Comparative metabolism of fenitrothion in aquatic organisms. III. Metabolism in the crustaceans, Daphnia pulex and Palaemon paucidens.

When the waterflea Daphnia pulex and the shrimp Palaemon paucidens were exposed to 1.0 ppb [14C]fenitrothion in a flowthrough system, the concentrations of fenitrothion and 14C in the body reached equilibrium, and the maximum bioaccumulation ratios of fenitrothion were 71 and 6 in the daphnia and shrimp, respectively. These crustaceans primarily metabolized the compound by oxidation of P = S to P = O, hydrolysis of P-O-aryl linkage, and demethylation. The liberated phenol was found to be conjugated with sulfate in the daphnia and with glucose in the shrimp. When the organisms were transferred to a freshwater stream, fenitrothion and its metabolites were rapidly excreted from their bodies, and the half-life of the parent compound was less than 0.2 day in both species.