Variation in the ontogeny of sex steroid levels between latitudinal populations of the medaka.
Variation in the ontogeny of sex steroid levels between latitudinal populations of the medaka.
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DOI：
10.1186/s40851-015-0032-1
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发表时间：
2015
影响因子：
2.7
通讯作者：
Yamahira K
中科院分区：
文献类型：
--
作者：
Kawajiri M;Uchida K;Chiba H;Moriyama S;Yamahira K
性类固醇在个体发育过程中介导性二态性的表达，并且性二态性程度不同的群体相应地其性类固醇水平的个体发生模式也可能不同。青鳉，Oryzias latipes 复合体，在肛鳍和背鳍长度方面表现出性别二态性程度的地理差异。低纬度人群的二态性大于高纬度人群。然而，性类固醇个体发育动力学的性别差异及其群体间变异尚未得到研究。我们测量了来自青森县（北部）和冲绳县（南部）这两个纬度种群的实验室饲养鱼类在整个个体发育过程中的睾酮 (T)、雌二醇-17β (E2) 和 11-酮睾酮 (11-KT) 浓度。在这两个种群中，所有三种类固醇的水平在早期个体发育阶段都很高，并随着生长而降低。标准长度达到约 15 毫米后，当鳍长度的性别二态性变得明显时，类固醇水平就会增加并趋于稳定。仅在个体发育后期才观察到类固醇水平的性别差异。男性的 T 和 11-KT 水平较高，而女性的 E2 水平较高。相应地，人群间的差异也变得更加明显。南方的鱼往往比北方的鱼表现出更高的T水平和更低的E2水平。性类固醇水平的个体发育模式与两个纬度种群中臀鳍和背鳍的个体发育平行，表明鳍长度两性二态性程度的种群间变异是由性类固醇依赖性鳍伸长调节介导的。
Sex steroids mediate the expression of sexual dimorphism during ontogeny, and populations that differ in the magnitudes of sexual dimorphism may accordingly differ in the ontogenetic patterns of their sex steroid levels. The medaka, Oryzias latipes species complex, shows geographic variation in the magnitude of sexual dimorphism with respect to the lengths of their anal and dorsal fins; dimorphism is greater in low-latitude populations than in high-latitude populations. However, sexual differences in the ontogenetic dynamics of sex steroids, and its interpopulation variation, have not been examined. We measured testosterone (T), estradiol-17β (E2), and 11-ketotestosterone (11-KT) concentrations throughout ontogeny of laboratory-reared fish from two latitudinal populations: Aomori (northern) and Okinawa (southern). In both populations, the levels of all three steroids were high during early ontogenetic stages and decreased with growth. After reaching about 15 mm in standard length, when sexual dimorphisms in fin lengths became apparent, steroid levels increased and tended to plateau. Sexual differences in the steroid levels were observed only in the later ontogenetic stages; T and 11-KT levels were higher in males, while E2 levels were higher in females. Accordingly, interpopulation differences also became clearer; the southern fish tended to show higher T levels and lower E2 levels than the northern fish. The ontogenetic patterns of sex steroid levels paralleled the ontogeny of anal and dorsal fins in the two latitudinal populations, suggesting that interpopulation variation in the degree of sexual dimorphisms in fin lengths is mediated by sex steroid-dependent regulation of fin elongation.