METAL-BINDING COMPOUNDS IN HEPATOPANCREAS AND HEMOLYMPH OF PORCELLIO-SCABER (ISOPODA) FROM CONTAMINATED AND REFERENCE AREAS

1. In order to evaluate the role of metal-binding proteins in the tolerance mechanism of Porcellio scaber to heavy metals, a comparative study was made using isopods from three locations: a zinc-lead mine (Plombieres), a zinc smelter (Budel) and a reference wood (Spanderswoud). The Cu, Zn and Cd concentrations and the protein composition were determined in the haemolymph and hepatopancreas from the isopods. 2. A constant Cu/Zn molar ratio of about 5 was found in the haemolymph of all populations and no correlation was found between hepatopancreas and haemolymph Cu and Zn content. 3. Using fast-performance liquid chromatography (FPLC), most of the haemolymph Cu and Zn appeared to be associated with a single UV absorbing peak corresponding with an apparent molecular weight of +/- 70 kD; this peak is probably the monomer of hemocyanin. 4. The hepatopancreas Zn and Cd concentration were elevated compared to the hepatopancreas of the smelter and mine isopods; after homogenization and centrifugation 70-80% of the metals were found in the supernatant. 5. In all populations the hepatopancreas Cu-, Zn- and Cd-binding compounds eluted in separate peaks of low molecular weight, suggesting the absence of an MT-like compound in Porcellio scaber. 6. The similarity of the protein profiles in haemolymph, and the similar distribution of the metals over the fractions in haemolymph and hepatopancreas suggests that inducible metal binding compounds are not involved in metal tolerance differences between populations.