Decorates itself with the polyps of the Dendronephthya soft coral it lives on.
About 1.5 cm across the carapace. Semi-transparent white, pink, yellow or red, matching whichever colony it is on, with dark crimson stripes running along conspicuous elongate spines on the back and sides. Those spines are the point: they imitate the sclerites of the host soft coral, and they are what identifies the animal. The chelae are small. In practice the confusion is not with another crab but with the coral itself — the animal is found by noticing that one bundle of polyps is the wrong shape.
Obligate on Dendronephthya soft corals, so far as anyone can tell: essentially every record is on one, though no host-specificity study has actually been done and the obligate status is inferred from the consistency of observation. It sits deep among the polyp bundles and moves round to the sheltered side of the colony as a diver approaches, which is the usual reason a photograph fails. It decorates itself further by attaching live polyps to its own carapace. It feeds on plankton and particles taken from the colony, and pairs are often found on one coral. Indo-West Pacific; the useful depth range is around 10 to 30 m, which is really the range over which divers and Dendronephthya overlap.
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.
