Evaluación toxicológica aguda de dos formulaciones del insecticida Dimetoato sobre Poecilia reticulata

Abstract

Dimethoate is an organophosphorus insecticide of systemic action, used for the control of agricultural pests. Its acute toxicity was evaluated in two non-target organisms from the aquatic biology Poecilia reticulata "Guppy" and Oreochromis niloticus "Nile tilapia". Preliminary tests were performed with the two species to establish the best conditions for the final tests and to minimize mortality in the controls. It was found that for guppies the ideal density is 5 individuals per liter and for tilapia 10 individuals in 3 liters. Once the ideal conditions for the bioassays have been determined, the preliminary test has been carried out to define the final test concentrations. In these tests the concentrations of the commercial dimethoate formulations were 1, 0.1, 0.01, 1x10-3 and 1x10-4 mg/L. From the results of these tests, the concentrations of the final assays that were 0.15, 0.115 , 0.08, 0.045 and 0.01 mg/l for formulation 1, and 0.03, 0.023, 0.016, 8x10-3 and 1 x 10-3 mg/l for formulation 2 in guppies and 0.03, 0.023, 0.015, 8x10-3, And 1.3x10-6 mg/l for formulation 1 and 3x10-4, 2.3x10-4, 1.5x10-4, 8x10-5 and 2x10-6 for formulation 2 in tilapia. Two final tests, one for each species of fish, were established using factorial design 2x5, where the two commercial formulations in five concentrations plus an absolute control were evaluated. Individuals were observed for 96 hours and the cumulative mortality was the response variable. One of the formulations was considerably more toxic than the other, with a lethal concentration of 50-96 of 0.082 and 2.8x10-3 mg/l for formulation 1 and 2 respectively in guppys and 2.9x10-5 0. and 7.7x10-6 mg/l for formulations 1 and 2 in tilapia.