Molecular characteristics of gonadal differentiation dimorphism in the ovoviviparous fish Sebastes schlegelii under gradient high-temperature induction

Abstract

Global warming can alter fish sex ratios and threaten population stability, particularly in species with temperature-sensitive sex differentiation. Sebastes schlegelii, an ovoviviparous species adapted to both cold and warm waters, may exhibit feminization or masculinization under high temperatures. However, the underlying molecular mechanisms remain unclear. We hypothesized that high-temperature exposure activates distinct sex-differentiation pathways and sought to identify the key genes and metabolites involved. Our findings reveal a balanced sex ratio at 18 °C, a notable feminization at 24 °C with 83.3 % of individuals being female, and a significant masculinization at 27 °C where 76.7 % are male. Transcriptomic and metabolomic analyses revealed at 24 °C, pathways related to steroid hormone biosynthesis, estrogen signaling, and progesterone, androgen, and estrogen receptor agonists/antagonists were activated, whereas at 27 °C, activation was prominent in steroid hormone biosynthesis, steroid biosynthesis, and cholesterol metabolism. Key genes and metabolites included cyp7a1, cyp1a1, hsd17b1, hsd17b2, erα, creb1, hsp70, and Estrone at 24 °C, and cyp7a1, lipa, lss, and Taurocholic acid at 27 °C. Quantitative reverse transcription PCR (RT-qPCR) revealed upregulation of female differentiation genes (foxl2, cyp19a1) at 24 °C and male differentiation genes (sox9, amh, dmrt1, hsd11b2) at 27 °C. Hormonal assays showed elevated 17β-estradiol (E2) at 24 °C and 11-ketotestosterone (11-KT) at 27 °C. In situ hybridization (ISH) revealed that, in stage II gonads, sox9 and amh are predominantly localized in Sertoli cells of the testis. These findings support our hypothesis and demonstrate that high temperature drives sex differentiation in S. schlegelii through distinct molecular programs, identifying core regulators and pathways underlying temperature-sensitive sexual development.