Presence In the Intestinal Lumen of Marine Fish of Corpuscles with a High Cadmium-, Zinc- and Copper-Binding Capacity: A Possible Mechanism of Heavy Metal Tolerance

Abstract

In various species of unfed fish (Anguilla anguilla, Myoxocephalus scorpius, Serranus cabrilla, Moena chryselis, Scorpaena sp.), white mucous corpuscles were observed in the intestinal lumen. This material is regularly evacuated. The corpuscles contain high concentrations of Ca and Mg; these elements are probably present in the form of carbonates precipitated from sea water contained in the intestine. In fish intoxicated with CdCl₂, ZnCl₂ or CuCl₂ added to sea water, the corpuscles contain enormous concentrations of these metals; although the weight of the corpuscles is small (about 0.1 % of the total wet weight of Anguilla anguilla), they may contain most of the Cd body burden. Corpuscles from non-intoxicated fish bind heavy metals in vitro: exposed to Cd, Zn or Cu enriched solutions, they retain these metals to the same extent as in vivo. It thus appears that metals are accumulated in the corpuscles directly from ingested sea water with a reduction in respective metal concentrations of the intestinal liquid. Intestinal corpuscles seem therefore to limit the entry of metals through the intestinal wall and to protect the fish against potentially hazardous concentrations of heavy metals.