Pisidia longicornis

Adult Pisidia longicornis typically have a carapace length of {{convert|1|cm|1}}. Its colouration is variable, with most individuals being reddish or orange, but some having patches of pearly white, or even being entirely white.{{cite web |author=Keith Hiscock |year=2008 |title=Pisidia longicornis. Long clawed porcelain crab |work=Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme |publisher=Marine Biological Association of the United Kingdom |accessdate=August 24, 2010 |url=http://www.marlin.ac.uk/speciesfullreview.php?speciesID=4134 |archive-url=https://web.archive.org/web/20110613040028/http://www.marlin.ac.uk/speciesfullreview.php?speciesID=4134 |archive-date=June 13, 2011 |url-status=dead }} One cheliped (claw-bearing appendage) is usually larger than the other, although this difference is less pronounced in females than in males.{{cite journal |author=G. Smalley |year=1973 |title=Some notes on the sexually dimorphic characters of Pisidia longicornis (L.) (Decapoda Anomura) |journal=Crustaceana |volume=25 |issue=2 |pages=220–222 |jstor=20102034 |doi=10.1163/156854073X00858}} The fifth pair of legs is reduced in size and may be difficult to see.

Pisidia longicornis is found in the north-eastern Atlantic Ocean from Norway to Angola, and throughout the Mediterranean Sea. It is found from the lower shore down to depths of {{convert|70|m}} in the north Atlantic, but at depths of {{convert|30|-|100|m|-1|abbr=on}} in some locations around the Mediterranean Sea. It lives under boulders and among bryozoan turfs, and may occasionally be found in fish markets among mussels and oysters.

It feeds by filtering suspended material from the sea water. Individuals from the intertidal zone tend to be larger than those from deeper water, which may be related to the greater churning of the sediment by the tide.{{cite journal |author=G. Smaldon |year=1972 |title=Population structure and breeding biology of Pisidia longicornis and Porcellana platycheles |journal=Marine Biology |volume=17 |pages=171–179 |doi= 10.1007/BF00347308}}

Females bear eggs from March to August around the British Isles, and from February to September in the Mediterranean Sea. Young Pisidia longicornis go through two zoeal (larval) stages before reaching the megalopa (post-larval) stage.{{cite book |author=C. D. Todd, M. S. Laverack & Geoffrey Allan Boxshall |year=1996 |title=Coastal marine zooplankton: a practical manual for students |edition=2nd |publisher=Cambridge University Press |isbn=978-0-521-55533-3 |chapter=Figure 31: A–D Phylum Arthropoda, Class Crustacea, Subclass Malacostraca – Order Decapoda (Section Anomura) |url=https://books.google.com/books?id=9KCRsSQQ-uwC&pg=PT73}} The zoea larvae bear "exceptionally long" spines on the carapace, one directed forwards, and two directed backwards. The second zoeal stage may reach a length of {{convert|10|mm|1}}, while the megalopa has a carapace width of {{convert|1.5|mm|2|abbr=on}}.

Pisidia longicornis was first described in 1767 by Carl Linnaeus, originally under the name Porcellana longicornis, in the 12th edition of his Systema Naturae. The specific epithet {{lang|la|longicornis}} is difficult to explain, it being Latin for "long-horned", from {{lang|la|longus}} and {{lang|la|cornu}}; it may refer to the long chelipeds (claw-bearing appendages).{{cite book |author=Ray W. Ingle |year=1997 |title=Crayfishes, lobsters, and crabs of Europe: an illustrated guide to common and traded species |publisher=Cambridge University Press |isbn=978-0-412-71060-5 |chapter=Pisidia longicornis |pages=112–113 |url=https://books.google.com/books?id=x-qVGbTAOiEC&pg=PA112}} The species was moved from the genus Porcellana by William Elford Leach when he established the genus Pisidia in 1820.

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• [http://www.glaucus.org.uk/Pisidia.htm Pisidia longicornis] British Marine Life Study Society

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Category:Porcelain crabs

Category:Anomura of the Atlantic Ocean

Category:Crustaceans described in 1767

Category:Taxa named by Carl Linnaeus