THE DIFFERENTIAL RADIOSENSITIVITY OF OOGONIA AND OOCYTES AT DIFFERENT DEVELOPMENTAL STAGES OF THE BRINE SHRIMP, ARTEMIA SALINA

¹ Division of Biology, National Institute of Radiological Sciences, Chiba, Japan

Histological changes in the gonads of -irradiated Artemia were studied. Three different developmental stages were irradiated; dry eggs, immature young and adults. Normal growing oocytes and some pycnotic oocytes were found in the ovaries of quite a few surviving adult animals derived from dry eggs irradiated with 100 krads of -rays Oogonia and primary oocytes in ovaries of immature Artemia irradiated with 5 krads of -rays became pycnotic within one day after irradiation, and became greatly reduced in number in 4 days. However, 10 to 14 days after irradiation, some surviving oogonia began to undergo mitosis. In adult animals, although pre-meiotic oocytes were damaged growing oocytes did not show any immediate damage after dose of 5 krads of -rays. Seven days after irradiation, they reached the mature stage, and normal maturation division occurred.