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Porcelain crab Family Porcellanidae Porcelain crabs are plentiful under the stones of Chek Jawa, scattering in all directions as a stone is lifted. Fragile Crab: The porcelain crab tends to shed limbs if stressed, hence its common name. This is a useful trait, in case a limb is trapped between rocks shifting in the currents, or grabbed by a predator. A dropped pincer may continue to move, to distract the predator while the crab makes its getaway. The lost limb eventually re-grows but this takes time. Flat Crab: The porcelain crab is really flat and so it is able to squeeze into nooks and crannies. Its flatness plus its oversized pincers makes the crab appear two-dimensional and cartoonish! Not a true crab! While true crabs (Suborder Brachyura) have four pairs of walking legs and short antennae, the porcelain crab has only three pairs and often has long antennae. The abdomen of the porcelain crab is long and folded under it. The abdomen remains free to move. In fact, when alarmed, the crab might swim by flapping its abdomen! Porcelain Food: Porcelain crabs filter feed at high tide. They have large mouthparts which are feathery with long silky hairs. These are extended into the water like nets to strain plankton from the water. Internal mouthparts scrape off any edible titbits caught on the hairs and transfer them to the mouth. Porcelain Babies: Porcelain crab eggs hatch into free-swimming larvae that only later settle down and develop into miniatures of their parents. Here is a fascinating photo of a porcelain crab larva on Image Quest 3-D Marine Library Role in the habitat: Some porcelain crabs live with other animals. On Chek Jawa, you might come across the porcelain crab that lives among the tentacles of the sea pen. Elsewhere, there are porcelain crabs that live with tubeworms, in the siphons of bivalves, among the tentacles of sea anemones, on or inside sponges, or up the backside of a sea cucumber!		Red porcelain crab Porcelain crab feeding Green porcelain crab With red-tipped pincers

quick facts
Body width to about 1-2cm, common under rocks in the rocky shore

Classification:
Order Decapoda
Class Malacostraca
Subphylum Crustacea
Phylum Arthropoda

See also ...
Porcelain crabs that live in sea pens

Links
Hermit crabs and their allies on the Marine Crustaceans of Southern Australia page on the Museum Victoria website: an introduction to porcelain crabs including a section on their biology which has lots of labelled diagrams, and photos and fact sheets on some porcelain crabs of Southern Australia.
Porcelain crab (Petrolisthes sp.) on the Monterey Bay Aquarium website: brief fact sheet and photo.
Flat Porcelain Crab (Petrolisthes cinctipes) on eNature.com of the US National Wildlife Federation: fact sheet on this temperate porcelain crab.

Other references

Barnes, Robert D. & Ruppert, Edward E., 1996. Invertebrate Zoology. Harcourt College Publishers. 6th Edition. pp. 1056, G-1-16, I-1-30.
Pechenik, Jan A., 2000. Biology of the Invertebrates. McGraw-Hill Book Co., Singapore. 578 pp.
Tan, Leo W. H. & Ng, Peter K. L., 1988. A Guide to Seashore Life. The Singapore Science Centre, Singapore. 160 pp. online version
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.
Ng, Peter K. L. & N. Sivasothi, 1999. A Guide to the Mangroves of Singapore II (Animal Diversity). Singapore Science Centre. 168 pp. online version
Davey, Keith, 1998. A Photographic Guide to Seashore Life of Australia. New Holland, Australia.144 pp.
Morten, Brian & John Morten, 1983. The Sea Shore Ecology of Hong Kong. Hong Kong University Press. 350 pp.

a companion website to the chek jawa guidebook website©ria tan 2003 www.wildsingapore.com

a companion website to the chek jawa guidebook
website©ria tan 2003 www.wildsingapore.com