Dietary composition affects levels of trace elements in the predator Podisus maculiventris (Say) (Heteroptera: Pentatomidae)

Abstract

Insects require small amounts of dietary trace elements because they serve as antioxidants, enzyme co-factors and as constituents of metalloproteins. We measured the levels of 10 trace elements (Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se and Zn) in the predatory insect, Podisus maculiventris, reared on natural prey and artificial diet; two food sources that differed in levels of trace elements. The levels of the trace elements varied greatly in insects reared on the two food sources and differed from the concentrations in the food. We also found that most of the trace elements in the eggs were present in low concentrations and in near-equal amounts in eggs laid by females reared on either of the two food sources. The homeostatic level of most trace elements in the eggs may reflect a commitment by the female to minimize the effect of dietary variation on her offspring. We conclude that trace element levels in P. maculiventris are substantially affected by the food source and can vary significantly from levels in the food source. Knowing this will improve the ability of researchers to determine optimal dietary requirements in insects for trace elements. Additionally, achieving the optimum trace element content within beneficial insects may improve their performance when used in biological control efforts.