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  Online Guide to Chek Jawa
mangroves
 
Horseshoe crabs

There are only four species of living horseshoes crabs in the world. On the Atlantic coast is Limulus polyphemus; in Southeast Asia are: the Mangrove horseshoe crab (Carcinoscorpius rotundicauda) which is also the smallest horseshoe, and the Coastal horseshoe crab (Tachypleus gigas); In Japan, China and southern Sabah are found the Chinese horseshoe (Tachypleus tridentatus). The species are distinguished by their size, colour, shape of tail and number of spines at the base of the tail.
    
click for enlarged image
Coastal horseshoe crab
Tachypleus gigas
click for enlarged image
Mangrove horseshoe crab
Carcinoscorpius rotundicauda
Two species of horseshoe crabs may be found in Singapore. Both may be seen on Chek Jawa. The Coastal horseshoe crab (Tachypleus gigas) is larger (diameter up to 25cm). It is greyish with a triangular, serrated tail. The Mangrove horseshoe crab (Carcinoscorpius rotundicauda) is smaller (diameter up to 15cm). It is brownish with a rounded tail.

Status and threats: Populations of these ancient creatures in Singapore have been severely reduced over the last two decades. In Singapore, the Coastal Horseshoe Crab (Tachypleus gigas) is listed as vulnerable. The main threats are habitat loss and pollution. 		 
quick facts
15-25cm, sometimes seen in the mangroves, sand bar and seagrass lagoon

Classification:
OrderXiphosura
Class Merostomata
Subphylum Chelicerata
Phylum Arthropoda
 
See also ...
Horseshoe crabs in general

Links
 Tai Ho Wan: breeding and nursery ground of horseshoe crabs by Terence Ching-wai Fong on the University of Hong Kong website: a study of breeding of Tachypleus and Carcinoscorpius.
Nursery beaches for Horseshoe crabs in Hong Kong by Huang Qin, Helen Chiu and Brian Morton on the Porcupine Homepage of the Department of Ecology & Biodiversity, The University of Hong Kong website: examines some of the possible causes of the decline in horseshoe crabs in Hong Kong.

Other references
  • Ng, Peter K. L. & N. Sivasothi, 1999. A Guide to the Mangroves of Singapore II (Animal Diversity). Singapore Science Centre. 168 pp. online version
  • Tan, Leo W. H. & Ng, Peter K. L., 1988. A Guide to Seashore Life. The Singapore Science Centre, Singapore. 160 pp. online version
  • Ng, P. K. L. and Wee, Y. C., The Singapore Red Data Book: Threatened Plants and Animals of Singapore, The Nature Society (Singapore), 1994, p. 157.
  • Chuang, S. H., On Malayan Shores, Muwu Shosa, 1961, p. 91
 

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