SUBLETHAL EFFECTS OF THE ORGANOPHOSPHATE FOLIDOL-600 (METHYL PARATHION) ON CALLICHTHYS-CALLICHTHYS (PISCES, TELEOSTEI)

1. The sublethal effects of Folidol 600, an organophosphate containing methyl parathion as its active principle, were analysed in the fish Callichthys callichthys. 2. After an intracoelomatic application of 500 mg/kg of Folidol 600, the behavior and the levels of plasmatic cholinesterase were analysed along the time, in acute experiments. 3. Plasma cholinesterase activity was inhibited by 90% after 4 hr from the initial time, keeping this level of inhibition for 4 days. 4. It recovered slowly in the next 8 to 10 days, reaching about 80-90% of the normal levels around the 35th day after the beginning of the experiment. 5. Many behavioral changes were observed in the first 96 hr, such as: lowering of motility with loss of equilibrium and frequent unnatural body positions; uncoordinated movements leading to incapacity of food intake; and increase in the levels of respiratory frequency.