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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans | Family Calappidae
Spotted box crab
Calappa philargius
Family Calappidae
updated Dec 2019

Where seen? This large boxy crab with four big spots on its flat pincers is sometimes seen on the sandy shores near seagrass areas on our Northern shores. It is more active at night and are rarely seen by daytime visitors as it is then usually buried in the sediments. Once, several pairs were seen half buried near one another.

Features: Body width 8-10cm. It does look rather box-like with a semi-circular body and wing-like extensions on the sides and back that cover part of the walking legs. The adult Spotted box crab has a total of six spots: two dark spots on each pincer and a dark ring around each eye. Small ones may have only one spot in the middle of the body just behind the eyes. It holds its pincers in front of its body to form a boxy shape. So it is sometimes also called the Shame-face crab as it appears to be covering its face in shame. The inner part of the flat pincers have striking brown patterns.

Changi, May 12

Two different kinds of pincers.

Eyes!
What does it eat? The pincers of box crabs are specialised for cracking open snail shells. The snail is gripped in the left pincer which has pointed claws. With the right pincer, which is stronger, the crab cuts pieces of the shell from the shell opening. Once the gap is big enough, the crab can enjoy its snail meal.

Changi, May 06

Underside.
Patterns on inside pincers.

Changi, May 12

A pair buried next to one another.
Changi, May 06
Status and threats: This crab is listed as Vulnerable in the Red Data List of threatened animals of Singapore.
Spotted box crabs seen on Singapore shores
On wildsingapore flickr

Chek Jawa, Jun 17
Photo shared by Loh Kok Sheng on facebook.
 

Changi, Aug 20
Photo shared by Vincent Choo on facebook.
Changi, May 17
Photo shared by Marcus Ng on facebook.

Changi, Jul 12
Photo shared by Loh Kok Sheng on flickr.

Changi, May 11

Tanah Merah, May 11

Seringat Kias, Apr 12
Photo shared by Loh Kok Sheng on his blog.

Cyrene Reef, May 11

Photo shared by Loh Kok Sheng on his blog.

Changi, May 11

Tanah Merah, May 11

Links

References

  • Lim, S., P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life and Times of Labrador Beach. Division of Biology, School of Science, Nanyang Technological University & Department of Zoology, the National University of Singapore. 160 pp.
  • Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore. Nature Society (Singapore). 285 pp.
  • Jones Diana S. and Gary J. Morgan, 2002. A Field Guide to Crustaceans of Australian Waters. Reed New Holland. 224 pp.
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