Shrimp larvae (Penaeus vannamei) collected from an uncontaminated area were challenged with sublethal concentrations of organochlorine pesticides, The effects of treatment with lindane, lorsban, chlordane and DDT, were a 5, -12, 13 and 21% increase in the larval respiratory rate, respectively, Glycogen synthesis decreased from the 0.471 mu g g(-1) h(-1) of the control, to 0.455, 0.415, 0.400 and 0.365 mu g g(-1) h(-1), for larvae submitted to DDT, chlordane, lindane and lorsban, In addition, we measured decreases in nucleic acid content, from 20.4 and 34.9% in larvae challenged by chlordane and lorsban, respectively, and values close to 25% for two other pesticides tested. These results indicate drastic metabolic changes, which may impinge on the commercial fishery and culture of this organisms. Copyright (C) 1996 Elsevier Science Ltd