A wide flared skirt, a raised horn behind the gill, and purple spots on both.
A large dorid to about 15 cm, orange to pink-brown with a scatter of purple-red spots ringed in white, a broad mantle skirt that flares widely on each side, and a conspicuous horn rising behind the gill plume. It is the sister confusion to Ceratosoma trilobatum: this species has the wider, more flared skirt and a proportionally larger horn, and the lateral lobes are less distinctly three-parted.
The horn does the same job in both. Defensive compounds taken from the sponge diet are concentrated in the mantle margin and most heavily in that horn, and the animal turns the horn towards a disturbance — so what a predator bites first is the part loaded with the deterrent, and losing a piece of mantle costs the slug very little. Feeds on sponges. Recorded from about 5 to 40 m, and one of the larger and more frequently seen dorids across the Indo-Pacific.
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.
