View source for Decapod

{{short description|Order of crustaceans}}
{{other uses}}
{{distinguish|Decapodiformes}}
{{Automatic taxobox
| name = Decapoda
| fossil_range = {{fossil_range|Devonian|recent}}
| image = Decapoda_montage.jpg
| image_caption = From left to right: ''[[Grapsus grapsus]]'' ([[Brachyura]]), [[Coconut crab]] ([[Anomura]]), ''[[Lysmata amboinensis]]'' ([[Caridea]]), ''[[Homarus gammarus]]'' ([[Astacidea]]).
| taxon = Decapoda
| authority = [[Pierre André Latreille|Latreille]], 1802
| subdivision_ranks = Suborders
| subdivision =
[[Dendrobranchiata]]<br/>
[[Pleocyemata]]<br/>
See text for superfamilies.
}}

The '''Decapoda''' or '''decapods''', from [[Ancient Greek]] δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large [[order (biology)|order]] of [[crustacean]]s within the class [[Malacostraca]], and includes [[crab]]s, [[lobster]]s, [[crayfish]], [[Caridea|shrimp]], and [[Dendrobranchiata|prawns]]. Most decapods are [[scavenger]]s. The order is estimated to contain nearly 15,000 extant species in around 2,700 genera, with around 3,300 fossil species.<ref name="Grave">{{cite journal|journal=[[Raffles Bulletin of Zoology]] |year=2009 |volume=Suppl. 21 |pages=1–109 |title=A classification of living and fossil genera of decapod crustaceans |author1=Sammy De Grave |author2=N. Dean Pentcheff |author3=Shane T. Ahyong |url=http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf |display-authors=etal |url-status=dead |archive-url=https://web.archive.org/web/20110606064728/http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf |archive-date=2011-06-06 }}</ref> Nearly half of these species are crabs, with the shrimp (about 3,000 species) and [[Anomura]] including [[hermit crab]]s, [[king crab]]s, [[porcelain crab]]s, [[squat lobster]]s (about 2500 species) making up the bulk of the remainder.<ref name="Grave"/> The earliest fossils of the group date to the [[Devonian]].

==Anatomy==
{{main|Decapod anatomy}}
Decapods can have as many as 38 appendages,<ref name="Decapod_characters">{{cite web|url=http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Decapoda/characters.html|website=University of Bristol: Decapoda characters|title=Decapoda characters and anatomy|access-date=11 December 2017|archive-url=https://web.archive.org/web/20131110024412/http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Decapoda/characters.html|archive-date=10 November 2013|url-status=dead}}</ref> arranged in one pair per body segment. As the name Decapoda (from the [[Greek language|Greek]] {{lang|el|[[:wikt:δέκα|δέκα]]}}, ''{{lang|el|[[:wikt:deca-|deca-]]}}'', "ten", and {{lang|el|[[:wikt:πούς|πούς]] / ποδός}}, ''[[:wikt:-pod|-pod]]'', "foot") implies, ten of these appendages are considered legs. They are the [[pereiopod]]s, found on the last five thoracic segments.<ref name="Decapod_characters" /> In many decapods, one pair of these "legs" has enlarged pincers, called [[chela (organ)|chelae]], with the legs being called chelipeds. In front of the pereiopods are three pairs of [[maxilliped]]s that function as feeding appendages. The head has five pairs of appendages, including [[Arthropod mouthparts|mouthparts]], antennae, and antennules. There are five more pairs of appendages on the abdomen. They are called [[pleopod]]s. There is one final pair called [[uropod]]s, which, with the [[telson]], form the tail fan.<ref name="Decapod_characters" />
[[File:Haeckel Decapoda.jpg|thumb|right|"Decapoda" from [[Ernst Haeckel|Ernst Haeckel's]] ''[[Kunstformen der Natur]]'', 1904]]

==Evolution==
A 2019 [[molecular clock]] analysis suggested decapods originated in the [[Late Ordovician]] around 455 million years ago, with the [[Dendrobranchiata]] (prawns) being the first group to diverge.  The remaining group, called [[Pleocyemata]], then diverged between the swimming [[shrimp]] groupings and the crawling/walking group called [[Reptantia]], consisting of [[lobsters]] and [[crabs]].  High species diversification can be traced to the [[Jurassic]] and [[Cretaceous]] periods, which coincides with the rise and spread of modern [[coral reefs]], a key habitat for the decapods.<ref name=Wolfe2019>{{cite journal |last1=Wolfe |first1=Joanna M. |last2=Breinholt |first2=Jesse W. |last3=Crandall |first3=Keith A. |last4=Lemmon |first4=Alan R. |last5=Lemmon |first5=Emily Moriarty |last6=Timm |first6=Laura E. |last7=Siddall |first7=Mark E. |last8=Bracken-Grissom |first8=Heather D. |display-authors=6 | date=24 April 2019 |title=A phylogenomic framework, evolutionary timeline, and genomic resources for comparative studies of decapod crustaceans |journal=Proceedings of the Royal Society B |volume=286 |issue=1901 |doi=10.1098/rspb.2019.0079 |doi-access=free |pmc=6501934 |pmid=31014217}}</ref> Despite the inferred early origin, the oldest fossils of the group such as ''[[Palaeopalaemon]]'' only date to the [[Late Devonian]].<ref>{{Cite journal |last1=Gueriau |first1=Pierre |last2=Rak |first2=Štěpán |last3=Broda |first3=Krzysztof |last4=Kumpan |first4=Tomáš |last5=Viktorýn |first5=Tomáš |last6=Valach |first6=Petr |last7=Zatoń |first7=Michał |last8=Charbonnier |first8=Sylvain |last9=Luque |first9=Javier |date=2020-10-25 |title=Exceptional Late Devonian arthropods document the origin of decapod crustaceans |url=http://biorxiv.org/lookup/doi/10.1101/2020.10.23.352971 |language=en |doi=10.1101/2020.10.23.352971|s2cid=226229304 }}</ref>

The [[cladogram]] below shows the internal relationships of Decapoda, from analysis by Wolfe ''et al.'' (2019).<ref name=Wolfe2019/>
{{Decapoda cladogram}}

In the cladogram above, the [[clade]] [[Glypheidea]] is excluded due to lack of sufficient DNA evidence, but is likely the [[sister taxon|sister clade]] to [[Polychelida]], within [[Reptantia]].<ref name=Wolfe2019/>

==Classification==
Classification within the order Decapoda depends on the structure of the [[gill]]s and legs, and the way in which the [[larva]]e develop, giving rise to two suborders: [[Dendrobranchiata]] and [[Pleocyemata]]. The Dendrobranchiata consist of prawns, including many species colloquially referred to as "shrimp", such as the "white shrimp", ''[[Litopenaeus setiferus]]''. The Pleocyemata include the remaining groups, including "true shrimp".<ref>{{cite book |author=Elena Mente |year=2008 |title=Reproductive Biology of Crustaceans: Case Studies of Decapod Crustaceans |publisher=[[Science Publishers]] |isbn=978-1-57808-529-3 |page=16}}</ref> Those groups that usually walk rather than swim (Pleocyemata, excluding Stenopodidea and Caridea) form a clade called Reptantia.<ref>{{cite journal |author1=G. Scholtz |author2=S. Richter |year=1995 |title=Phylogenetic systematics of the reptantian Decapoda (Crustacea, Malacostraca) |journal=[[Zoological Journal of the Linnean Society]] |volume=113 |pages=289–328 |doi=10.1006/zjls.1995.0011 |issue=3}}</ref>

This classification to the level of superfamilies follows De Grave ''et al.''<ref name="Grave"/>

[[File:Penaeus vannamei 01.jpg|thumb|right|[[Whiteleg shrimp]], ''Litopenaeus vannamei'' ([[Dendrobranchiata]]: [[Penaeoidea]])]]
[[File:Heterocarpus ensifer.jpg|thumb|right|''[[Heterocarpus ensifer]]'' ([[Caridea]]: [[Pandaloidea]])]]
[[File:Austropotamobius pallipes.jpg|thumb|right|''[[Austropotamobius pallipes]]'' ([[Astacidea]]: [[Astacoidea]])]]
[[File:Upogebia deltaura.jpg|thumb|right|''[[Upogebia deltaura]]'' ([[Gebiidea]]: [[Upogebiidae]])]]
[[File:Lobster 300.jpg|thumb|right|[[California spiny lobster]], ''Panulirus interruptus'' ([[Achelata]]: [[Palinuridae]])]]
[[File:Polycheles sculptus.jpg|thumb|right|''[[Polycheles sculptus]]'' ([[Polychelida]]: [[Polychelidae]])]]
[[File:CoenobitaVariabilis2.jpg|thumb|right|[[Australian land hermit crab]], ''Coenobita variabilis'' ([[Anomura]]: [[Paguroidea]])]]
[[File:Blue crab on market in Piraeus - Callinectes sapidus Rathbun 20020819-317.jpg|thumb|right|Atlantic blue crab, ''[[Callinectes sapidus]]'' ([[Brachyura]]: [[Portunoidea]])]]

Order '''Decapoda''' <small>Latreille, 1802</small>
*Suborder '''[[Dendrobranchiata]]''' <small>Bate, 1888</small>
**[[Penaeoidea]] <small>Rafinesque, 1815</small>
**[[Sergestoidea]] <small>Dana, 1852</small>
*Suborder '''[[Pleocyemata]]''' <small>Burkenroad, 1963</small>
**Infraorder '''[[Stenopodidea]]''' <small>Bate, 1888</small>
**Infraorder '''[[Caridea]]''' <small>Dana, 1852</small>
***[[Procaridoidea]] <small>Chace & Manning, 1972</small>
***[[Galatheacaridoidea]] <small>Vereshchaka, 1997</small>
***[[Pasiphaeoidea]] <small>Dana, 1852</small>
***[[Oplophoroidea]] <small>Dana, 1852</small>
***[[Atyoidea]] <small>De Haan, 1849</small>
***[[Bresilioidea]] <small>Calman, 1896</small>
***[[Nematocarcinoidea]] <small>Smith, 1884</small>
***[[Psalidopodoidea]] <small>Wood-....., 1874</small>
***[[Stylodactyloidea]] <small>Bate, 1888</small>
***[[Campylonotoidea]] <small>Sollaud, 1913</small>
***[[Palaemonoidea]] <small>Rafinesque, 1815</small>
***[[Alpheoidea]] <small>Rafinesque, 1815</small>
***[[Processoidea]] <small>Ortmann, 1896</small>
***[[Pandaloidea]] <small>Haworth, 1825</small>
***[[Physetocaridoidea]] <small>Chace, 1940</small>
***[[Crangonoidea]] <small>Haworth, 1825</small>
**Infraorder '''[[Astacidea]]''' <small>Latreille, 1802</small>
***[[Enoplometopoidea]] <small>de Saint Laurent, 1988</small>
***[[Nephropoidea]] <small>Dana, 1852</small>
***[[Astacoidea]] <small>Latreille, 1802</small>
***[[Parastacoidea]] <small>Huxley, 1879</small>
**Infraorder '''[[Glypheidea]]''' <small>Winckler, 1882</small>
***[[Glypheoidea]] <small>Winckler, 1882</small>
**Infraorder '''[[Axiidea]]''' <small>de Saint Laurent, 1979b</small>
**Infraorder '''[[Gebiidea]]''' <small>de Saint Laurent, 1979</small>
**Infraorder '''[[Achelata]]''' <small>Scholtz & Richter, 1995</small>
**Infraorder '''[[Polychelida]]''' <small>Scholtz & Richter, 1995</small>
**Infraorder '''[[Anomura]]''' <small>MacLeay, 1838</small>
***[[Aegloidea]] <small>Dana, 1852</small>
***[[Galatheoidea]] <small>Samouelle, 1819</small>
***[[Hippoidea]] <small>Latreille, 1825a</small>
***[[Chirostyloidea]] <small>Ortmann, 1892 </small>
***[[Lomisoidea]] <small>Bouvier, 1895</small>
***[[Paguroidea]] <small>Latreille, 1802</small>
**Infraorder '''[[Brachyura]]''' <small>Linnaeus, 1758</small>
***Section [[Dromiacea]] <small>De Haan, 1833</small>
****[[Dromioidea]] <small>De Haan, 1833</small>
****[[Homolodromioidea]] <small>Alcock, 1900</small>
****[[Homoloidea]] <small>De Haan, 1839</small>
***Section [[Raninoida]] <small>De Haan, 1839</small>
***Section [[Cyclodorippoida]] <small>Ortmann, 1892</small>
***Section [[Eubrachyura]] <small>de Saint Laurent, 1980</small>
****Subsection [[Heterotremata]] <small>Guinot, 1977</small>
*****[[Aethroidea]] <small>Dana, 1851</small>
*****[[Bellioidea]] <small>Dana, 1852</small>
*****[[Bythograeoidea]] <small>Williams, 1980</small>
*****[[Calappoidea]] <small>De Haan, 1833</small>
*****[[Cancroidea]] <small>Latreille, 1802</small>
*****[[Carpilioidea]] <small>Ortmann, 1893</small>
*****[[Cheiragonoidea]] <small>Ortmann, 1893</small>
*****[[Corystoidea]] <small>Samouelle, 1819</small>
*****[[Dairoidea]] <small>Serène, 1965</small>
*****[[Dorippoidea]] <small>MacLeay, 1838</small>
*****[[Eriphioidea]] <small>MacLeay, 1838</small>
*****[[Gecarcinucoidea]] <small>Rathbun, 1904</small>
*****[[Goneplacoidea]] <small>MacLeay, 1838</small>
*****[[Hexapodoidea]] <small>Miers, 1886</small>
*****[[Leucosioidea]] <small>Samouelle, 1819</small>
*****[[Majoidea]] <small>Samouelle, 1819</small>
*****[[Orithyioidea]] <small>Dana, 1852c</small>
*****[[Palicoidea]] <small>Bouvier, 1898</small>
*****[[Parthenopoidea]] <small>MacLeay,</small>
*****[[Pilumnoidea]] <small>Samouelle, 1819</small>
*****[[Portunoidea]] <small>Rafinesque, 1815</small>
*****[[Potamoidea]] <small>Ortmann, 1896</small>
*****[[Pseudothelphusoidea]] <small>Ortmann, 1893</small>
*****[[Pseudozioidea]] <small>Alcock, 1898</small>
*****[[Retroplumoidea]] <small>Gill, 1894</small>
*****[[Trapezioidea]] <small>Miers, 1886</small>
*****[[Trichodactyloidea]] <small>H. Milne-Edwards, 1853</small>
*****[[Xanthoidea]] <small>MacLeay, 1838</small>
****Subsection [[Thoracotremata]] <small>Guinot, 1977</small>
*****[[Cryptochiroidea]] <small>Paul'son, 1875</small>
*****[[Grapsoidea]] <small>MacLeay, 1838</small>
*****[[Ocypodoidea]] <small>Rafinesque, 1815</small>
*****[[Pinnotheroidea]] <small>De Haan, 1833</small>

==See also==
{{Portal|Crustaceans|Arthropods}}
*[[List of Atlantic decapod species]]
*[[Phylogeny of Malacostraca]]

==References==
{{Reflist|25em}}

==External links==
{{Commons category|Decapoda}}
*{{Wikispecies-inline}}
* [http://decapoda.nhm.org/ Decapod Crustacea] "Tree of Life" page at the [[Natural History Museum of Los Angeles County]]
{{Malacostraca}}
{{Decapoda}}

{{Taxonbar|from=Q4610}}
{{Authority control}}

[[Category:Decapods| ]]
[[Category:Crustacean orders]]
[[Category:Extant Devonian first appearances]]
[[Category:Taxa named by Pierre André Latreille]]