Publication: Ultrastructure of female germ cells in Haliotis asinina Linnaeus
No. of Pages/File Size
Invertebrate Reproduction and Development. Vol.39, No.1 (2001), 67-79
Somjai A. Wetakan, Vichai Linthong, Chaitip Wanichanon, Sasiporn Panasophonkul, Ardool Meepool, Maleeya Kruatrachue, Edward Suchart Upatham, Tanate Pumthong, Prasert Sobhon (2001). Ultrastructure of female germ cells in Haliotis asinina Linnaeus. Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/26414.
Ultrastructure of female germ cells in Haliotis asinina Linnaeus
Germ cells in the ovary of H. asinina are divided into six stages: oogonia and five stages of oocytes. The oogonium is a scallop-shaped cell 8-10 μm in diameter, closely adhered to a trabecula. Its nucleus exhibits small blocks of heterochromatin along the nuclear envelope and a small nucleolus. The cytoplasm contains abundant ribosomes. The stage I oocyte is a round cell 12-25 μm in diameter. Its nucleus contains numerous lampbrush chromosomes consisting of chromatin fibers with three sizes, i.e., 100-200, 40-60 and 7-12 nm in diameter. The cytoplasm has numerous mitochondria, few rough endoplasmic reticulum, and abundant ribosomes. The stage II oocyte is a round cell 25-35 μm in diameter. Its nucleus exhibits increasingly decondensed chromatin and a nucleolus, and the nuclear envelope exhibits numerous nuclear pores. The cytoplasm contains numerous and well-developed Golgi bodies, rough endoplasmic recticulum and abundant ribosomes. There are two types of secretory granules: both have a spherical shape, 350-450 nm in diameter, with an electron-dense and electron-lucent matrix, respectively. The stage III oocyte is a pear-shaped cell about 35×70 μm in size. Lampbrush chromosomes are almost completely unraveled. The two types of secretory granules are greater in number and cluster around the Golgi bodies. Larger and more electron-dense ovoid-shaped yolk granules start to appear. The stage IV oocyte is a flask-shaped cell about 50×80 μm in size. Its nucleus contains completely decondensed chromatin and a highly enlarged nucleolus. The cytoplasm is filled with lipid droplets (1.5-3 μm in diameter) and yolk granules (1.5-2.5 μm in diameter). The vitelline-cum-jelly coat starts to develop, and could be derived from the first type of secretory granules which are translocated to be exocytosed at the plasma membrane. The stage V oocyte is similar to the stage IV oocyte except its vitelline-jelly coat achieves maximum thickness and appears fibrous in comparison to the amorphous appearance at stage IV.