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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans > Family Grapsidae
Purple climber crab
Metopograpsus sp.*
Family Grapsidae
updated Dec 2019

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.
The pincers have scalloped edges and are used to scrape algae.

Where seen? This small purple crab is commonly seen on our rocky shores in the North and South. Usually only active at night. During the day, it is usually well hidden in crevices.

Features: Body width 2-4cm. Body somewhat squarish, eyes set wide apart. Colours vary from purplish, bluish to greenish, yellowish, grey. It has stout purplish pincers.
The walking legs are very long and tipped with well developed hooks. With these legs, the crab clings tightly so it doesn't get washed away in the waves, and can scramble quickly among slippery rocks. There are three different species of Metopograpsus but they are difficult to distinguish in the field. Males have larger pincers than females.

What does it eat? It eats mainly algae, scrapping this off with its pincers which are scalloped on the inner edge. But it will also scavenge on any other edible things it can find.

Kusu Island, Apr 04

Scalloped pincers

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

Purple climber crabs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Sembawang Park, Jan 12
Photo shared by Marcus Ng on flickr.

Pulau Ubin, Jun 08
Photo shared by Marcus Ng on flickr.

Grabbed a fiddler crab then headed back
to the boardwalk legs.
Chek Jawa, Jan 10

Pulau Sekudu, Jul 09
Photo shared by James Koh on his blog.

Terumbu Buran, Nov 10
Photo shared by James Koh on flickr.

A pair, getting ready to mate?
St. John's Island, May 10

Captured by a Purple climbing crab.
Pulau Hantu May 09
Photo shared by Marcus Ng on flickr.

Cyrene Reef, Jul 10
Photo shared by Loh Kok Sheng on his blog.

Seringat-Kias, Nov 14
Photo shared by Marcus Ng on facebook.

Pulau Semakau, Oct 10
Photo shared by Loh Kok Sheng on flickr.

Terumbu Pempang Tengah, May 11

Photo shared by Liana Tang on facebook.

Metopograpsus species recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore
+from The Biodiversity of Singapore, Lee Kong Chian Natural History Museum.
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

+Metopograpsus cf. frontalis
Metopograpsus latifrons
Metopograpsus messor
Metopograpsus oceanicus
Metopograpsus quadridentatus

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.
  • 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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