Tolerance changes of the potworm Enchytraeus albidus after long-term exposure to cadmium

Cadmium tolerance in Enchytraeus albidus was assessed for non-acclimatised organisms, as well as populations acclimatised for 18 months to 32, 100 and 320 mg Cd/kg dry wt. of standard artificial soil. Despite the increased concentration of metallothionein-like proteins in the acclimatised potworms, no changes in sensitivity to acute and chronic (juvenile production) cadmium toxicity could be observed. The 21-day LC50s ranged from 627 for the non-acclimatised enchytraeids to 748 mg Cd/kg dry wt. for the organisms acclimatised for 18 months to a cadmium concentration of 320 mg/kg dry wt. The 42-day EC50s varied from 96.2 (73.6-115) for the organisms acclimatised to 32 mg Cd/kg dry wt. to 234 (186-290) mg Cd/kg dry wt. for those acclimatised to 100 mg Cd/kg dry wt., while the value was intermediate for the non-acclimatised organisms and those acclimatised to the highest cadmium concentration. The elevated content of metallothionein-like proteins apparently only served for the detoxification of the increased cadmium body burdens.