The Study Of The Embryonic And The Larvae's Development Of Teleost, Spinibarbus Caldwelli And Its PGCs' Origin,Migration And Differentiation

In this paper, the embryonic and the larvae's development of teleost,Spinibarbus Caldwdli and its PGCs'origins migration and differentiation were studied at microscopic and submicroscopic levels.The fertilized eggs of Spinibarbus Caldwelli were obtained by artificial insemination. Based on the morphological features and developmental characteristics of the embryo, the process of embryonic development could be divided into 22 stages which belonged to 6 embryonic periods. At the water temperature of 25-28℃, the embryonic development lasted 45 hours and 15 minutes. And the process of the larvae's development could be divided into four stages.In comparison with somatic cells, PGCs were large with large nuclei, which contained one or two prominent nucleoli and possessed a distinct nuclear membrane. The cytoplasm of PGCs was weak-acidophilic. In addition, there were annulate lamellae and plenty of mitochondria in the cytoplasm. Ultrastructural analysis of PGCs had revealed that the presence of lots of "electron-dense bodies", which appeared as high-electron-dense cytoplasmic inclusions in the vicinity of nuclear membrane, often observed in association with mitochondria. These electron-dense bodies were strong-alkalophilic. During the migration, the deformed PGCs which were longer and slimmer with an extended nuclear were observed.Blastula stage was the earliest stage at which PGCs was observed. PGCs were associated with the blastoderm margin at first and subsequently remained in the hypoblast of the embryonic shield region during mid-gastrula and neurula stage. Later they migrated to the splanchnic mesoderm during the stage of muscular effect and then proceeded around the gut to the dorsal mesentery 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. The whole migration process had something to do with both the surrounding tissues and the active migration ability of PGCs themselves. The differentiation and development of Spinibarbus caldwelli testes were earlier than that of ovaries.