The development of primordial germ cells (PGCs) and testis in the quail embryo

Histological methods were conducted to detect the development of quail primordial germ cells (PGCs), the pattern of gonads differentiation and different characteristics of testis structure at various developmental stages. We found that on day 4 of post-incubation all PGCs migrated to gonad ridge and formed undifferentiated gonads; on day 5 the gonads differentiated into testis or ovary. On day 7 to 9 of post-incubation, the morphological characteristics of testis were distinguished, subsequently testicular cord appeared and the PGCs differentiated into spermatogonium on day 10. On day 12 of post-incubation, spermatogonia seemed like clusters of grape or chain in the middle of convoluted seminiferous tubule; simultaneously, a few of sustentacular cells and vascular were developed for filling into the testis lumen. Then on day 15, the seminiferous tubule become thicker and the amount of spermatogonia increased by mitosis. Finally, on hatch day (day 17), the testis almost be mature with numerous mesenchymal cells, connective tissue, vascular and clear and intensive seminiferous tubules. These results can lay data for future studies on sex determination mechanism and the more utilization of PGCs in poultry.