Sea squirt blood cells

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Vanadium is found in sea squirt blood cells (vanadocytes). Vanadium is V3+ and VO2+ in the blood cell vacuole. The function of vanadium may be as a sink for protons and electrons, not dioxygen carriage (used to be considered haemovanadin, probably still is ), vacuole pH was about 1 due to the presence of sulphuric acid (now believed to be unfounded).

Any help on this one?