Ascidiacea

Ascidiacea, commonly known as the ascidians or sea squirts, is a paraphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer test or "tunic" made of the polysaccharide cellulose.

right|thumb|Sea squirt ([[Didemnum molle) off Sulawesi, Indonesia]] Hemovanadin is a pale green vanabin protein found in the blood cells, called vanadocytes, of ascidians (sea squirts) and other organisms (particularly sea organisms). It is one of the few known vanadium-containing proteins. The German chemist Martin Henze first detected vanadium in ascidians (sea squirts) in 1911. Unlike hemocyanin and hemoglobin, hemovanadin is not an oxygen carrier.

thumb|3-D representation of the structure of Vanabin2 from Ascisia sydneiensis var. samea