Behavioral and endocrine effects of early-life exposure to etonogestrel in zebrafish

Progestin use as a contraceptive has increased exponentially in the last few decades, as has its disposal in the environment. These synthetic hormones can impair the physiology and behavior of non-target organisms, such as fish. In this study, we evaluated the effects of exposure to an environmentally relevant concentration of etonogestrel (ETO, 3.2 ng L^-1) on the behavior and endocrine system of zebrafish (Danio rerio) larvae. We found that ETO caused anxiogenic-like behavior in larvae, as demonstrated by the open-field and light-dark tests. The exposed larvae also presented an increase in whole-body cortisol levels. These changes may lead to an ecological imbalance, emphasizing the risk of early exposure to progestins in the environment.