bluuebunny/crossref_metadata_2025 huggingface dataset:
Diving behaviour and heart rate in tufted ducks (Aythya fuligula)
Authors: Stephenson R. , Butler P. J. , Woakes A. J.
Published: April 2021

Diving behaviour and heart rate were monitored in tufted ducks diving under circumstances which simulated various environmental conditions such as feeding under ice in winter.

When distance to food was increased on a covered outdoor pond, dive duration increased proportionately, but it was calculated that time available for feeding was reduced during the longer-distance ‘extended’ dives. There was a gradual reduction in heart rate to 77·3 ± 13·8 beats min-1, which is significantly lower than the resting value of 121·1 ± 14·1 beats min-1, during the course of extended dives, suggesting that the ducks could gradually switch over to a ‘classical’ oxygen-conserving response during these prolonged voluntary dives. The duration of the pre-dive preparatory period was positively correlated with dive distance.

When the ducks were briefly unable to resurface during an otherwise normal feeding dive in an indoor tank, a situation which may occur if they become dis-oriented under ice, there was an immediate switch to a full bradycardia. Reduction in heart rate during these ‘enclosed’ dives occurred only when the ducks were apparently aware of the situation and the rate of onset of bradycardia was very similar to that previously observed during involuntary submersion of tufted ducks. Minimum heart rate was the same at 46 beats min-1 after 15 s of enclosed dives and after 30 s of involuntary submersions, despite the differences in levels of activity in the two situations.
Acid-base regulation and ion transfers in the carp (Cyprinus carpio): pH compensation during graded long- and short-term environmental hypercapnia, and the effect of bicarbonate infusion
Authors: Claiborne J. B. , Heisler N.
Published: April 2021

To study both temporal and quantitative effects of hypercapnia on the extent of pH compensation in the arterial blood, specimens of carp (Cyprinus carpio) were exposed to a of about 7·5mmHg (1 mmHg = 133·3Pa) (1% CO2) in the environmental water for several weeks, and a second group of animals was subjected to an environmental of about 37 mmHg (5 % CO2) for up to 96 h. A third series of experiments was designed to test the possibility that infusion of bicarbonate would increase the extent of plasma pH compensation. Dorsal aortic plasma pH, and [HCO3−], as well as net transfer of HCO3−-equivalent ions, NH4+, Cl− and Na+, between fish and ambient water, were monitored throughout the experiments.

Exposure to environmental of 7·5 mmHg resulted in the expected respiratory acidosis with the associated drop in plasma pH, and subsequent compensatory plasma [HCO3−] increase. The compensatory increase of plasma bicarbonate during long-term hypercapnia continued during 19 days of exposure with plasma bicarbonate finally elevated from 13·0 mmol l−1 during control conditions to 25·9 mmol l−1 in hypercapnia, an increase equivalent to 80% plasma pH compensation.

Exposure to 5 % hypercapnia elicited much larger acid-base effects, which were compensated to a much lesser extent. Plasma pH recovered to only about 45 % of the pH depression expected at constant bicarbonate concentration. At the end of the 96-h exposure period, plasma [HCO3−] was elevated by a factor of 2·5 to about 28·2mmol l−1.

The observed increase in plasma bicarbonate concentration during 5 % hypercapnic exposure was attributable to net gain of bicarbonate equivalent ions from ( or release of H+-equivalent ions to) the environmental water. Quantitatively, the gain of 15·6 mmol kg−1 was considerably larger than the amount required for compensation of the extracellular space, suggesting that acid—base relevant ions were transferred for compensation of the intracellular body compartments. The uptake of bicarbonate-equivalent ions from the water was accompanied by a net release of Cl− and, to a smaller extent, by a net uptake of Na+, suggesting a 75 % contribution of the Cl−/HCO3− exchange mechanism.

Infusion of bicarbonate after 48 h of exposure to 7·5 mmHg had only a transient effect on further pH compensation. The infused bicarbonate was lost to the ambient water, and pre-infusion levels of bicarbonate were reattained within 24 h. Repetition of the infusion did not result in a notable improvement of the acid-base status. These observations are consistent with the idea of a ‘threshold’ of the bicarbonate retaining and resorbing structures of the fish.
Blood gases and respiratory pattern in exercising fowl: comparison in normoxic and hypoxic conditions
Authors: Brackenbury J. H.
Published: April 2021

Clavicular air sac pressure, arterial blood gases and pH, and rectal temperature were measured in treadmill-exercised cockerels breathing air, 10% O2 in N2 or a mixture of 10 % O2/3 % CO2 in N2. Air sac pressures were used to estimate changes in the rate and the relative depth of breathing. In air-breathing conditions exercise took place at two intensities corresponding to treadmill speeds of 3·2 and 5·0 km h−1, respectively. Rectal temperature increased by 0·5°C but there was no sign of thermal hyperventilation and arterial remained constant. Increased ventilation was mainly brought about by changes in respiratory rate, with relatively small increases in depth. During exercise at 3·2kmh−1 inhalation of 10% O2 in N2 produced a 35 % increase in ventilation and breathing became faster and shallower. Arterial fell by 3–4 Torr, apparently as a result of lung hyperventilation. Addition of 3 % CO2 to the hypoxic gas restored normal arterial and reversed the trend to polypneic breathing. However, it failed to produce an exact matching of respiratory characteristics with those observed during isocapnic exercise hyperpnea. It is concluded that rapid, shallow breathing during hypocapnic hypoxia in running birds serves as a mechanism to minimize lung hyperventilation and CO2 washout. This reflex, which may stem from the intrapulmonary CO2 receptors, occurs in the face of a severe hypoxic challenge. Failure to match respiratory characteristics during isocapnic hypoxia and isocapnic exercise may be due to an inibitory effect of the inhaled CO2 on these receptors.
Withdrawal Reflex and Conduction Block in the Giant Axons of a Sabellid Worm (Pseudopotamilla Occelata)
Authors: Higuchi Takashiro , Nakamura Hiroyuki , Sawauchi Katsuhiko , Okumura Hiroshi
Published: April 2021

Body contraction in the sabellid worm, Pseudopotamilla occelata, during the rapid withdrawal reflex occurred only in the anterior half of the body. End-to-end shortening was never observed. The longitudinal muscles are well-developed in the anterior half, and poorly developed in the posterior half. Conduction of action potentials along the giant axons was blocked at the midbody, and was responsible for the anteriorly restricted body contraction. Electrophysiological and histological studies excluded the possibility that conduction block resulted from a safety factor attributable to the special geometry of the axons. Current injection across the giant axon membrane in the region of the conduction block indicated that changes in the properties of the membrane were responsible for the conduction block.
Kinematics and aerodynamics of the greater horseshoe bat,Rhinolophus ferrumequinum, in horizontal flight at various flight speeds
Authors: Aldridge H. D.
Published: April 2021

The kinematics and aerodynamics of the greater horseshoe bat, Rhinolophus ferrumequinum, in horizontal flight at a range of velocities are described. As flight speed increases there is a gradual change in the bat’s wingbeat kinematics, wingbeat frequency decreasing and wingbeat strokeplane angles increasing. Associated with these changes are changes in the wings’ incidence angles, particularly during the upstroke. At low speeds these are large and negative, suggesting thrust generation, while at high speeds these are positive and large, indicating that weight support and negative thrust are being generated. The change from one kinematic pattern to the other occurred gradually. The possible energetic and aerodynamic reasons for these changes are discussed.
Downstream pH Changes in Water Flowing Over the Gills of Rainbow Trout
Authors: Wright Patricia , Heming Tom , Randall David
Published: April 2021

We investigated the pH of interlamellar water of trout (Salmo gairdneri) by following changes in the downstream pH of expired water using a stopped-flow method. As water flowed over the gills of control fish, there was a significant decrease in water pH. Acetazolamide added to the water increased the CO2 disequilibrium, while carbonic anhydrase (CA) eliminated the CO2 disequilibrium relative to control water. Mucus excreted by the fish was found to contain CA activity by the pH-stat technique. We conclude water acidification is due to the conversion of excreted CO2 to HCO3- and H+ at the gill surface.
Short Communications: Non-Invasive Measurement of Respiratory Tidal Volume in Aquatic, Air-Breathing Animals
Authors: Funk G. D. , Webb C. L. , Milsom W. K.
Published: April 2021

In recent years, a method which allows breathing patterns to be fully quantified in aquatic, air-breathing species while free-ranging and undisturbed, has come into common use (Brett & Shelton, 1979; Glass, Boutilier & Heisler, 1983, 1985; Butler, Milsom & Woakes, 1984; Silver & Jackson, 1985; Milsom & Chan, 1986). Use of this method in our laboratory, however, has revealed several potential sources of error in the normal procedures used for calibrating this system for the measurement of tidal volume (VT). In the present study we have systematically studied these potential sources of error under a variety of conditions and describe a technique for eliminating these errors in routine measurements.
Thermal dependence of sprint performance of the lizard Sceloporus occidentalis
Authors: Marsh R. L. , Bennett A. F.
Published: April 2021

Sprint velocity of the lizard Sceloporus occidentalis was maximal at preferred body temperature (Tb, 35°C). Mean running velocity (VR) and stride frequency (f) at this temperature were 3·23 ± 0·7 (mean ± S.E.M.) ms−1 and 15·6 ± 0·3 s−1, respectively. VR and f did not change significantly when Tb was raised to 40°C. At Tb values between 25 and 35°C the thermal dependencies of VR (Q10= 1·23) and f (Q10= 1·12) were quite low. At Tb values below 25°C the thermal dependence of these factors increased markedly. Stride length (Ls) was independent of Tb from 15 to 40°C. Lizards with a Tb of 10°C were largely incapacitated, and VR, f and Ls were all greatly reduced. Comparisons with measurements of the contractile properties of skeletal muscle of this species suggest that stride frequency is limited by the twitch contraction time at temperatures below 23°C. At higher temperatures, sprint performance is nearly independent of the thermal effects on the muscles.
Interspecific Comparisons of Endothermy in Honey-Bees (APIS): Deviations from the Expected Size-Related Patterns
Authors: Dyer Fred C. , Seeley Thomas D.
Published: April 2021

We report the first measurements of thoracic flight temperature (Tth) in foragers of the three Asian honey-bee species (genus Apis), which, together with the European species A. mellifera, span a five-fold range in body mass from the smallest species to the largest. Over a 15°C range in ambient temperature (Ta), we found that Tth in each species is strongly dependent upon T” as previously shown for A. mellifera. However, the temperature gradients (Tth-Ta) at a given T, do not appear to increase with body size in the four species, as expected from many previous studies of endothermy in insects. The smallest species, A. florea, shows the smallest Tth-Ta, but the intermediate-sized A. cerana and A. mellifera both show a consistently higher Tth-Ta than the largest species, A. dorsata. We found that the rate of passive convective heat loss from the thorax scales linearly and inversely with body size in the four species, as in most insects, and that there is no striking anatomical evidence for differences in efficiency with which heat flow from the thorax to the abdomen is restricted. However, two important correlates of heat production -wing-loading and flight speed -are disproportionately high in A. cerana and A. mellifera relative to A. dorsata and A. florea, suggesting that an elevated mass-specific metabolic rate in flight may account for their unexpectedly high Tth-Ta. Furthermore, compared on a mass-specific basis, A. dorsata and A. florea are more similar to each other than either is to the other two species. This physiological dichotomy among the four species parallels a dichotomy in nesting behaviour and colony demography. Hence our results, in addition to raising many questions about physiological mechanisms in the energetics of honey-bees, suggest that there may be functional links between the energetic constraints on individuals and on colonies.
Gas Exchange and Ventilatory Responses to Hypoxia and Hypercapnia inAmphisbaena Alba(Reptilia: Amphisbaenia)
Authors: Abe Augusto S. , Johansen Kjell
Published: April 2021

Total and cutaneous gas exchange and ventilatory responses to breathing hypoxic and hypercapnic gases were studied in Amphisbaena alba (Linnaeus), a burrowing squamate reptile. This species shows a very low oxygen uptake rate compared with other squamates of the same size (= 15·4, 36·2 and 49·0mlkg−1 h−1, at 20, 25 and 30°C, respectively). Cutaneous gas exchange represents a large fraction of the total uptake. Oxygen uptake was strongly affected by temperature [Q10 = 5·5 (20–25°C); 1·8 (25–30°C); 3·2 (20–30°C)]. A. alba shows a biphasic ventilatory pattern under hypoxic and hypercapnic conditions. A single breathing cycle, consisting of expiration-inspiration, includes a ventilatory period (VP) followed by a non-ventilatory (breath hold) period (NVP) of variable duration. When breathing air at 25°C the NVP typically occupied about 2 min. The ventilatory period occupied only 0·075 parts of a complete breath-to-breath cycle. Breathing hypoxic gases caused a pronounced rise in ventilation volume (VE) from an increase in tidal volume (VT) and frequency (f) at inspired O2 concentrations below 7%. Breathing hypercapnic gas mixtures induced a minor change in VT at CO2 concentrations below 3%, and VE increased mostly because of increases in f. End tidal O2 and CO2 tensions changed with increasing VE while breathing hypoxic and hypercapnic gas. The results are discussed in relation to the fossorial habits of A. alba, and are compared with data from other squamates.
Innervation of the Anterior and Posterior Levator Muscles of the Fifth Leg of the Crab Carcinus Maenas
Authors: Moffett Stacia , Yox Daniel P. , Kahan Linda B. , Ridgway Richard L.
Published: April 2021

In the fifth pair of legs, the anterior levator muscle of the basi-ischiopodite (AL) consists of a dorsal thoracic head (ALd), two closely aligned ventral thoracic heads (ALv) and a small coxal head (ALc). Major thoracic subdivisions are separately innervated, whereas the nerve innervating the coxal head projects from ALd. The posterior levator (PL) is located in the coxa and is separately innervated.

Nerve recordings, dye backfilling, muscle fibre recordings and nerve crosssections yielded somewhat different estimates for the levator motor innervation.

Nerve backfills reveal at least 10 motoneurones supplying AL: six shared by ALd and ALv, one unique to ALv and three unique to ALd.

Nerve recordings reveal six motoneurones supplying ALd and five supplying ALv. Four (including the common inhibitor) are shared by ALd and ALv and six project from ALd to ALc.

Most AL muscle fibres are innervated by two or three motoneurones, but fibres innervated by five were encountered. Postsynaptic potentials ranging from small (<l–5 mV) to large (15–25 mV) were found distributed throughout AL.

PL is innervated by two excitors not shared with AL and by the common inhibitor.

Electron micrographs reveal more axons than any of the methods for counting motoneurones. Neurones with axon diameters below 3 μm are likely to be sensory.
In Vitro and In Vivo Protein Synthesis Rates in a Crustacean Muscle During the Moult Cycle
Authors: El Haj A. J. , Houlihan D. F.
Published: April 2021

In vivo protein synthesis rates were measured in the carpopodite extensor muscle of the shore crab, Carcinus maenas, following a single, high-dose injection of [3H]phenylalanine, which stabilized specific radioactivities in the free pools. In intermoult animals the percentage of protein mass synthesized per day (the fractional rate of protein synthesis) was 1·15% day−1 for the whole extensor muscle. The small, slow-type tonic fibres in the extensor had fractional rates of protein synthesis some 2·1 times higher than those of the large, fast-type phasic fibres.

Measurement of protein synthesis rates of extensor muscles from intermoult animals using an in vitro incubation over 2h gave fractional synthesis rates three times lower than those found in in vivo experiments. Compared with the intermoult animals, six- and three-fold increases in fractional synthesis rates were found in the extensor muscles from stages immediately preceding and following ecdysis, respectively. Microdissection of the muscle fibres revealed that the increased synthesis in postecdysial animals was occurring mainly at the external cuticular end of the muscle fibres. Autoradiographic analysis confirmed the cuticular end of the muscles as the major site of muscle protein synthesis. We conclude that the postecdysial increase in muscle fibre length and the associated increase in the sarcomere number is accompanied by an increase in protein synthesis in the muscles.
Temperature Regulation, Energy Metabolism and Mate-Searching in Rain Beetles (PleocomaSpp.), Winter-Active, Endothermic Scarabs (Coleoptera)
Authors: Morgan Kenneth R.
Published: April 2021

Male rain beetles (Pleocoma; Scarabaeidae) of western North America engage in intense mate-searching activity at night during the winter. They may achieve a temperature excess greater than 35 °C in flight, even though their thoracic pile is ineffective as insulation. Males also maintain thoracic temperature at high levels while walking on the ground in search of females. Female Pleocoma are flightless and are non-endothermic. In the laboratory, males maintained elevated body temperatures for as long as 4·2 h while walking in a respirometer chamber at an ambient temperature of 9°C. Energy metabolism and body temperature during these periods of sustained endothermy oscillated. Walking speed increased exponentially with body temperature. Male rain beetles compete (scramble competition) for opportunities to mate. It is likely that their mating success and ability to avoid predators depend on flight and rapid walking, which in turn depend on their having a high internal temperature.
Developmental endocrinology of larval moulting in the tobacco hornworm, Manduca sexta
Authors: Bollenbacher W. E. , Granger N. A. , Katahira E. J. , O’Brien M. A.
Published: April 2021

A larval moult in the tobacco hornworm, Manduca sexta, involves an endocrine cascade that begins with the release of a cerebral peptide hormone, the pro-thoracicotropic hormone (PTTH). The release of PTTH is gated, occurs during the scotophase and appears to be developmentally cued. In fourth instar Manduca larvae, PTTH release into the haemolymph occurs as a single burst over a few hours during the head critical period, i.e. the time during which the head (brain) is needed for the initiation of the moult to the fifth (last) instar. Released PTTH activates the prothoracic glands (PGs), and within a few hours the cumulative effect of this event results in a dramatic increase in the haemolymph ecdysteroid titre, which then elicits the moult. An assessment of the capacity of the corpora allata (CA) to synthesize juvenile hormone (JH) in vitro indicates that the above sequence of endocrine events begins only when JH synthesis has reached a nadir for the instar. Since CA activity is an indirect measure of the haemolymph titre of the hormone, it is conceivable that the developmentally cued release of PTTH is permissively controlled by a decreasing haemolymph titre of JH. With the increase in the ecdysteroid titre which marks the end of this endocrine cascade, the CA again become active, presumably to cause the increase in the JH haemolymph titre which directs the larval moult. This in-vestigation has thus established the temporal and quantitative dynamics of the PTTH-PG axis that drive larval moulting and provides insight into the inter-endocrine regulatory relationships that may exist between the ecdysteroids and JHs. These possible relationships and the role of the brain in their regulation are discussed.
Integration of Wing Proprioceptive and Descending Exteroceptive Sensory Inputs by Thoracic Interneurones of the Locust
Authors: Elson Robert C.
Published: April 2021

The campaniform sensilla on the wings of the locust are strain-sensitive mechanoreceptors that provide proprioceptive feedback about wing forces, particularly aerodynamic lift, experienced during flight. They can be excited by imposed deformations of the wing, including those caused by imposed wing twisting. The afferents of the single subcostal group of sensilla on the hindwing had the same directional selectivity for supinating twist and shared the properties of a dynamic sensitivity and adaptation. A group of strain-sensitive mechanoreceptors with similar properties, presumably campaniform sensilla, is also found in the forewings. Four types of thoracic interneurones influenced by these factors were recorded and stained intracellularly. The response of interneurone 5AA to imposed de-formations of the hindwing ipsilateral to its soma is determined by excitatory chemical synaptic input from the campaniform sensilla. Interneurone and sensilla have a common directional selectivity and optimal stimulus, and similar qualitative dynamics of response. Each spike of individual afferents is followed at short, constant latency by an excitatory postsynaptic potential (EPSP) in the interneurone, even at instantaneous frequencies of about 90 Hz. Physiological evidence is consistent with direct, chemically mediated synaptic inputs from campaniform sensilla afferents. Interneurone 5AA is also excited by a short-latency, chemical synaptic input from the ocelli when lights are turned off. EPSPs could be elicited by light-off stimuli to the median and contralateral, but not the ipsilateral, ocelli. In addition, the interneurone is excited when the head is moved relative to the thorax. The other three interneurones respond to strains in more than one wing. Inputs are derived from specific combinations of wings, with the sign of response depending on the neurone and the particular wing. Interneurones 3AA and 1AA are also phasically excited by light-off stimuli. In 1AA this response was shown to originate from the ocelli. Median and contralateral, but not ipsilateral, ocelli could evoke EPSPs. This neurone was also excited by imposed head movements. It is argued that the interneurones described here at suited to monitor lift production in particular wings and its pattern among several wings. Convergence of ocellar and head-motion inputs implies a function in the exteroceptive detection and correction of flight instability. It is inferred that these thoracic interneurones may act as the nexus for several different feedback pathways, proprioceptive and exteroceptive, which modulate flight motor output.
The thermal dependence of locomotor performance and muscle contractile function in the salamander Ambystoma tigrinum nebulosum
Authors: Else P. L. , Bennett A. F.
Published: April 2021

The thermal dependence of locomotor performance and in vitro muscle mech-anical properties were studied after acclimation at 10° and 20°C in the salamander Ambystoma tigrinum nebulosum Hallowell. Performance measurements included burst and endurance capacities on land and in water. No significant differences in locomotor performance or muscle contractile properties were found between acclim-ation groups. Locomotor performance had only a slight thermal dependence, with Q10 values of 0·99—1·36 for running and swimming burst capacities (i.e. maximum speed and leg/tail cycling frequency). Running and swimming endurance capacities had thermal ratios of 1·58-1·66. Thermal dependence of muscle contractile rates was higher than that of locomotor performance: rates of force development for both isometric twitch and tetanus and maximal shortening velocity had Q10 values of 1·89—2·01. Maximal power output was also thermally dependent (Q10 = 2·33) and occurred at 38% of maximal (tetanic) force output. Force-generating capacities in isometric twitch and tetanus were relatively temperature-independent.
The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri:III. Renal ionic fluxes
Authors: Vermette M. G. , Perry S. F.
Published: April 2021

Rainbow trout were infused continuously for 24 h with epinephrine in order to evaluate the effects of elevated circulating levels of epinephrine on selected renal variables. Pronounced effects of epinephrine included elevation of urine flow rate and concomitant increases in the excretion of all measured electrolytes (Na+, Cl−, K+, Ca2+, inorganic phosphate) with the exception of ammonium and bicarbonate ions. Significant reductions in the tubular reabsorption of Na+ and Cl− also contributed to enhanced excretion of these ions. Similarly, epinephrine affected the tubular handling of NH4+ and HCO3− with NH4+ secretion decreasing and HCO3− reabsorption increasing. We speculate that the stimulation of HCO3− reabsorption was a consequence of elevated tubular H+ secretion. Such a mechanism may be important to permit plasma HCO3− retention during periods of internal acidosis. The results are discussed with reference to the role of the fish kidney in regulating acid-base disturbances and the possible interactive effects of elevated epinephrine.
Course-Control, Metabolism and Wing Interference During Ultralong Tethered Flight in Drosophila Melanogaster
Authors: Götz Karl G.
Published: April 2021

Tethered flight in a 3-day-old female Drosophila was sustained for 32·2 h with only short interruptions during uptake of sucrose solution. The course-control reactions derived from the difference of the wingbeat amplitudes on either side have been used to simulate the rotatory displacement of the surrounding landmarks during a comparable turn in free flight. Stabilization of a target in the preferred area of the visual field requires continuous visual attention. A rate of about 5 course-correcting manoeuvres per second was maintained throughout the experiment. Drosophila seems to be able to cover long distances in search of a favourable habitat.

Flight-specific carbohydrate consumption is equivalent to a metabolic power input per body weight of about 18 W N−1. The tethered fly produces about 40 % of the lift required to sustain hovering flight. The resulting mechanochemical efficiency of about 0·04-0·07 is within the expected order of magnitude for flying insects. Expenditure of reserve substances may account for the difference between the comparatively low power input of about 7 W N−1, derived from carbohydrate uptake in the first hours of flight (Wigglesworth, 1949), and the actual metabolic turnover of about 21 WN−1, derived from oxygen consumption during this period (Laurie-Ahlberg et al. 1985).

Weis-Fogh’s ‘clap and fling’, a widespread lift-generating process exploiting the aerodynamic wing interference at the dorsal end of the wingbeat, was in action throughout the flight. However, there were two significant modifications (as first conceived by Ellington, 1980) : (1) during ‘clap’, there is a progress of wing contact from the leading to the trailing edge, which is likely to ‘squeeze’ a thrust-generating jet of air to the rear; (2) during ‘fling’, there is a progress of wing separation in the same direction, which is described as a ‘peel’ resembling the progressive separation of two plastic foils pulled apart against forces of mutual attraction. The wings of the test fly survived about 23 million such peels without damage. Increasing airspeed decreases the intensity of ‘clap and fling’ in Drosophila : results obtained in the wind tunnel show the transition to a ‘near clap and fling’, lacking mutual wing contact.
Salinity Acclimation and Intestinal Salt Transport in the Flounder: the Role of the Basolateral Cell Membrane
Authors: Gibson J. S. , Ellory J. C. , Lahlou B.
Published: April 2021

Intestinal absorption of Na+ and Cl−, measured using bidirectional tracer fluxes, is higher in saltwater (SW)-acclimated flounders than in freshwater (FW)-acclimated ones. Removal of the selective permeability of the apical cell membrane by application of amphotericin B to the mucosal solution enhances the difference in Na+ transport, whilst the difference in Cl− absorption is lost. Transepithelial resistance and were similar between the two groups of fish, whilst , was always greatest in SW-acclimated tissues, even after mucosal application of amphotericin. Analysis of the present results and previous work suggests that the principal acclimatory changes following salt adaptation occur in the basolateral cell membrane, and that both the Na+,K+-ATPase activity and the basolateral cell membrane permeability to Cl− are increased in the SW-acclimated tissues.
The Tuned Singing Burrow of Mole Crickets
Authors: Bennet-Clark H. C.
Published: April 2021

During burrow digging by the mole cricket Scapteriscus acletus Rehn and Hubbard, the burrow is enlarged and shaped in a series of digging cycles, each lasting 1–2 min, and song chirps are produced after every cycle. The song becomes up to 18 dB louder and acoustically purer during burrow building. The shape of the song pulse envelope changes so that its average power density becomes greater and its build-up and decay become more gradual.

The forewings show a single resonance of the harp (Cu 1 cell) regions at 2·5-3·0kHz: the normal song carrier frequency is 2·5-2·7kHz. Removal of the outer parts of the forewings does not affect the radiated sound power.

The singing burrow has an exponential horn opening at the soil surface and an internal bulb. The calculated cut-off frequency of the horn is 1·34 kHz and that of the first resonance is 2·5-2·7 kHz. The volume of the bulb is close to that required to tune the throat: obliteration of the burrow bulb causes a substantial decrease in the radiated sound pressure levels before singing ceases.

The horn mouth acts as a finite sound source, with large acoustic reactance. The acoustics of the burrow were measured with a small doublet source inserted at the position at which the cricket sings. At this position, the burrow resonates at 2·75-3 kHz, with a quality factor (Q), measured both by the –3 dB bandwidth and by the build-up and decay of tone bursts, of 2·5-2·7. The sound pressure produced by the doublet source is up to 24 dB louder when it is in the burrow than when it is in free air. Further in or out from the insect’s singing position, the effective gain of the burrow is reduced and other resonances and anti-resonances are observed. Obliteration of the burrow bulb reduces the effective gain of the burrow by 6–10 dB and the burrow ceases to resonate at 2·75 kHz.

It is proposed that the tuned burrow acts as a resistive load on the vibrating harps, so allowing good coupling between the small wings and the surrounding medium while allowing a pure carrier frequency to be radiated.
Walking and Surface Film Locomotion in Terrestrial and Semi-Aquatic Spiders
Authors: Shultz Jeffrey W.
Published: April 2021

The walking and surface film locomotion of a terrestrial spider, Lycosa rabida Walckenaer, and a semi-aquatic spider, Dolomedes triton (Walckenaer), are compared. Stepping patterns during locomotion on a solid substrate resemble an alternating tetrapod in both species. L. rabida retains elements of the terrestrial gait when moving on water: propulsive thrusts are concentrated at the tarsi and intra-segmental legs step in alternation. However, protraction/retraction (p/r) values are generally greater and phase values of adjacent ipsilateral legs are lower compared to values for walking animals. D. triton shows greater behavioural specialization for aquatic locomotion: propulsive forces are generated along the length of the leg, intrasegmental legs move in synchrony and leg 4 (which is not used for propulsion on water) functions in yaw correction. Changes in p/r value and ipsilateral phase accompanying the transition from a solid substrate to the water surface are similar to those found in L. rabida. The fact that coordination within a segment and coordination between segments can be altered independently in both proximate and evolutionary time suggests that interleg coupling in spiders is governed by two distinct mechanisms: intrasegmental and intersegmental mechanisms. It is suggested that proximate changes in p/r value and ipsilateral phase in both spiders may be the effect of sensory modulation of similar motor control mechanisms and that certain specializations for aquatic locomotion in D. triton (such as yaw corrective movements of leg 4) are derived from elements of the primitive terrestrial motor programme.
The effects of temperature and pH on the contractile properties of skinned muscle fibres from the terrapin, Pseudemys scripta elegans
Authors: Mutungi G. , Johnston I. A.
Published: April 2021

Fibre types in the iliofibularis muscle of the freshwater terrapin Pseudemys scripta elegans have been characterized on the basis of their histochemical characteristics, nerve endings and contractile properties. Three types of focally innervated fibres are present, corresponding to the fast glycolytic (Fg), fast oxidative glycolytic (FOG) and slow oxidative (SO) fibre types of other vertebrates. Single fibres or small bundles of fibres representing each histochemical type were identified on the basis of their light scattering properties under dark-field illumination. Fibres were detergent-skinned using Brij 58, and their maximum isometric tension (Po) and unloaded contraction velocity (Vo) were determined by the slack test method. At 15 °C, fast glycolytic fibres generated maximum isometric tensions of 184 ± 5 kN m−2 and Vo values of 5·5 ± 0·3 muscle lengths per second (Los−1). Slow oxidative fibres produced tensions of 70·6±3kNm−2 and had Vo values of 1·3 Los−1. Tensions and Vo values of fast oxidative glycolytic fibres were between those of Fg and SO fibres. The force-velocity (P-V) characteristics of slow oxidative fibres were studied at 5° and 15°C. Points below 0·6 Po on the curves could be fitted by a linear form of Hill’s equation. Maximum contraction velocities (Vmax) extrapolated from the P–V relationship were 0·62 Los−1 at 5°C and 0·91 Los−1 at 15°C. The curvature of the P-V relationship was relatively independent of temperature over the range 5 to 15°C. Values for Hill’s constant a/P0 were 0·29 and 0·33 at 5°C and 15°C, respectively. The temperature dependence of P0 and contraction velocity at near zero load (Vi) were studied at constant pH, and under conditions designed to simulate the changes in intracellular pH which occur with temperature in vivo (ΔpH/ΔT = –0·0186). Changes in pH in the range 6·6 to 7·8 had no effect on either tension or V, at temperatures between 0° and 20°C. However, below and above this pH range, both tension and V, were depressed. It is concluded that pH changes within the normal physiological range (6·7–7·8) have no effect on the temperature dependence of P0 and Vi.
Hagfish (Eptatretus stouti) erythrocytes show minimal chloride transport activity
Authors: Ellory JC , Wolowyk MW , Young JD
Published: April 2021

Capnophorin (Band 3) is the major red cell transport protein, present in human erythrocyte membranes at 1 × 106 copies per cell. Under physiological conditions, the transporter is capable of moving 50 mol (Cl−/HCO3−) 1 cells−1 min−1 (Knauf, 1979), this high rate being necessary for carriage of CO2 in normal respiration (Wieth et al. 1982). In the present paper we demonstrate that, in contrast to the situation in all other vertebrate species studied except the lamprey (Ohnishi & Asai, 1985), capnophorin activity in hagfish red cells is very limited, amounting to only 40 μmol Cl− transported 1 cells-1 min-1 at 11 °C, the environmental temperature of this species. Five experimental approaches were used to characterize this transporter in hagfish red cells: pH regulation in lightly buffered medium; 36C1− uptake; 36C1− efflux; effects of H2DIDS (dihydro-4,4-diisothiocyanostilbene 2,2-disulphonic acid), a specific capnophorin inhibitor (Knauf, 1979); and sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis (PAGE).
Regeneration of Feathers After Thyroid Feeding
Authors: Hosker Anne
Published: April 2021

It may be concluded from these experiments that excessive doses of thyroid cause (a) moulting, followed by rapid regeneration of depigmented feathers in mature birds ; (b) depigmentation of growing feathers followed by increased melanisation in young birds, giving a white and black bar ; (c) accelerated growth rate in all feathers, regardless of the region considered or the age of the bird ; (d) stimulation of the papillae of plucked feathers causing rapid regeneration from each papilla.

From the variability in the measurements recorded, liver feeding appears to have no definite effect upon feather growth, but a slight stimulating effect upon the papillae causing them to regenerate.

In cases of lack of external signs of regeneration of feathers for some months after plucking in normal or liver-fed birds, the papilla regenerates a rudimentary calamus, or lies quiescent beneath cornified tissue which acts as a calamus, until the next moult, or until some substance with an accelerating influence upon feather growth (e.g. thyroid) is administered.
Calcium-Dependent Action Potentials in the Second-Order Neurones of Cockroach Ocelli
Authors: Mizunami Makoto , Yamashita Shigeki , Tateda Hideki
Published: April 2021

The ionic basis of the action potential in the large second-order neurones (L-neurones) of the ocellus of the cockroach, Periplaneta americana, was studied. L-neurones generated action potentials, usually once, at the off-set of hyperpolarizing light responses, or at the termination of hyperpolarizing current stimuli. The action potential was blocked by replacing saline Ca2+ with Mg2+ but maintained when Ba2+ was substituted. A block was produced by 2 mmol l−1 Cd2+ or 20 mmol l−1 Co2+. The peak amplitude of the action potential increased by 26 mV for a 10-fold increase in external Ca2+ concentration, at concentrations below 1·8 mmol l−1. The action potential was not affected by sodium-free saline or by 3×l0−6moll−1 tetrodotoxin (TTX). These observations suggest that calcium ions are the major carrier for the inward current of the action potential. This finding supports the suggestion that the off-set responses of hyperpolarizing visual neurones of both vertebrates and invertebrates have a common ionic mechanism, including voltage-sensitive calcium currents.
Lactate Uptake by Toadfish Hepatocytes: Passive Diffusion is Sufficient
Authors: Walsh Patrick J.
Published: April 2021

Mechanisms of hepatic lactate uptake were studied in the gulf toadfish, Opsanus beta by following the accumulation of [l4C]lactate by isolated hepatocytes in vitro. Uptake rates were linear for up to 5 s at external lactate concentrations of 1 and 20 mmol 1−1. 5-s uptake rates for several concentrations in the physiological range (i.e. 0 2-20 mmol 1−1) yielded a linear double reciprocal plot (1/v VS l/[lactate]) that passed through the origin. Lactate uptake was not inhibited by known inhibitors of carrier-mediated lactate transport (e.g. 5 mmol 1−1 α-cyano-4-hydroxycinnamate; 10 mmol 1−1 pyruvate), and was not stereospecific for L-( +)-lactate. These observations indicate that lactate uptake is by passive diffusion in toadfish hepatocytes. Lactate uptake by toadfish hepatocytes further differed from lactate uptake by mammalian tissues in that rates were not altered by changes in either pHe (6·5−8·0) or [Na+]e (3−151 mmol 1−1). Rates of lactate conversion to glucose and CO2 were measured and compared to uptake rates, and it appears that rates of lactate metabolism are not limited by passive diffusion. These results are discussed in relation to rates of lactate uptake and metabolism in mammalian hepatocytes.
Electric fish approach stationary signal sources by following electric current lines
Authors: Schluger James H. , Hopkins Carl D.
Published: April 2021

African electric fish of a pulse species, Brienomyrus brachyistius (Mormyridae), housed singly in a large, circular arena, were presented with electrical stimuli which mimicked a conspecific intruder. Stimuli were produced with either dipolar or bipolar electrodes in three different geometries. We tracked the unconditioned approach response paths taken by the fish and compared tracks for each of the geometries. The results suggest that B. brachyistius can determine neither the distance nor the direction of an electric dipole from afar, but that they do manage to find the source by maintaining a precise alignment of their body axis parallel to the direction of the local electric field vector (parallel to current lines) while swimming. This behaviour ultimately leads to the current source. We propose that this behaviour may be a simple mechanism mediating the approach response of one electric fish to another.
Bird Migration Across a Strong Magnetic Anomaly
Authors: Alerstam Thomas
Published: April 2021

Migratory flights of birds across a strong magnetic anomaly were recorded by tracking radar and, during the daytime, by simultaneous visual observations. The anomaly in central Sweden is about 12 km long and a few kilometres wide, with the total magnetic intensity at low altitude exceeding the normal field by up to 60 %, according to aeromagnetic measurements. Migrants change altitude, most often by starting to descend, to a significantly greater extent over those parts of the anomaly where the magnetic field intensity is abnormally high, and particularly where the magnetic inclination is steepest, than over other parts of the study area and at another study area with a normal geomagnetic field. The descents lasted on average about 2min, with a mean angle of descent of 2·6°, leading to a height loss of about 100 m before level flight was resumed. Flock formations were repeatedly broken up during these temporary descents. The changes in flight altitude were associated with gradients in magnetic inclination along the birds’ flight paths across the anomaly. This supports the possibility that birds use the geomagnetic field and associated gradients for continuous guiding and recording of migration. Additional visual observations of migrating birds at the lowest altitudes over the magnetic anomaly suggest that birds sometimes become briefly disturbed (clear weather) or disoriented for longer periods, because of difficulties in finding their way out of the anomaly area (poor visibility).
On the termination of ingestive behaviour by the medicinal leech
Authors: Lent C. M. , Dickinson M. H.
Published: April 2021

Hungry leeches, Hirudo medicinalis, ingest blood meals averaging 890% of their mass in 29min. Ingestion is terminated as a result of distension of the body: experimentally distending leeches as they feed causes an immediate cessation of ingestion and inhibits any subsequent biting behaviour; if distension is circumvented by various experimental procedures, leech ingestive periods are prolonged significantly. Ingestion is not terminated as a result of fatigue, chemical cues or mass change. Distension also underlies satiation, for removing blood from the crops of recently fed leeches qualitatively alters their satiated behaviour to biting. Biting is not a defensive reaction to injury.

In rostral ganglia, impulses of the serotonergic Retzius (RZ) and LL neurones evoke the physiological components of ingestion. Localized warming of the prostomial lip induces impulses in these large effector neurones. Distending the body wall tonically hyperpolarizes the RZ and LL cells. This inhibitory response to distension is conducted from the mid-body to the anterior neurones via the ventral nerve cord. Distensive inhibition antagonizes the synaptic excitation evoked in RZ and LL neurones by thermal stimulation. Thus, a stimulus which evokes feeding synaptically excites 5-HT neurones and a stimulus which terminates ingestion inhibits them. The integration of these inputs controls the expression of leech feeding behaviour and these connections match precisely a model proposed to regulate the ingestive behaviour of blowflies.
Functioning of identified snail neurones in electric fields
Authors: Ierusalimsky V. N. , Balaban P. M.
Published: April 2021

In both silent and spontaneously active neurones of the snail Helix lucorum, depolarization and spikes were elicited by low-frequency (0·1 Hz) sinusoidal currents applied to the bath solution. Threshold voltage gradients had a range of 1–10 V m−1, which is less than gradients in the nervous tissue during synchronous activation of the neurones. It is shown that the same neurone can generate spikes in response to opposite directions of polarizing currents. Thresholds of spontaneously active neurones to extracellular currents were significantly lower than thresholds of silent cells. A simple quantitative method for evaluation of the transmembrane voltage drop evoked by an electric field is presented. The role of neuronal branches in the response was studied by electrophysiological and morphological methods.
Laboratory studies of homing orientation in the eastern red-spotted newt, Notophthalmus viridescens
Authors: Phillips J. B.
Published: April 2021

The orientation behaviour of adult male eastern red-spotted newts (Notophthal-mus viridescens) was studied in laboratory tests. Newts were collected from ponds located 10-30 km from the laboratory, and housed in water-filled, all-glass aquaria located in a greenhouse or outdoors adjacent to the laboratory building. The aquaria were aligned on the magnetic north-south axis. Newts were tested in a dry, enclosed arena in four magnetic fields: the ambient magnetic field (magnetic north at North) and three altered fields (magnetic north rotated to East, West or South). Newts tested during January-March exhibited weak bimodal magnetic orientation along the axis of the holding tank. However, during the spring migratory period (April until early May), the bimodal response shifted to coincide with the direction of the pond from which the newts had been collected. Much stronger unimodal orientation was elicited by elevating the water temperature to 33-34°C immediately prior to testing. If newts were held in a training tank with an artificial shoreline at one end and exposed to elevation of water temperature after several days of stable water temperatures, they exhibited unimodal shoreward orientation and did not show the seasonal switch to homing behaviour observed in the earlier tests. If, however, the elevation of water temperature followed a period of fluctuating water temperature (over a 20°C range), the newts exhibited strong unimodal orientation in the direction of the pond from which they had been collected. These results suggest that newts possess a navigational system that enables them to home from distances in excess of 20 km. Moreover, these experiments provide the first opportunity to examine the sensory basis of navigational ability in any animal under controlled laboratory conditions.