This project has received funding from the European Union’s Horizon 2020 Programme under grant agreement No 862658. The meagre Argyrosomus regius (Asso, 1801) is a marine cultured fish species whose production in Europe is on the increase. Lowering the age at maturity of hatchery-produced juveniles would support meagre aquaculture by accelerating production cycles and reducing industrial costs for broodstock maintenance. The aim of this work was to assess the effects of a treatment with recombinant follicle stimulating hormone (rFsh), produced in ovarian cells of Chinese hamsters, on male germ cell proliferation and apoptosis in sexually immature meagre. Treatments involved two weekly increasing doses of rFsh (week 1: 6 µg kg-1 and week 2: 9 µg kg-1) followed by a constant dose of 12 µg kg-1 (weeks 3-6). Fish were sacrificed at week 0 (untreated control group, CONTROL 0) and at week 6 (saline-injected control group, CONTROL 6 rFsh-treated group, TREATED), and testis samples were fixed in Bouin’s solution and embedded in paraffin wax. Proliferating germ cells were identified through the immunohistochemical localization of the Proliferating Cell Nuclear Antigen (PCNA) apoptotic germ cells were identified using the terminal deoxynucleotidyl transferase-mediated d’UTP nick end labeling (TUNEL) method. TREATED fish had higher GSI, larger seminiferous tubules, more abundant luminal spermatozoa, a lower density of anti-PCNA positive single A spermatogonia, a higher density of anti-PCNA positive spermatocysts and apoptotic germ cells than both control groups. The present study demonstrated the effectiveness of the produced rFsh in stimulating testis development and spermatogenesis in pre-pubertal meagre. Moreover, the rFsh treatment proved to be highly efficient in removing the apoptotic block of spermatogenesis observed in juvenile meagre, allowing spermatogonial survival and progress towards meiosis. The administration of rFsh did not stimulate spermatogonial self-renewal, a process whose control still needs to be elucidated.
