Bioavailability of heavy metals and their effects on the midgut cells of a phytopaghous insect inhabiting volcanic environments

Organisms living in volcanic environments are chronically exposed to metals, either as particles or associated with gases, from volcanic emissions, being therefore potential sentinels of the effects derived from such exposure. Concentrations of Ca, Cd, Cu, Mg, Mn, Pb, Rb, and Zn were measured in soil, grass (Lolium perenne), and larvae of Pseudaletia uninpuncta captured in sites exposed and non-exposed to volcanic activity. The midgut epithelial cell morphometry and apoptosis of P. unipuncta larvae were also analyzed. Larvae from the site with volcanic activity showed higher levels of Cu, Mn, Rb and Zn. Metals such as Pb, Cd and Mg levels of P. unipuncta larvae were similar between sites. Apoptosis was higher in cells from digestive epithelium of larvae exposed to volcanic activity. Soils and grass not exposed to volcanic activity showed higher levels for most of the analyzed elements with the exception of Rb. Such result when compared with metal levels of larvae may reveal that bioavailability of elements differs between sites. The higher levels of Cd, Zn and Mg in soils and grass from the site with no volcanic activity are probably related to the severe artificial fertilization in the studied pastures. Such result, when compared with metal levels of larvae, suggest that the bioavailability of metals differs between sites.