Spanish dancer

Lore & Background

The Spanish dancer is a nocturnal creature, hiding in crevices during daytime and emerging late at night. It is hermaphroditic, and its egg ribbons range in color from bright red to pink, with a spiral shape related to the animal's size. After consuming sponges, it derives a potent chemical defense, which it passes into its egg ribbons via macrolides, giving the otherwise defenseless eggs a toxin defense. This toxin is coveted by other nudibranch species such as Favorinus tsuruganus or Favorinus japonicus.

Reader's Guide

The Spanish dancer is significant as a striking example of a nudibranch that uses both chemical and behavioral defenses. Its ability to swim when disturbed, unfolding its mantle edges and undulating its body, gives it its common name and distinguishes it from many other sea slugs. Its commensal relationship with the emperor shrimp, Periclimenes imperator, illustrates complex ecological interactions on coral reefs. The species also demonstrates how nudibranchs can sequester chemical compounds from their sponge diet for their own defense and that of their offspring. Its presence across the Red Sea, Western Indian Ocean, French Polynesia, and Western Pacific, with different color morphs not differentiated by morphology or DNA barcodes, suggests cryptic diversity that warrants further study.

Did You Know?

• The scientific name Hexabranchus sanguineus means 'blood-colored six-gills'.
• The emperor shrimp, Periclimenes imperator, is a commensal shrimp commonly found living on Hexabranchus sanguineus.
• The Spanish dancer passes defensive compounds into its egg ribbons via macrolides.