bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic Rates of Freely Diving Weddell Seals: Correlations With Oxygen Stores, Swim Velocity and Diving Duration
Authors: Castellini Michael A. , Kooyman Gerald L. , Ponganis Paul J. 
Published: April 2021

ABSTRACT
The metabolic rates of freely diving Weddell seals were measured using modern methods of on-line computer analysis coupled to oxygen consumption instrumentation. Oxygen consumption values were collected during sleep, resting periods while awake and during diving periods with the seals breathing at the surface of the water in an experimental sea-ice hole in Antarctica. Oxygen consumption during diving was not elevated over resting values but was statistically about 1.5 times greater than sleeping values. The metabolic rate of diving declined with increasing dive duration, but there was no significant difference between resting rates and rates in dives lasting up to 82 min. Swimming speed, measured with a microprocessor velocity recorder, was constant in each animal. Calculations of the aerobic dive limit of these seals were made from the oxygen consumption values and demonstrated that most dives were within this theoretical limit. The results indicate that the cost of diving is remarkably low in Weddell seals relative to other diving mammals and birds.
Multiple Serotonin-Activated Currents in Isolated, Neuronal Somata from Locust Thoracic Ganglia
Authors: Bermudez Isabel , Beadle David J. , Benson Jack A. 
Published: April 2021

ABSTRACT
Three different responses were evoked by pressure micro-application of serotonin onto freshly dissociated, current- and voltage-clamped neuronal somata from the thoracic ganglia of the locust Locusta migratoria. In some neurones, an inward current, I(5HT)K, resulting from a decrease in potassium conductance, with slow kinetics and maximum activation at membrane potentials of –60 to –70 mV, was evoked by serotonin and by the 5-HT3 agonist 2-methyl serotonin. This current was completely abolished by either 10 mmol l-1 caesium or 5 mmol I-1 rubidium and partially blocked by 50mmoll-1 tetraethylammonium or 5 mmol l-1 4-aminopyridine. The response was antagonised by the 5-HT2-specific compounds, ketanserin and ritanserin. In other somata, serotonin, 2-methyl serotonin and the 5-HT3 antagonist ICS 205 930 evoked a second current, I(5HT)Na, which was due to an increase in sodium permeability and had slow kinetics similar to that of I(5HT)K. This current was inward over the membrane potential range –30 to –80 mV and increased with hyperpolarisation. The response was blocked by sodium-free saline and the 5-HT3 receptor antagonist MDL 72222. In other neurones, at membrane potentials more positive than –50 mV, serotonin pulses could activate a third current, I(5HT)X, which increased with depolarisation of the membrane potential and had comparatively fast kinetics. Activation of the current was accompanied by a decrease in membrane conductance. This response was completely blocked by 4-aminopyridine and weakly inhibited by both caesium and tetraethylammonium and is, therefore, probably a potassium current. The three currents described here differ in their pharmacology, their ionic mechanisms and their dependence on membrane potential from the serotonin-activated currents reported for vertebrates and they provide evidence for the mechanism of action of serotonin as a neurotransmitter in insects.
Recovery From Acute Haemolymph Acidosis in Unfed Locusts: I. Acid Transfer to the Alimentary Lumen is the Dominant Mechanism
Authors: Harrison Jon F. , Wong Calvin J. H. , Phillips John E. 
Published: April 2021

ABSTRACT
Organismal homeostasis requires regulation of extracellular acid-base status; however, the mechanisms by which insects regulate haemolymph pH are poorly known. We evaluated the recovery of desert locusts Schistocerca gregaria Forskål from acute acid loads, initiated by HCl injections into the haemolymph (0.5 pH unit decrease). Haemolymph pH, and [HCO3−] recovered in 8–24h, providing the first unequivocal evidence that insects regulate extracellular pH. There were no changes in the concentrations of the primary haemolymph buffer compounds (protein, inorganic phosphate) during recovery. Within 1 h, the tracheal system effectively eliminated the carbon dioxide derived from bicarbonate buffering. During the remainder of the recovery, haemolymph was similar to control values; there was no respiratory compensation for decreased haemolymph pH. Approximately 75 % of the acid equivalents removed from the haemolymph during the recovery process were transferred to the lumens of the crop and midgut. Transfer of acid equivalents to the alimentary lumen provides unfed locusts with a mechanism of haemolymph pH regulation that does not compromise intracellular acid-base status or increase ventilatory water loss.
Power Output of Two Sizes of Atlantic Salmon (Salmo Salar) at Their Maximum Sustained Swimming Speeds
Authors: Tang J. , Wardle C. S. 
Published: April 2021

ABSTRACT
The maximum sustained swimming speeds (Ums) for large (0.45 m long) and small (0.15m) Atlantic salmon were respectively 0.91 ms−1 and 0.54ms−1. Video and ciné films of fish swimming close to Ums were analysed to obtain variables required for the application of two hydrodynamic models, those of Lighthill and Yates, to determine the mean thrust and mean power output at these swimming speeds (U) close to Ums. A large fish (‘Salmon’) and a small fish (‘Smolt’) were selected for analysis. For salmon using Lighthill’s model, and , and using Yates’ model, and (U=0.87ms−1=0.96Ums). For smolt using Lighthill’s model, and , and using Yates’ model, and (U=0.37ms−1=0.69Ums). The power output for smolt swimming at 0.69Ums was corrected to that required to swim at Ums, giving (Lighthill’s model) and (Yates’ model).
At Ums it was assumed that all the red muscle was used. Two fish were selected from each size group and cross-sectioned to estimate their red muscle masses. Using a maximum mass-specific power output of 5–8 W kg−1 for slow red muscle fibres allowed us to calculate that the large and small fish have a power output capacity of 0.125–0.3 W and 0.007–0.019 W, respectively.
The power output values at Ums derived from the different approaches for the large (0.25–0.26 W) and small (0.0059–0.0074 W) salmon agree closely. Effects of scaling are discussed.
Dimensional Analysis of The Ventricle of an in Situ Perfused Trout Heart Using Echocardiography
Authors: Franklin Craig E. , Davie Peter S. 
Published: April 2021

ABSTRACT
The linear dimensions of the ventricle of an in situ perfused trout heart were measured with an ultrasound scanner. Using a pyramidal model, linear dimensions taken from real-time, two-dimensional, echotomographic images of the ventricle were used to calculate ventricular end-diastolic and end-systolic volumes and, by the difference between them, stroke volumes for various filling and output pressures. Stroke volumes calculated from the ultrasound measurements were significantly correlated with actual stroke volumes determined from cardiac output and heart rate and had a regression line slope close to one. Increases in stroke volume with greater filling pressures resulted from increased ventricular end-diastolic volume with constant end-systolic volume; end-systolic volumes were negligible. Maintenance of stroke volume with increasing output pressure was by increases in both end-diastolic and end-systolic volumes. Decreases in stroke volume with very high output pressures may result from convergence of end-systolic and end-diastolic volumes.
The Reflex Mechanism of the Insect Leg
Authors: Pringle J. W. S. 
Published: April 2021

ABSTRACT
Variations in the frequency of the motor discharges to the leg muscles of Periplaneta americana are followed in the intact animal under different types of sensory stimulation by electrical recording from the muscles. Two main reflexes are described: the depressor reflex, evoked by stimulation of the campaniform sensilla on the legs, and a levator response to touch on the upper side of the leg. There is a direct antagonism in the excitation of the depressor and levator sets of muscles: also between similar muscles in the two legs of a segment. Reflex effects are not transmitted up or down the animal to other segments. The conditions for the reflex excitation of the two types of motor fibre are discussed. A suggestion is put forward for the explanation of rhythmic movements.
Studies of Tropical Tuna Swimming Performance in a Large Water Tunnel:I. Energetics
Authors: Dewar Heidi , Graham Jeffrey B. 
Published: April 2021

ABSTRACT
The metabolic rates of three tropical tunas [yellowfin tuna (Thunnus albacares), kawakawa (Euthynnus affinis) and skipjack (Katsuwonus pelamis)] were estimated using a large water-tunnel respirometer. Experiments lasting up to 31 h were used to determine the effects of velocity (U) on tuna over a range of U (17–150 cm s−1) and temperatures (18–30°C). Replicate tests were carried out on several fish. The swimming of yellowfin is temperature-dependent (Q10=1.67, determined over intervals of 3–5°C). For yellowfin and skipjack, it was also possible to partition metabolic costs between maintenance and locomotion. The standard metabolic rate was estimated by extrapolation of the function to U=0. Comparisons of for different size groups of yellowfin show that the mass-specific scaling exponent for is −0.40. The of tuna is comparable to values determined previously by stasis respirometry and is approximately three times higher than that of salmonids. Further comparisons with salmonids show that the slope of the function is less for tunas, which demonstrate a greater swimming efficiency.
Differential Tracer Coupling Between Pairs of Identified Neurones of the Mollusc Lymnaea Stagnalis
Authors: Ewadinger N. M. , Syed N. I. , Lukowiak K. , Bulloch A. G. M. 
Published: April 2021

ABSTRACT
Electrical coupling is a common means of cell-to-cell communication in both neuronal and non-neuronal tissues (Lowenstein, 1985). Within the nervous system, many electrically coupled neurones exhibit dye coupling (Bennett, 1973; Stewart, 1978; Glantz and Kirk, 1980; Spencer and Satterlie, 1980; Fraser and Heitler, 1993); however, some electrically coupled cells do not dye-couple (Audesirk et al. 1982; Murphy et al. 1983; Berdan, 1987; Robinson et al. 1993; Veenstra et al. 1993). Electrical coupling and dye coupling, often considered in parallel, are in fact two different parameters that can vary independently (e.g. Audesirk et al. 1982; Perez-Armendariz et al. 1991). The giant identified neurones of pulmonate and opisthobranch molluscs have frequently been used for studies of neuronal communication and its plasticity (Winlow and McCrohan, 1987; Bulloch, 1989). In the present study, we explored the relationship between electrical and tracer coupling in both strongly and weakly coupled pairs of molluscan neurones. Specifically, we examined electrically coupled, identified neurones in a freshwater pond snail, Lymnaea stagnalis L., and tested for tracer coupling with Lucifer Yellow CH and biocytin. The cells examined were the strongly electrically coupled neurones, visceral dorsal 1 (VD1) and right parietal dorsal 2 (RPD2) (Boer et al. 1979; Benjamin and Pilkington, 1986), and the weakly coupled neurones, left buccal 1 (LB1) and right buccal 1 (RB1) (Benjamin and Rose, 1979). The use of these particular neurones made it possible to compare electrical coupling with tracer coupling in the molluscan central nervous system (CNS).
Studies of Tropical Tuna Swimming Performance in a Large Water Tunnel: II. Thermoregulation
Authors: Dewar Heidi , Graham Jeffrey B. , Brill Richard W. 
Published: April 2021

ABSTRACT
The body temperatures (Tb) of nine yellowfin tuna (Thunnus albacares) were monitored while fish swam in a large water tunnel at controlled velocities (U) and ambient temperatures (Ta). Monitoring Tb during step changes in Ta at constant U permitted estimation of the thermal rate coefficient (k), an index of heat transfer. In the yellowfin, k is dependent on both Ta and the direction of the thermal gradient (i.e. whether Ta is greater or less than Tb). Modulation of k in response to Ta was further demonstrated during tests in which U was varied; the elevation of Tb in response to equal increases in U was 3–4 times less at 30°C than at 25 and 20°C. These experiments demonstrate that the yellowfin tuna can modulate heat transfer. This ability could prevent overheating during intense activity, retard heat loss during a descent into cool water and permit increased heat gain upon returning to warm surface waters (i.e. when Tb&lt;Ta).
Studies of Tropical Tuna Swimming Performance in a Large Water Tunnel: III. Kinematics
Authors: Dewar Heidi , Graham Jeffrey B. 
Published: April 2021

ABSTRACT
Yellowfin tuna (Thunnus albacares) swimming kinematics was studied in a large water tunnel at controlled swimming velocities (U). Quantified kinematic variables included the tail-beat frequency, stride length (l), caudal amplitude, yaw, the propulsive wavelength, the speed of the propulsive wave (C) and the sweepback angle of the pectoral fins. In general, all variables, except the propulsive wavelength and consequently C, are comparable to values determined for other teleosts. The propulsive wavelength for the tunas (1.23–1.29 L, where L is fork length) is 30–60% longer than in other cruise-adapted teleosts such as salmonids. The resulting thunniform swimming mode and the morphological and anatomical adaptations associated with the long propulsive wavelength (e.g. fusiform body shape, rigid vertebral column) act to minimize anterior resistance and maximize caudal thrust. The long propulsive wavelength also increases the maximum l which, in concert with the elevated muscle temperatures of tunas, increases their maximum swimming velocity.
Reconstitution of Metachronal Waves in Ciliated Cortical Sheets of Paramecium: I. Wave Stabilities
Authors: Okamoto Ken-Ichi , Nakaoka Yasuo 
Published: April 2021

ABSTRACT
We reconstituted metachronal waves on ciliated cortical sheets prepared from detergent-extracted Paramecium multimicronucleatum cells. Ciliary movements of the cortical sheet, whose intracellular side adhered to a glass coverslip, were reactivated by perfusion of a basic reactivation medium containing ATP. In this condition, the ciliary field showed only unstable localised ripples. Addition of either cyclic AMP or cyclic GMP to the basic reactivation medium generated propagating metachronal waves characteristic of each nucleotide. In order to estimate the stability of the metachronal waves, autocorrelation coefficients were calculated from images of an 8 μm diameter region within the reactivated ciliary field. The decay time for the correlation coefficient to decrease to 0.5 was only 0.04 s in the basic reactivation medium, but was increased to 0.4 or 0.9 s by the addition of cyclic AMP or cyclic GMP, respectively. The decay time was dependent not only on the concentration of cyclic nucleotide but also on the wave frequency. In order to test whether cyclic-nucleotide-dependent phosphorylation affected the generation of waves, the ciliated cortical sheets were thiophosphorylated by incubation in ATP-γ-S (adenosine-5′-o-3-thiotriphosphate) medium containing either cyclic AMP or cyclic GMP. Following this, perfusion with the basic reactivation medium generated metachronal waves only after cyclic GMP treatment. The effect of cyclic GMP is probably related to phosphorylation of ciliary proteins.
Stepping Patterns in Ants: I. Influence of Speed and Curvature
Authors: Zollikofer Christoph P. E. 
Published: April 2021

ABSTRACT
The locomotory behaviour of workers of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals walking on smoked-glass plates. Subsequent multivariate analyses of footfall positions and walking kinematics revealed a set of constant features characterizing ant locomotion. The alternating tripod gait prevails over a wide range of speeds. The temporal rigidity of tripod coordination is paralleled by spatially rigid footfall patterns. Tripod geometry is preserved irrespective of speed and curvature. When walking around curves, tripods are rotated relative to the walking trajectory. Whereas stride length on the inner side of the curve is shortened, that on the outer side is independent of curvature.
Detection of Magnetic Inclination Angle by Sea Turtles: A Possible Mechanism for Determining Latitude
Authors: Lohmann Kenneth J. , Lohmann Catherine M. F. 
Published: April 2021

ABSTRACT
For animals that migrate long distances, the magnetic field of the earth provides not only a possible cue for compass orientation, but a potential source of world-wide positional information. At each location on the globe, the geomagnetic field lines intersect the earth’s surface at a specific angle of inclination. Because inclination angles vary with latitude, an animal able to distinguish between different field inclinations might, in principle, determine its approximate latitude. Such an ability, however, has never been demonstrated in any animal.
We studied the magnetic orientation behavior of hatchling loggerhead sea turtles (Caretta caretta L.) exposed to earth-strength magnetic fields of different inclinations. Hatchlings exposed to the natural field of their natal beach swam eastward, as they normally do during their offshore migration. In contrast, those subjected to an inclination angle found on the northern boundary of the North Atlantic gyre (their presumed migratory path) swam south-southwest. Hatchlings exposed to an inclination angle found near the southern boundary of the gyre swam in a northeasterly direction, and those exposed to inclination angles they do not normally encounter, or to a field inclination found well within the northern and southern extremes of the gyre, were not significantly oriented.
These results demonstrate that sea turtles can distinguish between different magnetic inclination angles and perhaps derive from them an approximation of latitude. Most sea turtles nest on coastlines that are aligned approximately north–south, so that each region of nesting beach has a unique inclination angle associated with it. We therefore hypothesize that the ability to recognize specific inclination angles may largely explain how adult sea turtles can identify their natal beaches after years at sea.
Hydrodynamic Aspects of Design and Attachment of A Back-Mounted Device in Penguins
Authors: Bannasch Rudolf , Wilson Rory P. , Culik Boris 
Published: April 2021

ABSTRACT
Wind tunnel and water tank experiments were carried out on a penguin model in order to optimise the shape and attachment of a back-mounted datalogger. Device-induced turbulence was minimised when the unit was placed in the most caudal position. Drag was further reduced by shaping the device to match the body contour. The hydrodynamic resistance of the package could be reduced by 65% compared with an earlier unit. These results are discussed together with results from new studies on kinematics and energetics of underwater swimming of live instrumented penguins.
The Flexible Fly: Experience-Dependent Development of Complex Behaviors in Drosophila Melanogaster
Authors: Hirsch Helmut V. B. , Tompkins Laurie 
Published: April 2021

ABSTRACT
We demonstrate that Drosophila melanogaster provides a rich model system for studying behavioral development. Two additions to the many well-known advantages of this species are exploited here. First, as in mammals and higher vertebrates, early experience affects behavioral development of Drosophila. Second, the affected behaviors are complex and yet readily studied in the laboratory. Thus, Drosophila can be used to study the developmental mechanisms by which organisms can optimize their behavioral repertoires to enhance their chances for survival. Evidence that early experience affects development of preferences for specific visual patterns, male courtship and female responsiveness to courting males is reviewed; in each case, experience modifies responses to behavioral targets. Our results demonstrate that developmental plasticity allows adjustment of intrinsically determined responses to visual targets so that they can take into account the actual characteristics of the developing animal’s environment. Furthermore, plasticity makes it possible to introduce ‘cultural’ and ‘social’ elements into courtship and mate choice in insects. This previously unrecognized role for developmental plasticity in insects has broad theoretical and practical implications.
Calcium transport in gill plasma membranes of the crab Carcinus Maenas: Evidence for carriers driven by ATP and A Na+ Gradient
Authors: Flik Gert , Verbost Pieter M. , Atsma Wim , Lucu Cedomil 
Published: April 2021

ABSTRACT
A procedure was developed for the preparation of inside-out vesicles from plasma membranes isolated from the branchial epithelium of the green shore crab Carcinus maenas (L.). Procedures normally applied to fish branchial epithelium required the introduction of an additional hypotonic shock to obtain a preparation containing 22% inside-out vesicles, 33% right-side-out vesicles and 45% leaky membrane fragments. In such membrane preparations, the first direct evidence for uphill (against a [Ca2+] gradient) ATP-dependent and Na+-gradient-dependent Ca2+ transport in crustacean gills was found. The affinity for Ca2+ of the ATP-driven Ca2+ transporter was 149 nmol l−1 and that of the Na+/Ca2+ exchanger was 1.78 μmol l−1; the Vmax values were 1.73 and 9.88 nmol min−1 mg−1 protein respectively. The relative importance of these carriers for Ca2+ transport in the branchial epithelium of the crab is evaluated on the basis of their calcium kinetics.