Equilibrated body metal concentrations in laboratory exposed earthworms: can they be used to screen candidate metal-adapted populations?

The accumulated metal (Ca, Cd, Cu, Pb, Zn) concentrations in seven differen t populations of the earthworm, Lumbricus rubellus, maintained in the labor atory for 90 days on their 'own' native polluted soils were compared with t hose accumulated by two reference populations (sampled from uncontaminated calcareous and acidic sites, respectively), maintained for the same period on the same series of seven polluted soils. Worms native to the more heavil y polluted soils accumulated higher Cd and Zn concentrations than their ref erence counterparts, the striking exception being worms maintained on the e xceptionally acidic, Ca-poor, Cwmystwyth Stream soil; tissue Cu concentrati ons were consistently low and similar in 'native' and reference worms; tiss ue Pb concentrations were significantly higher in only one population of na tive worms, a site (Wemyss) that did not contain the highest soil Pb concen tration; Ca concentrations were generally similar in native and reference w orms, but reference worms normally inhabiting an acidic soil, Caerffili (CF ) tended to accumulate Ca more efficiently than reference worms derived fro m a more calcareous soil, Dinas Powys (DP). These observations indicated th at differentiation between natural populations as expressed by metal accumu lation patterns is probably a commoner earthworm response to Cd- or Zn-expo sures than it is to Pb- or perhaps Cu-exposures. Measuring and comparing ac cumulated metal concentrations is a crude method of early-stage screening f or metal-tolerant ecotypes; having identified candidate tolerant population s more definitive genetic tests must be undertaken. (C) 1999 Elsevier Scien ce B.V. All lights reserved.