Our Unusual Finds: Orangutan Crab, Ponta do’Ouro

On our recent trip to Ponta do’Ouro, our dive guide Karl pointed out something small, hairy and purple to me on the reef.  On closer inspection, it looked like a ball of fur being washed around in the surge.

From his expression, I realised it was something unusual so I took a couple of photos.  I chatted briefly to my dive buddies after the dive and said I thought it was an orangutan crab – but forgot about it again until we got home and I went through my photos and saw the one above.

After a number of enquiries, I discovered it WAS indeed an Orangutan Crab (although the photo was not great as the surge had been too strong to hang around for long).

These creatures are very rare and mainly only seen in the Western Pacific.  We were indeed very lucky to have seen this fellow in Mozambique!

About the Orangutan Crab:

Scientific name : Achaeus japonicus

Small decorator crab (carapace length 1.2 cm). Oval body, red eyes, long legs, short claws. The whole body and legs can be covered with a more or less thick reddish hair. Particles can be stuck on the hair, for camouflage.

Completely “naked” specimens can be seen, with a typical banding pattern on the legs. As they moult, they do lose their furry outer cover along with the carapace and these specimen are usually found hiding out amongst the anemones.

And here’s a “naked” specimen which I took on the same dive:

Naked Orangutan Crab
Could this be a Semi-Naked Orangutan Crab?

Living along the external reef. It feeds on plankton and suspended particles that collects with the hair on the first pair of walking legs (or that collect from the reddish fur).

Unique when hairy, in the naked form can be distinguished by the banded colour pattern.

Associated organisms
Often associated with hard corals, particularly of the family Cariophyllidae (Euphyllia glabrescens here, Plerogyra sinuosa). More mobile at night, when often climbs on sponges or soft corals.

Source:  http://www.seadb.net/en_Orang-utan-crab-Achaeus-japonicus_54.htm