The widespread use of pesticides in agriculture has increased their levels in water bodies, threatening aquatic ecosystems. Among these, glyphosate and chlorpyrifos are widely used in Mexico and can cause toxic effects even at low doses. In aquatic organisms, early exposure to these pollutants can disrupt vital processes, such as sex determination, through oxidative stress. This study assessed the effects of exposure to environmental concentrations of glyphosate (100 μg/L), chlorpyrifos (1.5 μg/L), and their combination on zebrafish (Danio rerio) from early stages to 90 days post fertilisation (dpf). Survival was measured using Kaplan–Meier curves; lipid peroxidation was assessed by malondialdehyde (MDA); sex-related gene expression was measured by qPCR of selected genes at 30 dpf; and gonadal development was assessed by histology at 65 dpf. The results showed increased MDA levels in exposed fish. Glyphosate caused early toxicity and a higher proportion of undifferentiated fish, implying delayed sex determination. Chlorpyrifos induced oxidative stress and affected amh gene expression linked to masculinisation. Combined exposure reduced survival and altered gene expression and gonadal development. Exposure shifted the sex ratio toward males, suggesting that pesticide-induced oxidative stress may alter the expression of sex determination genes during early development.
Arias-Camacho et al. (2026) studied this question.