Assessment of oxidative stress biomarkers in the threatened annual killifish Austrolebias charrua exposed to Roundup

This study aimed to analyze the toxic effects of Roundup Transorb® on the endangered Neotropical annual killifish Austrolebias charrua through the assessment of molecular and biochemical biomarkers. The fish were collected in temporary ponds and exposed to environmentally realistic concentrations of the herbicide (5 mg.L^-1 for 96 h). The production of ROS, lipid peroxidation, DNA damage, and membrane fluidity were evaluated in the blood cells by flow cytometry. The mRNA expression of the antioxidant-related genes sod2, cat, gstα, atp1a1, gclc, and ucp1 across the brain, liver, and gills was quantified. The acute exposure of annual killifish to Roundup significantly increased ROS production, lipid peroxidation, and DNA damage in their erythrocytes. Likewise, Roundup Transorb® decreased membrane fluidity in the blood cells of the exposed fish. Gene expression analysis revealed that Roundup exposure alters the relative expression of genes associated with oxidative stress and antioxidant defense. Our results give rise to new insights into adaptive mechanisms of A. charrua in response to Roundup. Since Brazilian annual killifishes strongly risk extinction, this study paves the way for developing novel biotechnologies applied to environmental monitoring and aquatic toxicology assessment.