Harlequin Swimming Crab

Lissocarcinus orbicularis is a visually striking small swimming crab from the Indo-Pacific, displaying a distinctive dark brown to black body adorned with bold, circular white markings that create a pattern resembling polka dots or moon phases across the carapace. In the wild it is commonly found associated with holothurians (sea cucumbers) and anemones, taking advantage of their chemical defenses for protection. In reef aquariums it adapts well to captive conditions, scavenging for meaty foods and organic detritus. It is a relatively peaceful species for its crab family but should not be housed with very small fish or ornamental shrimp that may be at risk from its opportunistic feeding.

Provide abundant live rock with crevices for shelter and daytime retreat. Feed with meaty frozen foods — mysis, chopped shrimp — target-fed near the crab, or allow it to scavenge naturally from uneaten food in the system. Generally reef-safe with corals. Keep with medium to large fish only; not suitable for tanks with nano fish or small ornamental shrimp. Avoid copper-based medications.