The clubs along its sides can light up, which is rare enough among sea slugs to be worth going out at night for.
Plocamopherus carry a row of stalked appendages down each flank, each ending in a knob, and in this genus those knobs are luminescent: disturbed in the dark, the animal produces flashes from them. Bioluminescence is common in the open ocean and almost unheard of in nudibranchs, and what it is for here has never been settled. Startling a predator is the usual guess.
The animal is brown to pale brown, scattered with yellow eyespots, up to six centimeters, and out on rubble and sand at night rather than on coral by day. That habit is most of the reason it is rarely recorded: the people who dive here after dark are a small fraction of those who dive here.
It was described in 1828 by Rüppell and Leuckart from 🌊 Red Sea material, which makes it one of the oldest names in this catalogue. It has also made the journey the other way through the Suez Canal (🇪🇬 Egypt) and is now recorded from the eastern Mediterranean off 🇮🇱 Israel, so the animal Rüppell collected here is now a Levantine species as well.
- brown to pale brown body scattered with yellow eyespots
- club-tipped appendages standing out along each side of the body
- out at night, on rubble and sand rather than on coral
- up to 6 cm
