Dark red and thickly bristled, with green eyes, out on open sand after dark.
A hermit crab reaching about 6 cm, dark red to maroon-brown and thickly covered in short stiff bristles that trap silt, so an animal on a black sand slope often looks grey until a light is on it. The eyes are green and set on short stalks, and the left claw is distinctly larger than the right. The species it is taken for is the anemone hermit crab, which is the same size and also in the genus, but that animal has cleanly red-and-white banded legs, long red-and-white eyestalks and normally a shell carrying several live anemones; this one is uniformly dark, hairy, green-eyed and usually in a bare shell.
Nocturnal, and one of the most numerous large animals moving on open sand at night. It is a scavenger and general feeder, working over carrion, detritus and anything dead it finds, and on a muck site it is regularly the thing that turns out to be moving a shell across the sand. It occupies whatever gastropod shell fits and shells are the limiting resource — animals in shells that are visibly too small are common, and competition and eviction are routine. It sometimes places Calliactis anemones on its shell but does so far less consistently than the anemone hermit crab, and a bare shell does not rule it out.
It is not shy and continues feeding with a diver alongside, which makes it one of the more workable subjects on a night dive. The bristles hold enough silt to scatter light back at a strobe, so a low angle across the animal tends to work better than a flat one.
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.