bluuebunny/crossref_metadata_2025_split huggingface dataset:
African Elephants Respond to Distant Playbacks of Low-Frequency Conspecific Calls
Authors: Langbauer William R. , Payne Katharine B. , Charif Russell A. , Rapaport Lisa , Osborn Ferrel 
Published: April 2021

ABSTRACT
We conducted 58 playback experiments with free-ranging African elephants in Etosha National Park, Namibia, to estimate the distance over which some of their low-frequency calls are audible to other elephants. We broadcast pre-recorded elephant calls to elephants that were 1.2 and 2.0 km from the speaker while making simultaneous video and audio recordings of their behavior. In order to reduce the risk of habituation, we used a variety of call types as stimuli. Elephants responded to playbacks at both 1.2 and 2.0 km, with a full response consisting of the elephant vocalizing, lifting and spreading its ears, remaining motionless in this position (‘freezing’), moving the head from side to side (‘scanning’) and, in the case of males responding to female estrous calls, orienting to and finally walking 1 km or more towards the loudspeaker.
We analyzed our data quantitatively for three of these responses. The occurrence of each behavior increased substantially immediately after playbacks.
Owing to limitations of the loudspeaker, we were only able to broadcast calls at half the sound pressure level (i.e. —6dB) of the strongest calls we have recorded. Since sound at the frequencies of these calls is predicted to suffer from little, if any, attenuation in excess of that caused by spherical spreading, we estimate these calls to be audible to elephants at least 4 km from the source (twice the distance over which we documented responses).
These results are consistent with the hypothesis that the very low-frequency calls of elephants function in communication between individuals and groups of elephants separated by distances of several kilometers.
Compensation of Visually Simulated Wind Drift in the Swarming Flight of the Desert Locust (Schistocerca Gregaria)
Authors: Preiss R. , Gewecke M. 
Published: April 2021

ABSTRACT
The visual control of translatory movements in the desert locust Schistocerca gregaria was investigated under open-loop conditions. When locusts were flown tethered in a wind tunnel, wind drift, visually simulated by ground pattern motion either in line with or transverse to their long body axis, induced a modulation of yaw-torque, thrust and lift correlated with the reversal of the direction of motion. Yaw-torque and thrust responses were independent of each other. Spon-taneous modulation of amplitude and differences in the time course of these responses indicate that a gain control mechanism is involved in the conversion of the visual stimuli to a behavioural response. Two opposing types of response were observed for each flight parameter and they were found equally often. They were elicited by either transverse or longitudinal pattern motion. The polarity of yaw-torque, thrust or lift responses was thus either positively or negatively correlated with the direction of pattern motion and was preserved throughout an experiment or reversed repeatedly. The yaw responses revealed a tendency for locusts to orient either upwind or downwind under the same stimulus situation. Modulations of thrust and lift confirm that locusts compensate for deviations of the retinal image flow from a preferred value by adjusting both air speed and altitude in free flight. They either speed up or slow down and either increase or decrease flight altitude under the same stimulus situation. The visually induced turning tendency often interacts with a variable internal turning tendency. The internal turning tendency might be responsible for the orientation menotactic to wind seen in the field. The threshold of optomotor responses in the visual control of translation is below 0.15°s-1 for both transverse and longitudinal pattern motion, indicating that wind-related orientation can occur at altitudes of several hundred metres. The orientation behaviour of locusts subjected to visually simulated wind drift depended on the transverse and longitudinal components of pattern motion and on internal factors. The observed variability of response is assumed to result from the locust’s ability to modulate independently the gain and sign of the optomotor responses for yaw-torque, thrust and lift.
Gain Control in the Femur–Tibia Feedback System of the Stick Insect
Authors: Kittmann Rolf 
Published: April 2021

ABSTRACT
This paper presents a quantitative description of the variability and the adaptive properties of information processing in the femur-tibia feedback system of the stick insect. The gain of this proprioceptive feedback system is determined by external stimuli changing the behavioural state of the animal and by internal properties that make it dependent on different parameters of the stimulus programme, e.g. stimulus frequency and amplitude, repetition rate and resting pauses.
The gain of the feedback loop in the inactive animal was investigated under open-loop conditions by applying mechanical sine-wave stimuli to the femoral chordotonal organ (fCO). The resistance movement of the tibia caused by these stimuli was measured with a new optoelectronic device.
A large increase or decrease in gain (up to a factor of 50) can be induced by stimulation, but also occurs spontaneously. The system shows habituation and sensitization. The initial gain can be decreased by repetitive sine-wave stimulation of the fCO. Disturbance of the animal (e.g. by tactile stimuli) increases the gain. The gain of the system decreases with increasing stimulus amplitude.
The described nonlinearities form a system which adjusts gain to a value that permits effective feedback and prevents instability. This was verified by closed-loop experiments.
Oxygen Consumption, Carbon Dioxide Production and Enzyme Activities of Isolated Working Octopus Heart
Authors: Agnisola C. , Driedzic W. R. , Foster A. R. , Houlihan D. F. , Stewart J. M. 
Published: April 2021

ABSTRACT
The heart of Octopus vulgaris (Lam.) presents an ideal tissue for in vitro studies. Its performance, when perfused with haemocyanin solutions or blood, closely matches that in vivo in terms of power output (Agnisola and Houlihan, 1991) and the heart tissue is self-perfused so that with each contraction a proportion of the fluid in the lumen passes through the heart wall in a system of blood vessels to produce coronary flow (Houlihan et al. 1987). Comparison of in vitro activity levels of key enzymes from energy-generating pathways (Driedzic et al. 1990) with rates of oxygen consumption of perfused hearts, working at subphysiological levels (Houlihan et al. 1987) suggested that the tissue is fuelled primarily by a glucose-based metabolism. In this experiment, the analysis is refined with the simultaneous measurement of oxygen consumption, carbon dioxide production and enzyme activity levels on the same tissues. Hexokinase activity was determined since it is a good indicator of maximal aerobic glucose use in a variety of muscles (Crabtree and Newsholme, 1972), citrate synthase and cytochrome oxidase activities were measured as markers of aerobic capacity, and 3-hydroxyacyl CoA dehydrogenase activity was assayed as a qualitative index of the capacity to oxidize fatty-acid-derived fuels.
A Motion-Sensitive Visual Descending Neurone in Apis Mellifera Monitoring Translatory Flow-Fields in the Horizontal Plane
Authors: Ibbotson M. R. 
Published: April 2021

ABSTRACT
Behavioural studies in insects have shown that simulated rotations of the visual panorama in the yaw, roll and pitch planes lead to optokinetic responses which, under natural conditions, counteract involuntary rotations of the body and thus maintain a stable visual orientation. Electrophysiological investigations have found neurones that respond selectively to rotatory motion in these planes. This evidence, in conjunction with lesioning and electrical stimulation studies, has led to the hypothesis that these rotation-sensitive neurones control optokinetic responses (for a review, see Hausen and Egelhaaf, 1989). Two other types of visually induced behaviour, landing responses and the control of forward flight speed, rely on the detection of translatory rather than rotatory visual flow-fields. For example, it has been shown that flight speed is controlled in insects by adjusting the power output of the wings such that there is a constant preferred angular velocity of image flow from front to back (progressive motion) over both eyes (Apis mellifera:Esch et al. 1975; Drosophila melanogaster:David, 1982). Similarly, landing responses can be induced in flies by moving visual images progressively over both eyes (Eckert, 1984). In spite of these behavioural data there is little evidence, except for a few preliminary reports (Baader, 1988; Rowell, 1989), of neurones that monitor translatory flow-fields, i.e. cells that are maximally sensitive to motion in the same direction over both eyes and not sensitive (or less sensitive) to rotatory motion.
N-Methyl-D-Aspartate (NMDA) and Non-Nmda Type Glutamate Receptors are Present on Squid Giant Axon Schwann Cells
Authors: Evans Peter D. , Reale Vincenzina , Merzon Rosa Maria , Villegas Jorge 
Published: April 2021

ABSTRACT
The role of the amino acid glutamate in neuronal-glial signalling is becoming increasingly recognised in both vertebrate and invertebrate nervous systems (Barres, 1989). Although the ability of glutamate to depolarize cultured astrocytes has been known for some time (Bowman and Kimelberg, 1984; Kettenmann and Schachner, 1985), there has been a debate over whether this was due to a direct activation of glutamate receptors or resulted from an electrogenic glutamate uptake mechanism (Brew and Attwell, 1987; Cull-Candy et al. 1988). However, recent evidence using patch-clamping techniques suggests the presence of ionic currents activated by glutamate receptors in cultured astrocytes (Sontheimer et al. 1988; Usowicz et al. 1989). Responses to glutamate have also been obtained from glial cells in a number of intact preparations, including the adaxonal glia of the squid giant axon (Villegas, 1978) and the glia of the optic nerve of Necturus maculosa (Tang and Orkand, 1986). The responses of the former preparation (Lieberman et al. 1989) and of the neuropile glia of the leech segmental ganglion (Ballanyi et al. 1989) have been demonstrated to be due to glutamate receptor activation. In all the above studies the glutamate receptors present on glial cells have been demonstrated pharmacologically to belong to the non-NMDA subtype. Here we present evidence, for the first time in any glial preparation, that NMDA type glutamate receptors are present in the adaxonal glial or Schwann cells of the giant axon of the tropical squid Sepioteuthis sepioidea and that they mediate a slow depolarization of these cells. In addition, these Schwann cells also possess a second distinct population of glutamate receptors that mediate rapid signalling responses and are pharmacologically similar to the non-NMDA glutamate receptors described in other glial preparations (Ballanyi et al. 1989; Lieberman et al. 1989; Sontheimer et al. 1988; Usowicz et al. 1989).
Renin, Atrial Natriuretic Peptide and Blood Plasma Ions in Parr and Smolts of Atlantic Salmon Salmo Salar L. and Rainbow Trout Oncorhynchus Mykiss (Walbaum) in Fresh Water and after Short-Term Exposure to Sea Water
Authors: Smith N. F. , Eddy F. B. , Struthers A. D. , Talbot C. 
Published: April 2021

ABSTRACT
Freshwater Atlantic salmon (Salmo salar L.) smolts were abruptly transferred to sea water in May and over 3 days blood plasma ion concentrations were determined together with atrial natriuretic peptide (ANP) and plasma renin activity (PRA) using antibodies raised against human ANP and angiotensin I. Blood plasma Na+ and Cl− levels in smolts increased and, between 24 and 72 h, PRA increased significantly to 0.9ngml−1 h−1, while there was a gradual rise in ANP levels to 10pmoll−1 at 72 h. Similar measurements were made on parr transferred to sea water in September; in these fish Na+ and Cl− levels increased as in smolts, PRA remained unchanged at about 0.6ngml−1h−1 and ANP levels increased significantly to about 20pmoll−1 at 24 and 72 h. After 2h in sea water parr showed wide variability in ANP levels, in keeping with circulatory stress, hypoxia and increased atrial stretching. Parr transferred to sea water in December showed 10w drinking rates of 1.95 ml kg−1 h−1, even after 20 days, compared to a high drinking rate of about 7 ml kg−1 h−1 reported for smolts transferred in May.
Rainbow trout acclimated to sea water for 3 weeks showed elevated levels of both ANP and PRA, similar to values reported for marine species. Freshwater rainbow trout fed a high-salt diet (12 % NaCl) showed significantly elevated levels of ANP compared to fish fed a normal diet (1.5 % NaCl), while PRA levels were depressed, though not significantly.
It is concluded that, in fish acclimating to sea water, ANP is involved in excretion of salt 10ads, while the response to dehydration is activation of the renin-angiotensin system, which is required to initiate drinking. It is suggested that, in freshwater salmonids, as is the case in mammals, ANP and the renin-angiotensin system are antagonistic, but successful acclimation to sea water requires the systems, in alternation with the renin-angiotensin system, to ‘break through’ ANP suppression.
Effect of Environmental Water Salinity on Acid–Base Regulation During Environmental Hypercapnia in the Rainbow Trout (Oncorhynchus Mykiss)
Authors: Iwama George K. , Heisler Norbert 
Published: April 2021

ABSTRACT
Acid-base regulation in rainbow trout acclimated to about 3, 100 and 300mmoll−1 Na+ and Cl−, at constant water [HCO3−], was assessed during 24h of exposure to 1% CO2 and during recovery. The respiratory acidosis induced by a rise in plasma to about 1.15kPa (8.5mmHg, 3mmoll−1), 1.33kPa (10 mmHg, 100 mmol I−1) or 1.5 kPa (11.2 mmHg, 300 mmol I−1) was partially compensated for by accumulation of plasma HCO3−. The degree of pH compensation depended on the salinity of the environmental water, being about 61,82 and 88% at 3, 100 and 300mmoll−1 Na+ and Cl−, respectively. [HCO3−] in animals acclimated to 100 and 300 mmol I−1 rose to higher values than that in fish at 3 mmol I−1.
Plasma [Cl−] decreased during hypercapnia as compared to control concentrations in all groups of fish. Plasma [Na+] rose during the first 8h of hypercapnia in fish acclimated to all three salinities, but recovered towards control values during the remainder of hypercapnia. The rise in plasma [HCO3−] was significantly related to the fall in plasma [Cl−], whereas the changes in plasma [Na+] were unaffected by simultaneous changes in plasma [HCO3−]. Time courses of changes in plasma [Na+] and total ammonia concentration, [Tamm], were similar but in opposite directions.
The transepithelial potential (TEP) of blood relative to water was negative, close to zero and positive, averaging —21, —5.8 and +6.2 mV for fish acclimated to 3, 100 and 300 mmol I−1 Na+, respectively. After initiation of hypercapnia, which caused a quite heterogeneous response among groups, a clear trend towards depolarization was observed during the remainder of hypercapnia.
These results confirm the role of active HCO3−/C1− exchange processes for the compensation of extracellular pH during respiratory acidoses in fish.
Characterization of β-Adrenoreceptors of Rainbow Trout (Oncorhynchus Mykiss) Erythrocytes
Authors: Reid Scott D. , Moon T. W. , Perry Steve F. 
Published: April 2021

ABSTRACT
Although many studies have characterized these receptors according to pharmacological criteria, this work represents only the second direct characterization of the rainbow trout β-adrenergic receptors. Radioligand binding assays using (±)-4-(3-t-butylamino-2-hydroxy-propoxy)-[5,7-3H]benzimidazol-2-one ([3H]CGP 12177) and l-[4,6-propyl 3H]dihydroalprenolol ([3H]DHA) were conducted to determine equilibrium binding times, ligand-receptor dissociation constants (KD) and binding capacities (Bmax). Furthermore, we assessed the influence of erythrocyte handling, suspension medium and endogenous catechol amines on Bmax and KD. Maximal binding was obtained when erythrocytes were handled minimally and maintained suspended in plasma rather than physiological saline. Washing and resuspending the erythrocytes, as well as the transfer of the erythrocytes into saline, significantly impaired apparent radioligand affinity and receptor density. Endogenous catecholamines, at levels considered normal for non-stressed animals, did not interfere with the radioligand binding assays, and thus eliminated the need to wash and resuspend erythrocytes. Based on the binding characteristics after intentional lysis of erythrocytes, it is shown that the total receptor population of trout erythrocytes can be estimated by propranolol-displaceable DHA binding, the density of high-affinity surface receptors can best be determined by isoproterenol-displaceable CGP binding, and the number of receptors located within the erythrocytes can be calculated from the difference between the total receptor density and the number of isoproterenol-displaceable DHA binding sites. Each of these components must be considered when performing radioreceptor assays using these radioligands and this has significant implications for the interpretation of erythrocyte β-adrenoreceptor localization and mobilization.
Circulatory Mechanics in the Toad Bufo Marinus I. Structure and Mechanical Design of the Aorta
Authors: Gibbons Carol A. , Shadwick Robert E. 
Published: April 2021

ABSTRACT
This study describes several important mechanical design features of the aorta of a typical poikilothermic vertebrate. A strong functional similarity to the aorta of mammals is apparent, but some structural and mechanical differences are seen that reflect the lower pressure and simpler haemodynamics of the poikilothermic circulation.
The aorta is highly distensible, resilient and non-linearly elastic, giving it the requisite properties to act as an effective storage element in the arterial circulation. An abrupt transition from high compliance (low elastic modulus) to relatively low compliance (high elastic modulus) takes place at pressures above the resting physiological range of 2-4 kPa. This behaviour reflects the composite nature of the artery wall in which rubbery elastin fibres and relatively rigid collagen fibres are the predominant elements. The longitudinal tethering of the aorta when inflated is due primarily to anisotropy in elastic properties, rather than to links to the axial skeleton by branch vessels or connective tissue. No significant changes in elastic properties or connective tissue content occur along the length of the toad arterial tree, in contrast to the situation in mammals.
The Auditory System of an Atympanate Bushcricket Phasmodes Ranatriformes (Westwood) (Tettigoniidae: Orthoptera)
Authors: Lakes-Harlan Reinhard , Bailey Winston J. , Schikorski Thomas 
Published: April 2021

ABSTRACT
The auditory system of the atympanate tettigoniid Phasmodes ranatriformes has been investigated using anatomical and physiological methods. The prothoracic tracheae show no specialization in terms of an acoustic spiracle, acoustic bullae or an enlargement of the trachea in the proximal tibia. Instead of a true tympanum, a depression with small cuticular protuberances is found on the proximal tibia of the foreleg. The complex tibial organ is formed from the three sensory organs usually found in tettigoniids. The crista acustica consists of about 16–18 receptor cells. Extracellular recordings from the leg nerve reveal sensitive responses to vibrational stimuli (at a threshold comparable to that found in other tettigoniids) only, and not to airborne sounds. The two possibilities either that this animal shows a secondary reduction of the auditory system or that it represents a primitive form are discussed. Developmental data from other tettigoniids seem to confirm the latter hypothesis.
Leg Design In Hexapedal Runners
Authors: Full R. J. , Blickhan R. , Ting L. H. 
Published: April 2021

ABSTRACT
Many-legged animals, such as crabs and cockroaches, utilize whole-body mechanics similar to that observed for running bipeds and trotting quadrupedal mammals. Despite the diversity in morphology, two legs in a quadrupedal mammal, three legs in an insect and four legs in a crab can function in the same way as one leg of a biped during ground contact. To explain how diverse leg designs can result in common whole-body dynamics, we used a miniature force platform to measure the ground reaction forces produced by individual legs of the cockroach Blaberus discoidalis. Hexapedal runners were not like quadrupeds with an additional set of legs. In trotting quadrupedal mammals each leg develops a similar ground reaction force pattern that sums to produce the whole-body pattern. At a constant average velocity, each leg pair of the cockroach was characterized by a unique ground reaction force pattern. The first leg decelerated the center of mass in the horizontal direction, whereas the third leg was used to accelerate the body. The second leg did both, much like legs in bipedal runners and quadrupedal trotters. Vertical force peaks for each leg were equal in magnitude. In general, peak ground reaction force vectors minimized joint moments and muscle forces by being oriented towards the coxal joints, which articulate with the body. Locomotion with a sprawled posture does not necessarily result in large moments around joints. Calculations on B. discoidalis showed that deviations from the minimum moments may be explained by considering the minimization of the summed muscle forces in more than one leg. Production of horizontal forces that account for most of the mechanical energy generated during locomotion can actually reduce total muscle force by directing the ground reaction forces through the leg joints. Whole-body dynamics common to two-, four-, six- and eight-legged runners is produced in six-legged runners by three pairs of legs that differ in orientation with respect to the body, generate unique ground reaction force patterns, but combine to function in the same way as one leg of a biped.