Metabolic responses of Parastacus defossus and Parastacus brasiliensis (Crustacea, Decapoda, Parastacidae) to hypoxia

The metabolic responses of two crayfish species living in different habitats, Parastacus defossus and Parastacus brasiliensis, were analyzed after different periods of hypoxia (2.0 mg O2/L of oxygen). In the laboratory, groups of animals were subjected to hypoxia for 1, 2, 4, and 8 h. The hemolymph, hepatopancreas, muscle, and anterior and posterior gills were removed for determination of glucose, free glucose, glycogen, lactate, total proteins, total lipids, total cholesterol, arginine, and arginine phosphate. In both species, glucose and lactate increased significantly after 4 h of hypoxia, but decreased after 8 h (p > 0.05) from the beginning of the experiment. Reductions of glycogen, lipids, and cholesterol were recorded in hepatopancreas and muscle tissue, especially of P. defossus, after 4 h of hypoxia. Free glucose levels decreased in all tissues of P. brasiliensis, mainly in the hepatopancreas and muscle (p < 0.05), while P. defossus showed smaller reductions of these reserves. All reserves in the anterior and posterior gills, with exception of the glycogen reserves, behaved similarly in both species. Both crayfishes stored and used arginine phosphate, mainly P. defossus, which also showed higher concentrations of all metabolites than did P. brasiliensis. Both species showed metabolic adaptations to hypoxia, but, as expected, P. defossus appeared to be better adapted.