ORIGINAL ABSTRACT

The growing pressure on food production has led to the widespread use of pesticides to ensure high crop yields. Herbicides are extensively applied in Brazil, with diquat-based herbicides (DBH) being one of the most commercialized. DBH has gained prominence as a substitute for paraquat and as a solution for glyphosate-resistant weeds. However, strict regulations govern the permissible levels of these substances in drinking water. In this context, we evaluated environmentally relevant concentrations of DBH in zebrafish (Danio rerio), a model organism in ecotoxicological studies. To evaluate the impact on behavior and early development, embryos were exposed to DBH at concentrations of 20, 50, or 250 µg L-1 during organogenesis (3-120 hpf). Developmental impacts were assessed through survival rates, spontaneous movement, and heart rate, while behavioral effects were analyzed using open-field and aversive stimulus tests. DBH exposure reduced survival, increased spontaneous movements and heart rate, and impaired larval behavior. Notably, all tested concentrations induced adverse effects in at least one endpoint, clearly demonstrating the detrimental impact of DBH on zebrafish embryos and larvae at environmentally relevant concentrations.