Gonadal Sex Differentiation in Tilapia mossambica, with Special Regard to the Time of Estrogen Treatment Effective in Inducing Complete Feminization of Genetic Males
Gonadal Sex Differentiation in Tilapia mossambica, with Special Regard to the Time of Estrogen Treatment Effective in Inducing Complete Feminization of Genetic Males
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莫桑比克罗非鱼的性腺性别分化，特别是有效诱导遗传雄性完全女性化的雌激素治疗时间
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发表时间：
1973
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影响因子：
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通讯作者：
Hiroya Takahashi
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作者：
Masaru Nakamura;Hiroya Takahashi
莫桑比克罗非鱼的成对原始性腺在孵化后8-10天形成，此时生殖细胞开始逐渐增殖并发育成生殖细胞。在20日龄左右，性腺的性分化即为卵巢或睾丸，一些生殖细胞发育进入减数分裂前期，伴随着卵巢腔的形成，卵巢开始分化，而性腺间质中的传出原基的出现，则促进了睾丸的分化。因此，卵巢中的生殖细胞能顺利地进行卵子发生过程，而精巢中的生殖细胞在50日龄以前一直处于静止状态。在一项实验中，以每克饲料50微克的恒定剂量口服炔雌醇，在6至25日龄期间进行治疗，包括性冷淡阶段到性别分化阶段，获得了完全雌性化的生殖雄性。在这两个阶段中的任何一个持续10天的处理都没有引起任何性改变，并且在这两个阶段中进行了10天的实验，结果在生殖雄性中出现了间性性腺。从这些结果推测，T.在mossambica中，获得完全性逆转对外源性激素敏感的时期可能是在hatohing后10 - 25天，在此期间性腺开始分化并进行。自从Yamamoto 1）通过雌酮处理实现了Oryzias latipes的功能性雌性化以来，人们普遍认为，通过施用异源性激素可以相当容易地诱导硬骨鱼的完全的和功能性的性逆转。从鱼类繁殖的观点来看，鱼类性别的人工控制可能是一个重要而有趣的课题，有待于进一步发展。然而，在实施外源性性激素人工性定向方面，仍有许多问题需要解决。根据Yamamot 02），要实现鱼类完全和功能性的性别逆转，需要满足的条件是，从性冷淡阶段开始，并持续到性腺性别分化阶段，以足够的剂量水平向鱼苗施用异源性激素。本文报道了日本北海道大学水产系淡水养殖研究室对青鳉（Oryziaslatipes 1）3）、网斑绿蝽（Lebistesreticula）进行的功能性性逆转实验。l！）
In Tilapia mossambica, paired primordial gonads are formed 8-10 days after hatching, when germ cells begin their gradual multiplication and development into gonial ones. Sex differentiation of gonads either into ovaries or into testes becomes histologically discernible about 20 days of age: the development of some germ cells into meiotic prophase and the concomitant start of ovarian cavity formation oharacterize ovarian differentiation, while the ooourrence of efferent duot anlages in gonadal stroma oonfirms testioular differentiation. Henoeforth, germ oells in the ovary advanoe their oogenetio processes smoothly, but those in the testis remain quiescent until about 50 days of age. By oral administration of ethinylestradiol at a constant dose of 50 p,g per g diet, a complete feminization of genetio males was obtained in an experiment in which the treatment was done during a period from 6 to 25 days of age covering the sexually indifferent stage through the stage of sex differentiation. The treatments lasting for 10 days in either of the two stages were without effeot in causing any sexual modification, and an experiment carried out for 10 days extending through the two stages resulted in the occurrenoe of intersexual gonads in genetio males. It is presumed from these results that, in T. mossambica, the period sensitive to exogenous sex hormones for attaining complete sex reversal may lie between 10 and 25 days after hatohing during whioh gonadal sex differentiation begins and proceeds. Since Yamamoto1) achieved the functional feminization of Oryzias latipes by treatment with estrone, it has become generally thought that a complete and functional sex reversal can be induced rather easily in teleost fishes by the administration of heterologous sex hormones. From a viewpoint of fish propagation, artificial control of sex of fishes may be an important and interesting subject which awaits future development. There still remain, however, many problems to be solved in practicing the artificial direction of sex by exogenous sex hormones. According to Yamamot02), the conditions to be fulfilled to attain a complete and functional sex reversal of fishes are that a heterologous sex hormone should be administered at adequate dosage levels to fish fry starting at the sexually indifferent stage and lasting through the stage of gonadal sex differentiation. The cases of functional sex reversal experimented so far in Oryzias latipes1)3), Lebistes reticula* Laboratory of Fresh-Water Fi8h-CUlture, Faculty of Fisheries, Hokkaido University (;ft~m*~7.kgi~$~7.k~~~~1!l!)