bluuebunny/crossref_metadata_2025_split huggingface dataset:
Luminescent Flash Avoidance in the Nocturnal Crab Portunus Xantusii : I. The Effects of Luminescence and Mechanical Stimulation on Heart Rate
Authors: Grober Matthew S. 
Published: April 2021

ABSTRACT
In crabs, the ratio of the heart rate before to that after sensory stimulation (the response ratio) provides a reliable indicator of the effects of sensory stimulation on cardiac activity. The nocturnally active crab Portunus xantusii (Stimpson) exhibits rapid decreases in heart rate in response to the luminescent flashes produced by the sea pansy Renilla kollikeri (Pfeffer) and to mechanical stimulation. Crabs move away from luminescent and mechanical stimuli and this behavior is well correlated with the cardiac responses. Therefore, cardiac response ratios can be used as a reliable bioassay to determine the components of sensory stimuli that are important in eliciting behavioral responses. The similar cardiac responses to both luminescent and mechanical stimuli suggest that a single command pathway may be responsible for triggering startle behavior in response to a wide variety of rapid, brief and intense sensory stimuli. Heart rate also varied depending on the body size of the crab and the ambient temperature. Small crabs had faster heart rates than larger crabs, and the relationship between heart rate and body size is described by the equation: f H=794 · 3X-− 0· 59222, where/H is heart rate in beats per minute and x is carapace length in millimeters. Heart rate increased with increasing temperature over a range of 10 – 22 ° C, but no further increases occurred at higher temperatures. TheQ10for the range 10 – 20 ° C was 1 · 8.
Luminescent Flash Avoidance in the Nocturnal Crab Portunus Xantusii:: II. Cardiac and Visual Responses to Variations in Simulated Luminescent Flashes
Authors: Grober Matthew S. 
Published: April 2021

ABSTRACT
Cardiac responses of Portunus xantusii (Stimpson) (Crustacea: Decapoda) to simulated luminescent flashes were similar to responses to real flashes produced by the sea pansy Renilla kollikeri (Pfeffer). Tethering the crabs did not significantly affect cardiac responses to light flashes and allowed for more control over stimulus presentation. Crabs were maximally responsive to wavelengths from 500 to 510 nm (175 nm width at half-maximum response). The wavelength of maximal sensitivity based on the electroretinogram was 510nm. The critical fusion frequency for P. xantusii was 25·6 Hz. Pulse rate and train duration of light flashes were the most important features of the stimulus for eliciting maximal cardiac responses, with pulse duration and inter-pulse interval having minor effects on flash effectiveness. Pulse rates of 4–5 Hz within a train elicited the largest cardiac responses. Increases in train duration from 1 to 5 s resulted in a linear increase in heart response, but stimuli with train durations longer than 5 s did not elicit concomitant increases in heart response. Habituation to pairs of stimulus trains occurred if inter-train intervals were less than 8–10 min. The characteristics of the luminescent signals produced by benthic invertebrates are well matched to the characteristics of light stimuli that are most effective at eliciting physiological and behavioral responses from Portunus xantusii.
Mechanics of Forward Flight in Bumblebees: II. QUASI-STEADY LIFT AND POWER REQUIREMENTS
Authors: Dudley R. , Ellington C. P. 
Published: April 2021

ABSTRACT
This paper examines the aerodynamics and power requirements of forward flight in bumblebees. Measurements were made of the steady-state lift and drag forces acting on bumblebee wings and bodies. The aerodynamic force and pitching moment balances for bumblebees previously filmed in free flight were calculated. A detailed aerodynamic analysis was used to show that quasi-steady aerodynamic mechanisms are inadequate to explain even fast forward flight. Calculations of the mechanical power requirements of forward flight show that the power required to fly is independent of airspeed over a range from hovering flight to an airspeed of 4·5ms−1.
Influence of organic phosphates on the root effect of multiple fish haemoglobins
Authors: Pelster Bernd , Weber Roy E. 
Published: April 2021

ABSTRACT
The influence of organic phosphates on the reduction in oxygen-carrying capacity at low pH (Root effect) in multiple fish haemoglobins has been analysed spectrophotometrically. In stripped haemolysates of carp, trout and eel, the Root effect in the presence of ATP was manifested below pH 7.0. In the absence of phosphates, it was only found in trout haemolysate.
In the pH range between 8.5 and 6.1 no Root effect could be induced in the cathodic component (Hbl) of either trout or eel haemoglobin, even in the presence of very high concentrations of ATP or GTP. This was also true for component II (Hbll) of trout. The anodic component (HblV) of both species, however, exhibited a strong Root effect potentiated by NTP. At the same NTP/Hb4 concentration ratio, GTP was much more effective than ATP in both species.
The involvement of different haemoglobin components in the generation of high oxygen tensions in the fish swimbladder is discussed by comparing in vivo Root effect data obtained with an eel swimbladder preparation with in vitro data measured in eel blood and haemoglobin.
Effect of temperature on cardiac vagal action in the toad Bufo marinus
Authors: Courtice G. P. 
Published: April 2021

ABSTRACT
The effect of temperature on the action of the vagus nerve on the heart was studied in the toad Bufo marinus. Experiments were performed on two groups of toads, in one the heart was perfused at a constant rate with oxygenated Ringer’s solution and in the other the circulation was left intact. In all toads there was a linear relationship between pulse interval (PI) and the frequency of vagal stimulation (fv) at any one temperature. The slope of this relationship changed with temperature, the effectiveness of the vagus (ΔPI/Δfv) increasing with decreasing temperature. At low temperatures the vagus nerves of intact toads were more effective than in those with perfused hearts. It is suggested that, in intact toads at low temperatures, cardiac output decreases and the consequent accumulation of acetylcholine leads to increased vagal effectiveness.
Effect of sprint training on swim performance and white muscle metabolism during exercise and recovery in rainbow trout (Salmo Gairdneri)
Authors: Pearson M. P. , Spriet L. L. , Stevens E. D. 
Published: April 2021

ABSTRACT
Experimental fish were sprint trained by individual chasing for 30 s on alternate days for 9 weeks. Ten trained and 10 untrained animals were rapidly freezeclamped at rest and 0,1, 3 and 6h after a 5-min chase. Swimming speed of 10 fish in each group was measured in a 2-min chase. Phosphocreatine (PCr), creatine, adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), glycogen, glucose-l-phosphate (G-l-P), glucose-6-phosphate (G-6-P), fructose-6-phosphate (Fru-6-P), glucose, glycerol-3-phosphate (Glyc-3-P), pyruvate and lactate were measured on extracts from freeze-dried white muscle. Trained fish swam 14% further in 2 min, with 90% of this difference occurring between 20 and 50 s. Trained fish accumulated 32% more lactate, but showed no differences in glycogen or PCr depletion, and 22 % less ATP depletion, suggesting increased use of exogenous glucose. Glycogen repletion in early recovery, and lactate clearance between 1 and 3h after exercise, were also enhanced in trained fish. Energy stores (ATP equivalents) were higher after exercise and especially during recovery in trained fish. Overall, sprint training minimizes endogenous fuel depletion during exhaustive swimming, even though swim speed (and distance) increases, and enhances the rate of metabolic recovery following the swim.
The Absorption Of Chloride Ions By The Anal Papillae Of Diptera Larvae
Authors: Koch H. J. 
Published: April 2021

ABSTRACT
Until recently the respiratory function of the anal papillae of Diptera larvae was unquestioned; they were generally called “anal gills”. There has been, however, much discussion concerning the part played by these organs in the uptake of oxygen. Using Protozoa as indicators of oxygen tension, Fox (1920) proved that the uptake of oxygen was only slightly, if at all, higher in these organs than in the other parts of the skin. Wigglesworth (1933a) investigated, by the same method, the respiratory uptake in Aedes and obtained similar results.
Experimental Studies On The Sexual Cycle Of The South African Clawed Toad (Xenopus Laevis). I
Authors: Alexander S. S. , Bellerby C. W. 
Published: April 2021

ABSTRACT
Retrogression of the ovaries of Xenopus laevis occurs if toads are kept for long periods in an insufficient volume of water. Atrophy takes place in spite of regular feeding and change of water and occurs more frequently and to a greater extent than in toads which are underfed. Overcrowding is followed by a diminution in food intake; the weekly consumption of food being halved in the case of females subjected to the maximum population density. Under natural conditions the seasonal decrease in water volume of the ponds in which Xenopus lives may induce or at least contribute to the maintenance of the retrogressive phase of ovarian activity which normally occurs.
The Respiration of Insects Through the Skin
Authors: Fraenkel Gottfried , Herford G. V. B. 
Published: April 2021

ABSTRACT
When blowfly larvae are paralysed by ligaturing behind the ganglion the resultant respiration of the hind parts represents the basal metabolism of the animal. When the hind spiracles are also ligatured off, all respiration takes place by diffusion through the skin and is about one-quarter of the basal value. The R.Q. of the twice-ligatured larvae is 1 · 34. This indicates that part of the metabolic processes are maintained by anaerobic respiration. The O2 tension inside the larvae has been measured and is about 15% inside the normal larvae and 2 · 4% inside the double-ligatured larvae. Therefore a much larger amount of oxygen diffuses through the skin in the double-ligatured than in the normal larvae, and it has been found by calculation for the normal larva to be one-tenth of the basal value. When insects are submerged in water their spiracles are not able to function and all respiration takes place by diffusion through the skin. In the normal blowfly respiration is independent of the O2 tension from 100 % O2 down to about 7 · 5 %, whereas in the double-ligatured larvae it is entirely dependent on the oxygen tension. Experiments with other insects, Chaerocampa elpenor larvae (spiracles blocked with grease), Tenebrio molitor larvae and Culex sp. larvae (submerged in water), gave results similar to those obtained with the blowfly larvae.
The Reorganization of Tissue Masses ofCordylophora Lacustrisand the Effect of Oral Cone Grafts, with Supplementary Observations onObelia Gelatinosa
Authors: Beadle L. C. , Booth F. A. 
Published: April 2021

ABSTRACTA method is described for the preparation of reconstitution masses from the expressed coenosarc tissues of Cordylophora lacustris. This brackish water hydroid is more suitable for the purpose than others which have so far been used. Under normal conditions (50 % sea water at 16–17° C.) such masses produce one or more hydranths within about 2 days and often additional unorganized outgrowths. The main histological features of the reconstitution masses as seen in sections are described. From these observations and from experiments with masses made from isolated ectoderm and endoderm it is concluded that there is no reduction of the cells to a pleuripotent condition. The cells of each original layer can form only the layer from which they were derived. Masses made from endoderm cells only are incapable of holding together for long and soon disintegrate. Pure ectoderm masses, however, rapidly round up and form hollow vesicles but do not produce hydranths. No signs of cell division during reconstitution were detected. The “interstitial” cells observed in the coenosarc ectoderm are thus not able to differentiate into endoderm when this is absent and there is no indication that they perform any essential part in the process of reconstitution. An oral cone when grafted into a mass will determine the position of the regenerated Hydranth which develops in relation to the graft. Evidence is given to prove that the action of the cone is one of pure induction and that it does not supply cells to the induced hydranth. The action of the cone is independent of its orientation and it will produce its effect even after previous chopping up and reuniting. Attempts to graft killed oral cones have so far failed. Grafts of distal halves of young gonophores do not induce hydranths. Calcium or magnesium deficiency in the medium results in complete suppression of hydranth formation from masses but not always of unorganized outgrowths. Oral cone grafts, however, can overcome this inhibition and tentacles are formed. A similar inhibitory effect is produced by potassium deficiency, but is not overcome by an oral cone graft. The quantity of calcium required to permit tentacle formation in plain masses is very small (c. 0·00006 M). Sodium cyanide (c. M/30,000), phenyl urethane (c. M/3000) and low temperature (5·5–0·5° C.) can inhibit hydranth formation in plain masses, but oral cone grafts overcome this inhibition and induce the formation of tentacles. Reconstitution masses which produced hydranths were also made from the coenosarc of another brackish water hydroid Obelia gelatinosa. Isolated ectoderm and endoderm were incapable of reorganization. Mixed masses of Cordylophora and Obelia coenosarc separated into regions composed of tissue from one species only and each produced hydranths independently.
The Double Innervation of Muscles in the Clam (Mya Arenaria)
Authors: Pumphrey R. J. 
Published: April 2021

ABSTRACT
It is a matter of common observation that lamellibranch molluscs may close the valves of their shell by a fairly rapid twitch-like contraction of the adductor muscles, and may thereafter in certain circumstances relax the adductors, immediately allowing the valves to gape, while in other circumstances these muscles may be maintained for a considerable time in the shortened state even when large tensions are applied to the valves.
An Apparatus for Measuring the Propulsive Forces of the Locomotory Muscles of the Earthworm and Other Animals
Authors: Gray J. , Lissmann H. W. 
Published: April 2021

ABSTRACT
A complete picture of the locomotory mechanism of any animal involves a knowledge of the forces required to overcome the external resistance of the animal’s environment. In the case of certain terrestrial animals (the earthworm in particular) it is possible to measure these forces by means of a modified form of the apparatus originally designed by one of us (H. W. L.) for the study of locomotion of the snail.
A Syringe Pipette Method for the Determination of Oxygen in the Field
Authors: Whitney R. J. 
Published: April 2021

ABSTRACT
The method usually employed for the determination of oxygen in natural waters is that described in Standard Methods of Water Analysis (1925). The basis of this method is the Winkler chemical method for the estimation of dissolved oxygen. A sample of the water to be examined is collected in a bottle of about 250 c.c. capacity. The usual Winkler reagents are added and the iodine liberated is titrated against a standard sodium thiosulphate solution. The amount of oxygen originally present in the sample can then be deduced.1
Aspects of Shark Swimming Performance Determined Using a Large Water Tunnel
Authors: Graham Jeffrey B. , Dewar Heidi , Lai N. C. , Lowell William R. , Arce Steve M. 
Published: April 2021

ABSTRACTA large, sea-going water tunnel was used in various studies of shark swimming performance. The critical swimming velocity (Ucrit, an index of aerobically sustainable swimming speed) of a 70 cm long lemon shark (Negaprion brevirostris Poey) was determined to be 1.1 Ls−1, where L is body length. The Ucrit of the leopard shark (Triakis semifasciata Girard) was found to vary inversely with body size; from about 1.6Ls−1 in 30–50cm sharks to 0.6Ls−1 in 120cm sharks. Large Triakis adopt ram gill ventilation at swimming speeds between 27 and 60cms−1, which is similar to the speed at which this transition occurs in teleosts. Analyses of tail-beat frequency (TBF) in relation to velocity and body size show that smaller Triakis have a higher TBF and can swim at higher relative speeds. TBF, however, approaches a maximal value at speeds approaching Ucrit, suggesting that red muscle contraction velocity may limit sustained swimming speed. The TBF of both Triakis and Negaprion rises at a faster rate with swimming velocity than does that of the more thunniform mako shark (Isurus oxyrinchus Rafinesque). This is consistent with the expectation that, at comparable relative speeds, sharks adapted for efficient swimming should have a lower TBF. The rates of O2 consumption of swimming lemon and mako sharks are among the highest yet measured for elasmobranchs and are comparable to those of cruise-adapted teleosts.
The Role of Magnetic Statoconia in Dogfish (Squalus Acanthias)
Authors: Hanson M. , Westerberg H. , Öblad M. 
Published: April 2021

ABSTRACTMineralogical and magnetic properties of the otolithic mass in the sacculus of dogfish, Squalus acanthias, were investigated. The endogenous statoconia were found to be either rhombohedral crystals of calcite or spherical particles of other calcium carbonate polymorphs. From 20 to 60% of the total otolithic mass consisted of exogenous material, sea sand, which had a high content of heavy mineral particles, some of which were magnetic. The concentration of the heavy particles was greater than that typically found in marine sand, and it is proposed that this could result from a separation process in the endolymphatic duct.A calculation of the acceleration of the otolithic mass in the sacculus caused by the geomagnetic field showed that the maximum linear acceleration due to magnetic forces would be one or two orders of magnitude smaller than the minimum sensitivity to acceleration in the auditory frequency range. This makes it unlikely that the magnetic particles are involved in detection of the geomagnetic field.The exogenous material raises the mass and density of the otolithic mass in the sacculus, thus increasing the sensitivity of this otolith organ.
Influence of input from the Forewing Stretch Receptors on Motoneurones in Flying Locusts
Authors: Pearson K. G. , Ramirez J. M. 
Published: April 2021

ABSTRACTPrevious studies on the forewing stretch receptors (FSRs) of locusts have suggested that feedback from these receptors during flight contributes to the excitation of depressor motoneurones and reduces the duration of depolarizations in elevator motoneurones. We have investigated these proposals by measuring the timing of FSR activity relative to depressor activity and by examining the effects of stimulating the FSRs on the membrane potential oscillations in flight motoneurones. Activity in the FSRs was recorded in tethered intact animals flying in a windstream and in preparations that allowed intracellular recordings from motoneurones during flight activity. The timing of FSR activity was similar in both preparations. In most animals we observed that at normal wingbeat frequencies (about 20 Hz) the activity in the FSRs commenced after the onset of activity in the wing depressor muscles. As wingbeat frequency declined there was a progressive advance of FSR activity relative to depressor activity. Most of the spikes in each burst of FSR activity occurred during the time that the membrane potential in depressor motoneurones was repolarizing. Electrical stimulation of the FSRs timed to follow the onset of depressor activity slowed the rate of repolarization, decreased the peak hyperpolarization and increased the rate of the following depolarization in depressor motoneurones. In elevator motoneurones, the same pattern of FSR stimulation produced an additional excitatory input during the depolarization phase and, at low wingbeat frequencies, reduced the duration of the peak depolarizations. The reduction in the duration of the peak depolarization in elevator motoneurones was not strongly correlated to the reduction in cycle period. We propose that the primary reason why input from the FSRs increases wingbeat frequency is because this input reduces the degree of hyperpolarization in depressor neurones and thus promotes an earlier onset of the next depolarization in these neurones.
The Effects of Reducing Water pH and Total CO2 on a Teleost Fish Adapted to an Extremely Alkaline Environment
Authors: Wright P. A. , Perry S. F. , Randall D. J. , Wood C. M. , Bergman H. 
Published: April 2021

ABSTRACTThe teleost fish Oreochromis alcalicus grahami is well adapted to an extremely alkaline environment (pH 10, total CO2 184 mmol I−1) in Lake Magadi, Kenya. O. a. grahami excretes all nitrogenous wastes as urea, and exposure to neutral water (pH7, total CO2&lt;1mmol l−1) results in a complete inhibition of urea excretion. In the present study, we further characterized the physiological effects of transferring O. a. grahami from alkaline to neutral water. Exposure to neutral water resulted in a significant decrease in blood pH, a large reduction in plasma HCO3− levels, a severe impairment of swimming ability, an increase in Na+ influx, but no change in O2 consumption. A closely related species of tilapia, O. nilotica, living in neutral waters of the Sagana River, was relatively unaffected by acute exposure to tapwater at pH 10, but showed a marked alkalosis in Lake Magadi water prior to death. These results demonstrate that O. a. grahami thrive in an environment of high pH and bicarbonate/carbonate concentration, conditions that are fatal to other species adapted to neutrality. O. a. grahami, however, is extremely unusual amongst aquatic animals in its adverse response to neutral water.
Reduction in extrasynaptic acetylcholine sensitivity of axotomized anterior pagoda neurones in the leech
Authors: Bigiani A. , Pellegrino M. 
Published: April 2021

ABSTRACTThe effects of axotomy on the sensitivity of the leech anterior pagoda (AP) neurone to acetylcholine (ACh) and carbamylcholine (CCh) have been studied 1–5 days after axon interruption. Hyperpolarizing responses to ionophoretically applied ACh and CCh have been recorded intracellularly from desheathed cell bodies of normal and axotom-ized neurones. The electrical properties of the membrane have also been measured in the same neurones. Axotomy produced a progressive loss of sensitivity to both ACh and CCh with a similar percentage reduction. No significant changes have been found in the time to peak and in the reversal potential of the responses to agonists, or in the number of drug molecules needed to combine with a single receptor to produce a response. Interruption of nerve roots and connectives which do not contain the AP axon did not induce the alterations of ACh sensitivity observed after axotomy. It is concluded that the loss of ACh sensitivity following axotomy is due to a reduction in density of functional ACh receptors (AChRs).