Tissue distribution ofcadmium and its effect on reproduction in Spodoptera exigua

Vegetablefields are often contaminated by heavy metals, and Spodoptera exigua is a major vegetable pest which is stressed by heavy metals mainly byfeeding. In this study, cadmiumaccumulation in the tissues of S. exigua exposed to cadmiumand its effects on the growth and development of the parents and the offspringwere investigated. Under the stress ofdifferent concentrations of cadmium (0.2, 3.2, and 51.2 mg kg–1),the cadmium content in each tissue of S. exigua increased ina dose-dependent manner. At the larvalstage, the highest cadmium accumulation was found in midgut in all threecadmium treatments, but at the adult stage, the highest cadmium content wasfound in fat body. In addition, thecadmium content in ovaries was much higher than in testes. When F1 S. exigua was stressed by cadmium and the F2 generation was not fed acadmium-containing diet, the larval survival, pupation rate, emergence rate andfecundity of the F2 generation were significantly reduced in the51.2 mg kg–1 treatment compared to the corresponding F1 generation. Even in the F2 generation of the 3.2 mg kg–1 treatment, the fecundity wassignificantly lower than in the parental generation. The fecundity of the only-female stressedtreatment was significantly lower than that of the only-male stressed treatmentat the 3.2 and 51.2 mg kg–1 cadmium exposure levels. When only mothers were stressed at the larvalstage, the fecundity of the F2 generation was significantly lowerthan that of the F1 generation in the 51.2 mg kg–1 treatment, and it was also significantly lower than in the 3.2 and 0.2 mg kg–1 treatments. The results of our study canprovide useful information for forecasting the population increase trends underdifferent heavy metal stress conditions and for the reliable environmental riskassessment of heavy metal pollution.