A small bristly crab, about 1.5 cm (0.6 in), with black claw tips and a shell covered in short hairs that trap sediment until the animal matches the coral base it sits on. It lives deeper in the colony than the guard crabs, close to the branch bases where light does not reach.
Its standing is more ambiguous than that of the guard crabs it shares corals with. It takes mucus and tissue from the host and does not defend the colony, and where numbers build up on a stressed coral the crabs feed on the dying tissue directly - which has led to arguments about whether they cause damage or simply follow it. A healthy colony carries a few and is none the worse; a bleaching one can carry many. Either way they are among the most abundant animals inside branching corals, and a torch shone into a colony usually catches one moving.
- small hairy crab with distinctly black claw tips
- shell covered in short bristles that collect sediment
- deep between coral branches, close to the base
- width up to 1.5 cm
