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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans > Family Portunidae
Blue swimming crab
Thalamita danae*
Family Portunidae
updated Dec 2019
Where seen? This blue swimming crab is commonly seen on many of our shores, especially near coral rubble and reefs. It is particularly active at night.

Features: Body width 5-7cm. Body somewhat rectangular, sides of the body with 5 dark blue-light blue-brown tipped spines. Spines about equal in size, the fourth spine might be slightly smaller. The eyes are wide apart. Between the eyes are 6 rounded equal-sized lobes.The body is usually densely covered in fine hairs so that it often has a layer of sand on its body. Last pair of legs are paddle-shaped. Body and pincers plain blue or greenish blue. Pinchers long, 'fingers' are often black with a white tip, some have white patch at the base of the 'fingers', some have bright orange patches on the inner 'elbow' and at the 'shoulders'.

Tanah Merah, Jul 11

6 rounded equal-sized lobes between the eyes.

5 spines on the side of the body.
Fine hairs on the body that traps sand.

Bright orange patch on inner 'elbow'.
Tuas, Apr 08

Changi Creek, Jul 23
Photo shared by Marcus Ng on facebook.

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

Blue swimming crabs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Punggol, Nov 20
Photo shared by Vincent Choo on facbeook.

Berlayar Creek, Oct 15
Photo shared by Loh Kok Sheng on facbeook.

Sentosa Serapong, May 16
Photo shared by Marcus Ng on facebook.

Pulau Tekukor, May 10
Photo shared by James Koh on his blog.

Terumbu Buran, Nov 10
Photo shared by Russel Low on facebook.

Terumbu Selegie, Jun 11
Photo shared by Jerome Pang on facebook.

Pulau Semakau East, Jan 16
Photo shared by Marcus Ng on facebook.

Terumbu Raya, Jan 15
Photo shared by Marcus Ng on flickr.

Terumbu Bemban, Jun 17
Photo shared by Abel Yeo on facebook.

Pulau Biola, Dec 09

Pulau Biola, Dec 09

Pulau Sudong, Dec 09

Terumbu Berkas, Jan 10

Terumbu Salu, Jan 10

Terumbu Bukom, Nov 10

Pulau Salu, Apr 21
Photo shared by Loh Kok Sheng on facebook.

Pulau Senang, Aug 10

Pulau Salu, Aug 10

Grateful thanks to Crabhunter for identification of some of these crabs.

 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.
  • 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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