[Effect of irradiation on early gametogenesis in Tilapia]

The 10 day old fries of Tilapia mossambica Peters were irradiated with 350 R dose. Dynamics of germ cells in control and after irradiation was studied. In 10 day old fry primordial germ cells and gonial cells were observed; in 15 days--mainly gonial cells were seen; in 20 days part of gonial cells move in the early prophase of meiosis; in 25 days gonial cells and oocytes of early prophase of meiosis are seen; in 30 days oogonial cells, oocytes of early prophase of meiosis and of previtellogenesis are observed. After irradiation of 13--14 day old fries some anomalies of mitosis were observed. But mass destruction of germ cells took place during the pachytene stage in 25 day old fries. The causes of the destruction of germ cells are discussed.