabolic Sources of Heat and Power in Tuna Muscles
Authors: Hulbert W. C. , Guppy M. , Murphy B. , Hochachka P. W.
Published: April 2021

As part of an investigation into the generation of muscle heat in the tuna, the histochemistry and ultrastructure of the myotomal muscles were studied. Both red and white fibres are differentiated into two forms. The two forms of red muscle are very similar except for differential electron absorbance and different kinds of glycogen granules stored. In both forms, capillarity, mitochondrial numbers, and intracellular lipid droplets are abundant, implying the potential for a vigorous aerobic metabolism. During bursts of swimming, glycogen granules and intracellular lipid droplets are both largely depleted. The two types of white fibre differ in electron absorbance, pinocyotic activity, glycogen abundance, and insertion pattern, all of which are more pronounced in the ‘dense’ fibre form. Several features of tuna white muscle are unique or unusually developed. Thus, tuna muscle contains more glycogen than does red muscle. Glycogen granules may be randomly dispersed in myofibrillar or peripheral regions or may be sequestered in membrane-bound structures termed glycogen bodies. During short bursts of swimming, glycogen granules from all storage sites are mobilized. The white muscle has an ample capillary supply, small, but significant, amounts of intracellular lipid, and unusual numbers of mitochondria.
Metabolic Sources of Heat and Power in Tuna Muscles
Authors: Guppy M. , Hulbert W. C. , Hochachka P. W.
Published: April 2021

Tuna appear able to maintain their muscles at 5–10°C above ambient by balancing heat produced in situ and conserved by a counter-current heat exchanger with heat lost to the sea. Metabolite profiles under three different activity states (rest, burst swimming, and steady state swimming during feeding frenzies at sea) were used to identify which metabolic processes in white and red muscles could account for observed excess temperatures.

During burst swimming, transient changes in metabolite levels indicate that the metabolism of both red and white muscle contributes to powering burst swimming; red muscle work is sustained mainly by oxidative metabolism while white muscle work depends upon an intense anaerobic glycolysis. The rate of metabolism in red muscle is easily high enough to account for the measured (10 °C) increase in temperature at this time. However, in white muscle, anaerobic glycolysis can account for only about a 2 °C maximum rise in temperature.

The highest sustained swimming speeds and the highest muscle temperatures in skipjack are found during feeding frenzies at sea. As in burst swimming, during steady-state swimming red muscle temperatures can be accounted for by oxidative metabolism. In the case of white muscle, the lactate measurements indicate that anaerobic glycolysis could only lead to a 0·3 °C temperature rise. However, if the fraction of utilized glycogen that is not fermented (about 60 %) is assumed to be fully oxidized, enough heat is generated to raise white muscle temperatures by over 10 °C. The observed excess temperature at this time is about 8–10 °C, showing that areobic carbohydrate metabolism in white muscle is probably the major heat source during feeding frenzies.

These interpretations are fully consistent with enzyme profiles of red and white muscles in tuna. They do not, however, explain why tuna have warm muscles. The latter problem is briefly discussed.
Acid-Base Relationships in the Blood of the Toad, Bufo Marinus
Authors: Boutilier R. G. , Randall D. J. , Shelton G. , Toews D. P.
Published: April 2021

Cutaneous CO2 excretion is reduced as the skin dries during dehydration but an increase in breath frequency acts to regulate the arterial blood and thus pHa. Moreover, the toad does not urinate and water is reabsorbed from the bladder to replace that lost by evaporation at the skin and lung surfaces. The animal does, however, produce a very acid bladder urine to conserve circulating levels of plasma [HCO3−] and this together with an increased ventilation effectively maintains the blood acid-base status for up to 48 h of dehydration in air. Water loss and acid production are presumably also reduced by the animal’s behaviour; animals remain still, in a crouched position or in a pile if left in groups.

Dehydrated toads are less able than hydrated toads to regulate blood pH during hypercapnia: they hyperventilate and mobilize body bicarbonate stores in much the same fashion as hydrated animals but due to the restrictions on cutaneous CO2 excretion and renal output, there is comparatively little reduction in the difference between arterial blood and inspired gas thereby resulting in a more severe respiratory acidosis. These factors further contribute to the persistent acidosis which continues even when the animals are returned to air.
Cation Accessibility of the Peripheral Nervous System in Limulus Polyphemus-An Electrophysiological Study
Authors: Willmer P. G. , Harrison J. Barrie
Published: April 2021

The nervous systems of many vertebrates, and of some invertebrate phyla, are known to possess a ‘blood-brain barrier’ conferring a selective impermeability to certain ionic and molecular constituents of the body fluids and thus protecting the excitable membranes within a relatively constant micro-environment; this subject has been recently reviewed by Abbott & Treherne(1977). In vertebrates the barrier may be a property of the tight junctions between capillary endothelial cells (Brightman & Reese, 1969). Similarly in insects, at least to the level of the large peripheral nerves, electrophysiological evidence (Treherne et al. 1970; Treherne, 1974) and fine- structural studies (Lane & Treherne, 1972; Lane, 1972) indicate the existence of a barrier preventing free diffusion, residing in the tight junction complexes of the perineurium. However, investigations of crustacean nervous systems (Abbott, 1970; Abbott, Moreton & Pichon, 1975) show rapid access of ions to the peripheral nerves, but a delayed entry to the central nervous tissue that may be related to gap junctions and/or to maculae occludentes between the perineurial sheath cells (Lane & Abbott, 1975). An analogous situation may occur in some gastropod molluscs, where a partial ‘neurone-haemolymph barrier’ has been described (Reinecke, 1976), though in many members of this phylum the nervous tissue is freely accessible to ions (Sattelle & Lane, 1972; Willmer, 1978).
A Differential Volumetric Micro-Respirometer For Use With Small Aquatic Organisms
Authors: Dixon D. R.
Published: April 2021

A micro-respirometer is described for use with small aquatic organisms whose rates of oxygen consumption fall within the range 0·1–5 μ l O2 h−1. The major design improvement which this apparatus has over existing models (e.g. Fenn, 1927) is a relatively large capillary bore. Kok, Veltkamp & Gelderman (1953) having shown a proportional decrease in the sensitivity of volumetric respirometers with capillaries smaller than 1 mm diameter. The most recent treatment of the theoretical aspects of differential respirometry is by Umbreit, Burris & Stauffer (1972).
Ionic Permeability of the Blood-Brain Barrier System of An Insect Carausius Morosus
Authors: Schofield P. K.
Published: April 2021

Large ionic gradients must be maintained across the blood-brain barrier system of Carausius morosus, for the neurones are apparently conventional in their ionic requirements (Treherne & Maddrell, 1967; Weidler & Diecke, 1969) while the haemolymph has been found to contain ionic concentrations as adverse as 9 mm-Na, 28 mm-K and 73 mm-Mg (Duchateau, Florkin & Leclerq, 1953). The ionic permeability of the system is here examined in the manner of Pichon, Moreton & Treherne (1971), by observing changes in extraneuronal potential produced by an alteration in the ionic composition of the saline bathing the first pair of thoracic connectives (from adults) from which the fat-body sheath had been removed. (The fat body has been shown to be a relatively leaky structure: Lane & Treherne, 1971; Treherne, 1972.)
Optomotor Control of Speed and Height by Free-Flying Drosophila
Authors: David C. T.
Published: April 2021

The optomotor reactions of Drosophila have been studied intensively, with the conclusion that in flight there are two main types of response. One of these controls the course of the animal by adjusting the relative amplitudes of the wingbeats on the two sides of the body. The other controls the total thrust produced by the wings (Gotz, 1968). Drosophila do not change the direction of the thrust produced relative to the body axis (Gotz, 1968; Vogel, 1966; David, 1978) but do change the distribution of their total power output between lift and thrust by changing the inclination of the body axis (David, 1978). This could not, however, be observed in tethered fliers on which previous work had been done. Nevertheless, it has been implied that free fliers alter only their lift, so that the control of power output is used only to control height (Gotz, 1972; Buchner, Gotz & Straub, 1978). Here I report some experiments on free-flying Drosophila hydei Sturtevant showing that speed (and hence thrust) as well as height (and hence lift) are controlled by optomotor reactions to features of the surroundings.
Permeability and Active Transport in Malpighian Tubules
Authors: Fletcher C. R.
Published: April 2021

In a paper on regional specialization in the lower Malpighian tubule of Rhodnius prolixus, Maddrell (1978) reported that active recovery of potassium chloride from the tubular fluid is confined to the lowest region of the tubule, and is inducible by 5-HT. He also reported that the gross influx of potassium, measured by movement of K42 from the bathing solution into the lumen, shows a 200-fold stimulation by 5-HT in this part of the tubule, but not in the non-transporting region. He could not explain the effect.
The Refractive Index Gradient in the Crystalline Cones of the Eyes of A Euphausiid Crustacean
Authors: Land M. F. , Burton F. A.
Published: April 2021

The eyes of the euphausiids, a group of malacostracan Crustacea, show a remarkable similarity to the superposition (Exner, 1891) eyes of moths. In both groups the eye has an outer layer of crystalline cones, a wide clear zone, and a layer of rhabdomes beneath it, whose radius of curvature is about half that of the eye itself (Fig. 2 a). We demonstrated recently that image formation in these eyes is indeed performed by a refracting superposition mechanism (Land, Burton & Meyer-Rochow, 1979), as supposed by Chun (1896). That is to say, light is bent by the crystalline cones in such a way that a ray reaching the outer surface of a cone, and making an angle α with the cone axis, is bent in the cone through an angle 2α (Fig. 1). This is the condition necessary if all parallel rays are to be brought to a focus in the rhabdome layer, where an erect image is produced (see Horridge, 1975). This mechanism, shared by moths, fireflies and some other beetles, is not the same as that of the decapod shrimps and prawns, where essentially the same trick is performed not by refracting cones, but by mirrors (Vogt, 1977; Land, 1978). Kampa (1965) proposed that the euphausiid eye was basically of the apposition type, with the cones funnelling light down light guides into the rhabdomes. However, the cones send light, as noted above, and the light-guides are not present (Meyer-Rochow & Walsh, 1979).
Phase Co-Ordination in the Cardiac and Ventilatory Rhythms of the Lobster Homarus Americanus
Authors: Young Ronald E. , Coyer P. E.
Published: April 2021

Relative co-ordination is demonstrated between the rhythms of the right and left scaphognathites (SG) and between the heart and either right or left SG or both simultaneously. The co-ordination between these rhythms results from mutual phasedependent alteration of the period lengths as demonstrated by the phaseresponse curves for the interactions. The standard deviation of the SG period lengths is an inverse linear function of the percentage coupling between the two SGs (r = 0·76; P < 0·01). The right SG motor output may show relative co-ordination with respect to a sinusoidal, dorso-ventral movement applied along the radial axis of that appendage. This is taken to indicate that sensory reafference resulting from the interplay between the applied and intended movements can alter the SG rhythm depending upon the relative phasing of the two movements. The effects of sensory reafference are therefore not merely tonic as has been believed until now. Cautery of the right oval organ, a major phasic mechanoreceptor of the SG, has no significant influence on any of the above relationships. The significance of this and of the widespread occurrence of relative co-ordination between rhythmic activities is discussed.
Calcium Regulation in Intermoult Gammarus Pulex
Authors: Wright D. A.
Published: April 2021

The compartmentation of calcium was studied in adult intermoult Gammarus pulex. The total body calcium concentration was 547 µmol g. wet wt.−1, which is weight for weight approximately one half of the calcium concentration found in decapod crustaceans. Over 96% of whole body calcium in G. pulex was found in the exoskeleton.

45Ca exchange curves for haemolymph and hepatopancreas had similar time constants indicative of a comparatively large pool of freely exchangeable calcium. The parallel exchange of calcium between the haemolymph and other soft tissue compartments confounded the satisfactory use of an algebraic model for indirect calcium influx measurement using haemolymph specific activity. All calcium influx was subsequently measured on a whole-body basis.

Passive absorption of calcium on to the cuticle was eliminated as a significant factor as the metabolic inhibitor 2:4-DNP almost completely inhibited any form of calcium uptake. The active nature of the calcium regulatory mechanism was further illustrated by potential difference measurements indicating that calcium is accumulated against an electrochemical gradient from media having a calcium activity less than 1 mmol 1−1.

When placed in calcium-free media, intermoult Gammarus pulex are able to achieve at least a tenuous calcium balance between 12 and 50 µmol Ca l−1 at a density of 1 animal per 10 ml medium. Some specimens show a slow calcium loss. The calcium regulatory mechanism is saturated at an external calcium concentration of 2 mmol l−1, which is the normal field calcium concentration for this population, and has a half saturation value of 0·3 mmol l−1.
Electrical Recording from the Contractile Ciliate Zoothamnium Geniculatum Ayrton
Authors: Moreton R. B. , Amos W. B.
Published: April 2021

The spherical body (200 μm in diameter) of this ciliate protozoan was easily immobilized on a suction pipette and penetrated with glass microelectrodes. No recordings could be made from the contractile stalk, but in the body a negative potential of 30· 3 ± 12· 5 mV was observed. Approximately 9 ms after the onset of a mechanical stimulus, a rapid depolarization was observed. This was apparently simultaneous throughout the body surface. The amplitude was 38· 9 ±13· 7 mV. Recordings with a photomultiplier showed that contraction of the stalk began 10 ms later. A slower depolarization of complex form was observed during systole of the contractile vacuole.
Ionic Regulation in Rainbow Trout (Salmo Gairdneri) Adapted to Fresh Water and Dilute Sea Water
Authors: Eddy F. B. , Bath R. N.
Published: April 2021

Small rainbow trout (5-20 g) adapt to salinities of up to at least 22%o but not to full strength sea water. In adapted fish plasma ions are regulated near the fresh water values, but there is an ionic invasion of the tissues, particularly by Cl− in muscle cells. Analysis of ionic regulation in adapted fish indicates that balance is maintained mainly by expending energy on Cl− regulation. Fish in full strength sea water can no longer regulate Na+ or Cl− in plasma or tissues, which results in high tissue concentrations of these ions and eventual death.
Swimming Energetics of Striped Bass (Morone Saxatilis) and Bluefish (Pomatomus Saltatrix): Gill Ventilation and Swimming Metabolism
Authors: Freadman M. A.
Published: April 2021

Striped bass and bluefish use cyclic ventilatory movements to accomplish gas exchange at rest and slow swimming speeds, whereas at intermediate and high velocities, both species routinely shift to ram gill ventilation. Metabolic characteristics of the shift in respiratory behaviour indicate that as an animal adopts the ram mode, energy expenditure departs from an exponential relationship and increases at a shallow rate over the next 15 cm. s−1 range in speed. At higher, ram-supporting velocities, oxygen uptake increases once again at an exponential rate. Similar determinations of oxygen uptake at imposed swimming velocities in hatchery-raised rainbow trout reveal an exponential relationship over the entire swimming range. Trout actively ventilate their gills over this velocity range as well. In striped bass, the requisite trans-gill pressure for ram ventilation, as developed between the mouth and opercular door margins, is about 0·5 cm H2O. Critical swimming velocities for striped bass are 2·9–3·3 bl.s−1 while bluefish can maintain station at 4·0–4·6 bl.s−1. The adoption of ram gill ventilation is a velocity-dependent phenomenon over the size-range tested. Transfer of the work load of ventilation from the branchial to the swimming musculature results in substantial metabolic savings well within the cruising ranges of striped bass and bluefish. The savings probably accrue from cessation of rhythmic pumping by the branchial musculature and a change in overall body drag at ram-supporting swimming speeds.
Mechanism of Inhibition of Active Potassium Transport in Isolated Midgut of Manduca Sexta by Bacillus Thuringiensis Endotoxin
Authors: Harvey William R. , Wolfersberger Michael G.
Published: April 2021

After incubation at pH 10 or higher, Bacillus thuringiensis spores and endotoxin, at concentrations above 0·1 lU/ml, affected transport parameters in the isolated midgut of Manduca sexta larvae. (Toxic activity was lost during roughly 1 week at pH 11.) About 60% of the short-circuit current was inhibited, and the remainder was reversibly inhibited by anoxia. Electrical resistance was reduced by about 55% and oxygen uptake stimulated by about 30%. Influx of potassium from blood-side to lumen-side (‘active’ flux) was unaffected but flux in the reverse direction was nearly tripled. These results suggest that hydrolysis of the toxin yields an inhibitor of potassium transport, presumably a polypeptide. It is argued that inhibition is not primarily by uncoupling of oxidative phosporylation, but instead by interference with an active depression of the efflux of potassium from lumen-side to blood-side.
The Effects of Oxygen Supply, Epinephrine, and Acetylcholine On the Distribution of Blood Flow in Trout Gills
Authors: Booth John H.
Published: April 2021

Injecting vitally stained blood cells into the ventral aorta of unrestrained, cannulated fish, and rapid freezing in liquid nitrogen, permitted the examination of the effects of oxygen supply, epinephrine and acetylcholine on branchial lamellar perfusion. Compared to the conditions in resting fish in air-saturated water, hypoxia and injection of epinephrine significantly increased the proportion of secondary lamellae receiving stained cells, and acetylcholine caused a significant reduction, but hyperoxia did not significantly affect the proportion of lamellae containing stained cells. Perfusion of the filamental central compartment was not affected by the treatments. It is concluded that trout can respond to changes in oxygen supply by varying the number of secondary lamellae perfused with blood, and that the distribution of blood flow is regulated by cholinergic and adrenergic receptors. It is suggested, however, that lamellar recruitment would not be useful in minimizing the costs of osmo- and iono-regulation.
Influence of Mild Hypercapnia on the Effects of Environmental Acidification on Rainbow Trout (Salmo Gairdneri)
Authors: Neville C. M.
Published: April 2021

The physiological consequences of lethal ambient acid levels in adult fish have been previously investigated (Lloyd & Jordan, 1964; Packer & Dunson, 1972; Lievestad & Muniz, 1976). Acidaemia associated with a loss of total carbonate and/ or electrolyte loss have been implicated as the cause of death but the sublethal physiological effects leading to one or both of these conditions have not been fully clarified. Neville (1979) has shown that the acidaemia of trout exposed to pH 4 under normocapnic conditions for 5 days is not due to build-up of lactic acid.
An Ocellar Dorsal Light Response in A Dragonfly
Authors: Stange Gert , Howard Jonathon
Published: April 2021

One of the functional roles suggested for the insect ocelli is their involvement in flight behaviour such as the maintenance of stability by monitoring movements of the animal relative to the horizon (Hesse, 1908). In a recent study on second order ocellar neurones in locusts, Wilson (1978) concluded from physiological and anatomical considerations that this system is ideally suited ‘to detect rapid movements of the whole visual field which represent instability in flight’. In fact, indirect behavioural evidence for this concept was provided by Mittelstaedt (1950), who observed that dragonflies with occluded ocelli go through a sequence of unstable flight attitudes and stalls when released in the presence of a single light source of small angular dimensions. We report here simple experiments which give direct evidence that the ocelli do function as equilibrium organs during flight.
Circadian Rhythm from the Eye of Aplysia: Temperature Compensation of the Effects of Protein Synthesis Inhibitors
Authors: Jacklet Jon W.
Published: April 2021

The circadian rhythm of compound action potentials (CAP) frequency recorded from the isolated eye of Aplysia in culture medium and darkness was subjected to step and pulse treatments with anisomycin, a protein synthesis inhibitor. The step application of anisomycin and its continued presence in the culture medium lengthened the period of the rhythm in a dose-dependent manner. At 10−8 M the period was increased from the normal 26·5 h to about 28 h and at io-7 M the period was lengthened to 31 h or longer. At 10−7 M the rhythm was suppressed but the CAP activity continued without the cyclic variations in CAP frequency. Six-hour pulses of anisomycin at 10−8 M caused phase-dependent phase-shifts of the rhythm. Maximum phase delays of 15 h were obtained at CT (circadian time) 2 and maximum phase advances of 4 h were obtained at CT 6. The phase response curves at 12, 15 and 17 °C were essentially identical. Anisomycin appears to act rather selectively on the circadian clock mechanism. It does not alter the CAP amplitude and duration and it does not alter the bursting pacemaker mechanism of the optic nerve CAP or central neurones. The results support the hypothesis that the synthesis of a protein or polypeptide on eucaryotic ribosomes is an essential part of the circadian clock timing mechanism. The sensitivity of the clock to anisomycin is the same at three different temperatures (12, 15 and 17 °C) within the physiological range of temperatures for Aplysia, as expected for a clock whose period length is temperature compensated (Q10 1·02) over that same range. At the critical phases of CT 1–4, anisomycin pulses often caused unusual perturbations of the rhythm. These effects are consistent with the hypothesis that the circadian rhythm is a multioscillator system.
Separable Phases of Light-Evoked Depolarizations in the Retina of Strombus
Authors: Quandt Frederick N. , Gillary Howard L.
Published: April 2021

The waveforms of light-evoked depolarizations in Strombus retinal neurones can exhibit two sequential peaks or phases, the relative amplitudes of which vary with changes in stimulus intensity and interstimulus interval. Experiments employing either the passage of constant intracellular current or voltage clamp techniques indicate that both phases reverse polarity at intracellular potentials less negative than the resting potential. The potential at which the first phase reverses its polarity is considerably more positive than that of the second phase. The results indicate that the light-evoked depolarizations are generated by at least two different processes ; these appear to be separate conductance changes, neither of which is voltage dependent. Under certain conditions, the second phase was inhibited by high extracellular concentrations of Mg2+, indicating that it may arise as a result of chemically mediated synaptic transmission. The first phase did not show such inhibition and appears to be caused by the direct action of light on the cell.
Involvement of Cyclic Gmp in the Release of Stereotyped Behaviour Patterns in Moths by A Peptide Hormone
Authors: Truman James W. , Mumby Susanne M. , Welch Susan K.
Published: April 2021

A peptide hormone, the eclosion hormone, triggers two behavioural patterns - the pre-eclosion and eclosion patterns - when injected into pharate silkmoths. Injection of cyclic nucleotides caused the same behavioural responses with cGMP being 10 to 100 times more potent than cAMP. Exogenous cGMP also acted directly on the isolated nervous system to evoke the characteristic motor programmes. Protection of endogenous cyclic nucleotides by pretreatment of moths with a phosphodiesterase inhibitor, theophylline, markedly enhanced the sensitivity of the moths to the hormone. Injection of partially purified hormone preparations was followed by an increase in nervous system cGMP but not cAMP. The increase preceded the behavioural response to the hormone. When various doses of hormone were tested, the behavioural effectiveness of each dose was correlated with its ability to cause a cGMP increase. It was concluded that the behavioural effects of the eclosion hormone are mediated through an increase in cGMP in the nervous system.
Neuroethological Studies of Freely Swimming Aplysia Brasiliana
Authors: Von Der Porten Kenneth , Redmann Greg , Rothman Barry , Pinsker Harold
Published: April 2021

Recently developed neurophysiological and behavioural techniques were used to study swimming in the marine gastropod Aplysia brasiliana. Aplysia swim by bilateral parapodial flapping with an anterior to posterior metachronal wave. Parapodial oscillations are measured from video records. Population recordings from nerves innervating the parapodia during normal swimming in intact Aplysia reveal synchronous phasic activity in large efferent units associated with parapodial opening. Isolated brain studies and stimulation of central pathways in intact animals suggest a central pattern generator. We conclude that the output of the neuronal oscillator that controls parapodial flapping radiates synchronously from each pedal ganglion. The putative command to swim originates within the cerebral ganglia.
The effects of enforced activity on ventilation, circulation and blood acid-base balance in the semi-terrestrial anuran, Bufo Marinus
Authors: McDonald D. G. , Boutilier R. G. , Toews D. P.
Published: April 2021

The ovulation hormone producing neuro-endocrine cells of Lymnaea stagnate, the caudo-dorsal cells (CDC), are comparable to the bag cells of Aplysia. Both cell types are capable of the production of a long-lasting activity (afterdischarge) during which an ovulation hormone is released. The CDC (30 cells in the left cerebral ganglion and 70 cells in the right) are usually electrically silent but an afterdischarge can be brought about in all cells of both groups by direct, repetitive electrical stimulation of single CDC. This is not possible in every preparation, indicating that the CDC can be in different states of excitability.

All cells participate in the afterdischarge and fire approximately synchronously. All CDC are electrotonically connected. Results of experiments in which neurones were injected with horseradish peroxidase suggest that the demonstrated electrotonic connexions between the two opposite groups of CDC are brought about by 10–12 special axons.
The Effects of Extracts From Neurosecretory Cells in the Anterior Vena Cava and Pharyngo-Ophthalmic Vein Upon the Hearts of Intact Free-Moving Octopuses
Authors: Wells M. J. , Mangold K.
Published: April 2021

Recordings of pressure and frequency were made from the hearts of free-moving Octopus vulgaris. The effects of extracts from neurosecretory endings in the anterior vena cava (AVC) and the pharyngo-ophthalmic vein (POV), injected through fine cannulae into a branchial heart, efferent branchial vessel or the dorsal aorta, were studied and compared with the effects of acetylcholine, 5-hydroxytryptamine, adrenaline, histamine and tyramine. AVC and POV extracts each produce a different spectrum of effects, unlike those of any of the drugs tested. AVC extract is effective at doses of less than 2 % of the material extractable from a single vein per kg, increasing the force and amplitude of the heartbeats. With a natural release point just upstream of the branchial hearts the AVC material must be relevant to the normal performance of the hearts. POV extract is effective only at doses equivalent to several veins per kg, and is unlikely to have a role in cardiac regulation. Section of the visceral nerves did not affect the action of drugs or extracts, indicating that effects were not indirectly mediated via the CNA. Further experiments were made with hearts and the aorta in vitro with effects that did not always parallel those found in vivo. Reasons for these differences are discussed.
Functional Anatomy of Feeding in the Bluegill Sunfish, Lepomis Macrochirus: In Vivo Measurement of Bone Strain
Authors: Lauder G. V. , Lanyon L. E.
Published: April 2021

The suction feeding mechanism of the bluegill sunfish, Lepomis macrochirus, was studied in unrestrained fishes by the simultaneous recording of cranial muscle electromyograms, opercular cavity pressures, and opercular bone strain patterns. The electromyographic profile was similar to that of other advanced teleosts and consisted of preparatory, expansive, and compressive phases. The pectoral girdle remained nearly stationary during the strike. Opercular cavity pressures showed peak negative values of 145 cm H2O followed by a positive afterpressure of up to 50 cm H2O as water flowed out of the opercular chamber. Characteristic ‘coughing’ patterns showed an initial positive phase, followed by a negative phase, and then a final positive pressure pulse. Bone strain on the operculum was measured with rosette and single element strain gauges. Peak principal compression during the strike was 1800 με and the peak strain rate was − 615 × 103με/s, more than ten times that previously recorded in vertebrate bone during normal activity. Opercular bone strain results from the rapid reduction of pressure in the opercular cavity which causes the operculum to deform medially and does not result from muscle activity. The observed strain pattern is consistent with a stress regime of bending and twisting moments applied to the operculum during feeding. Two prominent orthogonal bony struts on the medial opercular surface are hypothesized to resist these bending and twisting moments.
The Statistical Treatment of Hydrogen Ion Concentration and pH
Authors: Boutilier R. G. , Shelton G.
Published: April 2021

A certain amount of confusion exists amongst respiratory physiologists about the statistical treatment of pH measurements taken from animals during replicated experiments. In some cases average pH (with standard deviations or standard errors as appropriate) is calculated directly whilst in others, pH determinations are converted to corresponding hydrogen ion concentrations before the statistical calculations are carried out. Values for pH may or may not then be recalculated but, if they are, the result of these manipulations is an asymmetry of standard deviations or errors about the mean which is neither useful nor acceptable to the statistician. Our interest in this subject was the result of a mild irritation on being told by a referee of one of our papers that we made the common error of taking simple pH averages. Further enquiry and thought led us to the present paper.
Ba2+ influx measures the duration of membrane excitation in Paramecium
Authors: Ling Kit-Yin , Kung Ching
Published: April 2021

We have developed an assay for the duration of membrane excitation in Paramecium tetraurelia by tracing the influx of 133Ba2+. This assay is performed at physiological temperatures and in physiological solutions. Ba2+ enters the paramecia through the Ca channels, since mutants defective in Ca channels show no significant Ba2+ influx. Ba2+ enters only when the Ca channels are opened during excitation which can be triggered by Na+ or Ba2+ itself. The ionic species and relative concentrations determine the duration of the action potentials and hence the duration of spinning or backward swimming. The longer the average period of excitation, the larger the Ba2+ influx. In a Ba-Ca solution the cells spend 30% of their time in the excited state. The rate of Ba2+ entry into the paramecia in that state is 1·3 mM/min. Ba2+ influx occurs over a 50-fold range of Ba2+ concentration. There is very little Ba2+ efflux. The fate of the entered Ba2+, the consequences of the large and rapid influx, the advantages and drawbacks of the Ba2+ influx assay, and the possible use of the assay for Ca channel function in cell-free preparations are discussed.
Feeding Motor Programme in Limax. II. Modulation by Sensory Inputs in Intact Animals and Isolated Central Nervous Systems
Authors: Reingold Stephen C. , Gelperin Alan
Published: April 2021

The sources of variability in feeding motor programme (FMP) of the terrestrial slug, Limax maximus, were examined in relation to: (1) changes in load on the feeding apparatus; (2) changes in concentration of attractive food stimuli; and (3) changes in satiety signalled by feedback from the gut. These sources of variability, which affect both timing of the central pattern generator for feeding and probability of occurrence of FMP, were compared in intact animals and in isolated brain preparations.

The load on feeding apparatus of intact animals is altered by varying the hardness of their food. An animal will show a higher ‘bite cycle’ frequency on soft food as compared with hard food. In physiological preparations, weights attached to buccal muscles similarly increase load. Cycle frequency of FMP triggered by food extracts is increased when buccal muscles are-unloaded compared with FMP when muscles are loaded.

Increasing the chemostimulant concentration of food results in greater numbers of intact animals feeding for longer periods. Increasing the food extract concentration used to trigger FMP in physiological preparations causes similar increases in feeding duration.

Intact animals use cues from gut distention to indicate satiation and terminate feeding. Inflation of the crop in physiological preparations causes an early termination of feeding activity, along with decreased FMP cycle frequency.
Wing Mechanics and Take-Off Preparation of Thrips (Thysanoptera)
Authors: Ellington C. P.
Published: April 2021

All of the wing fringe cilia of Thrips physapus, except those along the hindwing leading edge, pivot in elongated sockets which lock them into two positions. The wings lie parallel over the abdomen when not in use, with the cilia locked in the closed position at an angle of 15-20° to the wing axis. The closing of the fringes prevents entanglement of the trailing edge cilia and lateral projection of the forewing leading edge cilia. During flight the cilia are locked in the open position, doubling the wing area. The locking force is stronger than the combined aerodynamic and inertial forces on the cilia. The fringes are opened by abdominal combing and closed by tibial combing. The same morphological features are found in other members of the sub-order Terebrantia. Parallel wings at rest are characteristic of this suborder, and the collapsible fringe system is viewed as an effective method for parking the wings. The fringes of the sub-order Tubulifera are not collapsible. The wings overlap on the abdomen at rest and a similar parking problem does not arise.
Synaptic Relationships of the Cerebral Giant Cells With Motoneurones in the Feeding System of Lymnaea Stagnalis
Authors: McCrohan C. R. , Benjamin P. R.
Published: April 2021

The cerebral giant cells (CGCs) of Lymnaea have a tonic, modulatory effect on the intensity of output from feeding motoneurones in the buccal ganglia. Short latency, excitatory and probably monosynaptic connexions occur between the CGCs and three identified feeding motoneurones. Unitary excitatory postsynaptic potentials in these motoneurones, following CGC spikes, are of different sizes and durations, and hence have different summation properties. The CGCs make long latency, excitatory polysynaptic connexions with four other feeding motoneurone types. Bursts of spikes in the CGCs, resulting from phasic synaptic input, synchronous with the feeding cycle, amplify their modulatory effect on burst intensity in feeding motoneurones. The different latencies of the CGCs’ effects on different motoneurones are appropriate for reinforcing their cyclic burst activity.
Magnesium Transport by the Urinary Bladder of the Crab, Cancer Magister
Authors: Holliday Charles W.
Published: April 2021

Anuric crabs, Cancer magister, in 100% sea water lose most of their ability to regulate serum magnesium levels below that of the external medium, indicating that the antennal gland is the site of most of the crab’s hypo-regulatory ability. In vitro measurement of unidirectional fluxes of 28Mg across tissue from the urinary bladder (the terminal element of the antennal gland) showed a significant, serosa-to-lumen (SL) net flux of 0.280 ± 0.059 µequiv cm-2h-1 which was greatly reduced by 5 mm ouabain. Based on the calculated surface area of the bladder in the crab, the net SL flux of magnesium in vitro is sufficient to account for the in vivo rate of magnesium excretion by the antennal gland. Bladder tissue from magnesium-depleted crabs which had stopped concentrating magnesium in the urine did not show a significant, net SL flux of MMg in vitro. It is speculated that magnesium enters the bladder cell by a sodium-coupled process at the serosal border and is actively transported into the urine at the luminal border. Eyestalk ablation caused no significant changes in urinary rate or magnesium levels in serum or urine ; thus neurosecretory centres in the eyestalk are apparently not involved in control of magnesium secretion by the antennal gland. Large, nearly equal, net effluxes of 22Na (1.33 ± 0.19 µequiv cm-2 h-1, ouabain-insensitive) and 36C1 (1.26 ± 0.34 µequiv cm-2 h-1) from the urine were measured in bladder preparations in vitro. It is speculated that this net efflux of salt may be the driving force for fluid reabsorption from the urine by the antennal gland.
Uses and Limitations of Inulin and Mannitol for Monitoring Gill Permeability Changes in the Rainbow Trout
Authors: Kirschner Leonard B.
Published: April 2021

Inulin and mannitol are excreted at measurable rates across gills in freshwater and sea-water-adapted trout. Clearance behaviour suggests that the effluxes may reflect passive permeation, which might make such compounds suitable for monitoring permeability changes. Application of poly-L-lysine and elevation of environmental temperature made FW trout gills reversibly ‘leaky’ to Na+. Mannitol efflux paralleled that of Na+ in both experiments. However, Na+ efflux was reduced in SW trout gills, by increasing external Ca2+ and mannitol efflux was unchanged. The data suggest that these nonelectrolytes can be used to assess permeability changes that do not involve highly selective ionic channels.
The Use of A New Tilting Tunnel Respirometer to Investigate Some Aspects of Metabolism and Swimming Activity of the Plaice (Pleuronectes Platessa L.)
Authors: Priede I. G. , Holliday F. G. T.
Published: April 2021

Plaice and other flatfish can be induced to swim down a slope of about 6o° against an upwelling water flow in a water tunnel. A tilting Brett-type tunnel respirometer based on the above principle enabled laboratory experiments on swimming plaice to be carried out. From trials at 5°, 10°, 15 °C, the relationship between specific swimming speed, V (body lengths s-1), oxygen consumption, R (mg-1, kg-1 h-1) and temperature, T is: log10 = 0·3318V+log10(2·4T + 26·52). If the fish is resting (i.e. V = 0), the oxygen consumption is lower than predicted by the above equation. At rest: The cost of swimming in plaice is very similar to that of typical round fish such as haddock but the resting metabolic rate is lower than for haddock. Before swimming, a negatively buoyant fish such as plaice must lift off the bottom. This cost of lift-off or posture effect makes it uneconomical for plaice to swim at speeds below 0·6V