| 摘要: |
| 为探究光裸星虫卵子发生的细胞学特点，利用电镜技术观察了光裸星虫体腔液中卵子发生过程的超微结构变化。结果表明：（1）光裸星虫体腔液中存在游离的卵原细胞和卵母细胞，卵母细胞的发育分为卵黄形成前期、卵黄形成初期、卵黄旺盛合成期和成熟期4个阶段。（2）卵原细胞的细胞器少，核质比大。卵黄形成前期，卵母细胞的细胞器有所增加，大量核仁外排物进入胞质中；出现卵黄膜和胶质膜，卵黄膜遍布微孔。卵黄形成初期卵母细胞核有较多突起，细胞器大量增加，出现分散分布的卵黄粒。卵黄旺盛合成期卵母细胞迅速增大，卵黄大量积累。成熟期卵母细胞核膜突起回缩，胶质膜易于脱落。（3）卵黄分为2种。Ⅰ型卵黄电子密度高，不发生融合，为内源性卵黄；II型卵黄中等电子密度，可融合为无定形卵黄块，为外源性卵黄。（4）成熟卵母细胞卵黄膜为三层，外层为颗粒层，表面具有粒状突；中层初始为均质结构，不断增厚并纤维化；内层致密，厚度不均。胶质膜电子密度极低。（5）卵子外有滤泡细胞，其核质比很大，细胞器少，在卵母细胞成熟期发生凋亡。文章还探讨了胶质膜、卵黄膜、滤泡细胞的功能，以及细胞器在卵黄形成中的作用。研究结果积累了光裸星虫卵子发生细胞学资料，为光裸星虫生殖调控与人工繁育研究提供理论参考。 |
| 关键词: 光裸星虫 卵子发生 卵黄 卵黄膜 超微结构 |
| DOI：10.11693/hyhz20160600123 |
| 分类号: |
| 基金项目:广东省科技计划项目，2012B020307008号。 |
附件 |
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| ULTRASTRUCTURE OF OOGENESIS IN COELOMIC FLUID OF SIPUNCULUS NUDUS |
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WANG Qing-Heng, ZHANG Jia-Wei, HAO Rui-Juan, HUANG Rong-Lian, DU Xiao-Dong
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Fisheries College, Guangdong Ocean University, Zhanjiang 524088, China
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| Abstract: |
| To understand the cytology underlying the oogenesis of Sipunculus mudus, scanning electron microscope and transmission electron microscope were applied to observe the morphology of oocytes in the coelomic fluid of S. nudus. The results show that the oogoniums and oocytes were free-floating in the coelomic fluid, and the development of oocyte could be divided into four stages, i.e., pre-vitellogenic stage, primary vitellogenic stage, active vitellogenic stage, and maturation stage. Fewer organelles were found in the oogonium having large nucleo-cytoplasmic ratios. During the previtellogenic stage, more organelles appeared in cytoplasm and plenty of nucleolar exudate was released into the cytoplasm of the oogonium. At the same time, vitelline membrane and jelly coat appeared and micropore was distributed widely in the vitelline membrane. In the primary vitellogenic stage, many enations formed on surface of oocyte nucleus, the number of organelles increased, and the yolk granules distributed scatteredly in the cytoplasm of oocyte. In the active vitellogenic stage, sizes of oocyte cells increased quickly and substantial accumulation of yolk took place. During the maturation stage, enations on surface of the oocyte nucleus disappeared and jelly coat fell off easily. Two types of yolk were found during the oogenesis. Type 1 was endogenous yolk in large electron density while Type 2 was exogenous yolk in medium electron density and undergone granules fusion to form a larger yolk mass. The mature oocyte vitelline membrane could be divided into three layers. The outer layer was with granular surface and no more thickening once the layer was formed; the middle layer was homogeneous in structure at beginning and then was thickened with fibrosis post oogenesis; the inner layer was compact in texture with uneven thickness. The jelly coat was very low in electron density. Oogonia and oocytes were with follicular cells having large nucleo-cytoplasmic ratio and few organelles. The follicular cells underwent apoptosis during the maturation stage. Furthermore, the function of the jelly coat, vitelline membrane, follicular cell and organelles during the formation of yolk were discussed. The results may enrich the cytology content of the oogenesis, and provide a reference to the procreation regulation and artificial breeding of S. nudus. |
| Key words: Sipunculus nudus oogenesis yolk vitelline membrane ultrastructure |
