bluuebunny/crossref_metadata_2025_split huggingface dataset:
Visual Function in Four Antarctic Nototheniid Fishes
Authors: Pankhurst N. W. , Montgomery J. C. 
Published: April 2021

ABSTRACT
Visual function was investigated in the antarctic fish Pagothenia borchgrevinki (Boulenger), Trematomus bernacchii Boulenger, T. centronotus Regan and T. hansoni Boulenger. All Trematomus species have large anterior aphakic spaces (indicating a forward feeding vector), whereas Pagothenia does not. Pagothenia and T. hansoni, which both feed in the water column, lack the corneal iridescence displayed by T. bernacchii and T. centronotus. This is thought to relate to the importance of downwelling light for image formation in Pagothenia and T. hansoni. Absolute sensitivity thresholds to white and monochromatic light were measured using electroretinogram (ERG) responses in light- and dark-adapted Pagothenia and dark-adapted Trematomus species. Dark-adapted fish (retinal screening pigment withdrawn from rod outer segments) had thresholds of l–3×10−3μEm_2s−1 to a 200ms pulse of white light, whereas that of light-adapted Pagothenia (rod outer segments covered by the retinal screening pigment) was l·9×10−2μE m−2s−1. We suggest that the thresholds approximate threshold stimuli for rods and cones, respectively. Measurement of thresholds of light-adapted Pagothenia made using a behavioural measure (feeding responses) gave a threshold of 5×10−3μEm−2s−1. Limits for photopic and scotopic vision are predicted to be reached at depths of 20–40 and 30–60 m, respectively, under snow and ice conditions typically encountered at this time of year. ERG-determined spectral sensitivity curves peaked around 500 nm in all four species and matched the spectral irradiance under the ice. Shifts to longer wavelengths in spectral irradiance caused by sub-ice phytoplankton growth may degrade visual ability. Flicker fusion frequencies (FFFs) reached a maximum value of 15 Hz in Pagothenia at the maximum stimulus intensity used, but at environmentally realistic light intensities they were less than 8 Hz. FFFs were lower in all Trematomus species than in Pagothenia.
Simultaneous Direct and Indirect Calorimetry on Normoxic and Anoxic Goldfish
Authors: Waversveld J. Van , Addink A. D. F. , Thillart G. Van Den 
Published: April 2021

ABSTRACT
Simultaneous direct and indirect calorimetry together with biochemical determinations of metabolite concentrations were used to compare the normoxic and anoxic energy metabolism of goldfish at 20°C. The normoxic and anoxic heat production levels determined by direct calorimetry were in agreement with previous results: 700 and 200Jh−1MW−1, respectively (where MW is metabolic weight, kg0 85). Metabolite determinations during normoxia and after 3 and 8 h of anoxia showed that during anoxia a thermodynamic steady state is reached. By simultaneous calorimetry the amounts of oxidized substrates during normoxia and anoxia and the amount of excreted ethanol, the end product of incomplete anaerobic oxidation, as well as normoxic and anoxic carbon dioxide production were determined. During normoxia and anoxia the same substrates for oxidation are used (carbohydrate and protein) by small starving goldfish, but the end products are different. During normoxia oxidation is complete (to CO2 and H2O; protein oxidation also has ammonia as an end product, but this is considered physiologically as complete oxidation), whereas during anoxia oxidation is incomplete, with ethanol, which is excreted, and CO2 as end products. From the indirect calorimetric calculations it appeared that anoxic goldfish also produce fat. Glycogen storage appears to be crucial in the anoxia survival strategy.
Thermal Sensitivity of Swimming Performance and Muscle Contraction in Northern and Southern Populations of Tree Frogs (Hyla Crucifer)
Authors: John-Alder Henry B. , Barnhart M. Christopher , Bennett Albert F. 
Published: April 2021

ABSTRACT
The effects of temperature on sprint swimming ability and muscle contractile properties were examined in northern and southern populations of the holarctic tree frog, Hyla crucifer Wied-Neuwied, acclimated to 20–23°C. Maximal swimming velocities of 29 (southern) and 32 (northern) cm s−1 and stroke frequencies of 4·1 (southern) and 5·5 (northern) strokes s−1 were attained at 30°C, and maximal stroke lengths (i.e. distance moved per stroke) of 8·0 (southern) and 7·4 (northern) cm at 20°C. The thermal dependence of swimming velocity decreases with increasing temperature (e.g. Q10 = 4·0 from 6 to 10°C, 1·2 from 20 to 30°C), as reported for locomotion in other ectothermic vertebrates. Over a temperature range of l·5–30°C, velocity increases by a factor of 5·5, frequency by a factor of 4, and length by a factor of 1·7. Thus, increased velocity at higher temperatures can be attributed mostly to increased stroke frequency; increments in stroke length contribute less. Muscle contractile properties have similar thermal dependencies to those of other vertebrates: rate processes [including twitch time-to-peak tension (TPT), twitch half-relaxation time (RT1/2), maximal rate of tetanic tension development and isotonic shortening velocity] are much more sensitive to temperature than is force generation (twitch and tetanic tension). Below 8°C, stroke frequency is limited by twitch contraction time (TPT + RT[/2), and leg extension in a swimming stroke by TPT. At higher temperatures, the thermal dependence of stroke time is lower than that of contraction time. Neither locomotor nor muscle contractile properties are different between the two populations (except for twitch tension at low temperatures). Inflexibility in the thermal dependence of muscle contraction and locomotion in this species may help to explain differences in breeding phenologies between northern and southern populations.
Gas Exchange and Air-Sac Composition in the Unanaesthetized, Spontaneously Breathing Goose
Authors: Scheid Peter , Fedde M. Roger , Piiper Johannes 
Published: April 2021

ABSTRACT
Gas exchange variables were measured in unanaesthetized domestic geese fitted with rubber facemasks and indwelling air-sac and arterial catheters. The results were analysed on the basis of functional models.
Ventilation was characterized by low frequency (8·4 min−1) and high tidal volume (29·3 ml kg−1). Average values (± S.E.) of arterial blood variables were as follows: kPa, pH = 7·52 ± 0·01. Body temperature was 41·4 ± 0·2°C. The gas exchange ratio (calculated with reference to inspired gas) of caudal air sacs (average 1·09) was higher, and that of cranial air sacs (0·73) lower, than that of mixed-expired (0·82) or end-expired gas (0·78). This pattern can be explained by a higher effective ventilation/perfusion ratio in the neopulmo than in the paleopulmo. During inspiration, the neopulmo was estimated to contribute about 7% to the overall inspiratory O2 uptake, and about 18% to the CO2 output. Total inspiratory gas exchange was twice that during expiration. Arterial , was close to, but lower than, the partial pressure in cranial air sacs and in end-expired gas. This can be explained on the basis of a crosscurrent gas exchange system with unequal distribution of ventilation to perfusion between functional compartments.
Do Presynaptic Muscarinic Receptors Regulate Acetylcholine Release in the Central Nervous System of the Cockroach Periplaneta Americana?
Authors: Hue Bernard , Lapied Bruno , Malecot Claire O. 
Published: April 2021

ABSTRACT
Although insects have proved to be suitable subjects for neuropharmacological investigations, the role of muscarinic acetylcholine (ACh) receptors remains unresolved. Up to now, this problem has mainly been investigated by studying the characteristics of ACh release from insect synaptosomes (Breer & Knipper, 1984) and by characterizing the binding to central nervous system (CNS) extracts from the cockroach of two muscarinic receptor-blocking drugs, L-[benzilic-4,4′-3H] quinuclidinyl benzilate (Meyer & Edwards, 1980; Lummis & Sattelle, 1985) and [N-methyl-3H]scopolamine (Lummis & Sattelle, 1986). These parallel approaches have shown that muscarinic receptors exist in the insect CNS. The functional role of these receptors is investigated in the present study by electrophysiological experiments on a synaptic preparation from the CNS of the cockroach, Periplaneta americana.
The Kinematics and Aerodynamics of the Free Flight of Some Diptera
Authors: Ennos A. Roland 
Published: April 2021

ABSTRACT
Seven representative species of the order Diptera were filmed in free flight using high-speed cinematography. Insects were killed after filming, and morphological measurements were made in the manner of Ellington (1984b).
The detailed kinematics of selected sequences were then found using frame-by-frame digitization, followed by computer reconstruction of the third dimension. Kinematics were qualitatively similar to those observed by Ellington (1984c), though in three species the wings often underwent ventral flexion near the base at the end of the downstroke.
For aerodynamic analysis of hovering flight, modified forms of the equations of Ellington (1984e,f) were used. Forward flight was analysed by a novel method, which assumes that an equal but opposite circulation is built up for each half-stroke and allows linear equations to be used.
The lift coefficients calculated for hovering were commonly well above those possible by quasi-steady mechanisms, but rotational coefficients were within those that could be achieved by the unsteady lift mechanisms: clap-and-fling (Weis-Fogh, 1973) and flex (Ellington, 1984d). The lift and rotational coefficients of the two half-strokes were often unequal.
In forward flight, the equal circulation assumption often led to an incorrect estimation of the aerodynamic force vector, showing that the circulations during the two half-strokes were unequal.
It is suggested that flies manoeuvre largely by altering the unsteady circulations produced at stroke reversal via alterations in the speed and timing of wing rotation. The differences in the mechanisms used by different fly species are related to their flight behaviour in the field.
Physiological Responses of the Crayfish Pacifastacus Leniusculus to Environmental Hyperoxia: I. Extracellular Acid-Base and Electrolyte Status and Transbranchial Exchange
Authors: Wheatly Michèle G. 
Published: April 2021

ABSTRACT
Extracellular acid-base and ionic status, and transbranchial exchange of acidic equivalents and electrolytes, were monitored in freshwater crayfish (Pacifastacus leniusculus’) during control normoxia ( = 148 mmHg; 1 mmHg = 133·3 Pa), 72 h of hyperoxia ( and 24 h of recovery. An initial (3 h) respiratory acidosis of 0·2 pH units was completely compensated within 48 h by a 50% increase in metabolic [HCO3−+CO32−] accompanied by a significant reduction in circulating [Cl−]. In addition, the original increase in was partially accommo dated. The time course of transbranchial acidic equivalent exchange paralleled the change in extracellular metabolic base load with a significant branchial output of H+ during the first 48 h of hyperoxia. This was associated with net branchial effluxes of Cl− and Mg2+. Unidirectional flux analysis revealed parallel reductions in Na+ influx and efflux during initial hyperoxic exposure, reflecting an alteration in exchange diffusion. The net Cl− efflux was due to an initial increase in efflux followed by a reduction in influx. The reverse sequence of events occurred more rapidly when normoxia was reinstated: metabolic base was removed from the haemolymph and control haemolymph acid-base and ion levels were re-established within 24 h. Transbranchial fluxes of acidic equivalents similarly recovered within 24 h although net Na+ output and Cl− uptake persisted.
The study attempted to identify relationships between branchial net H+ exchange and components of Na+ and Cl− exchange and quantitatively to correlate changes in the acidic equivalent and electrolyte concentrations in the extracellular fluid compartment with those in the external water.
Natural Dehydration Regimes as A Prerequisite for the Successful Induction of Anhydrobiosis in the Nematode Rotylenchulus Reniformis
Authors: Womersley Christopher , Ching Cherie 
Published: April 2021

ABSTRACT
Induction of anhydrobiosis in the nematode Rotylenchulus reniformis (Linford & Oliveira) was studied using direct exposure to elevated relative humidities and conditions resembling natural dehydration regimes. All larvae and preadults were unable to survive direct short-term exposure to 97 % relative humidity. However, dehydration of larvae on model substrates (0·5 % agar: 1·0 % agarose) that mimic the natural rate of soil moisture loss induced coiling and successful entry into anhydrobiosis. Coiling was maximized at 10–12 days and only coiled larvae survived dehydration, emerging as the preadult form. Larvae could withstand severe dehydration at 80 and 40 % relative humidity after the induction of coiling, but were unable to withstand direct exposure to 0 % relative humidity.
The levels of adaptation utilized by anhydrobiotes to ensure slow dehydration and the adaptive significance of this are discussed in relation to the different environments in which these organisms are found. The results suggest that R. reniformis is well-adapted to its environment and emphasize the importance of natural dehydration regimes for assessing anhydrobiotic potential.
The Treading-on-Tarsus Reflex in Stick Insects: Phase-Dependence and Modifications of the Motor Output During Walking
Authors: Schmitz J. , Haβfeld G. 
Published: April 2021

ABSTRACT
In stick insects walking forwards or backwards, a treading-on-tarsus (TOT) reflex of the middle leg could be elicited by mechanical stimulation of the ipsilateral front leg tarsus. The probability of eliciting a TOT reflex in the middle leg depended on the phase of the stimulus within the middle leg’s step cycle and on the position of the middle leg relative to its normal anterior and posterior extreme positions. During a TOT reflex the functional swing muscle (protractor coxae in forward walks and retractor coxae in backward walks) was inhibited while the functional stance muscle was activated. This suggests that the step generator of the middle leg contains two hierarchical levels: the higher level would determine the timing of swing and stance independent of walking direction; the lower one would drive the appropriate muscle groups for swing and stance depending on which programme -forward or backward walking -was running. The stimulus information from the front leg necessary to elicit a TOT reflex was observed only in the ipsilateral connective. In terms of the model, this information would have to be processed according to the actual state of the higher level of the step generator. Movement and position of the front leg and tarsal contact of the middle leg were not relevant for the TOT reflex of the middle leg. Steps with a TOT reflex were significantly prolonged, and compensation for this disturbance of walking coordination was made within the next step.
An Acoustic Telemetry System for Monitoring The Heart Rate of Pike, Esox Lucius L., and Other Fish In Their Natural Environment
Authors: Armstrong J. D. , Lucas M. C. , Priede I. G. , Vera L. De 
Published: April 2021

ABSTRACT
Heart rate can be telemetered from fish using FM radio transmitters (Nomura & Ibaraki, 1969), FM acoustic transmitters (Wardle & Kanwisher, 1974), acoustic pulsed transmitters (Priede & Young, 1977), electromagnetic transmitters (Priede et al. 1985) and acoustic transponders (Storeton-West et al. 1978). Most of these systems transmit only over short distances or cannot be used with the standard equipment used in animal-tracking studies. This paper describes an acoustic transmitter which emits a high-power pulse triggered by the R wave of the electrocardiogram (ECG) and is compatible with normal field equipment for tracking fish.
Modes of Ammonia Transport Across the Gill Epithelium of the Marine Teleost Fish Opsanus Beta
Authors: Evans David H. , More Kane J. , Robbins Steven L. 
Published: April 2021

ABSTRACT
The modes of ammonia transport across the gill epithelium of the marine teleost Opsanus beta were investigated using an isolated, perfused head preparation. During perfusion for approximately 2h there was no macro- or microscopic damage to the exterior surface of the gill filaments or lamellae, no swelling of lamellae, the structural leak was only 0·3%, the afferent perfusion pressure was constant, and the transepithelial electrical potential (TEP) approximated that measured in vivo. The rate of ammonia efflux was similar to that measured in vivo, was constant for at least 80 min, and approached zero when the perfusate was nominally ammonia-free. Addition of ouabain or bumetanide to the perfusate indicated that basolateral Na+/NH4+ exchange, but not Na+/NH4+/2C1− cotransport, was important in transbranchial ammonia transport. No evidence was found for apical Na+/ NH4+exchange. Specific increases in perfusate NH3 were nearly 100 times as effective as increases in NH4+ concentrations in stimulating ammonia efflux. Alteration of TEPs could not account for any of these effects. Calculated relative permeabilities to NH3 and NH4+indicate that the toadfish gill is relatively permeable to NH4+ compared to the shark gill and other ‘tight’ epithelia, consistent with the general conclusion that marine teleost gills are relatively cation-’leaky’. Computation of the relative roles of the three delimited pathways for ammonia efflux indicate that 22% is via basolateral Na+/ NH4+exchange, 57% via non-ionic diffusion of NH3 and 21% via ionic diffusion of NH4+. Comparison with other published data suggests that the relative roles of non-ionic and ionic diffusion of ammonia across epithelia may be correlated with relative ionic permeabilities.
The Seasonal Modulation of Na+/H+ Exchanger Activity in Trout Erythrocytes
Authors: Cossins Andrew R. , Kilbey Robert V. 
Published: April 2021

ABSTRACT
A pH-stat method is described for determining the initial rate of efflux of H+ equivalents from trout erythrocytes after stimulation with catecholamines. This measure of transport capacity of the Na+/H+ exchanger was sensitive to medium pH with a peak at 7·24 ± 0·09 pH units. After washing blood into a trout saline the exchange capacity recovered to a maximal value after 2 h and remained stable for at least 24 h at 5 °C. Internal Na+ concentration reached a low, stable value also within 2–3 h of washing. The antiporter was comparatively unstable when incubated at room temperature. The concentrations for half-maximal responses to the agonists adrenaline, noradrenaline and isoproterenol were 3·0 ± 1·1 × 10−7, 2·5 ± 3·0 × 10−8 and 1·5 ± 0·6× 10−8moll-1, respectively.
The variation of antiporter capacity with time of the year was followed over a 24month period. Capacity was highest during early summer at 200–250 mmol h-1 I-packed cell volume (pcv), but declined from November to March to a low of approximately 100mmolh-11-1 pcv. Exchange capacity increased rapidly during the early spring back to values characteristic of early summer. It appears that both temperature and photoperiod are involved in regulating the spring increase.
Metabolism of the Perfused Swtmbladder of the European EEL: Oxygen, Carbon Dioxide, Glucose and Lactate Balance
Authors: Pelster B. , Kobayashi H. , Scheid P. 
Published: April 2021

ABSTRACT
We have measured the metabolic activity in the vascularly isolated, salineperfused swimbladder of the eel (Anguilla anguilla) in order to investigate the pathways for CO2 formation in the gas gland tissue. Concentrations of O2, CO2, glucose and lactate were measured in the arterial inflow and venous outflow of the swimbladder, and metabolic rates were calculated by the direct Fick principle.
Total CO2 production, averaging 55·8 nmol min−1, was about 4·6 times the O2 consumption (mean 12·0 nmol min−1). This suggests that only about 22% of the CO2 is formed by aerobic glucose metabolism. CO2 formation from HCO3− or CO2 washout does not appear to be significant in our experiments with steady perfusion of a saline containing a low level of HCO3−. The ratio of lactate production to glucose uptake averaged 1·2, indicating that only 60% of the glucose is converted to lactate. Since only 1–2% of the glucose was found to be oxidized (2 nmol min−1), the extra glucose appears to be anoxidatively metabolized to CO2. The anoxidative CO2 formation appears to be of functional importance for producing the high gas partial pressures of both CO2 and O2 which are required for secretion of these gases into the swimbladder.
Metabolism of isolated fish gill cells: contribution of epithelial chloride cells
Authors: Perry S. F. , Walsh P. J. 
Published: April 2021

ABSTRACT
Gill cell suspensions from freshwater (FW)- and seawater (SW)-adapted teleosts were obtained by density gradient centrifugation. The proportion of chloride cells (CCs) in the mixed cell suspensions was estimated using the fluorescent mitochondrial stain, DASPMEI, and ranged from less than 1 % (FW-adapted tilapia) to approximately 13% (SW-adapted toadfish). The gill cells displayed relatively high viability based on Trypan Blue exclusion (&gt;75%), lactate dehydrogenase leakage (&lt;6·5% h−1), oxygen consumption rates (5–15μmolg−1 cell wet mass h−1) and ATP levels (1–3μmol g−1 cell wet mass). There were no obvious differences between the viability of CCs and the other cell types present.
An initial comparison of gill oxidative metabolism in SW-adapted tilapia (Oreochromis mossambicus) and toadfish (Opsanus beta) demonstrated that both species oxidized glucose and lactate at substantially greater rates than alanine or oleate. Metabolic rates were significantly higher in toadfish cell suspensions. Kinetic experiments revealed that toadfish gill cells displayed lower values of Km and higher values of Vm for both lactate and glucose, in comparison to tilapia. The elevated metabolism in toadfish gill cells was correlated with increased activities of the oxidative enzyme citrate synthase and Na+/K+-ATPase. The toadfish cell suspensions had a greater proportion of CCs and it is likely that the difference in CC numbers between the two species is the basis for the observed differences in enzyme activities and rates of oxidative metabolism. This idea is supported by the highly significant correlation between Na+/K+-ATPase activity (or CC numbers) and rates of lactate oxidation in gill cell suspensions from FW-and SW-adapted tilapia and toadfish, as well as SW-adapted tilapia chronically treated with cortisol to elevate CC numbers.
Although it has been assumed widely that the high metabolic rate of gill tissue reflects, in part, the oxidative demands of the chloride cell, the results of this study provide the first experimental, albeit indirect, evidence for differential rates of metabolism in the various cell types that comprise the gill.