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  • 1
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The oxygen and carbon dioxide transporting properties of the haemolymph from an amphibious Australian crab,Holthuisana transversa were investigated. Within the temperature range 15 to 35°C increasing temperature markedly decreased oxygen affinity (ΔH=−54 kJ·mol−1). The Bohr effect was small at all temperatures with a mean value of −0.13. Over the temperature range 15–35°C there was a significant increase in the cooperativity of oxygen binding. Changing the concentration of Ca,l-lactate or haemocyanin in the haemolymph could elicit no significant change in either O2 affinity or cooperativity of O2 binding. There was no evidence in support of a specific effect of CO2 on oxygen affinity of either non-dialysed or dialysed haemolymph. The amount of CO2 that could be carried byH. transversa haemolymph was significantly reduced by increased temperature (approx. 14 to 12.5 mmol·l−1 CO2). Comparisons of oxygenated and deoxygenated haemolymph at a fixed pH were unable to demonstrate the presence of a significant Haldane effect. Combining data from oxygenated and deoxygenated haemolymph the buffer value was calculated to be in the range −6.2 to −8.5 mmol·l−1 HCO 3 − ·pH unit−1. The insensitivity ofH. transversa haemocyanin function to all modulating influences except temperature is discussed with respect to the ecology of this crab.
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  • 2
    ISSN: 1432-136X
    Keywords: Crustacea ; Amphipoda ; Haemocyanin ; Temperature sensitivity ; l-Lactate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of pH, temperature, and l-lactate on the O2 bindign properties of haemocyanin (Hc) from three talitroidean species i.e., the aquatic Apohyale pugettensis, the semi-terrestrial Megalorchestia californiana, and the semi-/euterrestrial Traskorchestia traskiana was studied. The Hc of A. pugettensis was characterized by a higher O2 affinity (and more pronounced Bohr shift) than the Hc of either M. californiana or T. traskiana. Apohyale was the only species that possessed He that was sensitive to temperature change. Resuspending Hc from each of the three species in a stock Ringer's solution (based on the ionic composition of the haemolymph of T. traskiana) showed that the persistence of the difference in Bohr shift between Apohyale and the other two species was due to differences in the haemocyanins themselves and not attributable to their respective ionic environments. An inverse relationship was found between the cooperativity (n 50) and pH of Hc from T. traskiana and A. pugettensis but not for M. californiana. In each case adding l-lactate increased Hc O2 affinity, but this was most pronounced for A. pugettensis.
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  • 3
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Simultaneous measurements of whole body proton flux and both unidirectional and net ion fluxes together with assessment of the blood acid-base, respiratory gas, electrolyte and lactate status were performed in white suckers (Catostomus commersoni) originating from a natural soft water lake ([Ca++]=0.18 meq·l−1) in Ontario, Canada. Fish were examined under control (pH∼ 6.8) and acidic conditions (pH∼4.3) in natural soft water at 19–20 °C. Resting blood composition was similar to that previously reported for this species in natural hard water except for a marked enhancement of both plasma pH and bicarbonate levels. Acute acid exposure promoted a significant net influx of protons (or loss of base) concomitant with a plasma acidosis of mixed origin (metabolic+respiratory) as well as whole body Na+, Cl−, Ca++ and K+ losses. Circulating ion levels in plasma were partially conserved by intracellular ion depletion. Radiotracer studies showed that net body losses of Na+ and Cl− ensued largely through stimulation of efflux components and, to a lesser extent, inhibition of inward transport. Cl− loss eventually exceeded Na+, suggesting transport of an unmeasured substance to maintain electroneutrality. A markedly reduced blood $$P_{O_2 }$$ , enhanced plasma $$P_{CO_2 }$$ , elevated blood lactate levels and significant hemoconcentration were also observed. Thus, disturbances in acid-base regulation, ionoregulation and respiratory function may all contribute to acid toxicity in white suckers in natural soft water.
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  • 4
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Wild populations of white suckers (Catostomus commersoni) were exposed to a fluctuating ambient pH regime (pH 7 to 4 to 7 to 4) in natural soft water. Blood and muscle ionic composition together with the net flux rate of acid-base equivalents, other ion transfers as well as unidirectional Na+ and Cl− exchanges were measured simultaneously in intact fish. Exposure to a shift in water pH from 7 to 4 for 12 h resulted in a marked net influx of both H+ (or loss of base) and SO 4 2− concomitant with net losses of other major body ions (Na+, Cl−, K+, Ca2+, Mg2+) as well as inhibition of gill NaCl influx and stimulation of gill diffusional efflux, depressed plasma ion levels (Na+, Cl−, Ca2+) and epaxial white muscle intracellular ion loss (K+, Mg2+). These responses slowly reversed when the water pH was elevated back to pH 7 for 12 h. Complete recovery was not achieved for some variables, however, even by 48 h. The responses upon re-exposure to water pH 4 for 12 h paralleled those seen during the initial acid exposure period, indicating that the introduction of a short period of neutral pH between two periods of acid exposure, was not ameliorative. Exposure to a fluctuating ambient pH regime, therefore, seemed to be more detrimental to the fish than continued, gradual or prior acid exposure. A regression analysis was performed on the ion transfer rates measured simultaneously in individual fish over the fluctuating pH regime. The results showed that exchange diffusion appears to be an important mechanism of NaCl transfer in white suckers and that the net flux rate of acid/base equivalents via the gill is closely correlated with the difference between all major cation (Na+, K+, Ca2+, Mg2+) and anion (Cl−, SO 4 2− ) net transfer rates.
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  • 5
    ISSN: 1432-136X
    Keywords: Crustacea ; Amphipoda ; Haemocyanin ; O2 transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Haemolymph PO2 and pH of two amphipod species, Apohyale pugettensis (aquatic) and Megalorchestia californiana (semi-terrestrial) in vivo were examined during immersion and emersion at 15 and 25°C, and also after activity in air at 15°C. For M. californiana arterial O2 tensions were higher in air than in water. This situation was reversed in A. pugettensis, although all O2 tensions measured for both species were comparatively high. No arterial-venous PO2 difference was apparent in the haemolymph of quiescent M. californiana. Haemocyanin (Hc) was 100% saturated in vivo only in the following; A. pugettensis in water (15 and 25°C) and air (15°C), and M. californiana in air (15°C). The Hc of both species becomes important in O2 transport during activity; under such circumstances the haemolymph of M. californiana delivered more O2 to the tissues than did that of A. pugettensis, despite the greater O2 content of the latter. The animals studied here may exhibit a stage (size class?) where cutaneous gas exchange is sufficient for resting aerobic metabolism while specialized respiratory carriers (and respiratory structures) are important in meeting the increased aerobic demands of activity or environmental stress.
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  • 6
    ISSN: 1573-5117
    Keywords: Acid-exposure ; ion-regulation ; mortality ; euryhaline environments ; Artemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mortality, and whole-body levels of [Na], [Cl] and [K]were measured in adult and naupliar stages of Brine Shrimp, Artemia franciscana, after 24h exposure to a waters of a range of acid (H2SO4)concentrations (pH 8.3 to 4.5). Acid effects were tested in both dilute (20%) and full strength artificial seawater (ASW). All stages showed high sensitivity to acid stress whether tested in 20% or100% ASW. Nauplii were more sensitive than adults in either medium. Mortality in each case was correlated with dramatic changes in whole body [Na] and [Cll but animals in 20% ASW lost [Na] and [Cl] to the environment while animals in 100% ASW gained them from the environment. Clearly animals which ion-regulate in euryhaline media are more sensitive than expected to acid stress which may thus pose a serious threat to sensitive euryhaline habitats.
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  • 7
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 8
    ISSN: 1432-136X
    Keywords: Amphipoda ; Crustacea ; Haemocyanin ; Freezing ; Inorganic effectors ; Urate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of variations in [K], [Ca], [Mg], [NaCl], and [urate] on the in vitro O2 binding properties of haemocyanin (Hc) from three talitroidean species, viz. the aquatic Apohyale pugettensis, the semi-terrestrial Megalorchestia californiana, and the semi-/euterrestrial Traskorchestia traskiana were studied. Freezing altered the cooperativity of Hc from A. pugettensis and M. californiana but not T. traskiana. Variations in [NaCl], [K], and [Mg] had no effect on cither O2 affinity or cooperativity of the Hc except for A. pugettensis Hc where an increase in [Mg] resulted in an increase in both O2 affinity and cooperativity. Increasing [Ca] or [urate] increased O2 affinity of both A. pugettensis and M. californiana but not T. traskiana Hc. These effects were most marked in A. pugettensis. The results suggest a negative correlation between sensitivity to Hc effectors and the degree of terrestrial adaptation of a particular amphipod species.
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