Some animals, such as the sea cucumbers even have yellow blood. What could make blood yellow? The yellow coloration is due to a high concentration of the yellow vanadium-based pigment, vanabin. Unlike hemoglobin and hemocyanin, vanabin does not seem to be involved in oxygen transport. In addition to vanabin, sea cucumbers have enough hemocyanin in their blood to sustain their oxygen needs. Actually, the role of vanabin remains a bit of a mystery. Perhaps it is part of a defense mechanism to make the sea cucumbers unappealing or toxic to parasites and predators. However, sea cucumber is used for cooking in many cultures, where it is prized for its slippery texture and possible health benefits. Vanadium is a controversial dietary supplement, potentially affecting insulin sensitivity and athletic performance.