Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2007
Publication Date: 10/18/2007
Citation: Popham, H.J., Shelby, K. 2007. Effects of inorganic and organic selenium supplementation on development of larval Heliothis virescens. Entomologia Experimentalis et Applicata. 125(2):171-178. Interpretive Summary: When insects fed on plants they encounter both helpful and harmful chemicals. One element, selenium, is a necessary nutrient in some chemical forms and toxic in others. It is not known which forms of selenium are necessary and which are toxic to different insects. How selenium impacts an insect will, in part, determine the overall health of an insect. In this study we have examined the type of selenium which is optimal for growth and development of budworm larvae, Heliothis virescens. One organic and one inorganic form of selenium was found to have no impact on the development of the insect. One organic, one inorganic and one mixture of different forms of selenium was found to inhibit the growth of caterpillars and emergence of moths. Only one of these compounds caused the weight of pupae to decrease. These findings help scientists understand which individual compounds impact the development of different insects or groups of insects. This information can be extrapolated to developmental data collected both in the field and in the laboratory when insects fed on plants or artificial diets containing different forms of selenium.
Technical Abstract: Herbivorous insect larvae acquire the micronutrient selenium from plant tissues in the inorganic form of selenate and selenite, and in the organic form of selenoamino acids, selenomethionine and selenocysteine. In this study we document the effects of dietary supplementation with selenite, selenate, selenocysteine, selenomethionine and selenized yeast on the developmental rate of Heliothis virescens. Larvae tolerated high levels of Se (500 ppm Se) as selenate and selenocysteine. Lower levels of selenite (greater than 1 ppm Se) caused excess mortality, reduced rates of pupation, pupal/adult intermediates and adult emergence. Selenomethionine proved toxic to larvae at levels above 25 ppm Se significantly delaying pupation and raising mortality. Provision of Se as selenized yeast, which contains primarily selenomethionine, was also extremely detrimental to larval development and survival. The results indicate that the optimal dietary Se supplement for insects may differ from vertebrates.