[Effect of temephos on the acetylcholinesterase activity of the brain of Tilapia guineensis. 2: Experimental study of 24-hour exposure to the toxic compound].

The exposition of the Tilapia guineensis to concentrations used in the field to destroy the simulium larvae in their aquatic biotopes is 0,05 mg/l/10 minutes. The authors have previously remarked a significant lowering of acetylcholinesterasic brain activity in this fish. In the case of a much prolonged contact (24h corresponding 144 times the theoretic time of contact), it is noticed that, if this immediate effect is not more pronounced, on the other hand it is noticeable for a much longer acetylcholinesterasic activity extends beyond forty days. In the same conditions, three successive weekly treatments lead the acetylcholinesterasic activity to the level of vital activity.