The Spanish Dancer

The Spanish Dancer, Hexabranchus sanguineus (photo by David Doubilet, National Geographic)

Nudibranchs are among my favorite animals to look at.  These tropical marine mollusks feature extraordinary colors and fantastical shapes which would make the most flamboyant nineteen eighties rock star weep with envy. One of the largest and most powerful nudibranchs is also one of the most beautiful.  Hexabranchus sanguineus lives thoughout the tropical waters of the Indo-Pacific Ocean and can be found from the Red Sea to Hawaii. The creature’s common English name is the Spanish Dancer because, when it swims free, it undulates its bright red paradodia in the manner of a flamenco dancer.

A Spanish Flamenco Dancer

Hexabranchus sanguineus

Although the Spanish Dancer is surprisingly quick and agile when it uses this means of locomotion, it has an auxiliary method for getting around and can also be found crawling in a much more traditional slug-like manner.  The creature grows to be 40 centimeters or larger and has several distinctive color patterns ranging from bright red to bright yellow to pale pink (or sometimes various combinations of these colors).

The Spanish dancer can afford to be extravagantly colorful because it contains toxic chemicals inside its body (again one is drawn to comparisons with 1980’s musical entertainers).  Predators therefore avoid the creature as it proceeds about the reef feeding on various sponges and bryozoans.  Spanish Dancers are hermaphrodites.  Although each Spanish dancer possesses the reproductive organs of both genders, it is very rare for an individual to fertilize itself.  When they do mate, the parent carefully deposits a large pink rosette of eggs which is almost as distinctive and lovely as the adult.

The Egg Rose of a Spanish Dancer (photo by Peter Korn)

The Spanish dancer is sometimes inhabited by one or more Emperor Shrimps.  These little arthropods do not help their mollusk host, but neither do they harm it (a commensal relationship). Chameleon-like the little shrimp can adapt to the extraordinary coloring of their vivid hosts.

An Emperor shrimp living on a Spanish Dancer (photo by Goos van der Heide)

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