The commonest nudibranch on the site, and the one everybody stops photographing by Tuesday.
A firm-bodied dorid to about 6 cm, black with clusters of raised pink to pale grey tubercles arranged in irregular groups over the back, and with black rhinophores. There is no gill plume — the phyllidiids breathe through folds beneath the mantle margin — and the body is hard and rubbery rather than soft. Several close relatives share the pattern and are separated on the arrangement of the tubercle clusters and on the colour of the rhinophores, which is finer work than most photographs allow.
Probably the most abundant nudibranch across the Indo-Pacific, and certainly the one most often seen on a muck site. It feeds on sponges and carries their chemistry in its skin, which is why it moves about in the open with no attempt at concealment. Recorded from the shallows to about 30 m. Worth photographing properly once: it is the animal on which to learn that black subjects need light from the side, because a straight-on strobe turns it into a silhouette with pink dots.
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.
