<scp>EE2</scp> and the Fish Brain: Age‐Dependent Impact of 17α‐Ethinylestradiol on Brain Cell Proliferation and Behavior in Sea Bass Larvae

Endocrine-disrupting chemicals (EDCs), such as 17α-ethinylestradiol (EE2), have raised concerns about their potential effects on aquatic organisms, particularly during early developmental stages. In this context, the study of behavioral disruption has gained considerable attention, as it may have consequences on individual fitness and ultimately influence key ecological processes. However, little is known about the potential link between behavioral disruption and neurodevelopmental alteration in nonmammalian vertebrates. This study aimed to assess the effects of EE2 exposure on the larvae of the marine teleost, European sea bass (Dicentrarchus labrax), during two distinct larval periods (30-38 and 40-48 days posthatch (dph)), focusing on behavioral and neurodevelopmental outcomes. Our findings revealed that exposure to EE2 during the 30-38 dph period resulted in a positive correlation between gene expression of the brain aromatase, brain cell proliferation, and behavioral changes. In contrast, exposure between 40 and 48 dph led to an increase in brain cell proliferation without behavioral alterations. These results suggest that the age of exposure plays a critical role in the neurodevelopmental and behavioral outcomes of EE2, with distinct molecular pathways involved. Future research should further investigate the mechanisms underlying the observed age-dependent effects, particularly the relationship between the brain aromatase activity, gh expression, and brain cell proliferation.