The largest hermit crab on a muck slope: scarlet, bristled, and spotted white on black.
The largest hermit crab a diver meets in the region, the body reaching about 25 cm and occupying gastropod shells to match. The body, claws and legs are orange-red to scarlet, thickly set with dark bristles, and marked all over with small white spots each ringed in black. The eyestalks are long and pale with dark corneas, and the left claw is the larger. Two other Dardanus on the same ground are distinguished easily enough: Dardanus lagopodes is smaller and dark red-brown with heavy hair and no ringed white spots, and Dardanus pedunculatus carries a garden of Calliactis anemones on the outside of its shell, which this species does only occasionally and never in the same numbers.
Nocturnal, walking open sand and rubble at night and tucked under rubble or into the base of a coral head by day. It scavenges carrion and also takes live molluscs, which it breaks with the large claw. Recorded from a couple of metres to about 30 m. Large individuals need correspondingly large shells and are usually found in heavy ones such as tun, helmet or triton shells, which limits how big they can get on a slope where those shells are scarce; competition for a suitable shell is intense, and a crab that has been tipped over will right itself, withdraw entirely behind the claw and stay shut for several minutes. The claws are heavy enough to break skin, which is reason enough to leave the shell where it stands.
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.