A light- and electron microscopic study of primordial germ cells in the zebra fish (Danio rerio)

In sexually reproducing organisms, primordial germ cells (PGCs) give rise to the cells of the germ line, the gametes. In many animals, PGCs are set apart from somatic cells early during embryogenesis. This study explores the origin of primordial germ cells (PGCs) of the zebra fish and examines their morphology during early development (1st day-15th day). PGCs were selectively stained by the alkaline phosphatase histochemical reaction and viewed by light and electron microscopy from the time they are first detectable in the yolk sac endoderm. PGCs occurred in the subendodermal space on the syncytial periblast; differing from the surrounding endodermal cells. Later the PGCs moved to between the blastoderm and yolk sac and transferred to the dorsal mesentery where they formed gonadal anlage with mesoderm cells. PGCs were easily distinguished from somatic cells by their morphology and low electron density of their nuclei. Under light microscopy, PCGs were rounded with a distinct cytoplasmic membrane.

Ovary maturatýon stages and histological investigation of ovary of the Zebrafish (Danio rerio)

Microscopic ovary features of Zebrafish were analyzed. Samples were fixed in Bouin’s solution, mounted in parafin and cut into 6-7 µm-thick slices which were stained with Hematoxylin and Eosin (HE), methylene blue and using Periodic-acid Schiff method (PAS). The thin sections in ultramicrotome with the thickness of approximately 0,5 - 0,7 µm were examined by using Jeol electron microscope following contrasting with Uranyl Acetate-Lead Citrate. The zebrafish was an extremely dynamic organ in which follicles underwent asynchronous development. The oocytes of Zebrafish ovary were observed in various phases. The oocyte development of zebrafish was divided into four stages (primary growth, cortical alveolus, vitellogenic and mature oocyte). Oocyte diameters were observed to vary between 0.,08 mm and 0.76 mm.