The use of biomarkers to study the effects of the mixture of diuron and hexazinone on small and large O. niloticus

Pesticides have made possible a safer and plentiful supply of food; however, the ultimate sink for many of these contaminants is the aquatic environment. We analyzed the commercial mixture Velpar K® WG, which is composed of the pesticides diuron (46.8% m/m) and hexazinone (13.2% m/m), as well as inert ingredients (40.0% m/m). The present study aimed to evaluate the effects of the herbicide mixture on Oreochromis niloticus of different sizes. To this end, we analyzed biomarkers in small and large O. niloticus exposed to a mixture of herbicides at 125, 250 and 500 ug L-1 for 72h. EROD increased activity in small fish exposed to the herbicide mixture at 250 and 500 ug L-1. The GST activity and levels of the antioxidant enzymes GPx and CAT remained the same in the treated fish, compared with the control. The level of the antioxidant enzyme SOD measured in the fish gills was changed in animals exposed to the herbicide mixture at 250 ug L-1. MDA analysis did not show lipid peroxidation. The comet assay evidenced widespread DNA damage, but the micronucleus test did not show mutagenicity. Hepatosomatic (HSI) analysis did not indicate any alterations in liver morphology. The biomarkers response in the fish depended on the size of the individuals.