激素诱导斜带石斑鱼(Epinephelus coioides)雄性化的研究

MASCULINIZATION INDUCED BY ANDROGEN IN ORANGE-SPOTTED GROUPER EPINEPHELUS COIOIDES

石斑鱼属雌雄同体雌性先成熟鱼类,低龄鱼卵巢先成熟,表现为雌性,高龄鱼才性转变为雄性。本实验通过持续跟踪取样,分析了人工养殖条件下斜带石斑鱼(Epinephelus coioides)在36月龄内的性腺发育过程,发现其性分化完成后,雌性卵巢在9月龄后开始发育。因此,采取投喂含有雄激素甲基睾酮(MT)饲料的方法,可以在石斑鱼卵巢发育之前,成功诱导8月龄的斜带石斑鱼幼鱼向雄性方向发育。结果表明,以MT 10mg/kg饲料的剂量投喂3个月能够有效诱导卵巢未发育的幼鱼往雄性方向发育;但停止投喂MT后,幼鱼精巢又开始出现退化,不会继续往雄性方向发展,而转变为雌性。以上结果表明,斜带石斑鱼性别决定和分化除了受遗传因子和内分泌调控外,还受到年龄、体型和群体、环境等因子的影响,人工投喂MT激素的作用并不能从根本上影响石斑鱼幼鱼的性腺发育的方向,只有在持续剂量的MT激素诱导下,石斑鱼幼鱼才能发育为成熟的雄鱼。

Groupers are widely recognized as protogynous hermaphroditism with sex changeable from female in young age and then become male in adult. We observed the gonad development stage of orange-spotted grouper Epinephelus coioides cultured under artificial condition. The results show that ovarian development of the grouper originated in 9—12-month old age. Therefore, we fed fish with 17α-methyltestosterone(MT) in the 8th month before ovarian development started, and gonadal differentiation were successfully induced to be male. In addition, feeding with MT at dosage of 10 mg per kg pellets for 3 months could induce male sexuality. However, gonad development of the male individuals stopped developing into male but into female when MT feeding ended. In conclusion, the sex determination and differentiation of the grouper are not only influenced by genetic factors and reproductive endocrine, but also by the fish age, size, population, and environment factors. Artificial feeding MT hormone could not alter sex orientation into male entirely, but induce the development of testes. Young groupers would develop into female unless continuous feeding with MT is provided for inducing matured males ultimately.