bluuebunny/crossref_metadata_2025_split huggingface dataset:
The aerodynamic effects of wing rotation and a revised quasi-steady model of flapping flight
Authors: Sane Sanjay P. , Dickinson Michael H. 
Published: April 2021

SUMMARY
We used a dynamically scaled model insect to measure the rotational forces produced by a flapping insect wing. A steadily translating wing was rotated at a range of constant angular velocities, and the resulting aerodynamic forces were measured using a sensor attached to the base of the wing. These instantaneous forces were compared with quasi-steady estimates based on translational force coefficients. Because translational and rotational velocities were constant, the wing inertia was negligible, and any difference between measured forces and estimates based on translational force coefficients could be attributed to the aerodynamic effects of wing rotation. By factoring out the geometry and kinematics of the wings from the rotational forces, we determined rotational force coefficients for a range of angular velocities and different axes of rotation. The measured coefficients were compared with a mathematical model developed for two-dimensional motions in inviscid fluids, which we adapted to the three-dimensional case using blade element theory. As predicted by theory, the rotational coefficient varied linearly with the position of the rotational axis for all angular velocities measured. The coefficient also, however, varied with angular velocity, in contrast to theoretical predictions. Using the measured rotational coefficients, we modified a standard quasi-steady model of insect flight to include rotational forces, translational forces and the added mass inertia. The revised model predicts the time course of force generation for several different patterns of flapping kinematics more accurately than a model based solely on translational force coefficients. By subtracting the improved quasi-steady estimates from the measured forces, we isolated the aerodynamic forces due to wake capture.
Changes in metabolic rate and N excretion in the marine invertebrateSipunculus nudusunder conditions of environmental hypercapnia
Authors: Langenbuch M. , Pörtner H. O. 
Published: April 2021

SUMMARYIncreased CO2 partial pressures (hypercapnia) as well as hypoxia are natural features of marine environments like the intertidal zone. Nevertheless little is known about the specific effects of CO2 on metabolism, except for the well-described effects on acid—base variables and regulation. Accordingly, the sediment-dwelling worm Sipunculus nudus was used as an experimental model to investigate the correlation of acid—base-induced metabolic depression and protein/amino acid catabolism, by determining the rates of oxygen consumption, ammonia excretion and O/N ratios in non-perfused preparations of body wall musculature at various levels of extra- and intracellular pH, PCO2 and [HCO3-]. A decrease in extracellular pH from control level (7.9) to 6.7 caused a reduction in aerobic metabolic rate of both normocapnic and hypercapnic tissues by 40-45 %. O/N ratios of 4.0-4.5 under control conditions indicate that amino acid catabolism meets the largest fraction of aerobic energy demand. A significant 10-15 % drop in ammonia excretion, a simultaneous reduction of O/N ratios and a transient accumulation of intracellular bicarbonate during transition to extreme acidosis suggest a reduction in net amino acid catabolism and a shift in the selection of amino acids used,favouring monoamino dicarboxylic acids and their amines (asparagine,glutamine, aspartic and glutamic acids). A drop in intracellular pH was identified as mediating this effect. In conclusion, the present data provide evidence for a regulatory role of intracellular pH in the selection of amino acids used by catabolism.
Regulation of the respiratory central pattern generator by chloride-dependent inhibition during development in the bullfrog (Rana catesbeiana)
Authors: Broch Lise , Morales Rey D. , Sandoval Anthony V. , Hedrick Michael S. 
Published: April 2021

SUMMARYIsolated brainstem preparations from larval (tadpole) and adult Rana catesbeiana were used to examine inhibitory mechanisms for developmental regulation of the respiratory central pattern generator (CPG). Preparations were superfused at 20-22 °C with Cl--free artificial cerebrospinal fluid (aCSF) or with aCSF containing agonists/antagonists ofγ-aminobutyric acid (GABA) or glycine receptors. Respiratory motor output from the CPG, measured as neural activity from cranial nerve roots, was associated with fictive gill ventilation and lung ventilation in tadpoles and with fictive lung ventilation in adults. In tadpoles, fictive lung burst frequency was 0.8±0.2 min-1 and did not change significantly with Cl--free aCSF superfusion; however, lung burst amplitude increased by nearly 400 % (P&lt;0.01). Fictive gill ventilation averaged 41.6±3.3 min-1 and was reversibly abolished by Cl--free aCSF. Superfusion with Cl--free aCSF abolished lung bursts in two of seven adult preparations, and overall lung burst frequency decreased from 3.1±0.7 to 0.4±0.03 min-1(P&lt;0.01), but burst amplitude was unchanged. Low concentrations of GABA (0.5 mmol l-1) produced a significant increase in lung burst frequency followed by almost complete inhibition at 5.0 mmol l-1,accompanied by the abolition of gill ventilation at 2.5-5.0 mmol l-1. By contrast, fictive lung ventilation in adults was inhibited in a dose-dependent manner by glycine and GABA, and inhibition occurred at approximately 10-fold lower concentrations compared with tadpoles. The glycine receptor antagonist strychnine (2.5-25.0 μmol l-1) and the GABAA receptor antagonist bicuculline (1-10 μmol l-1)inhibited fictive gill ventilation and increased fictive lung ventilation in tadpoles. However, bicuculline and strychnine inhibited fictive lung ventilation in adults. These results suggest that lung ventilation in the tadpole brainstem may be driven by a pacemaker-like mechanism since Cl--free aCSF failed to abolish lung ventilation. Lung ventilation in adults and gill ventilation in tadpoles, however, appear to be dependent upon conventional Cl--mediated synaptic inhibition. Thus, there may be a developmental change in the fundamental process driving lung ventilation in amphibians. We hypothesize that maturation of the bullfrog respiratory CPG reflects developmental changes in glycinergic and/or GABAergic synaptic inhibitory mechanisms.
The mechanical basis ofDrosophilaaudition
Authors: Göpfert Martin C. , Robert Daniel 
Published: April 2021

SUMMARYIn Drosophila melanogaster, antennal hearing organs mediate the detection of conspecific songs. Combining laser Doppler vibrometry, acoustic near-field measurements and anatomical analysis, we have investigated the first steps in Drosophila audition, i.e. the conversion of acoustic energy into mechanical vibrations and the subsequent transmission of vibrations to the auditory receptors in the base of the antenna. Examination of the mechanical responses of the antennal structures established that the distal antennal parts (the funiculus and the arista) together constitute a mechanical entity, the sound receiver. Unconventionally, this receiver is asymmetric, resulting in an unusual, rotatory pattern of vibration; in the presence of sound, the arista and the funiculus together rotate about the longitudinal axis of the latter. According to the mechanical response characteristics, the antennal receiver represents a moderately damped simple harmonic oscillator. The receiver's resonance frequency increases continuously with the stimulus intensity, demonstrating the presence of a non-linear stiffness that may be introduced by the auditory sense organ. This surprising,non-linear effect is relevant for close-range acoustic communication in Drosophila; by improving antennal sensitivity at low song intensities and reducing sensitivity when intensity is high, it brings about dynamic range compression in the fly's auditory system.
Urine makes the difference
Authors: Breithaupt Thomas , Eger Petra 
Published: April 2021

SUMMARYChemical communication is a widespread phenomenon in aquatic animals but is difficult to investigate because the signals are not visible. Here, we present the results of a study into chemical communication in blindfolded fighting crayfish (Astacus leptodactylus) in which we employed a new method:visualisation of urine using the dye Fluorescein. The probability of urine release is greater during fights than during non-social activities or inactivity. The eventual winners are more likely to release urine during fights than the eventual losers. In both winners and losers, urine release is coupled to offensive behaviours, and the probability of urine release increases with increasing levels of aggression. In A. leptodactylus,urine is carried to the opponent by the forward-projecting gill currents. During spontaneous release, urine is fanned laterally with the aid of the exopodites of the maxillipeds. Aggressive behaviour is effective in intimidating blindfolded opponents only in conjunction with urine release:receivers decrease offensive behaviour and increase defensive behaviour. Aggressive behaviour alone does not intimidate opponents. The loser of a recent fight is deterred equally well by a familiar and an unfamiliar opponent. Hence, in crayfish, individual recognition of the urine scent of a dominant individual does not appear to be significant for the maintenance of dominance hierarchies. Our results suggest that urine contains information about the fighting ability and/or aggressiveness of the signaller. The chemical signals thus far unidentified appear to be important in determining the outcome of a fight.
Energetics of median and paired fin swimming, body and caudal fin swimming, and gait transition in parrotfish (Scarus schlegeli) and triggerfish (Rhinecanthus aculeatus)
Authors: Korsmeyer Keith E. , Steffensen John Fleng , Herskin Jannik 
Published: April 2021

SUMMARYTo determine the energetic costs of rigid-body, median or paired-fin (MPF)swimming versus undulatory, body-caudal fin (BCF) swimming, we measured oxygen consumption as a function of swimming speed in two MPF swimming specialists, Schlegel's parrotfish and Picasso triggerfish. The parrotfish swam exclusively with the pectoral fins at prolonged swimming speeds up to 3.2 total lengths per second (L s-1; 30 min critical swimming speed, Ucrit). At higher speeds, gait transferred to a burst-and-coast BCF swimming mode that resulted in rapid fatigue. The triggerfish swam using undulations of the soft dorsal and anal fins up to 1.5 L s-1, beyond which BCF undulations were recruited intermittently. BCF swimming was used continuously above 3.5 L s-1, and was accompanied by synchronous undulations of the dorsal and anal fins. The triggerfish were capable of high, prolonged swimming speeds of up to 4.1 L s-1 (30 min Ucrit). In both species, the rates of increase in oxygen consumption with swimming speed were higher during BCF swimming than during rigid-body MPF swimming. Our results indicate that, for these species,undulatory swimming is energetically more costly than rigid-body swimming, and therefore support the hypothesis that MPF swimming is more efficient. In addition, use of the BCF gait at higher swimming speed increased the cost of transport in both species beyond that predicted for MPF swimming at the same speeds. This suggests that, unlike for terrestrial locomotion, gait transition in fishes does not occur to reduce energetic costs, but to increase recruitable muscle mass and propulsive surfaces. The appropriate use of the power and exponential functions to model swimming energetics is also discussed.
Redistribution of immunofluorescence of CFTR anion channel and NKCC cotransporter in chloride cells during adaptation of the killifishFundulus heteroclitusto sea water
Authors: Marshall W. S. , Lynch E. M. , Cozzi R. R. F. 
Published: April 2021

SUMMARYCellular distribution of cystic fibrosis transmembrane conductance regulator (CFTR) immunofluorescence was detected by monoclonal antibody directed to the C terminus of killifish CFTR (kfCFTR) in chloride cells of fresh water (FW) adapted fish and animals transferred to sea water (SW) for 24h, 48h and 14+ days. Confocal microscopy allowed localization within mitochondria-rich (MR) cells to be determined as superficial (i.e. in the apical membrane) or deeper within the cytoplasm of the cells. In FW, 90 % of MR cells had diffuse kfCFTR immunofluorescence in the central part of the cytosol, with only 8.1 % having apical kfCFTR, which was 6.6±0.54 μm below the microridges of surrounding pavement cells. Curiously, FW but not SW pavement cells also had positive immunofluorescence to kfCFTR. After 24h in SW, a time when kfCFTR expression is elevated, a condensed punctate immunofluorescence appeared among 18.8 % of MR cells, 13.4±0.66 μm(mean ± S.E.M.) below the surface of the cells. By 48h, a majority(76.3 %) of MR cells had punctate kfCFTR distribution and the distance from the surface was less (7.8±0.2 μm), a distribution approaching the SW-acclimated condition (i.e. all MR cells showing kfCFTR immunofluorescence,6.1±0.04 μm below the surface). In contrast, NKCC immunofluorescence was condensed and localized in lateral parts of MR cell complexes in FW animals and then redistributed to the whole basal cytoplasm after acclimation to SW. CFTR, the anion channel responsible for Cl- secretion in marine teleosts, redistributes in MR cells during SW acclimation by condensation of a diffuse distribution below the apical crypt, followed by translocation and insertion in the apical membrane. NKCC, the cotransporter that translocates Cl- across the basolateral membrane, moves from an eccentric cytosolic location in FW to a diffuse basolateral localization in SW chloride cells.
Force enhancement following stretching of skeletal muscle
Authors: Herzog W. , Leonard T. R. 
Published: April 2021

SUMMARYWe investigated force enhancement following stretching in the in situ cat soleus muscle on the ascending and descending limb of the force-length relationship by varying the amount and speed of stretching and the frequency of activation (5 Hz, 30 Hz). There was a small but consistent(P&lt;0.05) amount of force enhancement following muscle stretching on the ascending limb of the force—length relationship for both stimulation frequencies. The steady-state active isometric forces following stretches of 9 mm on the descending limb of the force—length relationship were always equal to or greater than the corresponding forces from the purely isometric contractions at the length at which the stretch was started. Therefore, force production for these trials showed positive stiffness and was associated with stable behavior. Following active stretching of cat soleus on the descending limb of the force—length relationship,the passive forces at the end of the test were significantly greater than the corresponding passive forces for purely isometric contractions, or the passive forces following stretching of the passive muscle. This passive force enhancement following active stretching increased with increasing magnitude of stretch, was not associated with structural damage, and only disappeared once the muscle was shortened. For stretches of 6 mm and 9 mm, the passive force enhancement accounted for more than 50 % of the total force enhancement,reaching a peak contribution of 83.7 % for the stretches of 9 mm at a speed of 3 mm s-1. The results of this study suggest that a passive structural element provides a great part of the force enhancement on the descending limb of the force—length relationship of the cat soleus. Furthermore, the results indicate that mechanisms other than sarcomere length non-uniformity alone are operative.
Peripheral Nerve and Regeneration in Crustacea
Authors: Needham A. E. 
Published: April 2021

ABSTRACT
There is now good evidence that in the Vertebrata peripheral nerves exert an important trophic effect on the regeneration of the structures which they innervate (Millot, 1931; Needham, J. 1942; Hamburger, 1944). In invertebrates the nervous system is not always necessary; Millot (1931, p. 117) concluded that in types where regenerative powers are comparatively limited (e.g. Mollusca, some Nemer-tinea), the nervous system is necessary, while in types with extensive regenerative powers (Tunicata, many Platyhelmia) it may be unnecessary. Some of the Crustacea are outstanding among the higher invertebrates for their extensive regenerative powers, and from the evidence available in 1927 (Korschelt, 1927, pp. 600–1) it seemed probable that in this group regeneration does not depend on the nerve supply. Subsequent publications have not materially affected this conclusion. In the present experiments evidence on the question is. sought from the regeneration of a pair of thoracic limbs in Asellus aquaticus (L.).
The Oxygen Affinities of Certain Invertebrate Haemoglobins
Authors: Fox H. Munro 
Published: April 2021

ABSTRACT
For a variety of physiological and ecological reasons it is of importance to know the oxygen pressures at which the haemoglobins of different animals take up or part with oxygen. In the relatively few cases in which this has been studied in small animals, particularly invertebrates, the blood, since it is only available for investigation in very small amounts, has generally been considerably diluted with water. But the position of the oxygen dissociation curve of dilute haemoglobin is not necessarily the same as that in whole blood: the oxygen affinity may increase with dilution (Florkin et al., 1941). To survey the oxygen affinities of various invertebrate haemoglobins I therefore devised a method of working with one or two drops of whole, or very slightly diluted, blood. The method is as follows.
The Nutrition of the Larva of Aedes Aegypti L. I
Authors: Meillon B. De , Golberg L. , Lavoipierre M. 
Published: April 2021

ABSTRACT
Insects, because of their great diversity of form and habit, offer a very wide field for physiological research. Apart from the purely academic aspect it is obvious that there is much more hope of controlling harmful insects or encouraging beneficial ones if their life processes are more thoroughly understood. There is also the possibility that some of these life processes are similar or related to those of the vertebrates including man himself, in which case insects may yield interesting and valuable information of more direct importance. In fact, when more is known about them there appears to be no reason why some should not come into use as laboratory animals. A start in this direction has already been made since the larva of the wax moth Galleria mellonella has been used for the estimation of nicotinic acid (Rubinstein & Shekun, 1939).
The Nutrition of the Larva of Aedes Aegypti L. II. Essential Water-Soluble Factorb From Yeast
Authors: Golberg L. , Meillon B. De , Lavoipierre M. 
Published: April 2021

ABSTRACT
The study of the nutritional requirements of mosquito larvae has made comparatively little progress since Trager (1935) reported that they could be brought to maturity in a sterile medium consisting only of autoclaved yeast and liver extract. Subsequently a number of random observations were reported, dealing with the factors necessary for growth and metamorphosis of mosquito larvae. No concerted effort, however, has been made to replace the yeast-liver extract medium of Trager by a mixture of known components. This is the immediate object of our investigations, and the results presented below serve to bring it yet another stage nearer realization.
The Mechanism of Absorption from the Rumen as Exemplified by the Behaviour of Acetic, Propionic and Butyric Acids
Authors: Danielli J. F. , Hitchcock M. W. S. , Marshall R. A. , Phillipson A. T. 
Published: April 2021

ABSTRACT
The following conclusions were reached by placing a solution of sodium acetate, propionate and butyrate in the rumen of sheep and studying the rate at which these substances are absorbed :
When the rumen contents are at pH 7·5, fatty acid anion only is absorbed, i.e. no free fatty acid is absorbed, and the anion is accompanied by a roughly equivalent amount of sodium. The anion is absorbed by passage through water-filled pores, the diameter of which is large compared with butyric acid. These pores probably lie in the intercellular cement of the rumen epithelium. When the rumen contents are at pH 5·8, free acid is lost from the rumen in large amounts in addition to the loss of fatty acid anion. Part of this free acid is absorbed by passage through water-filled pores, but the greater part of it passes through the lipoid membranes of the epithelial cells. In consequence of the difference in the two mechanisms, at alkaline pH the substances are lost in the order acetate &gt; propionate &gt; butyrate, whereas at acid pH the order is butyrate &gt; propionate &gt; acetate. All the substances studied (fatty acid anions, sodium and water) move from regions of higher to regions of lower concentration. The total fatty acid absorbed from the rumen of a sheep on pasture grass may readily be twice that absorbed from the rumen by the same sheep on hay. The permeability of the rumen epithelium is such that the pH of the ingesta tends to move towards neutrality, independently of the neutralizing action of the saliva.
The Growth of Brown Trout (Salmo Trutta Linn.)
Authors: Brown Margaret E. 
Published: April 2021

ABSTRACT
Groups of trout fry of the same parentage were grown in environments where the following factors were controlled : temperature, amount and intensity of illumination, rate of water flow, aeration and chemical composition of the water, amount of living space and quality of food supply. They were allowed to eat as much as they would, and individual weights were recorded during the first 8 months after the beginning of feeding. There was soon an increase in the range of individual weight in each group of fry, and thereafter the larger fry grew faster than smaller ones. When the larger fry were removed, the smaller ones grew at an increased specific rate, and when larger fry were added, the smaller ones grew more slowly. It is suggested that a ‘size hierarchy’ was established within each group, and an individual’s specific growth rate depended on its position in the order of decreasing weight. There was an optimum degree of crowding for maximum productivity. Compared with the fry in this group, the specific growth rates of individuals in larger, more crowded groups depended on the number of fish of larger size, while in smaller, less crowded groups, individuals grew at rates depending on the proportion of fish which were larger and smaller. Alevin weight had little effect on the specific growth rates of fry. There were differences between the growth histories of fry derived from alevins of the same weight and descended from the same father but different mothers (all of the same stock, age and size). The specific growth rates decreased as the fry grew older, but there was no correlation between body weight and specific growth rate, except for the size hierarchy effect within each group. This effect had a greater influence on the size of individual fry than had either alevin weight or heredity.