Metal bioaccumulation and speciation in the epigeic earthworm (Lumbricus rubellus) : the interactive influences of population exposure histories, site-specific geochemistry and mitochondrial genotype

Andre, Jane and Sturzenbaum, Stephen R. and Kille, Peter and Morgan, A. John and Hodson, Mark E. (2010) Metal bioaccumulation and speciation in the epigeic earthworm (Lumbricus rubellus) : the interactive influences of population exposure histories, site-specific geochemistry and mitochondrial genotype. Soil Biology and Biochemistry, 42 (9). pp. 1566-1573. ISSN 0038-0717

Abstract

Subcellular fractionation techniques were used to describe temporal changes (at intervals from T0 to T70 days) in the Pb, Zn and P partitioning profiles of Lumbricus rubellus populations from one calcareous (MDH) and one acidic (MCS) geographically isolated Pb/Zn-mine sites and one reference site (CPF). MDH and MCS individuals were laboratory maintained on their native field soils; CPF worms were exposed to both MDH and MCS soils. Site-specific differences in metal partitioning were found: notably, the putatively metal-adapted populations, MDH and MCS, preferentially partitioned higher proportions of their accumulated tissue metal burdens into insoluble CaPO4-rich organelles compared with naive counterparts, CPF. Thus, it is plausible that efficient metal immobilization is a phenotypic trait characterising metal tolerant ecotypes. Mitochondrial cytochrome oxidase II (COII) genotyping revealed that the populations indigenous to mine and reference soils belong to distinct genetic lineages, differentiated by ∼13%, with 7 haplotypes within the reference site lineage but fewer (3 and 4, respectively) in the lineage common to the two mine sites. Collectively, these observations raise the possibility that site-related genotype differences could influence the toxico-availability of metals and, thus, represent a potential confounding variable in field-based eco-toxicological assessments.