Comparison of the Stage Sensitivity to X-rays during Meiosis in the Egg of the Silkworm, Bombyx Mori

Summary

Oocytes of the silkworm, Bombyx mori were irradiated with x-rays at various phases of the meiotic stage. The radiosensitivity was determined by scoring the hatchability of irradiated eggs in comparison with unirradiated control eggs.

Cells in the dividing phase were more sensitive to x-rays than those in any other phases in both the first and the second meioses, and cells in the first meiosis were more resistant than those in the second meiosis. Furthermore, the sensitivity of the second meiotic cells almost corresponded to that of early mitotic cells. These differences in radiosensitivity may be interpreted as being due to (1) whether or not cells are associated with DNA synthesis or chromosome duplication, and/or (2) the difference in the chromosomal structure at the time of irradiation.

It can be concluded that the radiosensitivity in cell-killing during meiosis of silkworm oocytes shows the same pattern as in other insect orders, although there are some differences in the degree of sensitivity.