A small crab with a smooth glossy shell in plain deep red, wider than it is long and finely scalloped along the front edges. About 2 cm (0.8 in) across, with short stout claws tipped dark.
The colour is the point. Bright uniform red on a small, slow, defenceless crab is the classic signature of a chemically defended animal, and several crabs in this family are known to carry paralytic toxins in their flesh - the same compounds found in pufferfish and in some cone snails. Predators learn the pattern; a diver only needs to know not to eat it. It shelters under coral slabs and in rubble by day, feeding at night on detritus and algal film, and turns up on night dives as a spot of red under a torch when everything else has gone grey.
How to recognise it
- smooth glossy shell in plain deep red
- shell wider than long, edges finely scalloped
- short stout claws with dark tips
- width up to 2 cm
