In mouse, chicken and newts, RA has been established as a paracrine signal involved in the onset of meiosis, however, in fish, the role of RA in this process is still far from being understood. To gain a better understanding of the influence of RA in the onset of meiosis of the European sea bass, we have studied the in vitro functional responses to the RA signaling pathway agonist, all-trans retinoic acid (atRA), and to the RA synthase inhibitor (aldh inhibitor) 4-diethylaminobenzaldehyde (DEAB) in two meiosis scenarios. The first one is represented by an increase of 11-ketotestosterone (11KT) that takes place during the transition from immature differentiated testis to early recrudescent testis. The second one is represented by an increase of follicle-stimulating hormone (Fsh) that takes place during early stages of meiosis. Among the studied genes, we focused our attention on those involved in RA synthesis (aldh1a2 and aldh1a3) and degradation (cyp26a1). The results show gene expression responses the increase of exogenous RA and to the different meiosis scenarios, confirming the functionality of the RA signaling pathway during this developmental stage. In particular, the upregulation of cyp26a1 as a result of increased RA levels, suggest that it could be used as a suitable molecular marker for the onset of meiosis in European sea bass males

12th Congress of the Iberian Association of Comparative Endocrinology (AIEC), 26-28 September 2019, Faro, Portugal