Ultrastructural localization of vanadium in the blood cells of Ascidiacea

X-ray histospectrographic analysis at the scanning and transmission electron microscope (STEM) are made on the blood cells of Phallusia mamillata Cuvier and Ciona intestinalis, to study the 'direct' intracellular sites of accumulation of vanadium. The results show a clear accumulation of vanadium on the membrane and in the granules of vacuoles of amebocytes, signet ring cell, compartment cell and traces of metal in the 'vanadophores' of vanadocytes.