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| porcelain crabs text index | photo index |
| Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Anomurans |
| Porcelain
crabs Family Porcellanidae updated Oct 08
Where seen? Porcelain crabs are plentiful under the stones of our rocky shores, scattering in all directions as a stone is lifted. Some porcelain crabs live on or with other larger animals. What are porcelain crabs? Porcelain crabs belong to the subgroup Anomura of the Order Decapoda. Anomurans includes hermit crabs. Porcelain crabs belong to Family Porcellanidae. Features: Body width 1cm or less. Body and pincers really flat, thus they are able to squeeze into nooks and crannies. The flatness of a porcelain crab, together with its oversized pincers makes it appear two-dimensional and cartoonish! Falling apart at the seams: 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. Not a true crab! The porcelain crab is not a true crab. True crabs belong to the subgroup Brachyura and have four pairs of walking legs and short antennae. In comparison, porcelain crabs have only three pairs of walking legs and often have long antennae. The abdomen of the porcelain crab is long and folded under the body. The abdomen remains free to move. In fact, when alarmed, a submerged porcelain crab may swim by flapping its abdomen! What do they eat? 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. One kind of porcelain crab lives on a sea pen. Elsewhere, there are porcelain crabs that live in a shell occupied by a hermit crab, 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! Status and threats: Some of our porcelain crabs listed among the threatened animals of Singapore. However, 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. |
 Big red porcelain crab Changi, Jun 05  Mouthparts  Last pair of legs bent over the sides of the body  The Painted porcelain crab is often seen in the Common sea pen. Changi, Jul 04 |
They are NOT true crabs. Some differences from true crabs:
only 3 pairs of walking legs, long antennae.
They drop their pincers when stressed, so don't harass
them
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Family Porcellanidae recorded for Singapore from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. *from our observation in red are those listed among the threatened animals of Singapore from Ng, P. K. L. & Y. C. Wee, 1994. The Singapore Red Data Book: Threatened Plants and Animals of Singapore.
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Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963.|
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