About Hexabranchus sanguineus (Rüppell & Leuckart, 1830)
Hexabranchus sanguineus is a large dorid nudibranch that commonly reaches a maximum length of 25 cm, though some reports note individuals up to 40 cm long found in the Red Sea. All species in the genus Hexabranchus have soft, flattened bodies. A pair of retractable rhinophores sits on the anterior dorsal portion of the body, while six contractile gills are inserted independently into the posterior part of the body. Its pair of oral tentacles is formed from a fine flexible membrane that bears large digital lobes. When crawling normally, the edges of this nudibranch's mantle curl upwards, creating a peripheral blister. If the animal is disturbed, it unfolds its mantle edges and can swim away from the threat using body contractions and undulations. This specific defensive behavior gives the species its common name, Spanish dancer. Hexabranchus sanguineus has been recorded in the Red Sea, Western Indian Ocean, French Polynesia, and Western Pacific. Each region hosts a different colour morph of the species, and these morphs are not differentiated by either morphology or DNA barcodes. This species inhabits rocky and coral reefs that have abundant sponges and shelters, at depths ranging from 1 to 50 meters.
