Widespread throughout the Solitary Islands Marine Park, although uncommon. World distribution is from South Africa to the Red Sea and to the Indo-West Pacific.
Frequents rocky reef areas where it is found from intertidal areas to a depth of at least 30 m. Feeds on sponges.
Adults are recognisable by the red or orange mantle and numerous white specks. At rest the mantle edge flaps usually lie folded against the body, the mantle margin is vivid white and there may be dark red radiating bars, see lowest photograph. The nudibranch is capable of swimming if disturbed by flexions of the body accompanied by flapping of the foot. The brightly coloured egg mass consists of closely packed spiral rings, the eggs are predated on by other nudibranchs, notably Favorinus japonicus. The shrimp Zenopontonia rex is often found living in a commensal relationship on the dorsal surface of the animal. H. sanguineus is the largest species of nudibranch and reaches lengths up to 600 mm.
Gary Cobb, David Mullins, Nudibranchs Encyclopedia, 2nd Edition, 2015. Publishers Thomas Slone, Masalai Press and Tim Hochgrebe, Underwater Australasia. p.64.
Australian Museum, Sea Slug Forum. http://www.seaslugforum.net/showall/hexasang. Accessed 08/09/2018.