Carries luminescent knobs on its side appendages and swims strongly when disturbed.
A polycerid to about 8 cm, translucent cream to orange-brown, blotched and speckled in red-brown and white, with two or three pairs of branched appendages standing out from the sides of the body, each ending in a swollen knob. The gill plume sits well back and the rhinophores are held in sheaths. The appendages are the identification: nothing else of this size on a sand slope carries them. Within the genus, Plocamopherus ceylonicus is separated from its relatives on the number and shape of those appendages and on ground colour, and several forms photographed in the region remain undescribed, so a specific name is not always warranted.
Feeds on bryozoans and is found on sand and rubble at night, usually in the open. The knobs at the tips of the lateral appendages are luminescent and flash when the animal is disturbed, which is unusual among sea slugs and appears to be a startle response. It also swims strongly, flexing from side to side, and will do so for some distance rather than settling.
Almost entirely a night animal in the shallows here, recorded from about 5 to 30 m. It is one of the few nudibranchs that is easier to find with a torch than in daylight, since the movement across open sand is what gives it away.
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.
