Creature Feature: The Japanese Shame-Faced Crab

Andrew Hosie's blog | Created 1 decade ago

The Japanese Shame-Faced Crab, Calappa japonica Ortmann, 1892.

The Japanese shame-faced crab was originally discovered in Tokyo Bay, Japan but has since been found as far away as Africa and can be found in depths up to ~250 m. This spectacular red and yellow crab was first reported in Western Australia only as recently as 1989 when crayfishers, off Rottnest Island, caught an unfortunate specimen in a craypot. The specimen in the photos was collected this year, near Ningaloo reef in 230 m.

This large species is an active predator feeding on other marine invertebrates such as oysters, snails as well as other crabs. The shame-faced crab’s right pincer is incredibly well adapted for getting past a snail’s protective shell. There is a large accessory tooth at the base of the moveable finger and a corresponding flat plate on the fixed finger which act like a vice to crack through the shell. The left pincer is relatively longer and sharper and used to extract the snail’s body from the broken shell.

Members of the genus Calappa get their common name because of the way the pincers appear to cover their face. In some species this impression is further enhanced by large reddish-pink spots on the pincers which leave the crab looking embarrassed. Calappa species are also known as box crabs because when the crab is threatened they pull the large pincers into position and hide their legs under the canopy-like expansions of the carapace forming a very well armoured “box”.

Japanese Shame-Faced Crab
Calappa japonica, Photo by Andrew Hosie, Image copyright of WA Museum

Japanese Shame-Faced Crab
Calappa japonica, Photo by Andrew Hosie, Image copyright of WA Museum

Japanese Shame-Faced Crab
Calappa japonica, Photo by Andrew Hosie, Image copyright of WA Museum