Abstract: Ragworm (Polychaeta) is an ecologically important species in intertidal mudflats and estuaries and is recognized as a sentinel species for environmental monitoring. In the intertidal belt of China, the ragworm Perinereis aibuhitensis is frequently exposed to various toxicants including cadmium (Cd) and petroleum hydrocarbons (PHCs). The present study investigated the influence of PHCs on accumulation of Cd and the induction of metallothionein (MT) in P. aibuhitensis by means of chronic microcosm experiment in which the ragworms were exposed to Cd or combinations of Cd and PHCs. The accumulation of Cd in P. aibuhitensis increased significantly with the Cd exposure concentration when exposed to Cd alone. Further, the bioconcentration factors (BCFs) for Cd in P. aibuhitensis increased with the duration of exposure. The addition of PHCs in Cd exposure solutions significantly increased the accumulation of Cd in P. aibuhitensis, compared with the control. Exposure to Cd induced the expression of MT, and the expression increased with the concentration up to 180 mg·kg^-1DM Cd at which point the level of induction did not increase. PHCs without Cd did not significantly induce MT in P. aibuhitensis, but the addition of PHCs with Cd did influence the induction of MT compared to Cd without PHCs. Results indicated that PHCs could modulate the expression of MT during coexposure with Cd. The potential substances other than metals influencing the interpretation of MT expression in wild P. aibuhitensis must be recognized when MT is used as a monitoring index.

Key words: Perinereis aibuhitensis, cadmium, petroleum hydrocarbons, bioaccumulation, metallothionein.