文昌鱼的精子发生及释精过程

PROCESS OF SPERMATCGFNSlS AND SPERMIATION IN AMPHIOXUS

本文较详细地描述了文昌鱼精巢重新形成过程中,精原细胞的增殖和分化。本工作首次观察到原始精原细胞的形态特点,初级精母细胞的成熟分裂、精子形成以及精子释放的过程。我们的研究结果表明,精原细胞至少经三次有丝分裂后才进入初级精母细胞,但未观察到文昌鱼精巢中有类固醇激素生成细胞。我们还观察到文昌鱼释精的另一途径,即精子先在鳃裂和内柱周围聚集。后经咽至口排出。

The paper describes the proliferation and differentiation of primitive spermatogonia, meiesis of primary spermatocyte, spermiogenesis and spermiation in the reforming process of amphioxus testis. The observations of light microscope indicated that the germinal capsulex were the first to be formed. Then, the gonadal rudiment appeared. At this time, the primitive spermatogonia which lie in clese morphological asscciation with the basement lamina of the testicular wall, had a rounded large nucleus and a thick nuclear envelope. On the nuclear membrane the chromatin was usually visualized. There was a nucleolus in the centre. The nucleus of a type spermatogonia was nucleus smaller than the primitive spermatogonia. The chromatin granule in the were more clearly than that of the primitive spermatogonia, usually 6—8 ones, and there was a nucleolus in the nuclear centre. The B type spermatogonia differenciates from the above two types of cells in no thickening of the nuclear envelope, with only a nucleolus and almost without chromatin granula. We considered that spermatogonia may enter the primary spermatocyte by three times of mitosis. The supporting or Sertoli cells in the amphioxus testis are large irregular cells with prominent vesicular uncleus. These cells located close to the gbasement membrane. However, no steroid secreting cell was observed. Some spermatozoa have been found in the gill clefts and the flagella of endostyle, which provided strong evidences for the escape of spermatozoa via pharynx to mouth, therefore, we considered that there ought be another way for the spermiation of amphioxus.