A small crab in a chocolate-and-cream pattern so contrasty it looks painted, with a smooth rounded shell and the flattened rear legs of a swimming crab. Width stays under 1.5 cm (0.6 in).
It lives on sea cucumbers, and that is where to look for it - riding the flank of a large holothurian, or tucked into the folds around the mouth. Some individuals go further and live inside the host's gut, coming out to feed. The crab takes mucus and food particles from the sea cucumber's surface and gains a walking fortress that predators avoid because of the saponins in its skin; the holothurian appears to lose nothing. Colour varies with the host species, dark on a pale animal and pale on a dark one, which is the usual reason a diver misses one. Look on Bohadschia and the larger Holothuria after dark.
- bold chocolate-and-cream blotches, like a harlequin costume
- smooth rounded shell, flattened swimming legs
- found riding on a sea cucumber, rarely on open bottom
- width under 1.5 cm
