Effect of gamma radiation and sex-linked recessive lethal mutations on sperm transfer in Ephestia kuehniella (Lepidoptera: Pyralidae)

Sperm quality and sperm competition play important roles in determining the efficiency of genetic methods for suppression of lepidopteran populations. Herein we have examined competitiveness of mutant and irradiated males of Ephestia kuehniella by counting eupyrene (fertile) and apyrene (non-fertile) sperm transferred to the female during copulation. Mutant BL-2 males, trans-heterozygous for two sex-linked recessive lethal mutations sl-2 and sl-15, produced 50% fewer of both types of sperm as compared to with WT-C (wild-type) males. However the ratio of apyrene to eupyrene sperm remained the same in both male types (9.5:1). Irradiation of mature male pupae, heterozygous for either sl-2 or sl-15 mutations, with doses between 150 and 350 Gy showed dose-dependent effects on the amount of sperm transferred and on the total length of mating times. As the treatment dose increased the volume of sperm transferred by the male decreased and the mating times got longer. In the F, descendants of the treated males, males mere found to transfer either a relatively normal or a very small volume of sperm, which could reflect changes in gamete segregation and in chromosomal aberrations that are inherited. The dose of 175 Gy is suggested as optimal for irradiation of Ephestia kuehniella.