关键词: 东北梅花鹿, 初级卵母细胞, 发育, 超微结构

Abstract: Seven 4 to 5 years old female Skia deer（Cervus nippon hortulorum）both in their reproductive and non-reproductive season were used to study the ultrastructural changes of the primary oocytes during their development by using transmission electron microscopy. The ovarian tissues were treated according the requirement for the examination via electron microscope. The follicles were divided into 4 groups according to their development. The results showed that at the primordial follicle stage, the oocyte was round and its plasma membrane closely adhered to the follicle cells,most organelles located were near the nucleus，the Golgi complex was not typical，and most mitochondria with fewer cristae were round. At primary　and secondary follicle stage，follicles locally formed zona pellucida when they consisted of 2 to 4 layers of follicle cells，irregular microvili on the oocyte were present in the zona pellucida. At teriary follicle stage with a diameter of 0.5 mm to 1.5　mm, the zona pellucida became thick，the number of rough endoplasmic reticulum decreased obviously, and all kinds of organelles　and the Golgi complex increased number in the cortex. At the 1. 5 mm to 3 mm diameter follicle stage，the zona ellucida kept on increasing in its thickness，the microvili on oocyte became short and curving and started to withdraw from he zona pellucida，and a large number of cortical granules began to laid beneath the plasma membrane of the oocyte.

Key words: Development, Primary oocyte, Sika deer（Cervus nippon hortulorum）, Ultrastructure