ISSN:
1432-136X
Keywords:
Key words Oxygen
;
Acid-base
;
Adenylates
;
Cherax
;
Air-breathing
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The Australian Yabby Cherax destructor voluntarily emerges from water to breathe air with increased frequency as water PO2 decreases. When the water PO2 declined below 2.7 kPa the crayfish spent 〉50% of time breathing air. The respiratory gas transport, acid-base, ionic and energetic status were quantified in simulations of this emersion behaviour to determine the benefits that the crayfish may gain from switching to air-breathing. C. destructor initially showed an elevated O2 uptake rate on emerging from hypoxic water, but after 1 h the O2 uptake rate was not different from that of crayfish in normoxic water. During 3 h of air breathing, subsequent to 2.7 kPa aquatic hypoxia, the haemolymph PO2 increased while oxygen content was essentially unchanged, although cardiac output increased 5-fold. The haemolymph PCO2 increased from 0.44 to 1.21 kPa after 3 h while the CO2 content increased from 3.47 to 8.66 mmol · l−1 and the pH decreased from 7.73 to 7.57 after 1 h in air. In air C. destructor eventually achieved an O2 uptake rate similar to that achieved in water. A general hyperglycaemia occurred without anaerobiosis. In air-breathing C. destructor, small changes in lactate appear to offset the decrease in haemocyanin-O2 affinity caused by acid Bohr shift. During air-breathing, decreased haemocyanin-O2 affinity assisted in maintaining O2 diffusion into the tissues, but the ATP content of the tail muscle decreased so that after 3 h in air the energy charge was only 0.59. The data are consistent with a specific depression of the Emden-Meyerhof pathway, preventing either lactate formation or oxidative phosphorylation in the tail muscle, despite a concomitant glycogenolysis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003600050158
Permalink
