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(187) Arsenic speciation in arsenate-resistant and non-resistant populations of the earthworm Lumbricus rubellus. Langdon, Caroline1, Meharg, Andrew2,3, Feldmann, Jorg3, Charnock, J4, Faquhar, M5, Cotter-Howells, Janet3, Semple, Kirk1, Piearce, Trevor1, 1 2 3 4 5 ABSTRACT- Lumbricus rubellus Hoffmeister inhabiting soil at Devon Great Consols, a copper and arsenic mine near Tavistock, Devon, UK, showed resistance to Cu- and As-toxicity (Langdon et al, submitted). L. rubellus were collected from Devon Great Consols and spoil at an arsenic-contaminated tungsten mine at Carrock Fell, Cumbria, UK, and at one uncontaminated site. Tissues were analised by AAS, LC-MS, LC-ICP-MS and XAS. Total tissue arsenic concentrations ranged from 2 mg As kg-1 in uncontaminated, to 1,358 mg As kg-1 in the earthworm tissue from contaminated soils. The major arsenic compound detected by LC-MS, in uncontaminated earthworms, was arsenobetaine. XAS on Carrock Fell samples showed As (V)-O to be present in addition to As-sulphur in the body wall and whole earthworm but not in the intestine. These data suggest that As is predominantly bound to S in a glutathione-type environment within contaminated earthworms, consistent with metallothionein complexation. Lumbricus rubellus from Devon Great Consols and from the uncontaminated site had their dorsal surfaces photographed, and the slide images digitised. Areas in the centre of each quarter of the body were analysed using standard image analysis software. All L. rubellus showed reddish-purple pigmentation of the body wall that declined in intensity posteriorly. Lumbricus rubellus from the Devon site displayed varying degrees of yellow pigmentation, possibly related to increases in the chlorogogenous tissue, which contains As-binding sulphydryl enzymes. This pigmentation may be a response to As toxicity or a result of As poisoning and may be linked to areas of accumulation of As in the earthworm tissues. An understanding of the detoxification mechanism of As in earthworms from contaminated sites together with the colouration, could provide a non-destructive biomarker in ecotoxicological studies and has potential value in the use of resistant earthworms in reclamation of contaminated land. Key words: earthworm, arsenate-resistance, speciation, toxicity |
