bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Eclipse Plumage of the Mallard (Anas Platyrhyncha Platyrhyncha)
Authors: Walton Arthur 
Published: April 2021

ABSTRACTThe eclipse plumage of the male mallard (Anas platyrhyncha platyrhyncha) which normally appears in June and July has been produced prematurely in February and March by subjecting the birds to artificial light in addition to normal daylight.Castration of male mallards did not prevent the assumption of eclipse in the first year but did so in the second year. Regenerated tissue was not found. It is concluded that the eclipse plumage is not caused by the direct action of a testicular hormone on the feather follicle, but that removal of the testis sooner or later produces an effect on some other endocrine organ or organs which consequently ceases to be sensitive to seasonal change (light) or fails to produce the hormones which bring about eclipse.
Studies on the Onychophora
Authors: Manton S. M. , Ramsay J. A. 
Published: April 2021

ABSTRACTAll terrestrial animals have to solve the problem of resistance to desiccation, and adaptations associated with this difficulty are of two main types: (1) the development of waterproof external surfaces, and (2) the reduction of the amount of water lost by excretion. In some animals there is also an increase in the formation of metabolic water. In a previous paper it has been shown that the second method has been employed by the Onychophora (Manton& Heatley, 1937). A uricotelic metabolism has been acquired, and nitrogenous excretion by the intestine has reduced the water passing out by the segmental excretory organs to a minimum. The presence of large fat stores in the body may indicate that a fatty metabolism is also increasing the production of metabolic water.
Inositol Transport by Hepatopancreatic Brush-Border Membrane Vesicles of the Lobster Homarus Americanus
Authors: Siu Teva , Ahearn Gregory A. 
Published: April 2021

ABSTRACT
The mechanism of [3H]myo-inositol transport by the lobster hepatopancreas was examined using purified brush-border membrane vesicles. Transport was stimulated by a 100 mmol 1−1 inward Na+ gradient, but other cation gradients were ineffective, suggesting a Na+-dependent transfer mechanism. The transport system was most efficient at pH7·0 (both sides), rather than in the presence of a pH gradient (pHin = 7·0; pHout = 5·5) or at bilaterally low pH (pHin = pHout = 5·5). The system was shown to be electrogenic in two different ways. First, myo-inositol uptake was stimulated by anions of increasing permeability (SCN− &gt; Cl− &gt; gluconate). Second, an outwardly directed, valinomycin-induced K+ diffusion potential (inside negative) enhanced uptake in comparison with vesicles lacking the ionophore. Myo-inositol was transported by a carrier mechanism with an apparent Kt of 0·79mmoll−1, a Jmax of 6·3pmolmg protein−1 s−1, and by apparent diffusion with a permeability coefficient of 5·92 pmol mg protein−1s−1 (mmoll−1)−1. D-Glucose was a noncompetitive inhibitor of myo-inositol uptake, but myo-inositol did not significantly reduce the transport of D-[3H]glucose. Vesicles preloaded with myo-inositol trans-stimulated [3H]myo-inositol uptake, whereas those preloaded with D-glucose did not, suggesting that the inositol carrier did not transport D-glucose. It is proposed that myo-inositol does not share the glucose carrier, and that D-glucose may modulate inositol influx by binding to a ‘regulator’ site on the inositol carrier.
Differences in Force-Frequency Relationships and Calcium Dependency between Elasmobranch and Teleost Hearts
Authors: Driedzic William R. , Gesser Hans 
Published: April 2021

ABSTRACT
Ventricle strips from little skate (Raja erinacea), spiny dogfish (Squalus acanthias), black dogfish (Etmopterus spinax), sea raven (Hemitripterus americanas), cod (Gadus morhua), hagfish (Myxine glutinosa) and white sturgeon (Acipenser transmontanus) were mounted for isometric force recording. Force development was assessed as a function of external calcium concentration and frequency of contraction. Post-rest potentiation was determined in skate and the teleost species to assess indirectly calcium storage capacities. Sea raven and cod preparations were also treated with ryanodine to assess the importance of calcium release from the sarcoplasmic reticulum.
Ventricle strips from skate and black dogfish showed a five-fold increase in force development when external calcium was raised from a physiological to a saturating level. Force development by ventricle strips from other species tested increased by only about 50% over the same range of calcium concentration.
For all elasmobranchs tested, an elevation in frequency of contraction of ventricle strips resulted first in an increase and subsequently in a decrease in force development. The apices of the curves were well within the physiological range of heart rates exhibited by these species. Preparations from teleosts showed only a decrease in force development when contraction frequency was elevated.
Skate ventricle strips exhibited a very marked post-rest potentiation at 3 mmol 1−1 external calcium. This protocol is considered to reflect the importance of intracellular calcium stores in the beat-to-beat maintenance of contractility. Sea raven and cod ventricle strips did not show any major post-rest potentiation, suggesting that calcium storage in hearts of these species is minimal. Ryanodine treatment had no effect upon sea raven and cod heart preparations. This approach further implies that calcium release from sarcoplasmic reticulum is not critical in these species.
In Vivo Cardiac Pressure and Heart Rate, and Heart Mass, of Busycon Canaliculatum (L.)
Authors: Jones H. D. 
Published: April 2021

ABSTRACT
In vivo cardiac pressure and heart rate, and relative heart mass, have been measured in Busycon canaliculatum. Base pressure was about l·3cmH2O above ambient and effectively the same in the ventricle, atrium, pericardium and veins. Ventricular systolic pressures were very variable. Highest pressure was over 80cmH2O, but sustained levels were lower, up to about 40cmH2O. Heart rate was also very variable, 5-15 beats min−1. Heart mass was about 0·19% of body mass. Cardiac refilling, control and power output are discussed.
Visual Discrimination of Distance by Octopuses
Authors: Muntz W. R. A. , Gwyther J. 
Published: April 2021

ABSTRACT
If two stimuli are presented to an octopus simultaneously, but at different distances from the animal, the nearer of the two is usually attacked. This preference was used to test the ability of octopuses to discriminate distance. White discs, 37 mm in diameter, were used as stimuli, and two parameters were varied: the distance of the farther stimulus from the animal (D), and the difference between the distances of the farther and nearer stimulus (d). Animals chose the nearer stimulus on 70% of occasions under the most difficult conditions used, where D was 370 mm and d was 50 mm. This percentage increased as D decreased or d increased. Further tests showed that varying the size of the discs, or using white vertical or horizontal rectangles instead of discs as stimuli, did not affect performance.
The most likely cue being used by the animals to discriminate distances is accommodation. If this is the case octopuses can detect blurring of points on the retinal image comparable in size to a single retinal receptor, and lens displacements of around 10 μm.
The Functions of Eye and Body Movements in Labidocera and Other Copepods
Authors: Land Michael F. 
Published: April 2021

ABSTRACT
Male Labidocera have three eyes derived from the nauplius eye. The dorsal pair have large lenses and are fused to give a single mobile eyecup containing a transverse row of 10 rhabdoms. This rhabdom row scans across 35° of the dorsal visual field at rates of up to 3 Hz, and it is suggested that the scanning movements are concerned with the detection of conspecifics. In addition there are movements which enable the eyecups to track a source of light, and these are mediated by three other receptors in each eyecup. The tracking movements are closely linked to tail movements which tend to keep the animal’s back directed towards the light. The total effect is to stabilize both body and eye direction against involuntary disturbance. Other pontellid copepods show similar visually controlled tail movements, but without the eye movements.
Adaptations to a Terrestrial Existence by the Robber Crab Birgus Latro: I. An in vitro Investigation of Blood Gas Transport
Authors: Morris S. , Greenaway P. , Mcmahon B. R. 
Published: April 2021

ABSTRACT
The gas-transporting properties of the haemolymph of Birgus latro L. were investigated in vitro. This terrestrial anomuran is restricted in distribution to the tropics, and on Christmas Island inhabits a highly stenothermal environment.
The effect of temperature on haemocyanin oxygen-affinity was pronounced (ΔH = –39 kJ mol−1) and was considered to represent the absence of any specific adaptation to environmental temperature. The Bohr effect was large for a terrestrial decapod (ϕ = –0·60), although reduced at low pH. Changes in [Ca] had a significant effect on oxygen affinity of dialysed haemolymph (ΔlogP50/ Δlog[Ca] = –0·39) whereas [Mg] had no effect. Increasing, [L-lactate] had a small effect on the oxygen affinity of dialysed haemolymph (ΔlogP50/ Δlog[lactate] =–0·013) but not whole haemolymph. Dialysis increased oxygen affinity, suggesting the presence of a dialysable component that suppresses affinity. The effect of L-lactate was inhibited in whole haemolymph.
The oxygen affinity of Birgus haemolymph was largely insensitive to effector substances, with the possible exception of Ca. In the case of lactate, at least, this was not due to a reduced sensitivity of the haemocyanin, a situation different from that in closely related species.
Carbon dioxide transport was also affected by temperature. Birgus haemolymph showed a high nonbicarbonate buffer capacity which could be correlated with a high haemocyanin concentration. It is concluded that terrestrial anomuran decapods depend on mechanical adjustments of ventilation and perfusion, rather than employing direct modulation of haemocyanin function, to optimize oxygen delivery.
Adaptations to a Terrestrial Existence by the Robber Crab Birgus Latro: II. in vivo Respiratory Gas Exchange and TRANSPORT
Authors: Greenaway P. , Morris S. , Mcmahon B. R. 
Published: April 2021

ABSTRACT
The lungs are responsible for essentially all uptake of oxygen in Birgus latro. Elimination of CO2 in resting crabs appears to occur largely across the gills but during exercise approximately half the output of CO2 is pulmonary. was high in resting crabs (43·8 mmHg; 1 mmHg = 133·3 Pa) but fell during exercise (to 27 mmHg). remained constant at 10–12 mmHg. rose substantially during exercise (from 7·1 to 14·6mmHg).
Haemocyanin delivered 90% of oxygen in resting crabs rising to 97% following exercise. Oxygen delivery at rest was 0·46 mmol l−1 haemolymph rising to 0·72 mmol l−1 following exercise. Pigment-bound oxygen capacity was 1·1 mmol l−1. Oxygen delivery to the tissues was diffusion-limited during exercise.
Anaerobic metabolism during exercise raised the concentration of L-lactate in the haemolymph 100-fold (from 0·25 to 25 mmol l−1) and concomitantly caused a fall in pH of 0·7 units. This acidosis was partially compensated by the end of the 30-min exercise period.
Ammonia and Acid-Base Balance During High Ammonia Exposure in a Marine Teleost (Myoxocephalus Octodecimspinosus)
Authors: Claiborne James B. , Evans David H. 
Published: April 2021

ABSTRACT
For the first time in a marine teleost (the long-horned sculpin; Myoxocephalus octodecimspinosus), the maintenance of blood pH, , [HCO3−] and the net movements of NH4+, HCO3− and H+ between the fish and the water have been studied during exposure to ammonia stress induced either by infusion (NH4C1 or NH4HCO3; 5 mmol kg−1) or by external application (NH4C1; approx. 1 mmol I−1).
Following NH4C1 infusion, a rapid decrease in blood pH (0·36units) and [HCO3−] (2·38 mmol I−1) was observed, and within 1h about 40% of the ammonia load had been excreted to the water. Analysis of NH4+ and HCO3− transfers revealed that the total ammonia (TAmm) efflux was due to a loss of NH3 and NH4+ in approximately equal proportions when an outwardly directed NH3 diffusion gradient was established.
Infusion of NH4HCO3 induced only small changes in plasma pH, and the rate of net HCO3− excretion was some 90% higher than that of NH4+ over 20 h. These data indicate a predominance of NH3 as the form of ammonia lost. In both infusion experiments, a presumed intracellular buffering of a majority of the ammonia load was noted.
High external TAmm induced an initial uptake of NH4+, but after 4 h of exposure ammonia efflux resumed even though NH3 diffusion gradients were negligible. Thus, in this seawater teleost, a role for the excretion of ammonia in the form of NH4+ is also likely.
Relative Importance of Song Parameters During Flight Phonotaxis and Courtship in the Bladder Cicada Cystosoma Saundersii
Authors: Doolan Jane M. , Young David 
Published: April 2021

ABSTRACT
Parameters of the calling song that were necessary to evoke phonotaxis in female bladder cicadas (Cystosoma saundersii) were determined for both long-range and short-range communication between the sexes.
Females flew to loudspeakers that were broadcasting model calling songs that resembled the natural calling song of the males. They also initiated courtship in response to the model calling songs. When flying females were offered a choice between a model resembling the natural song in all parameters (the control model) and a model in which one of the temporal parameters had been changed (the experimental model), they were attracted equally to the control and experimental models. When the carrier frequency of the experimental model was changed, the females were attracted exclusively to the control model. When the same model calling songs were presented to tethered, flying females in the laboratory, they turned only towards models with a carrier frequency close to that found in the natural song. Changing the temporal parameters of the model did not affect either the turning preferences of the females or their reaction times. When the same series of control and experimental models were played, one at a time, to caged females in the laboratory, courtship responses were elicited only by models with temporal parameters similar to those of the natural song. In contrast, a wide range of carrier frequencies was found to elicit courtship, provided that the temporal parameters were similar to those of the control. It is concluded that, in C. saundersii, identification of conspecific males by females is a two-stage process, with the carrier frequency of the male calling song being more important in long-range communication (flight) and the temporal parameters of the calling song being more important in short-range communication (courtship).
The Use of Alpha-Methyl-p-Tyroslne to Control Circulating Catecholamines in the Dogfish Scyliorhinus Canicula: the Effects on Gas Exchange in Normoxia and Hypoxia
Authors: Metcalfe J. D. , Butler P. J. 
Published: April 2021

ABSTRACT
We assessed the effectiveness of alpha-methyl-p-tyrosine in inhibiting catecholamine synthesis in the dogfish and examined the effects of catecholamine depletion on the cardiovascular system in normoxia and in response to hypoxia.
Although alpha-methyl-p-tyrosine (50 mg day−1 intraperitoneally for 5 days) substantially reduced the dogfish’s ability to increase the level of circulating catecholamines in response to hypoxia, it also substantially reduced normoxic oxygen consumption in the whole animal, an observation not previously reported. Metabolic studies on isolated dogfish hepatocytes indicate that this is a direct effect on oxidative metabolism at the cellular level rather than any effect on the oxygen delivery function of the fish’s cardiovascular system. Despite the effects of alpha-methyl tyrosine on normoxic oxygen consumption, the present results indicate that the lack of any large increase in the circulating levels of catecholamines in response to hypoxia in fish treated with alpha-methyl tyrosine does not compromise their gas exchange ability.
Metabolic Stimulation of Transepithelial Potential Difference Across the Midgut of the Tobacco Hornworm (Manduca Sexta)
Authors: Chamberlin M. E. 
Published: April 2021

ABSTRACT
The maintenance of in vitro transepithelial potential difference (PD) across the larval midgut of Manduca sexta is dependent upon the presence of metabolic substrates. Deletion of exogenous substrates from the bathing saline results in a rapid decline in PD. The PD can be restored by the bilateral addition of a saline containing physiological levels of amino acids and sugars. This stimulation is largely dependent upon the presence of potassium. The following substrates stimulate the PD more than twofold: citrate, succinate, malate, fructose, sucrose, trehalose, glucose, hexanoate and octanoate. Acetate and some amino acids stimulate the PD, but to a lesser extent. Of the substrates tested, only proline, glycine and 3-methyl-O-glucose fail to stimulate the PD. To determine if the observed stimulation of PD is due to absorption of anions, negatively charged substrates were added to either the haemolymph or luminal side of the tissue and the PD was monitored. The results indicate that diffusion of anions cannot account for the stimulation of PD. These results are discussed with regard to midgut oxidative metabolism and the metabolic support of active potassium secretion.
The Structural Basis for Iridescent Colour Changes in Dermal and Corneal Iridophores In Fish
Authors: Lythgoe J. N. , Shand Julia 
Published: April 2021

ABSTRACT
The reflectance from the iridophores in the skin of the neon tetra Paracheirodon innesi (Myers) and the iridophores in the cornea of the sand goby Pomatoschistus minutus (Pallas) changes in response to light. In both cases the reflectance comes from the constructive interference of alternating plates of material of high and low refractive index. In the neon tetra the high refractive index plates are mainly guanine, and the low refractive index plates are cytoplasm. In the goby cornea the plates are made of intercellular matrix and cytoplasm, but it is not known which has the higher refractive index. In neon tetra dermal iridophores, the response to light is a shift to longer wavelength reflection without an accompanying increase in the amplitude of reflectance. In goby cornea, light can induce an increase in the amplitude of reflectance without a shift in wavelength. It is suggested that the wavelength shift is produced by an inflow of material into the iridophore and that the change in amplitude, without a shift in wavelength, is produced by a transfer of material, such as water, between the high and low refractive index layers of the multilayer stack.
Enhancement of Desensitization of Quisqualate-Type Glutamate Receptor by the Dissociative Anaesthetic Ketamine
Authors: Ashford M. L. J. , Boden P. , Ramsey R. L. , Usherwood P. N. 
Published: April 2021

ABSTRACT
Application of ketamine (10−4–10−3mol l−1) to locust retractor unguis muscle produced a reversible, dose-dependent reduction in neurally evoked twitches, and blocked agonist-induced contractions. With increasing ketamine concentration (5×10−5–10−3mol l−1), the amplitude of glutamate potentials was reduced and dose-response curves for ionophoresis of L-glutamate were shifted to the right, particularly after concanavalin A treatment. Ketamine (10−4mol l−1) enhanced the rate of desensitization to consecutive pulses of L-glutamate and this action was eliminated by concanavalin A. The amplitude of the excitatory postsynaptic current (EPSC) was reduced by ketamine (10−5×5×10−4mol l−1) in a dosedependent manner but without a concomitant reduction in EPSC rise time. The decay phase of the EPSC was usually biphasic in the presence of ketamine (&gt;5×10−5mol l−1) but did not exhibit any voltage dependence. It is concluded that ketamine enhances desensitization and blocks the channel, particularly the closed form.
Hypoxic Responses in a Fish From a Stable Environment: Blood Oxygen Transport in the Antarctic Fish Pagothenia Borchgrevinki
Authors: Wells R. M. G. , Grigg G. C. , Beard L. A. , Summers G. 
Published: April 2021

ABSTRACT
The effects of hypoxic exposure on whole-blood oxygen-affinity were examined in the antarctic fish Pagothenia borchgrevinki. Fish exposed to for 11–14 days at −1·5°C had a P50 value of 20·6 ± 4·8 mmHg (S.D., N =13) at pH8-16, compared with 31·1 ± 4·3mmHg (N = 10) at pH8-00 for normoxic fish. Exposure to low oxygen levels resulted in a significant (66 %) rise in haemoglobin concentration, and erythrocyte [ATP] decreased by approximately 27%. There was no evidence for erythrocyte swelling. An aberrant gill morphology was observed in six fish and these showed unexpectedly high erythrocyte ATP levels. Oxygen-carrying capacity increased by approximately 40% in hypoxic fish and was correlated with a 34 % decrease in spleen mass. Despite the fact that antarctic fish have exceptionally low demands for oxygen and are unlikely ever to encounter environmental hypoxia, this antarctic fish has the necessary machinery to respond to hypoxia in a way that is typical of teleosts that naturally inhabit oxylabile environments. The ability to make short-term adaptive changes in the O2 delivery system in response to hypoxic exposure may be typical for vertebrates in general, rather than a feature seen only in those organisms which encounter environmental hypoxia on a regular basis.
The Insecticide Avermectin Bla Activates A Chloride Channel In Crayfish Muscle Membrane
Authors: Zufall F. , Franke CH. , Hatt H. 
Published: April 2021

ABSTRACT
Effects of avermectin Bla (AVM) have been tested on excised outside-out or inside-out patches of crayfish stomach muscle membrane. Continuous superfusion of AVM (0·1–1 pmoll−1) to the outside-out patches induced openings of channels (22 pS) which were similar in conductance and kinetics to the chloride channels activated by glutamate, quisqualic acid, ibotenic acid and nicotinic agonists, whereas GABA mainly activated a second, larger conductance state (44pS). This effect was reversible. AVM did not activate the excitatory, glutamate-activated cation channel. Upon raising the AVM-concentration to 10 pmol I−1 and above, an enormous increase in the rate of openings of channels (22 pS) occurred. This effect could not be washed out during the lifetime of the patch. Using inside-out patches, it was shown that the single-channel current amplitude, for both the reversible and irreversible drug actions, strongly depended on intracellular chloride concentration. Applied to the sarcoplasmic side of inside-out patches, AVM did not activate any channel. The distribution of open times for 0·1 pmoll−1 AVM could be fitted by a single exponential (τ =3·3ms). For a higher AVM concentration (1 pmol I−1) two exponentials (τ1 = 0·5 ms, τ2 = 2·4ms) were needed to fit the distribution. A similar effect was elicited by decreasing the extracellular Ca2+ concentration from 13-5 to 1 mmol I−1 during the application of 0·1 pmol I−1 AVM. Picrotoxin blocked the activation of chloride channels for both the reversible and irreversible effects of AVM. It is suggested that AVM activates the multitransmitter-gated chloride channel in this preparation. Binding sites for the drug are discussed.