Ingestion and effects of cerium oxide nanoparticles on Spodoptera frugiperda (Lepidoptera: Noctuidae)

The objective of this study was to evaluate the biological and nutritional characteristics of Spodoptera frugiperda (Lepidoptera: Noctuidae), an arthropod pest widely distributed in agricultural regions, after exposure to nano-CeO₂ via an artificial diet and to investigate the presence of cerium in the body of this insect through X-ray fluorescence mapping. Nano-CeO₂, micro-CeO₂, and Ce(NO₃)₃ were incorporated into the diet (0.1, 1, 10, and 100 mg of Ce L^-1). Cerium was detected in caterpillars fed with diets containing nano-CeO₂ (1, 10 and 100 mg of Ce L^-1), micro-CeO₂ and Ce(NO₃)₃, and in feces of caterpillars from the first generation fed diets with nano-CeO₂ at 100 mg of Ce L^-1 as well. The results indicate that nano-CeO₂ caused negative effects on S. frugiperda. After it was consumed by the caterpillars, the nano-CeO₂ reduced up to 4.8% of the pupal weight and 60% of egg viability. Unlike what occurred with micro-CeO₂ and Ce(NO₃)₃, nano-CeO₂ negatively affected nutritional parameters of this insect, as consumption rate two times higher, increase of up to 80.8% of relative metabolic rate, reduction of up to 42.3% efficiency of conversion of ingested and 47.2% of digested food, and increase of up to 1.7% of metabolic cost and 8.7% of apparent digestibility. Cerium caused 6.8-16.9% pupal weight reduction in second generation specimens, even without the caterpillars having contact with the cerium via artificial diet. The results show the importance of new ecotoxicological studies with nano-CeO₂ for S. frugiperda in semi-field and field conditions to confirm the toxicity.