Abstract
In this study, we systematically investigated the process of sex reversal induced by 17-methyltestosterone (MT) feeding and MT-feeding withdrawal at the ovary differentiation stage in orange-spotted groupers, Epinephelus coioides. Gonadal histology showed that MT feeding induced a precocious sex reversal from immature ovaries to testes, bypassing the formation of an ovarian cavity, and MT-feeding withdrawal led to an ovarian fate. In both the MT feeding and MT-feeding withdrawal phases, cytochrome P450 family 11 subfamily B (cyp11b) gene expression and serum 11-KT levels were not significantly changed, suggesting that the MT-treated fish did not generate endogenous steroids, even though active spermatogenesis occurred. Finally, by tracing doublesex-expressing and Mab-3-related transcription factor 1 (dmrt1)-expressing cells and TUNEL (terminal deoxynucleotidyl transferase 2-deoxyuridine, 5-triphosphate nick end labeling) assays, we found that the efferent duct formed first, and then, the germ cells and somatic cells of the testicular tissue were generated around the efferent duct during MT-feeding-induced precocious sex reversal. Collectively, our findings provide insights into the molecular and cellular mechanisms underlying sex reversal induced by exogenous hormones during sex differentiation in the protogynous orange-spotted grouper.
Highlights
Groupers are hermaphroditic protogynous fish that develop ovaries at a young age and undergo sex changes to become male later in life [1,2,3,4,5,6,7]
Endogenous sex steroid hormones play a crucial role in sustaining phenotypic sex, and the most effective period to induce a sex change is during the gonadal sex differentiation stage [24]
In Nile tilapia (Oreochromis niloticus), exogenous androgen feeding can induce permanent sex reversal by suppressing cyp19a1a expression, which is essential for estrogen synthesis [25]
Summary
Groupers are hermaphroditic protogynous fish that develop ovaries at a young age and undergo sex changes to become male later in life [1,2,3,4,5,6,7]. Permanent sex reversal from female to male was reported in response to exogenous androgen or aromatase inhibitors in groupers [14,15,16,17,18,19,20,21,22,23]. Our previous study found that exogenous androgen treatment induced permanent sex reversals in orange-spotted groupers if endogenous androgens were produced [28]. We analyzed the gonad histology, serum estrogen, and androgen levels, gene expression profiles and cellar changes during MT-feeding-induced sex reversal at the sex differentiation stage in orange-spotted groupers. Our results provide insights into the molecular and cellular mechanisms underlying impermanent sex reversal induced by exogenous hormones in this protogynous species
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