내인성 호르몬을 이용한 자바리 Epinephelus bruneus 치어의 웅성화 유도

Abstract

The purpose of this study was to examine the effects of endogenous and exogenous hormones for the induction of sex reversal in juvenile longtooth grouper Epinephelus bruneus. This study was investigated endocrine mechanism during sex change by radioimmuno -assay, real-time RT-PCR and histological observation. Experimental fish were juvenile longtooth groupers (body weight, 113 ± 17 g, body length 16.2 ± 1.2 cm). The fish were injected with a non-steroidal aromatase inhibitor (AI, Fadrozole) in a dose of 3 and 5 mg/kg·BW and 17α-methyltestosterone (MT) in a dose of 5 mg/kg·BW. The fish were sampled at 7th and 21st week after the injection. 1. Changes of gonad by endogenous hormone treatment during masculinization Immature ovaries with oogonia and a few perinucleolus oocytes were observed in the gonad of the control groups at the beginning of the experiment. The control groups 7 weeks after the injection exhibited a similar trend as the initial control. A few atretic oocytes and oogonia were found in the gonad of MT 5 mg treatment group. Gonad of AI 3 mg treatment group mostly contained oogonia, and a few perinucleolus oocytes. Gonad of AI 5 mg treatment group were observed to induce sex change. The gonad was observed to have various stages of spermatogenic germ cell and mostly spermatozoa with no ovarian germ cells. Gonad of control group 21 weeks after the injection contained mostly perinucleolus oocytes. Gonad of MT 5mg treatment group contained oogonia, atretic oocytes and was observed to have spermatogenesis from spermatogonia to spermatocyte. Gonad of AI 3 mg treatment group were observed to contain a few perinucleolus oocytes, atretic oocytes and observed spermatogenesis from spermatogonia to spermatocyte. Goand of AI 5 mg treatment group were observed to contain a few perinucleolus oocytes and atretic oocytes, and it was observed that spermatogenesis was occurring from spermatogonia to spermatocytes more than that in the other treatment groups. In conclusion, the findings in this study support the hypothesis that the induction of sex change from female to male in juvenile longtooth grouper could be controlled by aromatase inhibitor. 2. Changes of endocrine mechanism during masculinization Serum levels of E2 showed no significant differences from initial to the end of the experiment except for the control group (P>0.05). In contrast, 11-KT was significantly increased in AI 5 mg treatment groups at 7th and 21st weeks after the injection (P<0.05). Real-time RT-PCR analysis showed that FSHβ mRNA in initial group and whole group after 7 weeks were not significantly different (P>0.05). In contrast, only AI 5 mg injected groups after 21 weeks significantly increased expression of FSHβ mRNA (P<0.05). mRNA levels of LHβ were not significantly different in this experimental period (P>0.05). These results suggest that FSHβ mRNA and 11-KT may trigger masculinization in juvenile longtooth grouper.