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

Subcellular fractionation techniques were used to describe temporal changes (at intervals from T-0 to T-70 days) in the Pb, Zn and P partitioning profiles of Lumbricus rubellus populations from one calcareous (M-DH) and one acidic (M-CS) geographically isolated Pb/Zn-mine sites and one reference site (C-PF). M-DH and M-CS individuals were laboratory maintained on their native field soils; C-PF worms were exposed to both M-DH and M-CS soils. Site-specific differences in metal partitioning were found: notably, the putatively metal-adapted populations, M-DH and M-CS, preferentially partitioned higher proportions of their accumulated tissue metal burdens into insoluble CaPO4-rich organelles compared with naive counterparts, C-PF. 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 similar to 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. (C) 2010 Elsevier Ltd. All rights reserved.