IRRADIATED PARASITIC WASPS: The Effect on Progeny Production and Sex Ratio

Abstract

An effort was made to increase the genetic variability of laboratory populations of the diaspine scale parasite Aphytis lingnanensis, in order to increase the probability of successful artificial selection of a parasite strain with improved tolerance to temperature extremes. Thus studies were made on the effects of x irradiation on the longevity of mated adult females, and on the numbers and sexes of their progeny as well as an evaluation of the susceptibility of the species to irradiation. The numbers of progany surviving to become F/sub 1/ adults (termed net fecundity) served as a criterion of the production of lethal mutations, chromosomal aberrations, and somatic effects. Irradiation of adults at doses of 250, 500, 1000, 2000, and 4000 r produced: no effect on longevity of treated adults, pronounced reduction in net fecundity with increasing x-ray dosage, indications that mature eggs were less affected by x-ray treatment than the less mature ones, and sharply reduced percentage of females in the progeny of those groups which received the highest dosages. Thus the percentage of females among the progeny of irradiated female parasites was drastically lowered by 2000 and 4000 r, but no clear indication of an effect on sex ratio was evidentmore » at the 250, 500, or 1000 r. Possible explanations of the lowered female productivity phenomena are offered. (H.H.D.)« less