Many teleost fishes undergo natural sex change, and elucidating the physiological and molecular controls of this process offers unique opportunities not only to develop methods of controlling sex in aquaculture settings, but to better understand vertebrate sexual development more broadly. Induction of sex change in some sequentially hermaphroditic or gonochoristic fish can be achieved in vivo through social manipulation, inhibition of aromatase activity, and steroid treatment. However, the induction of sex change in vitro has been largely unexplored. In this study, we established an in vitro culture system for ovarian explants in serum-free medium for a model sequential hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). This culture technique enabled evaluating the effect of various treatments with 17β-estradiol (E₂), 11-ketotestosterone (11KT) or cortisol (CORT) on spotty wrasse ovarian architecture for 21 days. A quantitative approach to measuring the degree of ovarian atresia within histological images was also developed, using pixel-based machine learning software. Ovarian atresia likely due to culture was observed across all treatments including no-hormone controls, but was minimised with treatment of at least 10 ng/mL E₂. Neither 11KT nor CORT administration induced proliferation of spermatogonia (i.e. sex change) in the cultured ovaries indicating culture beyond 21 days may be needed to induce sex change in vitro. The in vitro gonadal culture and analysis systems established here enable future studies investigating the paracrine role of sex steroids, glucocorticoids and a variety of other factors during gonadal sex change in fish.

中文翻译：

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体外卵巢外植体培养系统，检查雌雄同体鱼的性别变化

许多硬骨鱼类经历了自然的性别变化，阐明这一过程的生理和分子控制不仅提供了独特的机会，不仅可以开发水产养殖环境中控制性别的方法，而且可以更广泛地更好地了解脊椎动物的性发育。通过社会操纵，抑制芳香化酶活性和类固醇治疗，可以在体内诱导某些顺序的雌雄同体或性腺生殖器发生性变化。然而，在很大程度上尚未探索体外诱导性别变化。在这项研究中，我们建立了无血清培养基中用于卵巢外植体的体外培养系统，用于模型连续雌雄同体，新西兰斑点濑鱼（Notolabrus celidotus）。这种培养技术能够评估用17β-雌二醇（E ₂），11-酮睾酮（11KT）或皮质醇（CORT）进行的各种处理对斑点状濑鱼卵巢结构的影响，持续21天。还使用基于像素的机器学习软件开发了一种定量方法，用于测量组织学图像内的卵巢闭锁程度。在包括无激素对照在内的所有治疗中均观察到可能由于培养引起的卵巢闭锁，但通过治疗至少10 ng / mL E ₂可使卵巢闭锁最小化。11KT或CORT给药都不会在培养的卵巢中引起精原细胞增生（即性别改变），表明体外培养21天以上可能不需要诱导性别的改变。在体外 这里建立的性腺养殖和分析系统使未来的研究能够研究性激素，糖皮质激素和鱼类性腺性别变化期间各种其他因素的旁分泌作用。