Impact of low-level radiation on fertility and fecundity of Nezara viridula (Hemiptera: Pentatomidae)

Abstract

The southern green stink bug, Nezara viridula (L.), was exposed to ionizing radiation of <10 Gy in the 4th instar and rendered partially sterile. Females laid nonviable eggs in high proportions and had significantly lower fecundity than controls. Diet and inbreeding status affected fecundity, fertility, and the reproductive response after irradiation. One inbred group became sterile with the combined stress of radiation and diet. When irradiated (5 Gy) and nonirradiated wildtypes mated, the proportion of nonviable eggs laid was intermediate to that laid by pairs of irradiated wildtype bugs and pairs of nonirradiated bugs. Other mixed-treatment pairings and outcrosses gave variable results. Adult progeny from irradiated pairs showed an 'all or none' form of recovery with regard to fitness. Fertile pairs laid egg masses with a majority of eggs hatching. However, almost half the pairs were infecund or laid only sterile eggs. Overall, fecundity was significantly less in progeny of irradiated inbred or irradiated wildtype bugs. At higher levels of radiation, nymphs either died before reaching the adult stage or became sterile. At 20 Gy, half survived to the adult stage. One female laid sterile eggs when mated to a nonirradiated male. Nonirradiated females produced no egg masses after mating with the irradiated males. At 40 and 60 Gy, mid-instar 4th-instar nymphs became emaciated. Most underwent a delayed molt and died in the 5th instar. At 80 Gy, most died in the 4th instar.