Ligand Activity in the Clearance of Metals from the Blood of the Crayfish (Austropotamobius Pallipes)

Abstract

The rate at which metal ions are cleared from the blood of the crayfish Austropotamobius pallipes can be described as the sum of fast and slow exponential processes. The rate constants of these processes were determined and discussed in terms of ligand chemistry. The half life (t½) of the fast component shows a typical Irving- Williams series for the various metals. This is interpreted as showing that the retention of metals in the blood is due to binding to protein ligands. The concentrations of metals in the various tissues also reflect their binding characteristics. Class (a) metals (Ca and Sr) become associated with oxygen donors in the exoskeleton and stomach. Class (b) and borderline metals become bound to nitrogen and sulphur donor ligands in the hepatopancreas. The rapid disappearance of Cd²⁺ and Zn²⁺ from the blood can be attributed to specific ligands in the hepatopancreas.