INHIBITION OF ACETYLCHOLINESTERASE IN THE AUSTRALIAN FRESH-WATER SHRIMP (PARATYA-AUSTRALIENSIS) BY PROFENOFOS

Profenofos induced significant inhibitory effects on the AChE activity of Paratya australiensis ranging from >40% inhibition at sublethal co ncentrations of 0.1 to 1.0 mu g/L to >80% inhibition at lethal concent rations of greater than or equal to 10 mu g/L. Sublethal chronic expos ure (21 d) at a concentration of 0.15 mu g/L caused persistent reducti on in AChE activity of up to 60%, whereas recovery of AChE activity to normal levels from a 24-h exposure to 0.1 mu g/L profenofos required less than 9 d. Shrimp were exposed to 0.1 mu g/L profenofos for 24 h a nd then allowed a period of recovery in pesticide-free water; at the e nd of this treatment the AChE activity of affected shrimp approached c ontrol level. Subsequent 24-h exposures with intermittent stay in pest icide-free water for the same duration as the initial recovery phase r esulted in greater inhibition in AChE activity as compared to the init ial 24-h exposure. Furthermore, the AChE activity of shrimp at the end of the recovery phases remained significantly depressed.