The Effect of Irradiation on Reproduction in Two Strains of Tribolium castaneum Herbst

Abstract

The effects of x radiation on the reproductive performance of two strains of Tribolium castaneum were measured. The two strains differed in body weight, one strain being two and one-half times as heavy as the other. Females of the heavier strain were more resistant to somatic damage than were females of the light strain. Genetic damage, as measured by a reduction in fertility of irradiated individuals, was not so great in the heavy strain as in the light strain, especially when both parents were irradiated. When only one parent in a mating was irradiated, no sex differences in response to increasing dose were found. When both parents of a mating were treated, since the effective dose was doubled, there was a greater increase in genetic damage than if only one parent were treated. The effect of irradiating both parents can be predicted from the results obtained when only one parent is irradiated. The response curve for somatic damage showed a linear decline at high doses (1000 and 5000 r) but no significant effect at low doses (0 to 800 r). The response curve for genetic damage, as measured by an orthogonal polynomial analysis, was sigmoid in shape with a linearmore » decline at low doses and a curvilinear decline at the high doses. The genetic response curve over all doses can be fitted to a function of the type Y = a + bX + cX/sup 2/, where the different coefficients of X and X/sup 2/ change with the strain. The coefficients also depend on whether one or both parents are treated. The drop in fertility at doses over 5000 r was an average of 66.9% for irradiated foundation adults (summed over mating combinations) and an average of 58.8% for irradiated selected adults, (auth)« less