No abstract

Pesticides are serious contaminants because they are designed to eliminate pests, but they also affect non-target species. The present study aimed to evaluate the biochemical and genetic effects of the herbicide tebuthiuron in Oreochromis niloticus of different sizes. Thus, we analyzed biomarkers in small and large O. niloticus specimens exposed to 62.5, 125 and 250 mg L-1 of tebuthiuron for 72 hours. Fish exposed to 250 mg L-1 had high mortality rates; therefore, the data could not be used. The results showed an increase in EROD activity in fish exposed to 125 mg L-1 , but no GST alteration. Antioxidant enzymes GPx and CAT were altered only in the liver of treated fish compared to the control group: CAT decreased in large fish, and GPx increased in small fish. The MDA analysis did not evidence lipid peroxidation. High DNA damage in exposed small fish (not in large fish) was observed using comet assay, but a micronucleus test did not show mutagenicity. Moreover, a comparison between control groups with specimens of different sizes revealed that small fish are more susceptible than large fish to the tebuthiuron effects, since increased comet scores was observed only for smaller fish.

No abstract

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.

No abstract