Segregation of primordial germ cells: Their numbers and fate during early development of Barbus conchonius (Cyprinidae, Teleostei) as indicated by 3H‐thymidine incorporation

摘要: 3 H-Thymidine incorporation experiments in Barbus conchonius showed that presumptive primordial germ cells (PGCs) terminated their mitotic activity between midepibolys, and late epiboly. At the ten-somite stage, shortly after labeling of PGCs by uptake H-thymidine became arrested, they could be recognized relatively large size nucleus. They were located two longitudinal rows mesoderm periblast, always at same distance to left right notochord. Contact with endoderm was not observed before 16- 23-somite stage. The numbers small (mean number, 18-19) remained for nearly weeks. Mitotic during period; thereafter, rapid proliferation began. There is no evidence active migration PGCs; it assumed are merely translocated passively together surrounding tissues. No specific constituents detected histochemical methods glycogen, alkaline phosphatase, RNA. Electron microscopy revealed presence "nuage" around nucleus PGCs. This material corresponded perinuclear dense bodies as seen light from 19-somite stage onward. It concluded segregate somatic midepiboly epiboly, three layers have been formed, locations endodermal or mesodermal layer may transitory stages translocation toward gonadal primordia.