Porcelain crabs Petrolisthes elongatus, the New Zealand half crab Scientific classification Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Order: Decapoda Infraorder: Anomura Superfamily: Galatheoidea Family: Porcellanidae Haworth, 1825 Genera See text Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They are typically less than 15 mm (0.6 in) wide, and have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attacked, and use their large claws for maintaining territories. Contents 1 Description 2 Evolution 3 Biogeography and ecology 4 Diversity 5 References Description

Porcelain crabs are small, usually with body widths of less than 15 millimetres (0.6 in).1 They share the general body plan of a squat lobster, but their bodies are more compact and flattened, an adaptation for living and hiding under rocks.2 Porcelain crabs are quite fragile animals, and will often shed their limbs to escape predators,3 hence their name. The lost appendage can grow back over several moults. Porcelain crabs have large chelae (claws), which are used for territorial struggles, but not for catching food.1 The fifth pair of pereiopods are reduced and are used for cleaning.4 Evolution

Porcelain crabs are an example of carcinisation, whereby a non-crab-like animal (in this case a relative of a squat lobster) evolves into an animal that resembles a true crab.5 Porcelain crabs can be distinguished from true crabs by the apparent number of walking legs (three instead of four pairs, the fourth pair is reduced and held against the carapace), and the long antennae originating on the front outside of the eyestalks.3 The abdomen of the porcelain crab is long and folded underneath it, free to move.3 Biogeography and ecology Porcellana platycheles Neopetrolisthes maculatus Porcelain crabs live in all the world's oceans, except the Arctic Ocean and the Antarctic.6 They are common under rocks, and can often be found and observed on rocky beaches and shorelines, startled creatures scurrying away when a stone is lifted. They feed by combing plankton and other organic particles from the water using long setae (feathery hair or bristle-like structures) on the mouthparts.4 These animals will also scavenge on the sea floor for detritus and in aquaria, they will consume meaty pieces of fish or shrimp. Diversity

As of 2010[update], some 277 species porcelain crab had been described,7 divided among the following 30 genera:78 Aliaporcellana Nakasone & Miyake, 1969 Allopetrolisthes Haig, 1960 Ancylocheles Haig, 1978 Capilliporcellana Haig, 1978 Clastotoechus Haig, 1960 Enosteoides Johnson, 1970 Euceramus Stimpson, 1860 Eulenaios Ng & Nakasone, 1993 Heteropolyonyx Osawa, 2001 Heteroporcellana Haig, 1978 Liopetrolisthes Haig, 1960 Lissoporcellana Haig, 1978 Madarateuchus Harvey, 1999 Megalobrachium Stimpson, 1858 Minyocerus Stimpson, 1858 Neopetrolisthes Miyake, 1937 Neopisosoma Haig, 1960 Novorostrum Osawa, 1998 Orthochela Glassell, 1936 Pachycheles Stimpson, 1858 Parapetrolisthes Haig, 1962 Petrocheles Miers, 1876 Petrolisthes Stimpson, 1858 Pisidia Leach, 1820 Polyonyx Stimpson, 1858 Porcellana Lamarck, 1801 Porcellanella White, 1852 Pseudoporcellanella Sankarankutty, 1961 Raphidopus Stimpson, 1858 Ulloaia Glassell, 1938

Some of the common species of porcelain crabs in the Caribbean Sea are Petrolisthes quadratus, found in large numbers under rocks in the intertidal, and the red-and-white polka-dotted Porcellana sayana, which lives commensally within the shells inhabited by large hermit crabs. In Hong Kong, Petrolisthes japonicus is common.2 References ^ a b Mark W. Denny & Steven Dean Gaines (2007). "Crabs". Encyclopedia of Tidepools and Rocky Shores. Issue 1 of Encyclopedias of the Natural World. University of California Press. pp. 164–176. ISBN 9780520251182. http://books.google.co.uk/books?id=uufQnE7MzMkC&pg=PA167.  ^ a b Brian Morton & John Edward Morton (1993). "Boulder shores". The Sea Shore Ecology of Hong Kong. Hong Kong University Press. pp. 86–125. ISBN 9789622090279. http://books.google.co.uk/books?id=r79kKRbkzMwC&pg=PA95.  ^ a b c Gary C. B. Poore & Shane T. Ahyong (2004). "Porcellanidae Haworth, 1825". Marine decapod Crustacea of southern Australia: a guide to identification. CSIRO Publishing. pp. 242–246. ISBN 9780643069060. http://books.google.co.uk/books?id=ZZWnuGc0xlMC&pg=PA242.  ^ a b Gerald R. Allen. "Anemone Crab Neopetrolisthes maculatus". Tropical Marine Life. Periplus nature guides. Tuttle Publishing. p. 35. ISBN 9789625931579. http://books.google.co.uk/books?id=vpMSjJ5DVDYC&pg=PA35.  ^ C. L. Morrison, A. W. Harvey, S. Lavery, K. Tieu, Y. Huang & C. W. Cunningham (2001). "Mitochondrial gene rearrangements confirm the parallel evolution of the crab-like form" (PDF). Proceedings of the Royal Society B 269 (1489): 345–350. doi:10.1098/rspb.2001.1886. PMC 1690904. PMID 11886621. http://www.biology.duke.edu/cunningham/pdfs/Morrison%20et%20al.pdf.  ^ P. McLaughlin, S. Ahyong & J. K. Lowry (October 2, 2002). "Porcellanidae Haworth, 1825". Anomura: Families. Australian Museum. http://crustacea.net/crustace/anomura/www/porcella.htm.  ^ a b Masayuki Osawa & Patsy A. McLaughlin (2010). Part II – Porcellanidae. In Martyn E. Y. Low and S. H. Tan. "Annotated checklist of anomuran decapod crustaceans of the world (exclusive of the Kiwaoidea and families Chirostylidae and Galatheidae of the Galatheoidea)" (PDF). Zootaxa Suppl. 23: 109–129. http://rmbr.nus.edu.sg/rbz/biblio/s23/s23rbz109-129.pdf.  ^ WoRMS (2010). "Porcellanidae". World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=106734. Retrieved November 13, 2010.