Contents of Vanadium and Sulphur in the Blood Cells ofAscidia Mentula and Ascidiella Aspersa

Abstract

Henze (1911) was the first to discover large amounts of vanadium and sulphuric acid in the blood of certain species of tunicates. Webb (1939) established that both the sulphuric acid and the vanadium were present in blood in the same cell type, termed a vanadocyte. Since then much further work (reviewed by Goodbody, 1974) has been done on these highly unusual cells. Some species of tunicates accumulate other metals, including iron, titanium, niobium and tantalum (Carlisle, 1968) but the role(s) of these metals and indeed of vanadium itself remains unclear. The vanadium is present in vanadocytes in a reduced cationic form largely as vanadium(III) (Carlson, 1975; Tulliuset al.1980) which is complexed with a chromagen of as yet undefined structure and with sulphate as the counter anion (Bieliget al.1966). The blood ofAscidia nigrais not capable of reversible oxygen binding (Macara, McLeod & Kustin, 1979), and there has been speculation that the reduced vanadium is involved in the synthesis of the tunic material (see Goodbody, 1974). The tunic of ascidians also contains cells rich in vanadium and sulphuric acid and roles for them in anti-fouling and anti-predation have been considered (Stoecker, 1980a, b).