Characterization of early gonadal differentiation and estrogen-induced feminization in Chinese longsnout catfish (Leiocassis longirostris)

Abstract

In this study, we investigated the growth performance and early sex differentiation in Chinese longsnout catfish (Leiocassis longirostris), and further systematically evaluated its feminization by oral administration of various doses and treatment durations of 17β-estradiol (E₂). Under the same breeding condition, the growth rate of male Chinese longsnout catfish was 20.8 % and 33.9 % faster than that of the female sibling at one- and two-year-old, respectively. The ovarian cavity began forming on 15 dph and completed by 21 dph, while the primary oocytes were at chromatin-nucleolus stage by 33 dph and at the peri-nucleolus stage oocytes by 65 dph. In presumptive testis, the seminiferous lobule appeared on 15 dph and the efferent duct anlage presented on 53 dph. Subsequently, germ cells entered into mitosis and formed the spermatogonia at 69 dph. Compared with the control group (no E2 diet), the fries treated with E2 at 10, 50, 100 or 150 mg/kg diet from 10 to 90 dph were 100 % female by morphology and histology observation. However, the growth and survival rate rapidly decreased as the E₂ dosage rose. Furthermore, fries treated with10 mg/kg E₂ during 15–85 dph, 20–80 dph, 25–75 dph, 30–70 dph, 35–65 dph and 40–60 dph were explored. 3.33 ± 3.33 % and 45.55 ± 5.09 % sex reversal ratio was identified in 30–70 dph and 35–65 dph group, respectively. All female populations were observed in 15–85 dph, 20–80 dph and 25–75 dph groups, despite slow development of ovary among them compared with the control group. Additionally, the growth performance of fries in 25–75 dph group was closest to that of the control group, while their serum E₂ and 11-KT levels were consistent with XX females. Transcriptomic analyses were performed to assess gene expression difference among the XX females, XY males and feminized XY females, and most DEGs were shared between XY male vs XX female and XY male vs XY female. In addition, qRT-PCR validation of 12 DEGs associated with gonadal differentiation were consistent with RNA-Seq analysis (r=0.942, P<0.000). This study suggests that 10 mg/kg E₂ treatment from 25 to 75 dph is the optimal approach for the feminization of Chinese longsnout catfish.