EFFECTS OF ORGANOPHOSPHATE AND CARBAMATE PESTICIDES ON ACETYLCHOLINESTERASE AND CHOLINE-ACETYLTRANSFERASE ACTIVITIES OF THE POLYCHAETE NEREIS-DIVERSICOLOR

A toxicity test for organophosphates (OP) and carbamates (C) was impro ved with the adult ragworm Nereis diversicolor. Animals were maintaine d in U-shaped glass tubes of 4-mm inner diameter fixed vertically on a plastic plate and placed in glass aquaria, Each tank was covered with glass in order to reduce evaporation and heat dissipation. Temperatur e varied between 15 and 16 degrees C and salinity was constant (34 par ts per thousand) during the entire length of the experiment. Experimen ts were performed with a fixed day length of 12 h and seawater was gen tly aerated. The maintenance system allowed the administration of OP a nd C compounds via the seawater. An acclimatization period of 48 h was not sufficient to accomodate worms to their artificial burrows; accor dingly, we chose to acclimate worms for a week before beginning the ex posure. Choline acetyltransferase (ChAT) activity was very low and was not significantly modified by two OP compounds: malathion and parathi on-ethyl. ChAT is not a target for these pesticides and should not be used for future studies about OP and C toxicity. On the other hand, in hibitory effects on acetylcholinesterase (AChE) activity were determin ed at concentrations of 10(-6) M for three OP compounds-malathion, par athion-ethyl, and phosalone-and a carbamate pesticide-carbaryl. We mea sured only short-term effects and no cumulative effect was determined, the maximum percentage of AChE activity inhibition being between 2 (c arbaryl) and 7 (OP compounds) days after exposure and then remaining s table. Mortality occured only after a period of intoxication of 14 day s. N diversicolor; which can be easily maintained at the laboratory, s eems to be a good candidate for future laboratory studies to test the toxicity of other pollutants.