Sperm storage and viability within females of Euscepes postfasciatus: effect of irradiation on sperm abundance and viability within female.

Irradiation has been widely used in suppression or eradication programs that use the sterile insect technique (SIT) or in studying sperm competition. Although it is well known that irradiation has negative impacts on reproductive (sperm) cells, previous studies have assumed that sperm from irradiated males behave identically to normal sperm in the female reproductive tract after mating. In this study, we used the West Indian sweetpotato weevil Euscepes postfasciatus to investigate the effect of irradiation on the abundance and viability of sperm in female spermatheca for 14 days after copulation. The abundance of sperm in females did not change throughout the experimental period, and sperm viability gradually decreased regardless of irradiation. In this weevil, irradiated sperm appear to behave identically to normal sperm in females for 14 days following irradiation/copulation. Therefore, the effect of irradiation on sperm viability within the female spermatheca is considered to be insignificant.