诱导性成熟雌性大黄鱼性逆转的初步研究

Preliminary study on inducing sex reversal in mature female large yellow croaker(Larimichthys crocea)

【目的】大黄鱼雌鱼生长显著快于雄鱼,全雌苗种受到养殖业者期待。用雄激素处理性腺未分化的遗传雌性鱼苗,使其发育成为生理性雄鱼(XX♂),进而与原系雌鱼(XX♀)杂交,是制备全雌鱼苗的常规方法,但存在周期长、大黄鱼苗经雄激素甲基睾酮(MT)处理后生长受到严重抑制等问题。若能直接诱导雌性成鱼性逆转成为生理性雄鱼则可避免上述问题。本研究旨在探索通过诱导性成熟雌性大黄鱼性逆转培育为生理性雄鱼的可能性和诱导方法,为高效制备生理性雄鱼开辟一条新途径。【方法】在MT中加入一定比例的PHTPP作为诱导药物,将混合药物用壳聚糖制成胶条或溶解于大豆油中制成缓释液,注射到大黄鱼成熟雌鱼的腹腔进行诱导性逆转实验,观察性腺的组织学变化,并检测血清中性激素浓度和性腺中雌激素受体基因表达量的变化。【结果】MT-PHTPPA-大豆油混合液的诱导效果优于壳聚糖-MT-PHTPP药条;用(40μg MT+4μg PHTPP)/kg鱼体质量的剂量腹腔注射MT-PHTPPA-大豆油混合液,持续处理80 d后,实验组大黄鱼的卵巢退化,形态变成与精巢相似,其中形成大量精原细胞,血清中雌二醇(E2)浓度显著下降、11-酮基睾酮(11-KT)浓度显著上升(P<0.05),性腺中E2受体Esr2基因的表达受到严重抑制。【结论】通过诱导性腺分化完成乃至发育成熟的雌性大黄鱼性逆转培育生理性雄鱼是可能的。

[Objective]The growth rate of female large yellow croaker(Larimichthys crocea)is significantly faster than that of males,making all-female fry highly desirable to aquaculturists.A common method to produce all-female fry involves treating genetically female fish(XX)with androgens before gonadal differentiation to develop them into physiological males(neomale,XX♂),and then crossing them with original females(XX♀).However,this method is time-consuming and androgen treatment(using methyltestosterone,MT)severely inhibits the growth of L.crocea fry.Directly inducing sex reversal in adult female L.crocea to become physiological males could circumvent these issues.This study aims to explore the possibility and methods of inducing sex reversal in sexually mature female L.crocea to cultivate physiological males,providing an efficient new approach to produce physiological male fish.[Methods]A combination of MT and PHTPP was used as an inducing agent.The mixed drug was made into chitosan gel strips or dissolved in soybean oil to create a sustainedrelease solution.The mixture was injected into the abdominal cavity of mature female L.crocea to induce the sex reversal of the fish.The histological changes in the gonads were observed,and changes in serum sex hormone levels and the expression of estrogen receptor gene in the gonads were measured.[Results]The results showed that the MT-PHTPP-soybean oil mixture had a better inducing effect than the chitosan-MT-PHTPP gel strips.Injecting a dose of(40μg MT+4μg PHTPP)per kg of fish body mass of the MT-PHTPP-soybean oil mixture into the abdominal cavity and continuing treatment for 80 days resulted in ovarian degeneration in the experimental group.Morphologically,the ovaries exhibited changes resembling testes.A large number of spermatogonia were formed,serum estradiol levels significantly decreased,and 11-ketotestosterone levels significantly increased(P<0.05).The expression of the estrogen receptor Esr2 gene in the gonads was severely inhibited.[Conclusion]The experimental results indicate that it is possible to cultivate physiological male L.crocea by inducing sex reversal in sexually mature females through gonadal differentiation and development.