Paddle-shaped cerata like a stack of leaves, and it drops them when attacked.
A sacoglossan to about 3 cm, the body covered in broad flattened paddle-shaped cerata arranged like overlapping leaves, black with a bright yellow or orange margin and scattered white flecks. It is not a nudibranch: sacoglossans are sap-suckers with a single-rowed radula built for piercing algal cells, and they sit in a different branch of the sea slugs entirely.
The cerata are detachable. Attacked, the animal sheds several, and the shed cerata go on twitching for a considerable time — a distraction that buys the slug the seconds it needs, and one it can afford because they regrow. Feeds on green algae, chiefly Halimeda and Chlorodesmis, in shallow water. Recorded from about a metre to 15 m. Small, slow and strongly patterned, so the difficulty is finding it rather than photographing it: at 2 cm on a green algal turf it is a fleck.
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.
