Oxygen consumption and whole body lactate accumulation during progressive hypoxia in the tropical freshwater prawn, Macrobrachium rosenbergii (de Man)

Daytime and nighttime rates of oxygen consumption (VO2) were determined for young freshwater prawns during progressive hypoxia. During daytime hypoxia VO2 fell slightly, then was maintained at 0.200 ml O2/gm/h to 40 mm Hg partial pressure of oxygen. Below 40 mm Hg VO2 fell markedly. At night VO2 averaged 0.310 ml O2/gm/h before falling at a critical pressure (Pcr) of 65 mm Hg. Sets of prawns were exposed to progressive hypoxia both day and night at rates simulating conditions during the closed respirometry studies. Prawns were sacrificed at different PO2s and analyzed for whole body lactate concentrations. Concentrations of 0.153 mg lactate/gm body weight were unchanged until the respective Pcr was reached during either day or night. Below Pcr lactate concentrations increased at a constant rate regardless of the severity of hypoxia. Combined aerobic metabolism and anaerobic glycolysis did not increase as a result of progressive hypoxia, indicating a small energy requirement for oxyregulation. Anaerobic energy production via glycolysis during hypoxia proceeded at only 1–3% of the regulated aerobic metabolism. This is much less than in other crustaceans, underscoring the importance of well-aerated environments both in Machrobrachium rosenbergii's natural habitat and under aquaculture conditions.