Cadmium accumulation and detoxification in a Cd-resistant population of the oligochaete Limnodrilus hoffmeisteri

It was reported earlier that the oligochaete Limnodrilus hoffmeisteri from metal-polluted Foundry Cove has evolved resistance to a combination of cadmium, nickel and cobalt (Klerks and Levinton, 1989). This paper addresses the possible physiological mechanisms by which this resistance is achieved. Exposing animals from both the control population and the resistant population to Foundry Cove sediment or to 109Cd in water, shows that the resistance is not achieved by a reduced cadmium accumulation. HPLC gel-permeation of the cytosol obtained after the exposure to 109Cd in water reveals that the resistant worms have significantly higher levels of a cadmium-binding, metallothionein-like protein than control worms. This elevated protein level is shown to be genetically determined and is proposed to contribute to the resistance of L. hoffmeisteri from Foundry Cove. In addition, electron microprobe anaiyses of Foundry Cove worms exposed to metal-rich sediment demonstrated the presence of Cd in granules. High levels of Cd were found in S-rich granules, possibly in the form of cadmium sulfide. These granules occurred both as individual ones and as large granular aggregates.