Spanish Dancer

• It sequesters toxins from the sponges it eats and puts them straight into its eggs, protecting them from predators.
• It is hermaphrodite but never self-fertilises, always mating with another individual.
• It eats marine sponges, toxic species included.
• It is one of the largest nudibranchs in the world, at up to 60 cm, and its name of Spanish dancer comes from the way it swims: it unfurls its red-and-white mantle and undulates the edges like a flamenco skirt, an unusual spectacle because almost all nudibranchs only crawl.
• Its chemical defence is borrowed: it obtains toxic compounds from the sponges it eats, above all macrolides of the latrunculin and kabiramide groups, and concentrates them in its mantle.
• And it passes them on to its spawn: the egg ribbons carry even higher concentrations of those toxins than the adult itself, protecting them from predators.
• Those compounds have turned out to be potent inhibitors of actin polymerisation and are being studied as antitumour agents.
• It often carries passengers: small shrimps of the genus Periclimenes live on its mantle, camouflaged in its same colour, and feed on its mucus.
• Its eggs form a pink, ruffled spiral ribbon, highly visible on the reef.

Skeleton type

Invertebrate - no skeleton (soft-bodied mollusc, shell-less as an adult)

Habitat & environment

Coral reefs of the tropical Indo-Pacific, from the Red Sea and East Africa to French Polynesia, Japan and Australia

Birth weight

A microscopic, translucent veliger larva after hatching

Size at birth

Microscopic veliger larva after hatching

Sexual maturity

Months — quick maturity, given a life cycle of only a year

Gestation / incubation

~6 days for the trochophore larva to develop inside the egg capsule

Litter / clutch size

1.5 to 3.6 million eggs per clutch, laid in a spiral ribbon known as a sea rose

Sources consulted: University of Wisconsin-La Crosse (bioweb); ScialertJFAS (spawn larval development study); Hexabranchus Sanguineus Life Cycle (WordPress); Reef Life Survey; Murex Dive Resorts; MarineBio; Animalia.bio; Wikipedia (Spanish dancer)