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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans > Family Portunidae
Banded-leg swimming crab
Charybdis annulata*
Family Portunidae
updated Dec 2019

Where seen? This swimming crab with bands on its legs is sometimes seen on some of our rocky and reefy shores, especially at night.

Features: Body width 5-7cm. Body somewhat fan-shaped with 6 spines on the sides. The eyes are not wide apart. Last pair of legs are paddle-shaped and rotate like boat propellers, so the crab swims well in all directions. It is a fully marine crab and cannot live long out of water. Body colours include plain olive, greenish grey, orange. The legs have alternating bands of dark brown and bright blue. The tips of the pincers are also banded dark brown and bright blue. There is a fine network of brown lines on the pincers.

Sentosa, Jul 08

East Coast, May 11

*Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.

Banded-leg swimming crabs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

East Coast, Aug 09
Photo shared by Loh Kok Sheng on his blog.

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

Sentosa, Apr 13
Photo shared by Marcus Ng on flickr.

St John's Island, Dec 20
Photo shared by Vincent Choo on facebook.

Grateful thanks to Crabhunter for confirmation of ID. 


  • 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.
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