Document Type : Original Article


1 Department of Basic Sciences, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran

2 Department of Biology, Faculty of Education for Pure Science ibn Al-Haitham, University of Baghdad, Baghdad, Iraq

3 Stem Cell Biology and Regenerative Medicine Research Group, Research Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran


Stage X is one of the formation stages in birds at which the blastoderm area is distinguished by two areas of area pellucida being responsible for formation of embryonic tissues and primordial germ cells, and area opaca forming the extra-embryonic tissues. Primordial germ cells are multi-potent stem cells giving rise to spermatogonia or oogonia. The present study was carried out to describe the characteristics of primordial germ cells in stage X of pheasants’ embryo using a transmission electron microscope. The blastoderm was dissected out from embryos which were already incubated for 12 hr. Toluidine blue was used for staining semi-thin sections; lead citrate and uranyl acetate were also used to stain ultra-thin sections. Images of primordial germ cells elucidated that the nucleus was situated eccentrically and had a compact spherical structure. Moreover, the nucleolus appeared elongated and was located eccentrically. The cytoplasm was composed of yolk granules and glycogen particles. Mitochondria were observed as round structures in the cytoplasm. The most important finding was that the primordial germ cells contained yolk granules, mitochondria and small amount of glycogen at this stage.


  1. Nieukoop PD, Sutasurya LA. Primordial germ cells in the chordates.1st London, UK: Cambridge University Press 1979; 54-56.
  2. England MA. The migration of primordial germ cells in avian embryos. In: McLaren A. Wyli CC. (Eds). Current problems in germ cell differentiation. Cambridge, London: Cambridge University Press 1983; 91-114.
  3. Eyal-Giladi H, Ginsburg M, Farbarov A. Avian primordial germ cells are of epiblastic origin. J Embryol Exp Morphol 1981; 65:139-147.
  4. Sutasurya LA, Yasugi S, Mizuno T. Appearance of primordial germ cells in young chick blastoderms cultured in vitro. Develop Growth Differ 1983; 25(5): 517-521.
  5. Clawson RC, Domm LV. Origin and early migration of primordial germ cells in the chick embryo: a study of the stages definitive streak through eight somites. Am J Anat 1969; 125(1): 87-111.
  6. Ysuda Y, Tajima A, Fujimoto T, et al. A method to obtain avian germ-line chimeras using isolated primordial germ cells. J Reprod Fertil 1992; 96(2): 521-528.
  7. Fujimoto T, Ninomyiya T, Ukeshima A. Observations of the primordial germ cells in blood samples from the chick embryo. Dev Biol 1976; 49(1): 278-282.
  8. Fujimoto T, Ukeshima A, Kiyofuji The origin, migration, and morphology of the primordial germ cells in the chick embryo. Anat Rec 1976; 185(2): 139-145.
  9. Ginsburg M, Eyal-Giladi H. Temporal and spatial aspects of the gradual migration of primordial germ cells from the epiblast into the germinal crescent in the avian embryo. J Embryol Exp Morphol 1986; 95: 53-71.
  10. Fenderson BA, Eddy EM, Hakomori S. Glycoconjugate expression during embryogenesis and its biological significance. Bioessays 1990; 12(4): 173-179.
  11. England MA, Matsumura G. Primordial germ cells in the primitive streak stages chick embryo as studied by scanning electron microscopy. J Anat 1993; 183(Pt 1) (Pt 1): 67-73.
  12. Ginsburg M, Eyal-Giladi H. Primordial germ cells of the young chick blastoderm originate from the central zone of the area pellucida irrespective of the embryo-forming process. Development 1987; 101(2): 209-219.
  13. Karagenç L, Cinnamon Y, Ginsburg M, et al. Origin of primordial germ cells in the prestreak chick embryo. Dev Genet 1996; 19(4): 290-301.
  14. Petitte JN, Karagenç L, Ginsburg M. The origin of the avian germ line and transgenesis in birds. Poult Sci 1997; 76(8): 1084-1092.
  15. Pardanaud L, Buck C, Dieterlen-Lièvre F. Early germ cell segregation and distribution in the quail blastodisc. Cell Differ 1987; 22(1): 47-59.
  16. Ginsburg M, Hochman J, Eyal-Giladi H. Immunohisto-chemical analysis of the segregation process of the quail germ cell lineage. Int J Dev Biol 1989; 33(3): 389-395.
  17. Yoshinaga K, Nakamura M, Ukeshima A. Ultrastructural characteristics of primordial germ cells in the quail embryo. Anat Rec 1993; 236(3): 547-552.
  18. Scheer U, Thiry M, Goessens G. Structure, function and assembly of the nucleolus. Trends Cell Biol 1993; 3(7): 236-241.
  19. Kim JN, Lee YM, Park TS, et al. Detection and characterization of primordial germ cells in pheasant (Phasianus colchicus) embryos. Theriogenology 2005; 63(4): 1038-1049.
  20. Rogulska T. Primordial germ cells in normal and transected duck blastoderms. Development 1968; 20(3): 247-260.
  21. Kheirabadi M, Nabipour A, Dehghani H, et al. Ultra-structure of ovarian germ cells in the ostrich (Struthio camelus) Bulg J Vet Med 2019; 22(3): 266-274.
  22. Nagai T, Yamaha E, Arai K. Histological differentiation of primordial germ cells in zebra fish. Zool Sci 2001; 18(2): 215-223.
  23. Yön ND, Akbulut C. Identification of primordial germ cells: cytological, histological, and immunohisto-chemical aspects. Braz Arch Biol Technol 2015; 58(2): 222-228.
  24. Deniz Koç N, Yüce R. A light- and electron microscopic study of primordial germ cells in the zebra fish (Danio rerio). Biol Res 2012; 45(4): 331-336.
  25. Hajji K, Martin C, Perramon A, et al. Sexual phenotype of avian chimeric gonads with germinal and stromal cells of opposite genetic sexes. Biol Struct Morphog 1988; 1(3): 107-116.
  26. Armengol C, Carretero A, Nacher V, et al. Carbohydrate characterization of quail primordial germ cells during migration and gonadal differentiation. J Anat 2007; 210(1): 98-111.
  27. Qin J, Cai LL, Li BC, et al. In vitro culture of chicken primordial germ cells (PGCs). Chin J Vet Sci 2006; 26(4): 444-447.
  28. Ginsburg M. Primordial germ cell formation in birds. Ciba Found Symp 1994; 182: 52-61.
  29. Urven LE, Erickson CA, Abbott UK, et al. Analysis of germ line development in the chick embryo using an anti-mouse EC cell antibody. Development 1988; 103(2): 299-304.
  30. Pokhrel N, Ben-Tal Cohen E, Genin O, et al. Cellular and morphological characterization of blastoderms from freshly laid broiler eggs. Poult Sci 2017; 96(12): 4399-4408.
  31. Hamburger V, Hamilton HL. A series of normal stages in the development of the chick embryo. 1951Dev Dyn 1992;195(4): 231-272.
  32. Cheville NF, Stasko J. Techniques in electron microscopy of animal tissue. Vet Pathol 2014; 51(1): 28-41.
  33. Kuwana T. Migration of avian primordial germ cells toward the gonadal anlage. Develop Growth Differ 1993; 35(3): 237-243.
  34. Ando Y, Fujimoto T. Ultrastructure evidence that chick primordial germ cells leave the blood-vascular system prior to migrating to the gonadal anlagen. Develop Growth Differ 1983; 25(4): 345-352.
  35. Ukeshima A, Yoshinaga K, Fujimoto T. Scanning and transmission electron microscopic observations of chick primordial germ cells with special reference to the extravasation in their migration course. J Electron Microsc (Tokyo) 1991; 40(2): 124-128.
  36. Matsumura G, England MA. Isolation of chick primordial germ cells from stages 4-8 embryos. Anat Rec 1993; 235(4): 604-610.
  37. Didier E, Fargeix N. Quantitative aspects of the colonization of the gonads by germ cells in the quail embryo (Coturnix coturnix japonica) [French]. Development 1976; 35(3): 637-648.
  38. Reimer CL, Crawford BJ. Identification and partial characterization of yolk and cortical granule proteins in eggs and embryos of the starfish, Pisaster ochraceus. Develop Biol 1995; 167(2): 439-457.
  39. Prates EG, Nunes JT, Pereira RM. A role of lipid metabolism during cumulus-oocyte complex maturation: Impact of lipid modulators to improve embryo production. Mediators Inflamm 2014; 2014: 692067. doi: 10.1155/2014/692067.
  40. Prats C, Graham TE, Shearer J. The dynamic life of the glycogen granule. J Biol Chem 2018; 293(19): 7089-7098.
  41. Ukeshima A. Ultrastructure of the ovarian germ cells in the quail embryos, with special reference to the oocytes. Okajimas Folia Anat Jpn 2003; 80(4): 85-91.
  42. Lee H, Karasanyi N, Nagele RG Jr. The role of the cell surface in the migration of primordial germ cells in early chick embryos: effects of concanavalin A. J Embryol Exp Morphol 1978; 46: 5-20.
  43. Fujimoto T, Ukeshima A, Miyayama Y, et al. Observations of primordial germ cells in the turtle embryo (Caretta caretta): Light and electron microscopic studies. Develop Growth Differ 1979; 21(1): 3-10.
  44. Chang Gb, Cheng Xm, Li Bc, et al. Migration and accumulation of primordial germ cells of the early embryo in quail. Ital J Anim Sci 2010; 9(2): e45. doi: 10.4081/ijas. 2010. e45.
  45. Ohata M, Tanuma Y, Ito T. Electron microscopic study on avian livers with special remarks on the fine structure of sinusoidal cells. Okajimas Folia Anat Jpn 1982; 58(4-6): 325-368.
  46. Al-Hamawandy DHD. Morphological, histological, and histomorphometric study on embryonic development of the liver and gall bladder in the local chicken Gallus gallus domesticus (Linnaeus, 1758). PhD Thesis, College of education for pure science Ibn Al-Haitham, University of Baghdad, Baghdad: 2019.
  47. Jeon KW, Kennedy JR. The primordial germ cells in early mouse embryos: light and electron microscopic studies. Dev Biol 1973; 31(2): 275-284.