The host most emperor shrimps are found on, and it feeds by eating the sand.
A large holothurian to about 50 cm, the body wall pale grey to cream and mottled with brown, and the mouth surrounded by a ring of dark, heavily branched feeding tentacles that are extended and wiped into the mouth one at a time. Juveniles are strikingly different — white with bold dark blotches — and were long treated as a separate species. Disturbed animals eject sticky white Cuvierian tubules, which is worth knowing before picking one up, and is a further reason not to.
It processes sediment: sand goes in at one end, organic material is stripped out, and clean sand comes out at the other in a coiled cast. A hectare of soft bottom is turned over by these animals repeatedly in a year, and their casts are a normal feature of a muck site’s surface. For a diver the point is what rides on it — the emperor shrimp Zenopontonia rex and the sea cucumber crab Lissocarcinus orbicularis are both found here more reliably than anywhere else, usually on the underside or near the anal opening.
Older references list it as Bohadschia graeffei.
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.