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) 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.