A comparison of trace metal accumulation in indigeneous and alien freshwater macro-decapods.

Concentrations of Cd, Cu, Fe, Mg, Mn, Ni, Pb and Zn were determined in the exoskeleton and hepatopan- creas of three freshwater macro-decapods widely distributed in Tuscany, Italy. The species were the indigenous Austropotamobius pallipes (the white-clawed crayfish) and Potamon fluviatile (the river crab) and the alien Procambarus clarkii (the red swamp crayfish, in Italy aquacultured since 1977 and invasive since 1989). Water and sediments from the three environments in which they occur were analysed for trace metals to evaluate the degree of contamination of the habitats. Procambarus clarkii showed a significantly higher accu- mulation of most of the metals analysed, including the non-essential cadmium, nickel and lead. Interspecific differences were not related to exposure to higher concentrations of metals, but indigenous and alien macro- decapods possibly differ in their physiological requirements for essential trace metals and/or in their rates of essential and non-essential metal uptake, accumulation, detoxification and excretion.