单环刺螠生殖腺的发生及雌体的生殖周期

Gonadal Ontogenesis and Annual Development of Ovary and Oogenesis in Urechis unicinctus

采用组织学方法观察单环刺螠(Urechis unicinctus)生殖腺的发生、卵巢的结构及其年周期变化。结果显示:3.5cm幼螠中,原始生殖细胞迁至后肠管壁外的结缔组织膜处,并数个集群与该处的体细胞共同构成性腺原基;至4cm幼螠,性腺初具雏形;随着个体的生长和成熟,构成卵巢的细胞不断增殖,于虫体尾部后肠腹侧形成长条形膜状的卵巢,外周为卵原细胞,中央为结缔组织,其两端分别与后肠管壁外侧和体壁内侧相连。根据卵巢的组织学和体腔液中雌性生殖细胞的细胞学特征,单环刺螠的卵巢发育可划分为增殖期、生长期、成熟期、排放期和休止期5个时期。单环刺螠生殖腺为低等的定型类型,其卵巢成熟期较生殖期早半个月。

Gonad ontogenesis, histological structure were observed. Results showed that PGCs located at and annual development of Urechis unicinctus ovary connective tissue membrane outside respiratory intestine wall and constitute a gonadal primordium with ambient somatic cells as to 3.5 cm juveniles. And 4 cm juveniles own their initial conformation of ovary. With the individual growing and maturing, the cells composing the ovary increased gradually. Results of adult U. unicinctus paraffin slicing indicate that the gonad located at respiratory intestine as thin film shape consisted of germ ceils and connective tissue; oo- gonia distributed at external of gonad and connective tissue at the middle of gonad; both ends of the gonad connected with exterior of respiratory intestine wall and interior of body wall through developed fascicles. Based on histological observation results, annual cycle of ovary development of U. unicinctus were divided into five stages, proliferatbre, growing, mature, spawning and resting. The gonad of U. unicinctus be- longs to the lower and committed style. In addition, the ripe stage of U. unicinctus ovary is about 15 days earlier than its reproductive stage.