Respiratory and Circulatory Responses to Hypoxia in the Sturgeon, Acipenser baerii

Siberian sturgeon, Acipenser baerii, when exposed to progressive hypoxia, was able to maintain standard oxygen consumption until a low critical level of ambient PO2 (PwO2 < 40 mm Hg). During the post-hypoxic period, an O2 debt was repaid by an elevated oxygen consumption indicating that a shift to anaerobic metabolism had occurred during the exposure to severe hypoxia. Gradually increasing ambient hypoxia initially induced a respiratory alkalosis. Below the critical level of PwO2 and during normoxic recovery, a flush of lactate into the blood was associated with a metabolic acidosis which was totally compensated 3.5 h after return to normoxia. Respiratory responses of the sturgeon to progressive hypoxia reveal a typical O2 regulatory behavior.