Relationship between PGCs Settle and Gonad Development in the Early Chicken Embryo

Chick embryos from stage 14 to stage 31 were studied by means of serial section and light microscopy in order to learn the relationship between the settlement sites of the primordial germ cells (PGCs) and the forming genital ridge. The results showed that: when embryo hatched for 53-56 h, the PGCs reached the coelomic epithelial tissue where gonad would be formed, meanwhile the epithelial tissue began thicker before the PGCs reached. Before stage 19, the final region the PGCs arrived was the thickened portion of the coelomic epithelium, the glycogen in the PGCs cytoplasm maintenance remained unchanged. However at the 3.5-5th hatching day, the glycogen in the PGCs cytoplasm reduced gradually. On the 6th hatching day, the gonad of the embryo appeared the feature of ovary, and the glycogen in the PGCs cytoplasm reduced further. On the 7th hatching day, the differentiation of ovary or testis was obvious and the glycogen in the PGCs cytoplasm later disappeared.