Nuclear microprobe studies of grasshopper feeding on nickel

摘要

Grasshopper Stenoscepa sp is an insect species feeding on the South-African Ni-hyperaccumulating plants. Large amounts of Ni ingested by them have no effect on their development. To explain their ability to survive in such extreme conditions, we investigated the distribution of elements in the insect body by means of a nuclear microprobe [micro-particle induced x-ray emission (PIXE) and backscattering (BS)]. GeoPIXE II software was used for quantitative elemental mapping complemented by evaluation of data extracted from arbitrarily selected micro-areas. Micro-PIXE analysis in Stenoscepa sp tissues showed the highest Ni level in the gut and Malpighian tubules. The activity of glutathione-dependent enzymes and glutathione (GSH) content in the tissues of second-stage larvae were measured. One of the ways to survive under chronic Ni exposure conditions is an intensified GSH synthesis. GSH concentration in tissues of the grasshoppers was very high, about six times higher than in larvae of other Acrididae species from areas contaminated with heavy metals in Europe. Catalase (CAT) activity was 5-10 times lower in comparison to other Orthoptera species. Glutathione reductase (GR) activity was unexpectedly low (at the detection limit level). Likely, the studied grasshoppers may use other metabolic pathways for regeneration of the reduced form of GSH, e.g. thioredoxine system. Copyright (C) 2008 John Wiley & Sons, Ltd.