Background: Among the birds, chicken was the model used in the majority of studies on germ cells and other birds like quail, turkey and pheasant had some interest but ostrich has been lacking from these researches. Aims: The present study was conducted to confirm the presence of ostrich primordial germ cells (PGCs) in the embryonic blood and to determine the appropriate time for having them in the blood. Methods: Embryos were extracted in embryonic day (E) 6-12, their blood was obtained and the rest of the embryos were processed for histological examinations. Staining by periodic acid-Schiff (PAS) method and immunohistochemistry (IHC) using stage-specific embryonic antigen 1 (SSEA1) and stage-specific embryonic antigen 4 (SSEA4) antibodies (Abs) were used for identification of the PGCs. Results: While the blood circulating ostrich PGCs were SSEA1-negative and SSEA4-positive, in the presumptive gonads PGCs showed negative immunoreactivity for both Abs. Although the ostrich PGCs were PAS-positive in both blood and presumptive gonad, their PAS-positive contents reduced during development from E 10 to E 12. Conclusion: E 9, when the hind limb buds appear, is the best time for detecting PGCs in the ostrich embryonic blood.

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