Bioavailability of heavy metals and apoptotic effects on the midgut cells of Pseudaletia unipuncta (Lepidoptera: Noctuidae) inhabiting volcanic environments

Abstract

In Sao Miguel Island (Azores, Portugal) volcanic activity is manifested by the occurrence of soil degassing, hydrothermal vents and gas emissions on geothermal grounds; consequently, organisms living in such volcanic environments are chronically exposed to metals, as particles or associated with gases, being therefore potential sentinels of the effects derived from such exposure. Concentrations of seven trace elements (Ca, Cd, Cu, Mg, Mn, Pb, Rb, and Zn) were measured in soil, grass leaves (Lolium perenne), and larvae of Pseudaletia unipuncta from sites exposed and non-exposed to volcanic activity. Morphometry and semi-quantification of apoptotic nuclei (TUNEL test) of the midgut epithelial cells of P. unipuncta larvae were also analyzed. Soils and grass not exposed to volcanic activity showed higher levels for most of the analyzed elements with the exception of Rb. 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. Contrarily to soil and grass, larvae from the site with volcanic activity showed higher levels of Cu, Mn, Rb and Zn, suggesting that the volcanic environment (characterized by a lower pH, etc.) could contribute to an increase in the bioavailability of these elements to the larvae. Apoptosis was significantly higher in cells from digestive epithelium of larvae exposed to volcanic activity, probably as a cellular response and adaptation of these organisms when inhabiting active volcanic environments.