Metal concentrations in selected organs of crayfish – Orconectes limosus and Pacifastacus leniusculus from Mazurian Lakes

Crayfish accumulate trace metals, which is why they often serve as environmental indicators. Among heavy metals, Hg, Cd and Pb are considered toxic substances, while Fe, Zn, Cu, Cr, Ni, Mn, V, Al and Li are involved in vital functions, which makes them essential elements in animal organisms. The study objective was to determine concentrations of the above metals in the abdominal muscles, hepatopancreas and exoskeleton of spinycheek crayfish (Orconectes limosus Raff.) and signal crayfish (Pacifastacus leniusculus Dana) from Dga³ Wielki Lake and Pob³êdzie Lake in the Mazurian Lake District, Poland. The analyses were carried out with the use of the following methods: CV AAS (Hg), GF AAS (Cd, Pb) and ICP-AES (Al, Cr, Cu, Fe, Li, Mn, Ni, V, Zn) after wet digestion in HNO3 and HClO4 concentrated acid mixture. Regarding mean concentrations (mg kg-1 wet weight) in crayfish, metals formed the following order: Al (14.8-123.4) > Mn (0.26-91.3) > Fe (0.54-81.1) > Zn (6.80-51.91) > Cu (1.21-4.34) > Ni (0-0.782) > Cr (0.032-0.606) > V (0-0.245) > Li (0.011-0.215) > Pb (0.018- 0.079) > Hg (0.004-0.045) > Cd (0.001-0.017).Metal concentrations in crayfish organs were varied, and for different metals they decreased in different order: Al, Mn, Cu, Ni, Cr, V and Li – exoskeleton > hepatopancreas > muscles; Zn and Hg – hepatopancreas > muscles > exoskeleton; Fe – hepatopancreas > exoskeleton > muscles, while for lead and cadmium no overall correlation was observed. The comparison of metal concentrations in the organs of spinycheek crayfish from Dga³ Wielki Lake and Pob³êdzie Lake did not prove any statistically significant discrepancies. Also, some minor interspecies differences in the metal content proved insignificant. According to the European Union regulations, concentrations of toxic heavy metals (Hg, Cd, Pb) in the muscles of both species of the tested crayfish were significantly below the maximum levels.