Yellow with black-ringed spots, hard as rubber, and it moves about in daylight.
A firm-bodied phyllidiid to about 6 cm, bright yellow to orange with a pattern of raised tubercles, many of them ringed or capped in black — the arrangement of those rings varies between individuals and between regions enough that several forms have carried this name. The rhinophores are orange. As in the whole family there is no gill plume on the back; respiration is through folds under the mantle margin, which is the quickest way to place any hard, warty slug of this shape.
Feeds on sponges and takes their chemistry into its own skin, secreting it when attacked. Nothing eats it, and it correspondingly makes no attempt at concealment: it is one of the sea slugs most often seen crossing open rock and rubble in daylight. Recorded from the shallows to about 30 m. The yellow and black is a warning signal shared with several unrelated slugs on the same ground, which is why the group is so easily confused and so consistently left alone by fish.
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.
