The aim of this study was to investigate the histological development of right and left ovaries in ostrich embryo. The research was carried out on the ovaries of 20-, 26-, 30-, and36-day-old embryos. At first, anatomical observation was done, and then 5 μm sections of ovaries were stained by hematoxylin and eosin, periodic acid Schiff, and Masson’s trichrome staining methods. Some ovaries embedded in Epon and 1 μm thickness sections were stained with toluidine blue and examined using regular optical microscopy. The results showed ovaries had an unequal growth resulting into a larger left ovary with obvious cortex and medulla. Cortex consisted of germinal cells and germinal epithelium along with somatic cells. At 26 days, the left ovarian cortex was developed with increasing the size of secondary sex cords and numerous germ cells. At more advanced stages of development, germ cells grew in size and contained more granules in the cytoplasm. In the right ovary cortex, there was none visible, and germinal epithelium had a thin layer. Lacunar channels, blood vessels, and interstitial cells along with germ cells were present in the medulla of both ovaries. The medullary germ cells were observed as solitary cells or group of several cells. In general, we demonstrate the histological changes in the left and right ovaries of ostrich from 20- to 36-day-old embryos. In addition, this work is the first study that provides histological evidence for the normal structure of ovaries and suggests the time of onset of meiosis in the ostrich embryo

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