What Divers Should Know About Orang Utang Crab

The orang utang crab, Achaeus japonicus, is a fascinating member of the spider crab family found in the tropical waters of the central Indo-Pacific. This small crustacean measures only about 2 centimetres, or 0.8 inches, across its carapace. Its reddish-brown body and relatively long arms are densely covered with fine hairs, giving it a shaggy appearance reminiscent of its primate namesake.

These crabs are masters of blending in; their hairy arms are often laden with small bits of debris for further camouflage, making them challenging yet rewarding to spot. While they can be observed in various reef environments, divers have the best chance of encountering an orang utang crab by carefully inspecting bubble coral (Plerogyra sinuosa), where it is frequently found in close association.