Blue-grey with black lines, and white specks scattered over the gills and rhinophores.
A chromodorid to about 5 cm, pale blue-grey to almost white, marked with three to five black longitudinal lines and a fine opaque white margin. The gill plume and the rhinophores are translucent and dusted with small opaque white specks, which is the feature that separates it from the several very similar blue-and-black species — Chromodoris lochi, C. dianae and C. boucheti among them — that occur on the same ground and are routinely confused in photographs. If the gills are speckled, it is willani; if they are plain, look again.
Feeds on sponges of the genus Chelonaplysilla and carries the defensive chemistry of its food in the mantle margin, which is why it moves in the open in daylight. The group is a standing example of aposematic mimicry — several unrelated species converging on one blue-and-black pattern that reef fish have learned to leave alone. Recorded from about 3 to 30 m. Common, and a good animal on which to practise getting the rhinophores and gill both sharp.
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.
