A study of the utilization of I131 by the lamellibranchs Anodonta cygnea, Sphaeriumcorneum, and Mytilus edulis has been made with particular reference to the secretion of the valves and ligament.
While autoradiographs show that I131 is localized in the alimentary canal and digestive gland, the main distribution of the isotope is on the surfaces of the shell and body exposed to the radioactive medium. The iodine associated with the shell occurs principally on the periostracum. There is, however, no positive evidence to show that I131 is actively incorporated into the shell by the secretory activity of the mantle. The results are discussed in relation to the ability of other invertebrates to accumulate protein-bound iodine.