纳木错裸鲤性腺发育的组织学研究

HISTOLOGICAL STUDIES ON THE GONADAL DEVELOPMENT OF AN ENDEMIC TIBET FISH GYMNOCYPRIS NAMENSIS

采用常规的组织切片方法 ,对西藏特有鱼类纳木错裸鲤的性腺发育进行了组织学研究 ,系统地描述了各期精巢和卵巢的形态结构、特征及其变化。尤其论述了其卵巢中卵细胞的卵黄核破碎与分解的特点、卵膜的结构、核仁排出物在卵黄形成过程中的作用 ,以及卵粒重吸收的过程。根据各期卵巢中卵母细胞的组成情况 ,认为纳木错裸鲤已达性成熟的个体并不是每年都参与繁殖活动是对高原极端、多变气候环境的一种生态适应 ;阐明了纳木错裸鲤属于分批同步产卵鱼类。

The histology of the gonadal development of namucuo naked carp,Gymnocypris namensis which is endemic to the Namucuo Lake, Northern Tibet, was studied. The volume of the ovary increased markedly in August and attained at maximum in December, egg-laying was from April to August. At the end of the spawing, a larger number of oocytes which remained in ovary became astrophied and were re-absorbed subsequently. The oogenesis is composed of six phase. In the phase 2 of the development of the oocytes, the yolk nucleus, which was possibly related to the formation of yolk, broke up and formed a ring in the outer cortex. From the later phase 2 to the middle phase 3, the nucleoli of the oocytes contained substance, which was probably related to the formation of protean yolk granules, and entered into cytopalsm by the part rupture of the nuclear membrane. In the phase 4, vitelline membrane was composed of 2 layers: zona radiata or the primary membrane which is mostly formed by oocyte and the second membrane which is possibly formed by granulosa. The micropyle canal was blocked by more than 10 micropylar cells whichs formed a vesicle. In a reproductive season, the ovary of namucuo naked carp matured only once in a year and the mature fish could spawn surely more than one time.