Spanish Dancer

Identification

The Spanish dancer is the largest nudibranch species in the world, with mature individuals reaching 60 cm. At rest on the reef, the mantle is folded tightly along the body and the animal appears as a bright red or red-orange oval. When disturbed, it unfurls the full mantle — bright red above, white-fringed below — and swims by rhythmic flexing, a movement that resembles a flamenco skirt in motion.

Distribution & Habitat

Hexabranchus sanguineus is widely distributed across the tropical Indo-Pacific, from the Red Sea east through the central Pacific. During the day it hides under ledges or rubble; at night it emerges to graze on sponges.

Behavior

Unlike most nudibranchs, the Spanish dancer can actively swim — a rare ability in sea slugs. It is also famous for its egg mass: a delicate pink or red ribbon coiled in a rose-shaped spiral, often attached to reef structure. The ribbon contains hundreds of thousands of tiny eggs and is itself a photogenic subject on night dives.

Where to See Them

Night dives in the Red Sea (especially Egypt), the Maldives, Indonesia, and the Philippines are the best bet. They are extremely photogenic and are a common target for underwater photographers. Do not pick them up to watch them swim — repeated handling is stressful and the sight of a naturally swimming individual, while rarer, is the one worth waiting for.