About Achaeus japonicus (De Haan, 1839)
Achaeus japonicus, commonly called the orang-utan crab, is a species of crab belonging to the family Inachidae, a group that includes spider crabs and decorator crabs. This crab is found in tropical waters of the central Indo-Pacific. It has a carapace only around 2 centimeters (0.8 inches) in diameter, and has comparatively long arms that are densely covered in fine hairs. The crab is red or reddish-brown in color, and often carries small pieces of debris to improve its camouflage. It is commonly, though not always, found living in association with the bubble coral Plerogyra sinuosa. Authors Humann and DeLoach classify this orang-utan crab as Oncinopus sp. 1, and state it was formerly classified as Achaeus japonicus, while noting that their own genus identification is tentative.
