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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans
Grapsid crabs
Family Grapsidae
updated Dec 12

if you learn only 3 things about them ...
These crabs have long pointy legs to cling to and scramble over rocks.
They have a flat body to slip through narrow crevices.
They are very shy and disappear at the slightest sign of trouble.

Where seen? Small grapsid crabs are commonly seen on many of our rocky shores and mangroves, especially at night. They are among the colourful crabs you might see even at high tide. But they are more active at night and fast moving. During the day, you will rarely see more than a purplish hairy leg peeking out from a crevice! The larger species are sometimes seen on the offshore Southern Islands.

Features: Body width 4-6cm. Grapsid crabs are adapted for scrambling over rocks and other slippery surfaces. Many can stay out of the water for some time. Grapsid crabs are also sometimes called Shore crabs. They have well-developed hooks on the tips of their long legs that grip these surfaces. Their bodies and legs are flattened, allowing them to squeeze deep into narrow cracks and crevices. In some species, males have larger pincers than females.

The Tuberculated Sally-light-foot crab (Plagusia squamosa) is sometimes mistaken for a grapsid crab. But it belongs to another family.

What do they eat? Grapsid crabs are scavengers and will eat almost anything. They also eat seaweed.

Family Grapsidae recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore
**Ng, Peter K. L. & N. Sivasothi, 1999. A Guide to the Mangroves of Singapore II (Animal Diversity).
***Ng, Peter K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema Brachyurorum: Part 1. An annotated checklist of extant Brachyuran crabs of the world.
in red are those listed among the threatened animals of Singapore from Ng, P. K. L. & Y. C. Wee, 1994. The Singapore Red Data Book: Threatened Plants and Animals of Singapore


  Family Grapsidae
 

**Grapsus albolineatus/strigosus (Sally-light-foot crabs)

Metopograpsus sp. (Purple climber crabs) with list of species recorded for Singapore


Links References
  • Ng, Peter K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema Brachyurorum: Part 1. An annotated checklist of extant Brachyuran crabs of the world. The Raffles Bulletin of Zoology. Supplement No. 17, 31 Jan 2008. 286 pp.
  • 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.
  • Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. National Council on the Environment. 163pp.
  • Ng, P. K. L. & Y. C. Wee, 1994. The Singapore Red Data Book: Threatened Plants and Animals of Singapore. The Nature Society (Singapore), Singapore. 343 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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