Environmental relevant concentrations of a chlorpyrifos commercial formulation affect two neotropical fish species, Cheirodon interruptus and Cnesterodon decemmaculatus.

The increase of cultivated areas together with the intensive use of pesticides have greatly contributed to impair the quality of aquatic systems along different areas of South America. The main goal of the present study was to assess the effects of a commercial formulation of chlorpyrifos at environmentally relevant concentrations on two native fish species, Cheirodon interruptus and Cnesterodon decemmaculatus. Adult individuals were exposed during 48 h to the following concentrations: 0.084 nl/l (Ci-Cf 1) and 0.84 nl/l (Ci-CF 2) in C. interruptus (Ci) of Clorfox (CF), and 0.84 nl/l (Cd-CF 1) and 8.4 nl/l (Cd-CF 2) in C. decemmaculatus (Cd). Fish behavior was evaluated through locomotor activity and space usage variables. The activity of acetylcholinesterase (AChE) in brain and muscle, catalase (CAT) and glutathione-S-transferase (GST) in brain, liver, muscle and gills, and aspartate amino-transferase (AST), alanine amino-transferase (ALT), AST/ALT ratio and alkaline phosphatase (ALP) in liver, were measured. Both locomotor activity and space usage varied between the two species studied and between CF treatments. The enzyme activities showed significant variations in CAT for C. interruptus and in CAT, GST, AChE, AST, and AST/ALT for C. decemmaculatus under the exposure conditions. Given that both species responded to CF and the concentrations we tested are environmentally relevant, the presence of this pesticide in freshwater systems could impose a risk for populations of both native fish studied at field.