Arsenic accumulation, biotransformation and localisation in bertha armyworm moths

Insects are important in bioaccumulation and dispersal of environmental contaminants such as arsenic, and biotransformation of arsenic to various chemical forms directly impacts its toxicity to insects and to their predators. In a model study, the toxic effects and biotransformation of arsenic were examined in larvae, pupae and adults of bertha armyworm moth (Mamestra configurata Walker) (Lepidoptera: Noctuidae). A synthetic diet containing 100 mu M arsenate caused reduced larval survival and increased pupal stage duration but no effect on pupal weight or larval stage duration. Synchrotron X-ray absorption spectroscopy (XAS) showed that larvae biotransformed dietary arsenate to yield predominantly trivalent arsenic coordinated with three aliphatic sulfurs, modelled as AsIII-tris-glutathione. Similar species were found in pupae and adults. XAS imaging with micro X-ray fluorescence imaging revealed highly localised arsenic species, and zinc and copper within the gut. The implication of these arsenic species in the diets of predators is discussed.