The ultrastructural localization of metals in specimens of Littorina littorea collected from clean and polluted sites

Abstract

The ultrastructural organization of various metal-containing cells of Littorina littorea is described. These cells occur in the connective tissue, digestive gland, kidney, stomachand ctenidia. Specimens were compared from animals collected from clean and metal-polluted sites and it was shown that the majority of the metals were bound to intracellular ligands. These are usually compartmentalized within membrane-delineated structures.The basophil cells and connective tissue calcium cells appear to contain oxygen donor ligands which mainly bind class A metals (e.g. Ca, Mg, K, Mn). The pore cells and ctenidium contain sulphur donor ligands which mainly bind copper. Ligands of unknown composition occur in the nephrocytes and stomach epithelial cells. The ligands in the basophil cells and the nephrocytes appear to bind a wide range of metals and may therefore serve a detoxification function. Ligands in the connective tissue calcium cells and pore cells are very specific in their binding characteristics, and this presumably reflects some particular metabolic pathway within these cells. Ligands associated with the stomach and ctenidial epithelia appear to be responsible for preventing the penetration of metals through these layers.The effects of ligand specificity, induction and turnover rates are discussed in relation to the use of L. littorea as a monitoring system for metal pollution.IntroductionThe use of biological organisms to monitor the levels of pollutant metals in the environment has attracted extensive interest in recent years (Phillips, 1980). In the most arbitrary use of this procedure, the animal is simply regarded as a biological sink' which traps and accumulates the pollutants which gain access across its epithelial layers. The net result of the retention or excretion of these captured metals is represented by the final body load that is then related to the environmental levels of the metal.