Metabolic Responses of Pleustonic and Burrowing Freshwater Crabs Exposed to Endosulfan

This work focused on the effects on metabolism of environmental concentrations of endosulfan in the freshwater crabs Dilocarcinus pagei and Zilchiopsis collastinensis. The concentrations used were 0, 6 and 62 mu g of endosulfan l super(-1). Oxygen consumption, oxyregulation capacity and critical oxygen concentration were modified by the presence of endosulfan in D. pagei. In contrast, Z. collastinensis crabs showed a decrease in the ammonia-N excretion rate, but the oxygen consumption was similar between exposed and control crabs. A significant increase in the O:N ratio was evidenced in Z. collastinensis exposed to this biocide, demonstrating a shift toward lipid and carbohydrate primary metabolism. Dilocarcinus pagei controlled its oxygen consumption through isolation as a defense mechanism, while Zilchiopsis collastinensis modified the ammonia excretion. These different defense mechanisms might be related to the dissimilar habitats that each species occupies.