A crab under 2 cm (0.8 in) that lives its whole life on one soft coral and looks like part of it. The body carries pointed tubercles arranged to imitate the sclerites studding the host's branches, and the colour - pink, orange, white or red - matches whichever colony it settled on, so a photograph of the coral alone often turns out to contain a crab.
The host is a Dendronephthya, one of the tree-like soft corals that inflate with water after dark. The crab feeds on the mucus and captured plankton the coral produces, and adds fragments of the host to its own shell to complete the disguise. Finding one is a matter of scanning inflated soft corals on a night dive and looking for a pattern that is slightly too regular. Females carry a clutch of eggs beneath the abdomen until they hatch. Nothing about the animal is dangerous; the difficulty is entirely in seeing it at all.
- tiny crab sitting among the branches of a soft coral
- body colour matches the host exactly - pink, orange or white
- spines on the back mimic the coral's own sclerites
- width under 2 cm
