The Spanish dancer is not a fish at all; it is a species of sea slug. Also called nudibranchs, sea slugs are mollusks that live without the protection of a shell. Many nudibranch species – including Spanish dancers – are boldly colored. Scientists consider this a form of aposematic coloration, in which animals adopt bold colors to warn of noxious, dangerous or toxic properties.
Spanish dancers do not produce their own defenses. Instead, they rely on their prey to supply them with protection. Spanish dancers subsist entirely on sponges. They incorporate some of the compounds from within the sponges' bodies into their own, which makes them distasteful to predators. Such defense mechanisms are common among particularly vulnerable animals, such as sea slugs, which lack shells or other protective structures. When the adults deposit egg sacs, they coat them with some of their defensive, foul-tasting substances.
Spanish dancers live in the Pacific and Indian Oceans. The name "Spanish dancer" refers to the species' appearance when swimming, which is said to resemble a flamenco dancer. Spanish dancers move through open water by swimming, but they also crawl along rocks and coral.
Spanish dancers are hermaphroditic, meaning that each individual possesses male and female reproductive structures. However, they must mate to fertilize their eggs.