Gamma-ray irradiation of the sperm of the fish oryzias latipes and induction of gynogenesis

When sperm of the fish Oryzias latipes were irradiated with γ-rays (137Cs) and allowed to fertilize normal eggs, the so-called 'Hertwig effect' was observed with a dose-dependent decrease in survival rate at low doses (0 - 12.5 kR) but a better survival rate at higher dose range (50 - 150 kR). Compared with the UV-induced Hertwig effect previously reported, the result of γ-irradiation of sperm showed differences in survival rates and in percentage of embryos exhibiting paternal characteristics. It suggested the possibility of the difference in the mechanisms of Hertwig effect caused by UV and by γ-rays. (author)