人工诱导点带石斑鱼性逆转的组织学证据及其机制探讨

Histological Evidence and Mechanism in Artificial Inducement of Sex Reversal of the Grouper, Epinephelus malabaricus

对外源混合激素药条肌体埋植法诱导点带石斑鱼提早性逆转的发育过程进行了组织学观察,结果表明:(1)3～5龄的雌鱼能在50～70天内转变为功能性雄鱼,年龄较小的雌鱼性转时间相对长些。(2)性转雄鱼精巢组织的雄性生殖细胞包括:精原细胞、初级精母细胞、精子细胞和精子,精子头部呈球型直径约1.5～2.5μm.尾长12.4～44.5μm,与天然雄鱼相似。(3)人工诱导性转雄鱼可取代天然雄鱼进行人工繁殖。(4)点带石斑鱼的性逆转机制为性类固醇依赖型。外源雄性激素通过抑制“雌性相关基因”的表达,而成为石斑鱼性逆转的启动因子,诱发卵巢退化和精巢的发育,直至精子生成。

Treatment with exogenous mixed-hormones in a strip, using the method of intramuscular implantation, for a period about 50-70 days induced precocious sex reversal from the mature female of 3-5 years old to functional male grouper, Epinephelus malabaricus, and the duration of mixed -hormones for sex reversal treatment was longer on young mature female than on old female. The gonads of complete sex-reversed fish contained functional testicular tissue with spermatogonia, first spermatocytes, secondary spermatocytes, spermatids and spermatozoa, their diameters were 6.5-10.5μm,4.5-5.5μm,3.5-4.5μm,2.5-3.5μm,1.5-2.5μm, respectively. The head of spermatozoon from artificial inducted functional male is in the shape of ball, spermatozoon caudal length 12.4-44.5μn, that is homologue with the spermatozoa of natural male . The artificial induced functional male was used for artificial fertilization with the ova out of ovary of natural female, producing successfully more than 1.45 million seed fry of E. malabaricus over 3cm of total length during breeding season of E. malabaricus , 2002. So that the artificial induced sex-reserved functional male could replace the natural male in production of the seed fry of E. malabaricus. The paper discussed the above results, considered it that the mechanism of sex reversal of the E. malabaricus was the type of depending on the concentration of male sex steroid. The expression ofcorrelative female developmental gene was restrained when the exogenous male sex steroid of fish got to certain concentration, and could induce that the female degenerated ovarian tissues into the spermary tissues, up to appearing the spermatozoa, finally becomed functional male.