Dominant lethal mutations induced by MMS and mitomycin C in the fish Oryzias latipes.

Males of the fish Oryzias latipes were treated with various chemicals and then mated with normal females. The fertility and hatchability of the eggs laid by the parents were examined, and the dominant lethal effects were estimated. Mitomycin C induced dominant lethals in the fish spermatids and spermatocytes after the males had been treated with concentrations of 2.5 and 25 micrograms/ml. Methyl methanesulfonate (MMS) induced dominant lethals in spermatozoa and spermatozoa and spermatids after the injection of 200 and 400 mg/kg. These results are in good agreement with the results obtained with mice. However, the effects of ethyl methanesulfonate (EMS) were not clear on spermatogenic cells at any stage. We could not recognize any significant induction of dominant lethals by urethanes, bleomycin, caffeine, and two kinds of food-color additives, at least under the present experimental conditions.