The impact of lead on the assimilation efficiency of laboratory-held Diplopoda (Arthropoda) preconditioned in different environmental situations.

In five diplopod species from three families collected from locations with different soil metal contents, the following parameters were examined: the litter mass (and energy) ingested per day, the mass (and energy) assimilation rates, and the litter mass (and energy) assimilated per day, when the diplopods were fed (1) uncontaminated and (2) artificially lead-enriched leaf litter. These parameters were compared between species and between animals from different sites. The mass and energy assimilation efficiencies depend on (1) the size of the species and (2) the collection site of the animals. Relative mass (and in three of the species examined also energy) assimilation was highest in those animals collected from the less contaminated sites. With artificial diets, specimens from a site with soil contaminated by heavy metals showed greater assimilation of both mass and energy than originally unaffected specimens. One species (Glomeris conspersa) was able to compensate for the low assimilation rate by increased consumption, and thus guarantee a sufficient energy supply. One of the other species (Polydesmus denticulatus), however, did not show this compensation. Animals of this species from less contaminated sites showed a very low absolute energy assimilation rate and high mortality under lead treatment.