ACETYLCHOLINESTERASE INHIBITION IN THE CRAYFISH PROCAMBARUS-CLARKII EXPOSED TO FENITROTHION

Laboratory and field studies were conducted to evaluate the effects of fenitrothion (O, O-dimethyl O-4-nitro-m-tolyl phosphorothioate) on th e crayfish Procambarus clarkii. Acetyl- and butyrylcholinesterase acti vities were measured in the muscle of P. clarkii exposed to different doses of fenitrothion (4, 20, and 100 mu g/liter) for different times (up to 48 hr). A positive correlation was found between both cholinest erases, and acetylcholinesterase (AChE) was selected as a biomarker of exposure to this compound. Significant AChE depression (20%) was dete cted 2 hr after exposure to 20 mu g/liter of fenitrothion, reaching a maximum at 48 hr (47%), followed by a slow recovery. Reactivation tech niques using the nucleophilic reagent pyridine 2-aldoxime methiodide w ere assayed in fenitrothion-poisoned specimens, and the results sugges ted the utility of this method to diagnose exposure, particularly when control animals are not available, Finally, AChE inhibition was used to test a field population of P. clarkii potentially exposed to high c oncentrations of the organophosphorus pesticide fenitrothion, and a 55 % inhibition was detected. (C) 1996 Academic Press, Inc.