Sub-lethal 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.