Studies On The Differentiation And Development Of The Gonad Of Varicorhinus Macrolepis

In the paper, the PGCs' origin and migration of Varicorhinus macrolepis was studied, as well as the differentiation, development and maturation of gonad at microscopic and submicroscopic levels.The first EXP was the study on the origin and migration of PGCs and the featues of PGCs by light microscopy, transmission electron microcopy and PAS reaction. The PGCs of Varicorhinus macrolepis first appeared in the mesoderm of early gustrula and subsequently remained in the hypoblast of the embryonic region during late gustrula and neurula stage. At the stage of muscular effect they were found in the splanchnic mesoderm and the proceeded around the gut to the dorsal mestery during hatching stage. In the end, they translocated to the genital ridges where they formed the indifferent gonad with the somatic cells of genital ridges. PGCs were larger in comparison with somatic cells. They had big and bright nucleus which possessed the distinct nuclear membrance. The cytoplasm of PGCs was weak acidophilic. By transmission electron microcopy, the electron–dense bodies (EDB) were observed in the vicinity of PGCs' nuclear membrance. During the migration, the PGCs deformed. The PAS reaction was positive.The second study suggested that the ovarian differentiation of Varicorhinus macrolepis was happyed 60 days age, it needed about 44 days for ovary to finish the differentiation, then it enters theⅠperiod. At the age of 70 days', the testis differentiation of Varicorhinus macrolepis took place. On the 118th day, the testis differentiation completed. So the differentiation of ovary was earlier than that of testis. During the differentiation of ovary, the ovary antrum was first formed. Before testis differentiation, there was an antrum at the stem of gonad. In the future it can develop into the ductus deferens. Therefore, the ovary antrum and ductus deferens were the symbols of the gonad differentiation of Varicorhinus macrolepis. The ovary and testis of Varicorhinus macrolepis came from the same gonad and kept the same sexual distinction in its all life, so it was belonged to the gonochorism.The third EXP was the development of ovary during the first sexually mature and the ultrastructure of different stages of oocytes in Varicorhinus macrolepis by light microscopy and transmission electron microcopy. The ultrastructural feature of oocytes in different stages and the formation of yolk granules were described. The ovarian development before the first sexually mature and oocytes were divided into five stages. It needed about 3 years for the Pref. Varicorhinus macrolepis to develop into sexually mature, while some Varicorhinus macrolepis, which developed fast became maturally when they were even 2 years old. When the condition was improved, the matural age could be ahead of 1~2 years. In the last EXP, the testis development during the first mature and the ultrastructure of spermatocytes of were studied. The process of spermatid formation was described. The testis development during the first mature and different stages spermatocytes were also divided into five stages. The development of testis was faster than that of ovary, and it took Male Varicorhinus macrolepis 2 years to attend the reproductive activity. In addition, the matural age was closed with development speed. The faster individual can take part in the reproductive ahead.