Effects of Irradiation on Germ Cells and Embryonic Development in Teleosts

Publisher Summary This chapter discusses the effects of irradiation on germ cells and embryonic development in teleosts. Sterility and weight reduction of testes after irradiation are mainly because of actual cell loss, and the order of decreasing sensitivity of spermatogenic cells is from the most sensitive spermatogonia, through primary and secondary spermatocytes and spermatids, to sperm, which are quite radioresistant. Even in morphologically homogeneous populations of spermatogonia, heterogeneity of sensitivity exists. The results of local irradiation of the testes are different from those of irradiation of the ovaries. The radiosensitivity of gametogenesis in the ovary and testis cannot be directly compared, except probably from the viewpoint of genetic effects of radiation. Most studies concerning radiosensitivity of fish embryos have so far been performed for the end points of hatchability and lethality during development. This is mainly because of the simplicity of the technique. Many irradiated larvae that appear normal at hatching carry radiation damage that becomes evident at some future stage.