Population variation in hypoxic responses of the cichlid Pseudocrenilabrus multicolor victoriae

F-1 offspring of the African cichlid Pseudocrenilabrus multicolor victoriae Seegers, 1990 from swamp (low oxygen) and lake (high oxygen) origin were raised under normoxia and submitted to hypoxia acclimation (0.8 +/- 0.4 mg.L-1) and normoxia acclimation (7.4 +/- 0.3 mg.L-1) for 4 weeks. Haematocrit and lactate dehydrogenase (LDH) specific activities in the liver, white skeletal muscle, heart, and brain were measured. For haematocrit and LDH activities of liver, muscle, and heart, the response to acclimation depended upon population of origin. In general, fish from the swamp population showed a more typical'' hypoxic response (increased haematocrit and LDH activities), whereas fish from the lake population either did not respond or showed the opposite response. The results suggest that populations of P. m. victoriae sampled from habitats with diverse oxygen regimes differ in their physiological and biochemical responses to hypoxia.