CONICET | Buscador de Institutos y Recursos Humanos

Endosulfan (ES) is an organochlorine pesticide widely used in agriculture despite its high toxicity towardsnon-target organisms such as fish. It has been demonstrated that ES can cause negative effects onaquatic animals, including disruption of hormonal systems. However, the alterations produced by thispesticide on the reproductive axis of fish prior to sexual maturity, as well as possible modes of actionhave hardly been studied. This study aimed at assessing the effect of waterborne exposure to the pesticideES on the reproductive axis during sexual differentiation of juveniles of the South Americanfreshwater cichlid fish Cichlasoma dimerus. No mortality was observed due to ES subchronic exposure (90days post-fertilization). Exposure to ES did not affect body weight nor morphometric parameters, indicatingthat larvae nutritional state was not affected. Timing of sexual differentiation, gonadal morphologyand sex ratio were likewise not altered by ES. However, ES acted as an endocrine disruptingchemical in this species as the morphometry of gonadotropin-releasing hormones (GnRH) producingcells was altered. Exposure to ES altered nuclear area, cell area and nucleus/cytoplasm ratio of GnRH IIneurons, and cell and nuclear area and diameter of GnRH III neurons. Interestingly, in our previous study,exposure before sex differentiation (30 day exposure) caused no alteration to GnRH II and III, and didalter GnRH I and FSH cells. These alterations could lead to changes in circulating hormone levels,especially when fish are exposed for prolonged periods, ultimately impairing reproductive fitness. C.dimerus juveniles can be an interesting biological model to perform toxicological studies with the intentto assess early disruption endpoints in the reproductive axis during development