摘要:The present study was undertaken to evaluate the toxicity and effects of a commercial formulation of the organophosphorous insecticide, Diazinon on acetylcholinesterase and lipid peroxidation activity in the freshwater guppy fish Poecilia reticulata . The fish exposed for 96 h to 50, 100 and 150 μg L-1 concentrations of diazinon at 24.0±1.0°C. Some characteristics of this aquarium water were dissolved oxygen , 7.2-7.9 mg L-1 and conductivity, 0.212-0.260 mS. Each exposure involved 3 treatments with 3 replicates and 1 control (without diazinon). In each aquarium (Volume: 5 L) were 10 fishes. Induction of oxidative stress in various tissues was evidence by increased lipid peroxidation levels. Acetylcholinesterase activity responded positively in a concentration dependent pattern, thus, suggesting the use of these two parameters as potential biomarkers of toxicity associated with contaminations exposure in freshwater fishes.