ORIGINAL ABSTRACT

The objective of this study was to evaluate the effects of glyphosate-based herbicides on the morphological, biochemical, and histological parameters of the tissues of male and female Astyanax lacustris. Animals were exposed to concentrations of 0.0065, 0.065, and 0.65 mg/L of glyphosate contained in Roundup for 7 days. The fish were euthanized, and their organs (brain, gills, gonads, liver, and muscles) were collected and evaluated by biometry, oxidative stress, and histopathological analysis. A significant reduction in the gonadosomatic index was observed in females exposed to glyphosate. The total antioxidant potential was enhanced in the brain (females) and gills (males), but was reduced in female gonads. Non-protein thiol levels increased in the muscles (males and females) but decreased in the gills (males). Reactive oxygen species levels increased in the gills (females), gonads (females), liver (males and females), and muscles (females). Lipid peroxidation levels increased in the gonads (female), liver (female), and muscles (male and female) and decreased in the brain (female). The gills showed vasodilation of the vascular axis of the primary lamella, hyperplasia of the primary and secondary lamellae, and detachment of the epithelium after exposure to glyphosate. Liver fat degeneration was observed, and its severity correlated with increased concentrations of glyphosate. The gonads of males exposed to glyphosate exhibited significant reductions in the number of spermatozoa and the prevalence of spermatocytes. These results reinforced the concepts that even small quantities of glyphosate are toxic to fish, causing oxidative stress, and that females appear to be more susceptible to its effects.