Friday, July 26, 2013

Red-eyed Crabs (Phylum Arthropoda: Family Eriphiidae) of Singapore

Red-eyed crabs (phylum Arthropoda, subphylum Crustacea, class Malacostraca, order Decapoda, superfamily Eriphioidea, family Eriphiidae) typically have red eyes, though this is not a useful distinguishing feature since may other crabs share this characteristic.

Red-eyed Reef Crab (Eriphia ferox)
They have hexagonal to ovate carapace, and the chelipeds are usually large and powerful. The carapace and chelipeds are usually covered in fine, spiky bumps, and the front margin of the carapace is usually marked with lobes or spines. They typically have large and powerful asymmetrical chelipeds, and a large molar-like tooth can be found near the base of the top finger, allowing them to crush and break shells of molluscan prey. Studies suggest that some species include algae as part of their diet as well.

Like other true crabs, red-eyed crabs have a broad carapace, and a very short and flattened abdomen which is usually folded underneath the body. They also have five pairs of "legs" (including the clawed arms, or chelipeds), and hence they are placed in the order Decapoda ("deca" means "ten", while "poda" means "feet"). The gills are leaf-like - a distinctive characteristic of decapods from the suborder Pleocyemata. And as with other crustaceans from the class Malacostraca, their body comprises three main parts - a head with five segments, a thorax with eight segments, and an abdomen with six segments. The head is fused to the thorax, forming a cephalothorax. They have a tough exoskeleton strengthened with calcium carbonate, and the carapace covers the gills but not the abdomen.

Red-eyed crabs reproduce sexually, and have separate sexes. They mate face-to-face, usually with the male on top and the female below. The females can usually be distinguished from the males by having a broader abdomen. This is an adaptation to allow them to carry the eggs under their abdomen until they hatch.

At the moment, I have only photographed one species of red-eyed crabs in Singapore.

Red-eyed Reef Crab (Eriphia ferox)
The Red-eyed Reef Crab (Eriphia ferox) is usually found in intertidal or subtidal coral reefs or coral rubble flats. It has a dark reddish brown, somewhat rectangular carapace covered in spiky granules. It is sometimes collected for consumption, but is said to be poisonous in some areas, possibly depending on their diet. The maximum carapace width is about 6cm.

Red-eyed crabs are sometimes confused with rubble crabs (family Xanthidae) and other crabs of the same superfamily Eriphioidea, such as forceps crabs (family Oziidae) and stone crabs (family Menippidae). Unlike rubble crabs, forceps crabs have the large curved tooth near the base of the top finger of the bigger pincer. They can be distinguished from other crabs of the superfamily Eriphioidea by the spiky granules on their carapaces.

  • Carpenter, K. E. & V. H. Niem (eds), 1998-2001. FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volumes 1 to 6. FAO, Rome. pp. 1-4218.
  • De Grave, S., N. D. Pentcheff , S. T. Ahyong, T.-Y. Chan, K. A. Crandall, P. C. Dworschak, D. L. Felder, R. M. Feldmann, C. H. J. M. Fransen, L. Y. D. Goulding, R. Lemaitre, M. E. Y. Low, J. W. Martin, P. K. L. Ng, C. E. Schweitzer, S. H. Tan, D. Tshudy & R. Wetzer. 2009. A classification of living and fossil genera of decapod crustaceans. The Raffles Bulletin of Zoology, supplement 21, pp. 1-109.
  • Ng, P. K. L., S. S. L. Lim, L. K. Wang & L. W. H. Tan. 2007. Private lives: An exposé of Singapore's shores. The Raffles Museum of Biodiversity Research, Department of Biological Sciences, National University of Singapore. 212 pp.
  • World Register of Marine Species. 2012. Retrieved Jun 10, 2013, from

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