bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lateral-Line Input and Stimulus Localization in the African Clawed Toad Xenopus Sp.
Authors: Görner Peter , Moller Peter , Weber Wolfgang 
Published: April 2021

ABSTRACT
Intact Xenopus sp. responded to a train of surface waves with a single, stimulus-directed motor response which consisted of a turning component and a displacement component. The turning angle increased in a linear fashion with the stimulus angle. The magnitude of the turning angle was not affected by (a) the size of the animal, (b) the way the surface wave was elicited (with a drop of water or by dipping a rod into the water), (c) reflected waves and (d) the number of successively administered stimuli. With no lateral-line organs left intact Xenopus could still localize the origin of a surface wave, but with reduced accuracy. With only two stitches left intact on the left and on the right occipital lines, the turning angles were more widely scattered for stimuli placed at angles larger than 90°. The scatter was even larger than that of the equivalent responses from animals without a functional lateral-line system, i.e. the directional responsiveness in the partly lesioned animals was less accurate than in those with their entire lateral-line inoperative. Xenopus with four or two ipsilateral occipital stitches left intact were no longer able to orientate accurately. When the animal was stimulated on the lesioned side it frequently turned to the wrong side. These errors were absent or less frequent when the animal was stimulated on the intact side. The lesion experiments indicated that (a) a few organs provide sufficient information for an appropriate turning response, but the turnings were only roughly directed towards the stimulus, and (b) the decision whether Xenopus localizes a stimulus on the left or right side depends on whether the central nervous system receives information from one or both sides.
α-Aminoisobutyric Acid Transport In The Midgut Of Two Lepidopteran Larvae
Authors: Sacchi V. F. , Hanozet G. M. , Giordana B. 
Published: April 2021

ABSTRACT
A net absorption of a-aminoisobutyric acid (AIB) takes place in vitro in the midgut of two lepidopteran larvae, Philosamia cynthia Drury and Bombyx mori L. In P. cynthia the midgut epithelium accumulates AIB from the lumen, while in the same conditions AIB accumulation is not observed in B. mori midgut cells. In P. cynthia, when the lumen is bathed with a low K solution, the net absorption of AIB is reduced and the intracellular accumulation from the lumen is abolished. Brush border membrane vesicles, prepared from the midgut of both species, show a transient K-dependent concentrative uptake of AIB. The relationship between AIB uptake and AIB concentration in the presence of a transmembrane K gradient was studied inB. mori vesicles and the kinetic constants were calculated. These results confirm that there is a K-amino acid co-transport system on the brush border of columnar cells in the midgut of both larvae.
A Sensory System Initiating Swimming Activity in the Medicinal Leech
Authors: Brodfuehrer Peter D. , Friesen W. Otto 
Published: April 2021

ABSTRACT
Water-wave stimulation, which was previously shown to elicit swimming in intact leeches, can initiate swimming in a semi-intact leech preparation via activation of the sensillar movement receptors (SMRs), provided that 50 μ-serotonin is added to the physiological saline. The neuronal responses resulting from near-field stimulation of the leech body wall with a vibrating probe were recorded in peripheral nerves and in nerve-cord connectives. The response in the dorsal posterior nerve to a single vibratory pulse consists of a graded compound action potential. The units contributing to this action potential have a much lower threshold for near-field stimulation than do touch cells. They appear to be the same sensory units, the SMRs, that mediate leech sensitivity to water waves. The frequency domain of the SMR sensitivity extends as low as 1 Hz. Thus, leeches could receive self-stimulation from the water vibrations created by their own swimming movements. Leech physiological saline containing 20–40 m-Mg2 does not eliminate the SMR response to near-field stimulation recorded in the DP nerve; however, elevated Mg2 concentrations do eliminate the neuronal responses in the nerve cord connectives. Thus, while no chemical synapse occurs between the peripherally situated SMRs and nerve cord ganglia, a synapse may be interposed between the SMRs and the intersegmental neurones activated by near-field stimulation. The swim-facilitating action of serotonin occurs at unidentified sites within the ventral nerve cord, since serotonin does not alter the sensitivity of the SMRs.
Changes in Activity and Ventilation in Response to Hypoxia in Unrestrained, Unoperated Dogfish (Scyliorhinus Canicula L.)
Authors: Metcalfe J. D. , Butler P. J. 
Published: April 2021

ABSTRACT
Daily activity cycles, together with changes in activity and ventilation frequency in response to hypoxia ( about 8 kPa), have been measured in unrestrained, unoperated dogfish. Continuous recording of activity over 48 h reveals that dogfish are essentially nocturnal, being three to four times more active at night than during the day. In relatively inactive, diurnal dogfish, rapid reduction of environmental does not cause any significant increase in swimming activity, whereas prolonged hypoxia actually appears to suppress activity. In more active, nocturnal dogfish, rapid reduction of environmental causes an immediate reduction in activity which remains suppressed throughout the hypoxic period. It is concluded therefore that increases in circulating catecholamines in response to hypoxia are the result of hypoxia alone, rather than of any increase in locomotory activity.
In resting diurnal dogfish, ventilation frequency is lower than has previously been reported for this species and, contrary to previous reports, increases markedly by 49% in response to hypoxia. It appears that in previous studies on confined dogfish, respiratory frequency, and probably ventilation volume, may have been elevated to near maximum levels even in ‘resting’ normoxic fish. This may have profound effects on so-called resting values for oxygen transfer in this species.
Heart Rate and Aerobic Metabolism in Humboldt Penguins, Spheniscus Humboldti, During Voluntary Dives
Authors: Butler P. J. , Woakes A. J. 
Published: April 2021

ABSTRACT
Heart rate and aerobic metabolism have been recorded from three Humboldt penguins, Spheniscus humboldti, freely diving on a freshwater pond (9 × 4·6 × 2·7 m deep), using an implanted radiotransmitter and an open circuit respirometer. Oxygen uptake at mean dive duration (46·2 s) was 26 % greater than the resting value, but the difference was not statistically significant. Heart rate was also similar to the resting value. It is concluded that voluntary dives of penguins are completely aerobic and that oxygen stores are sufficient to allow metabolism to continue at the rate estimated in the present study for 2·27 min during voluntary submersion. This is longer than that calculated for tufted ducks, probably because the penguins are more efficient at underwater locomotion and because they are almost neutrally buoyant.
A Comparison of Neuronal and Behavioural Thresholds in the Displacement-Sensitive Pathway of the Crayfish Procambarus
Authors: Ebina Yoshio , Wiese Konrad 
Published: April 2021

ABSTRACT
Velocity thresholds of neurones in the displacement-sensitive pathway of the crayfish were investigated using a stimulus programme of ramp fluid movements, with a range of velocities from 0·01–55 cm s−1 at the source (in both forward and backward directions). The velocity of the stimulus was calculated to produce particle movements with velocities of between 0·001–1·0 cms−1 at the receptors of the telson. The distribution of threshold values for afferents in the fourth root of the sixth abdominal ganglion and interneurones of abdominal 4–5 connectives was plotted. Thresholds were similar for afferents and interneurones, differing in absolute value from 0·001–1·0 cm s−1. Although neurones had threshold values throughout this range, there were peaks in the distributions. For the sample of 143 interneurones these were at 0·002–0·004, 0·01–0·08, 0·1–0·4 cm s−1. In the sample of 43 afferents the middle peak fell at 0·02–0·06 cm s−1, but the other two were the same as those for the interneurones. The threshold for a behaviour pattern which makes crayfish turn to face the water current was around 0·1 cm s−1 continuous fluid speed. Escape behaviour elicited by pure displacement stimuli was observed in our experiments only in animals of 2–3 cm body length which responded to displacement amplitudes of 28 mm s−1 and 6·7 cm s−1 maximum particle velocity. Strongly phasic interneurones in the pathway obviously contribute significantly in triggering escape and need high acceleration transients to become fully active.
A Method for the Neurophysiological Study of Reflexes Elicited by Natural Statocyst Stimulation in Lobsters
Authors: Miyan Jaleel Ahmad 
Published: April 2021

ABSTRACT
In the neurophysiological investigation of crustacean statocyst function, the requirement to administer a physiological stimulus is not easy to reconcile with the need to maintain a stable preparation for microelectrode recordings. In studies of sensory activity this dilemma has been overcome by using an isolated statocyst preparation with its associated sensory nerve (Cohen, 1955). In many cases where such preparations have been used, stimulation has nevertheless been by artificial means: irrigation of the statocyst sac (Sandeman & Okajima, 1972; Silvey & Sandeman, 1976), magnetic attraction of an artificial iron lith (Ozeki, Takahata & Hisada, 1978) or displacement of individual hairs with a needle (Cohen, 1960; Takahata & Hisada, 1979; Takahata, 1981). For studying reflex activity, it has proved possible to record with needle electrodes from large statocyst interneurones in dissected crabs mounted on pivoted platforms (Fraser, 1974, 1977; Fraser & Sandeman, 1975).
The Extent Of Short-Term And Long-Term Compensation To Temperature Shown By Frog And Toad Sartorius Muscle
Authors: Renaud J. M. , Stevens E. D. 
Published: April 2021

ABSTRACT
The effect of pH at different temperatures was studied on the force velocity characteristics of the sartorius muscle to estimate short-term compensation to temperature. The effect of thermal acclimation was also studied in order to estimate long-term compensation. A decrease in either pH or temperature reduced both tetanic tension and shortening velocity. There was a significant pH-temperature interaction for tetanic tension and for maximum mechanical power, but not for Vmax It is shown that this pH-temperature interaction was large enough to provide a mechanism for short term compensation only for the maximum strength (tetanic tension) in both species. Shortening velocities at small loads of the sartorius muscle of frogs and toads acclimated to 25 C were faster than those acclimated to 5 C. The difference between the two acclimation groups increased with test temperature and was almost 1 muscle length per second (m.l. s−1) at 25 C for both species. Acclimation temperature had no significant effect on tetanic tension or on maximum mechanical power at any of the test temperatures. It is proposed that the small capacity for long-term compensation in frog and toad sartorius muscles is related to the strategy employed during winter: frogs and toads hibernate.
Bluefin Tuna Warm Their Viscera During Digestion
Authors: Carey Francis G. , Kanwisher John W. , Stevens E. Don 
Published: April 2021

ABSTRACT
Acoustic telemetry showed that stomach temperature from large bluefin tuna, Thunnus thynnus, held in an impoundment, changes markedly during feeding. The stomach cools rapidly on ingesting cold food. It then warms to a maximum of 10–15 °C above water temperature over a period of 12–20 h. Temperature decreases slowly over the next 20–30 h to a final state where it remains 3–6 °C above water temperature. The viscera are thermally isolated. Conductive heat losses are reduced by an overlying gas bladder and by the thick fatty muscle of the body wall. Convective heat losses are prevented by heat exchangers in the circulation. The temperature rise can be accounted for by heat released in the hydrolytic processes of digestion and by an increase in metabolic rate. The elevated temperatures should speed digestion and allow the tuna to feed frequently when food is abundant.
Fiddler Crab Exercise: the Energetic Cost of Running Sideways
Authors: Full Robert J. , Herreid Clyde F. 
Published: April 2021

ABSTRACT
The fiddler crab, Uca pugilator, used sideways octapedal locomotion during 15 min of treadmill exercise. At each velocity tested (0·06, 0·11 and 0·16 km h−1), oxygen consumption showed only a modest, sluggish elevation; a ‘steady-state’ was never attained. The highest recorded, 0·22 ml O2g−1 h−1, was 4·4 times the resting rate. Net whole body lactate (WBL) was found to increase at a constant rate throughout the exercise period.
During recovery, and WBL removal followed a similar time course and returned to pre-exercise rates in 30–45 min. Although the fate of lactate after exercise is unknown for crustaceans, calculations suggest that not enough oxygen is consumed by the crab during recovery to oxidize lactate completely to CO2 and H2O. A gluconeogenic fate is compatible with the data.
As running velocity was increased, increased only slightly, while the net rate of WBL production showed a substantial elevation. At low velocity aerobic metabolism accounted for 60 % of the ATP produced when aerobic metabolism and anaerobic fermentation are considered. Anaerobic fermentation dominated at medium and high velocity and produced 60 and 70 % of the ATP, respectively.
The minimum cost of transport, the least amount of energy required to transport a given mass a distance, was determined using both aerobic and anaerobic sources. This estimation of locomotion economy for Uca pugilator was within the range predicted for a vertebrate of a similar mass.
Fast Continuous Swimming of Two Pelagic Predators, Saithe (Pollachius Virens) and Mackerel (Scomber Scombrus): a Kinematic Analysis
Authors: Videler J. J. , Hess F. 
Published: April 2021

ABSTRACT
Straight, forward, unrestrained swimming behaviour, with periodic lateral oscillations of body and tailfin, was described and compared for saithe and mackerel. A method was developed for kinematic analysis of forward motion, lateral displacements and body curvature, based on a Fourier-series approach.
The dimensionless kinematic quantities showed relatively small variations over large ranges of swimming speeds. The speed range of mackerel was twice as fast as that of saithe. The main difference in swimming style between the species was a somewhat greater tail amplitude and a correspondingly stronger curvature near the caudal peduncle in mackerel than in saithe.
The swimming style of both species yields a Froude efficiency close to the maximum value possible, given the observed amplitude increase in the posterior part.
Crayfish extraretinal photoreception. I. Behavioral and motorneuronal responses to abdominal illumination
Authors: Edwards D. H. 
Published: April 2021

ABSTRACT
Stimulation of blinded and sighted crayfish with ventrally directed light evokes a slow tail flexion response or a tail flexion accompanied by backward walking. The response latencies and durations of sighted animals are shorter than those of blinded animals, which indicates that visual inputs can speed a response which can be released by extraretinal photoreceptors alone. Recordings from electrodes implanted in intact, freely behaving animals demonstrate that ventral illumination tonically excites abdominal postural flexor motoneurones. The motoneurone discharge occurs first in caudal segments and then spreads rostrally, as does abdominal flexion around each segmental joint. Illumination of individual abdominal ganglia (A2–A5) tonically excites a similar flexor motoneurone response in cells of the stimulated ganglion and more caudal ganglia. Swimmeret motoneurones are also tonically excited by this stimulus. These responses can be evoked in isolated abdominal nerve cords, indicating that extraretinal photoreceptors present in these ganglia activate motor circuits that are local to the abdomen. Stimulation of A6 excites the caudal photoreceptor neurones, but only excites flexor motoneurones if the abdominal ventral nerve cord is connected to the rostral part of the CNS. The motoneurones respond with repeated bursts of activity that long outlast the stimulus or the initial high-frequency burst of the caudal photoreceptor neurones. These motoneurone responses are similar to those evoked by stimulation of command fibres that also evoke backward walking (Kovac, 1974a).
Chloride transport in toad skin (Bufo viridis) The effect of salt adaptation
Authors: Katz U. , Larsen E. H. 
Published: April 2021

ABSTRACT
The steady-state Cl− current across the skin of Bufo viridis adapted to tap water was found to be rectified. In skins bathed with NaCl Ringer on both sides, a large outward current, carried by influx of Cl−, was observed at a clamping voltage (V) of &lt; − 50mV (outside of the skin negative). For V = −50 mV the transepithelial Cl− conductance calculated from isotope flux measurements was 2·5 ± 0·3 mS cm−2, N= 10. When the skin was clamped at +50 mV the net flux of Cl− was reversed, but Cl− conductance was only 0·3 ± 0·1 mS cm−2. Flux ratio analysis indicated that the potential-activated Cl− conductance carries Cl− ions by way of passive transport. With NaCl Ringer bathing the outer surface of the skin the spontaneous potential was about −30 mV. At this potential the Cl− conductance of the skin was about half of its maximum value. The time course of Cl− current activation following a fast, stepwise change of V from 50 mV to a potential below 0 mV showed an initial delay of a few seconds, and proceeded with a halftime (T1/2) which varied as a bellshaped function of V. The maximum T1/2 was about 100 s for V = −10 mV in skins exposed to KCL Ringer on the outside. Following adaptation of the toads to a 250 mm-NaCl solution, the fully activated Cl− conductance of the skin was greatly reduced, and the conductance-voltage curve was shifted to the left along the voltage-axis. With NaCl Ringer on the outside the spontaneous potential was about −20 mV, and Cl− conductance activation was possible only outside the physiological range of potentials. The time constant of Cl− conductance activation from closed to fully activated state was more than doubled following salt adaptation of the toads. The active inward Cl− flux disappeared in skins of toads adapted to a 250 mm-NaCl solution, and apparent leakage conductance was reduced. Application of the phosphodiesterase inhibitor 3-isobutyl-l-methylxanthine to skin of fully salt-adapted toads increased the transepithelial Cl− conductance, and the time courses of voltage clamp currents became more like those of water-adapted toads. Apparent leakage conductance was increased. Salt adaptation of B. viridis was followed by a statistically significant reduction in the number of mitochondria-rich cells relative to the number of granulosum cells of the replacement layer, from a ratio of 0·50 to 0·25. The volume of the mitochondria-rich cells was reduced following salt adaptation of the toads.
The Electrical Properties of Isolated Frog Skin
Authors: Francis W. L. 
Published: April 2021

ABSTRACT
The relation of the electrical potential across isolated frog skin in Ringer to oxygen concentration and oxygen pressure has been experimentally investigated. The dependence of the respiration of isolated frog skin in Ringer on oxygen concentration has also been determined. The potential and respiration depend in the same way on the oxygen concentration. The potential is diminished by inhibitors of respiratory processes.
The rôle of oxygen consumption in maintaining the skin potential is discussed.
Histological Changes in the Ovaries and Ovarian Blood Vessels of Xenopus Laevis Associated With Hypophysectomy, Captivity and the Normal Reproductive Cycle
Authors: Shapiro B. G. , Shapiro H. A. 
Published: April 2021

ABSTRACT
Seasonal changes in the ovaries of Xenopus laevis (the South African clawed toad) are described. Degenerative changes in the large mature central ova occur more rapidly as a result of hypophysectomy than as a result of captivity. The suggestion is made that the pituitary may be concerned with the maturation of ova in Xenopus laevis. Hypophysectomy results in severe arteriosclerotic changes in the ovarian blood supply as early as 412 months after the operation. Control animals show no such changes. The histological changes observed in the ovaries after hypophysectomy, whether total or partial, are probably due to the removal of the anterior lobe alone.
The Physiology of Contractile Vacuoles
Authors: Kitching J. A. 
Published: April 2021

ABSTRACT
The rate of output of fluid from the contractile vacuole of a fresh-water Peritrich Cihate was decreased to a new steady value immediately the organism was placed in a mixture of tap water and sea water. The rate of output returned to its original value immediately the organism was replaced in tap water. The contractile vacuole was stopped when the organism was treated with a mixture containing more than 12 per cent, of sea water. Transference of various species of marine Peritricha from 100 per cent, sea water to mixtures of sea water and tap water led to an immediate increase of the body volume to a new and generally steady value. Return of the organism to 100 per cent, sea water led to an immediate decrease of the body volume to its original value or less. Marine Peritricha showed little change in rate of output when treated with concentrations of sea water between 100 and 75 per cent. In more dilute mixtures the rate of output was immediately increased, and then generally fell off slightly to a new steady value which was still considerably above the original (100 per cent, sea water) value. The maximum sustained increase was approximately x 80. Return of the organism to 100 per cent, sea water led to an immediate return of the rate of output to approximately its original value. When individuals of some marine species were placed in very dilute concentrations of sea water, the pellicle was frequently raised up in blisters by the formation of drops of fluid underneath it, and the contractile vacuole stopped. Evidence is brought forward to suggest that in the lower concentrations of sea water marine forms lost salts. The contractile vacuole probably acts as an osmotic controller in fresh-water Protozoa. Its function in those marine Protozoa in which it occurs remains obscure.
Effects of Body Size and Slope on Acceleration of a Lizard (Stellio Stellio)
Authors: Huey Raymond B. , Hertz Paul E. 
Published: April 2021

ABSTRACT
The agamid lizard Stellio ( = Agama) stellio L. accelerated quickly on a level track. Lizards reached 95 % of maximum speed in an average of only 0·31 m and 0·19s. Large lizards had higher initial accelerations (∼M1/3) and accelerated over longer distances and times than did small lizards. As a result, larger lizards achieved higher maximum speeds. Lizards of a given size that accelerated quickly also achieved high maximum speeds. Acceleration was also measured on slopes ranging from −15° to +60°. Steep inclines did not differentially reduce the initial acceleration of large versus small lizards, a result which contrasts with a previous demonstration that such inclines significantly reduce the maximum speed of only large lizards. Simulations of simple predatory-prey chases suggest that large lizards will be more successful if they attack distant prey on level or downhill slopes and that small lizards will be more likely to escape larger quadrupedal predators by fleeing uphill, unless the predators are near.