Grows cerata shaped like the polyps of the coral it eats, then sits in it.
An aeolid to about 5 cm, brown to grey-green, the back covered in cerata that are not the smooth spindles of a typical aeolid but branched, blunt-ended structures the shape and colour of the polyps of Briareum soft coral. On its host the animal is effectively invisible; taken off it, it looks like a piece of the coral that has come loose.
Phyllodesmium is the genus that gave up stinging cells. Unlike other aeolids these species do not store functional nematocysts from their prey — they eat soft corals, which have few worth stealing — and have gone instead to camouflage and to farming: several species, this one included, retain the coral’s symbiotic zooxanthellae alive in branches of the digestive gland running through the cerata, and draw nutrition from their photosynthesis. That is the same trick as the sacoglossans, arrived at independently. Found on its host coral from about 3 to 25 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
