Barnacle
159512
225718880
2008-07-15T01:51:19Z
The Ogre
307408
[[WP:UNDO|Undid]] revision 225717701 by [[Special:Contributions/65.185.2.130|65.185.2.130]] ([[User talk:65.185.2.130|talk]])
{{otheruses}}
{{Taxobox
| name = Barnacles
| fossil_range = Early [[Palæozoic]]<ref name=Foster1987/> - recent, although only common from [[Neogene]]<ref name=Doyle1997/>
| image = Haeckel Cirripedia.jpg
| image_width = 240px
| image_caption = "Cirripedia" from [[Ernst Haeckel|Ernst Haeckel's]] ''[[Kunstformen der Natur]]'' (1904). The crab at the centre is nursing the externa of the parasitic cirripede ''[[Sacculina]]''
| image2=Chthamalus_stellatus.jpg
| image2_width=250px
| image2_caption = ''[[Chthamalus stellatus]]''
| regnum = [[Animal]]ia
| phylum = [[Arthropod]]a
| subphylum = [[Crustacean|Crustacea]]
| classis = [[Maxillopoda]]
| subclassis = [[Thecostraca]]
| infraclassis = '''Cirripedia'''
| infraclassis_authority = [[Hermann Burmeister|Burmeister]], 1834
| subdivision_ranks = [[Superorder]]s
| synonyms = Thyrostraca, Cirrhopoda (meaning "tawny-footed"), Cirrhipoda, and Cirrhipedia.
| subdivision =
[[Acrothoracica]]<br/>
[[Thoracica]]<br/>
[[Rhizocephala]]
}}
A '''barnacle''' is a type of [[arthropod]] belonging to [[infraclass (zoology)|infraclass]] '''Cirripedia''' in the [[Subphylum (biology)|subphylum]] [[Crustacean|Crustacea]], and is hence distantly related to [[crab]]s and [[lobster]]s. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have two [[nektonic]] larval stages.
Around 1,220 barnacle [[species]] are currently known.<ref>Walters, Martin & Johnson, Jinny. ''The World of Animals''. [[Bath, Somerset]]: [[Parragon]], [[2007]].</ref> The name "Cirripedia" is Latin, meaning "curl-footed".
==Ecology==
[[Image:Semibalanus balanoides upernavik 2007-07-05.ogg|180px|left|thumb|Image:Semibalanus balanoides upernavik 2007-07-05.ogg
]]
Barnacles are encrusters, attaching themselves permanently to a hard substrate. The most common, "acorn barnacles" ([[Sessilia]]) are sessile, growing their shells directly onto the substrate.<ref name=Doyle1997/> The order [[Pedunculata]] ("[[goose barnacle]]s" and others) attach themselves by means of a stalk.<ref name=Doyle1997>{{cite journal
| author = Doyle, P.
| coauthors = Mather, A.E.; Bennett, M.R.; Bussell, A.
| year = 1997
| title = Miocene barnacle assemblages from southern Spain and their palaeoenvironmental significance
| journal = Lethaia
| volume = 29
| pages = 267–274
| doi = 10.1111/j.1502-3931.1996.tb01659.x
}}</ref>
Most barnacles are suspension feeders; they dwell continually in their shell - which is usually constructed of six plates<ref name=Doyle1997/> - and reach into the water column with modified legs. These feathery appendages beat rhythmically to draw plankton and detritus into the shell for consumption.<ref>[[Encarta]] Encyclopedia 2005 DVD. Article — Shore Life</ref>
Other members of the class have quite a different mode of life. For example, members of the [[genus]] ''[[Sacculina]]'' are [[parasitism|parasitic]], dwelling within crabs.<ref>[[Carl Zimmer|Zimmer, Carl]] (2000), ''Parasite Rex: Inside the Bizarre World of Nature's Most Dangerous Creatures'', [[Free Press (publisher)|Free Press]].</ref>
Although they have been found at water depths up to 600m,<ref name=Doyle1997/> most barnacles inhabit shallow waters, with 75% of species living in water depths of less than 100m,<ref name=Doyle1997/> and 25% inhabiting the {{wict|intertidal}} zone.<ref name=Doyle1997/>
Within the intertidal zone, different species of barnacle live in very tightly constrained locations, allowing the exact height of an assemblage above or below sea level to be precisely determined.<ref name=Doyle1997/>
Since the intertidal zone periodically desiccates, barnacles are well adapted against water loss. Their calcite shells are impermeable, and they possess two plates which they can slide across their aperture when not feeding. These plates also protect against predation.{{Verify source|date=April 2008}}
[[Image:CornishBarnacles.JPG|thumb|left|Barnacles and [[limpets]] compete for space in the intertidal zone.]]Barnacles are displaced by [[limpet]]s and [[mussel]]s, who compete for space. They also have numerous predators.<ref name=Doyle1997/>
They employ two strategies to overwhelm their competitors: "swamping", and fast growth. In the swamping strategy, vast numbers of barnacles settle in the same place at once, covering a large patch of substrate, allowing at least some to survive in the balance of probabilities.<ref name=Doyle1997/> Fast growth allows the suspension feeders to access higher levels of the water column then their competitors, and to be large enough to resist displacement; species employing this response, such as the aptly named ''[[Megabalanus]]'', can reach 7 cm in length;<ref name=Doyle1997/> other species may grow larger still.
Competitors may include other barnacles, and there is (disputed) evidence that balanoid barnacles competitively displaced chthalamoid barnacles. Balanoids gained their advantage over the chthalamoids in the Oligocene, when they evolved a tubular skeleton. This provides better anchorage to the substrate, and allows them to grow faster, undercutting, crushing and smothering by the latter group.<ref name=Stanley2008>{{cite journal
| author = Stanley, S.M.
| year = 2008
| title = Predation defeats competition on the seafloor
| journal = Paleobiology
| volume = 34
| issue = 1
| pages = 1–21
| url = http://www.bioone.org/perlserv/?request=get-document&doi=10.1666%2F07026.1
| accessdate = 2008-05-13
| doi = 10.1666/07026.1
}}</ref>
==Life cycle==
Barnacles have 2 distinct larval stages, the [[nauplius (larva)|nauplius]] and the [[cyprid]], before developing into a mature adult.
===Nauplius stage===
A fertilized egg hatches into a nauplius: a one eyed larva comprising a head and a telson, without a thorax or abdomen. This undergoes 6 molts before transforming into the bivalved cyprid stage. Nauplii are typically initially brooded by the parent, and released as free-swimming larvae after the first molt.
[[Image:Barnacle cypris larva.jpg|thumb|The barnacle [[cyprid]] larva]]
===Cyprid stage===
{{main|Cyprid}}
The cyprid stage lasts from days to weeks. During this part of the life cycle, the barnacle searches for a place to settle. It explores potential surfaces with modified [[Antenna (biology)#Crustaceans|antennules]] structures; once it has found a potentially suitable spot, it attaches head-first using its antennules, and a secreted glycoproteinous substance. Larvae are thought to assess surfaces based upon their surface texture, chemistry, relative wettability, colour and the presence/absence and composition of a surface biofilm; swarming species are also more likely to attach near to other barnacles. As the larva exhausts its finite energy reserves, it becomes less selective in the sites it selects. If the spot is to its liking it cements down permanently with another proteinacous compound. This accomplished, it undergoes [[Metamorphosis (biology)|metamorphosis]] into a juvenile barnacle.
===Adult stage===
Typical [[acorn barnacle]]s develop six<ref>[http://www.enature.com/fieldguides/ eNature: FieldGuides]</ref> hard calcareous [[plate]]s to surround and protect their bodies. For the rest of their lives they are cemented to the ground, using their feathery legs (cirri) to capture plankton.
Once metamorphosis is over and they have reached their adult form, barnacles will continue to grow by adding new material to their heavily calcified plates. These plates are not [[ecdysis|moult]]ed; however, like all [[ecdysozoa]]ns, the barnacle itself will still molt its [[Cuticle#Invertebrate zoology|cuticle]]<ref>Bourget, E. 1987 Barnacle shells: Composition, structure, and growth. In: ''Crustacean Issues 5: Barnacle Biology'' (A.J. Southward, ed). pp. 267-285. ISBN 90-6191-628-3</ref>.
===Sexual reproduction===
Most barnacles are [[Hermaphrodite|hermaphroditic]], although a few species are [[Gonochorism|gonochoric]] or [[Androdioecy|androdioecious]]. Typically, recently molted hermaphroditic individuals are receptive as females. Self-fertilization, although theoretically possible, has been experimentally shown to be rare in barnacles <ref>{{cite web |url=http://www.museum.vic.gov.au/crust/barnbiol.html |publisher=[[Museum Victoria]] |title=Barnacle general biology |year=1996}}</ref> <ref>Charnov, E.L. 1987. Sexuality and hermaphroditism in barnacles: A natural selection approach. In: ''Crustacean Issues 5: Barnacle Biology'' (A.J. Southward, ed). pp. 89-103. ISBN 90-6191-628-3</ref>.
The sessile lifestyle of barnacles makes [[sexual reproduction]] difficult, as the organisms cannot leave their shells to mate. To facilitate genetic transfer between isolated individuals, barnacles have extraordinarily long [[penis]]es, up to 15cm in length: the largest penis to body size ratio of the animal kingdom.<ref>http://www.museum.vic.gov.au/crust/barnbiol.html</ref>
==Fossil record==
[[Image:Megabalanus on breccia.JPG|thumb|280px|[[Miocene]] ([[Messinian]]) ''[[Megabalanus]]'', smothered by sand and fossilised.]]
The geological history of barnacles can be traced back to the early Palaeozoic (in the order of 4-500 million years ago),<ref name=Foster1987>Foster, B.A. & Buckeridge, J.S. 1987: ''Barnacle palaeontology''. In Southward,
A.J. (ed.): Barnacle Biology, '''41-63'''. Balkema, Rotterdam.</ref> although they do not become common in the fossil record until the [[Neogene]] (last 20 million years). In part their poor preservation is due to their restriction to high-energy environments, which tend to be [[erosion]]al - therefore it is more common for their shells to be ground up by wave action than for them to reach a depositional setting. It is also possible that the group was more minor in the past.{{Verify source|date=April 2008}}
Barnacles can play an important role in estimating palæo-water depths. The degree of disarticluation of fossils suggests the distance they have been transported, and since many species have narrow ranges of water depths, it can be assumed that the animals lived in shallow water and broke up as they were washed down-slope. The completeness of fossils, and nature of damage, can thus be used to constrain the tectonic history of regions.<ref name=Doyle1997/>
==In human culture==
Barnacles were first fully studied and classified by [[Charles Darwin]] who published a series of [[monographs]] in 1851 and 1854. Darwin undertook this study at the suggestion of his friend [[Joseph Dalton Hooker]], in order to thoroughly understand at least one species before making the generalisations needed for his theory of [[evolution]] by [[natural selection]] <ref>{{cite web |url=http://www.sparknotes.com/biography/darwin/section9.rhtml |title=Charles Darwin |publisher=[[SparkNotes]] |accessdate=2007-08-30 |author=Étienne Benson}}</ref>. Historian of science and novelist Rebecca Stott has published a detailed account of Darwin's eight years studying barnacles in a book called Darwin and the Barnacle (Faber, 2003) which challenges the supposition that Darwin was using the barnacle project as a way of delaying writing the book on species which would become Origin of Species by Natural Selection.
[[Image:corrosion.jpg|thumb|[[Corrosion]] caused partly by barnacles, considered biofouling.{{Verify source|date=April 2008}}<!--Do barnacles really cause COrrosion? Do you mean Erosion?-->]]
Barnacles are of economic consequence as they often attach themselves to man-made structures, sometimes to the structure's detriment. Particularly in the case of ships, they are classified as [[Biofouling|fouling]] organisms.{{Fact|date=April 2008}}
Some barnacles are edible by humans, and [[goose barnacle]]s (''e.g.'' ''[[Pollicipes cornucopia]]'') are treasured as a delicacy in many Mediterranean countries.{{Fact|date=April 2008}} The resemblance of this barnacle's fleshy stalk to a goose's neck gave rise in ancient times to the notion that geese, or at least certain seagoing species of wild goose, literally grew from the barnacle. Most notably, the wild [[Barnacle Goose]] (''Branta leucopsis''), whose eggs and young were rarely seen by humans because it breeds in the remote [[Arctic]], got its popular name because it was imagined to grow from gooseneck barnacles.<ref>[[Encarta]] Encyclopedia 2005 DVD. Article — Barnacle.</ref>
==Classification==
[[Image:Barnacle.JPG|thumb|Goose Neck Barnacle]]
Some authorities regard Cirripedia as a full [[class (biology)|class]] or [[Subclass (biology)|subclass]], and the orders listed above are sometimes treated as [[superorder]]s.
This article follows Martin and Davis in placing Cirripedia as an infraclass of [[Thecostraca]] and in the following classification of cirripedes down to the level of orders <ref>{{cite book|author = Joel W. Martin & George E. Davis| url=http://www.nhm.org/research/publications/CrustaceaClassification.pdf | title=An Updated Classification of the Recent Crustacea |year = 2001|publisher = [[Natural History Museum of Los Angeles County]]}}</ref>{{lopsided}}:
Infraclass '''Cirripedia''' <small>[[Hermann Burmeister|Burmeister]], 1834</small>
* Superorder [[Acrothoracica]] <small>Gruvel, 1905</small>
** Order [[Pygophora]] <small>Berndt, 1907</small>
** Order [[Apygophora]] <small>Berndt, 1907</small>
* Superorder [[Rhizocephala]] <small>Müller, 1862</small>
** Order [[Kentrogonida]] <small>Delage, 1884</small>
** Order [[Akentrogonida]] <small>Häfele, 1911</small>
* Superorder [[Thoracica]] <small>[[Charles Darwin|Darwin]], 1854</small>
** Order [[Pedunculata]] <small>[[Jean-Baptiste Lamarck|Lamarck]], 1818</small>
** Order [[Sessilia]] <small>Lamarck, 1818</small>
==External links==
[[Image:Barnacles in tidepools.JPG|thumb|Barnacles in [[California]]n [[Tide pool]]s.]]
{{commonscat|Cirripedia}}
*[http://www.vattenkikaren.gu.se/fakta/arter/crustace/cirriped/balacren/balacre.html Rock barnacle] at Aquascope
*[http://www.mesa.edu.au/friends/seashores/barnacles.html Barnacles] from the Marine Education Society of Australasia
*[http://www.iberianature.com/material/barnacles.htm Barnacles in Spain] Article on barnacles in Spain, and their collection and gastronomy.
*[http://www.ncl.ac.uk/barnacles] Newcastle University's barnacle and biofouling information site.
==References==
[[Image:Seepocke fg1.jpg|thumb|240px|Balanidae, Mission Beach National Park, Queensland, Australia, 2002]]
{{reflist}}
[[Category:Crustaceans]]
[[Category:Barnacles| ]]
[[Category:British Isles coastal fauna]]
[[ca:Cirrípede]]
[[de:Rankenfußkrebse]]
[[es:Cirripedia]]
[[fa:کشتیچسب]]
[[fi:Siimajalkaiset]]
[[fr:Cirripedia]]
[[gd:Bàirneach]]
[[he:זיפרגליים]]
[[lt:Ūsakojai]]
[[lv:Sprogkāji]]
[[nl:Rankpootkreeften]]
[[pl:Wąsonogi]]
[[pt:Cirripedia]]
[[ru:Усоногие]]
[[simple:Barnacle]]
[[sv:Rankfotingar]]