Histological Studies on Gonad of Trachycardium Flavum(Linnaeus)

A survey on the morphological changes of the gonad of clam Tracycardium flavum (Linnaeus) was conducted from June 1999 to May 2001 along the southeast coastal line of Hainan. The observation on the sexual maturity individuals showed that the normal ones were synchronous hermaphroditism and no dioecism. The gonad is composed of branch gonaduct, vasa deferentia and vasa efferentia. The gonaducts consist of great number of branchy genital ducts and follicles, the follicle is a capsular structure formed by enlargement of the end of branches and tubulus in the gonad, especially, the gonad showed by the transverse section is made up of adventitia and large amounts of twing seminiferous tubules and ovarioles. The adventitia consists of simple columnar and thin layer lamina. Each seminiferous tubule is made up of germinative area which constantly produces spermatogonium, spermatoccyte, spermatid and sperm, and the ovariole is made up of endogenic epithelium that grows into germinative zone which produces oogonium developing into other female germ cells. This paper gives the detailed description of the cytological characteristics of each developmental stage. They were primary and secondary spermatogonium or oogonium, primary and secondary spermatotyte or oocyte, matured sperm or egg. In addition, the reversal of the follicles in the gonad of the clam were reported.