可口革囊星虫(Phascolosoma esculenta)卵黄合成期卵母细胞发育及卵黄发生与卵膜形成的超微结构

ULTRASTRUCTURAL OBSERVATION ON OOGENESIS,VITELLOGENESIS AND VITELLINE MEMBRANE FORMATION DURING YOLK-SYNTHESIZING STAGE IN PHASCOLOSOMA ESCULENTA

采用电镜技术观察研究了可口革囊星虫卵黄合成期卵母细胞发育及卵黄发生与卵膜形成的超微结构特征。结果表明,可口革囊星虫卵黄合成期卵母细胞发育经历了卵黄合成初期、卵黄旺盛合成期及生长成熟期三个阶段。卵母细胞卵黄发生途径主要由线粒体、内质网、高尔基体等细胞器演变成卵黄粒,以及吞饮作用形成卵黄粒。卵母细胞质膜外被有卵黄膜,由卵母细胞自体形成,且随生长而加厚;卵黄膜具通透性,外源营养物质能透过卵黄膜进入卵内。生长成熟的卵母细胞卵黄膜厚7—9μm,从内向外由纤维层、致密层、粒状突层及外膜构成,保护卵母细胞维持特定的形状。

Electron microscopy technology was employed to investigate the ultrastructural changes during oogenensis, vitellogenesis and vitelline membrane formation in the sipunculan Phascolosoma esculenta. The results show that oogene- sis in this species could be divided into three stages： the primary yolk synthesis stage, rapid yolk synthesis stage and maturation stage. Organelles including mitochondria, endoplasmic reticulum and Golgi apparatus can evolve into yolk granules via pinocytosis. The plasma membrane of oocyte is covered by vitelline membrane which is formed by the oocyte itself and thickens as the oocyte grows. The vitelline membrane is permeable, so external nutrients can penetrate through it and be utilized during oocyte development and vitellogenesis. The vitelline membrane of the growth mature oocyte is 7--9ktm thick, consisting of the fiber layer, the dense layer, granular protuberance layer and jelly coat. This tough and flexible structure could help the oocyte to maintain the specific shape.