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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans
Pebble crabs
Family Leucosiidae
updated Oct 2016

Where seen? These crabs really do resemble tiny pebbles and are sometimes seen on our Northern shores. Silty, sandy areas near seagrasses. They are usually buried under the sand.

Features: Body width 1-2cm. Body smooth somewhat rhomboid, indeed resembling a tiny pebble. The head forms a blunt pointed tip with a pair of tiny eyes. In this way, its eyes can peep out while the rest of the crab is buried underground. It has powerful long flat pincers with pointed claws. The crab can bury itself in the sand very rapidly. Some may be colourful.

According to the Singapore Red Data Book, the Rubble crab (Favus granulatus) is known only from Singapore and was a new genus and species discovered from Singapore and is not yet known elsewhere. It was found on Siloso Beach of Sentosa which has since been 'improved', and Pulau Semakau. Alox somphos, a related species in another genus was also first described from Singapore.

Status and threats: Some of our pebble crabs are listed as 'Endangered' on the Red List of threatened animals of Singapore.
Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors also have an impact on local populations.

Changi, Apr 08

Leucosia craniolaris
Pulau Semakau, Mar 08
Photo shared by Loh Kok Sheng on his blog

Seulocia vittata
Chek Jawa, Jan 02

Leucosia anatum
Mating pebble crabs
Changi, Jul 05

Pebble crabs on Singapore shores

Photos of Pebble crabs for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map

Leucosia anatum

Changi, Jul 08

Leucosia anatum

Changi, May 12

Leucosia anatum

Changi, Jul 12

Changi, Jun 13
Photo shared by Loh Kok Sheng on flickr.

Tanah Merah Ferry Terminal, Jun 15
Photo shared by Heng Pei Yan on facebook.

Kusu Island, Apr 17
Photo shared by Toh Chay Hoon on facebook.

St John's Island, May 09
Photo shared by Loh Kok Sheng on his blog.

Family Leucosiidae recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore
in red are those listed among the threatened animals of Singapore from 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.
^from WORMS

  Family Leucosiidae
  *Alox somphos (EN: Endangered)

Arcania erinacea
Arcania undecimspinosa

Ebalia malefactrix=^Philyra malefactrix
(Mangrove pebble crab)

Favus granulatus
(Rubble crab) (EN: Endangered)

Heteronucia aff. mesenensis

Ixa cylindra=^Ixa cylindrus

Leucosia craniolaris

Myra fugax

Nursia malefactrix
Nursia punctata

Oreophorus rugosus=^Alox rugosum

Pariphiculus coronatus

Philyra heteograna=^Lyphira heterograna

Praosia punctata
(EN: Endangered)

With grateful thanks to Ondrej Radosta for identifying the species of the crabs on this page.


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