Variation of metallothioneins in gills of the clam Ruditapes decussatus from the Gulf of Gabès (Tunisia)

Cadmium (Cd) and metallothionein (MT) concentrations were determined in the subcellular fractions of the gills of the clam Ruditapes decussatus. Clams were collected monthly during the period of sexual development (from June to August 2001) from two different sites situated in the Gulf of Gabès (Tunisia). These sites differ by their degree of metal contamination. Differences in condition index (CI) were observed in June and August between clams from both sites. In clams from both sites, cadmium was approximately equally distributed between the soluble (S1) and insoluble (C1) fractions. MT levels varied according to month but not sex. Site and body mass of clams seem to be important factors to explain the variation of MT levels compared to cadmium.