ISSN:
1432-136X
Keywords:
Key words Respiration
;
Hypoxia
;
Haemocyanin
;
Acid-base
;
Adenylates
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The Australian Yabby, Cherax destructor, inhabits occasionally hypoxic water. The respiratory gas, acid-base, metabolite and energetic status of this crayfish was assessed during progressive hypoxia and during 3 h at a water PO2 of 1.33 kPa. The O2 affinity of haemocyanin from C. destructor was increased by lactate (Δlog P 50/Δlog[lactate] = −0.111) and by Ca (Δlog P 50/Δlog[Ca] = −0.62) but not by urate. While the non-bicarbonate buffering capacity was low (Δ[HCO3 −]/ ΔpH=−4.89) the haemocyanin had a low sensitivity to pH changes (ϕ = −0.33). The crayfish showed a compensatory hyperventilation, which induced a respiratory alkalosis, until the water O2 partial pressure declined below 2.67 kPa, after which the O2 uptake rate was approximately 10% of normoxic rates. The high haemocyanin-O2 affinity maintained haemolymph O2 content during progressive hypoxia despite the normally low arterial O2 partial pressure of C. destructor. During severe hypoxia, pH decreased but increased lactate aided in maintaining haemocyanin-O2 saturation. The importance of regulated haemocyanin-O2 affinity in hypoxic C. destructor was reduced by lowered metabolism, including reduced cardiac output, and the consequent reduction in O2 requirement. Anaerobiosis became important only at very low PO2 but thereafter proceeded rapidly, supported by a marked hyperglycaemia. There was no depletion of adenylates, even after 3 h of severe hypoxia. The tail muscle of C. destructor held small amounts of glycogen which would sustain anaerobiosis for a only a few hours. Hypometabolism seems an important hypoxic response but severe hypoxia may encourage the crayfish to breathe air.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003600050157
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