View source for Brachyura

{{Short description|Crustacean}}
{{distinguish|text=[[Argulidae|Branchiura]], a subclass of parasitic crustaceans}}
{{Use mdy dates|date=January 2024}}
{{Automatic taxobox
| fossil_range      = {{fossil range|Early Jurassic|Present}}
| image             = Brachyura_montage.jpg
| image_caption     = '''Top row, left to right:''' ''[[Dromia personata]]'' (Dromiidae), [[Dungeness crab]] (Cancridae), [[Tasmanian giant crab]] (Menippidae); '''Middle row:''' ''[[Corystes|Corystes cassivelaunus]]'' (Corystidae), ''[[Liocarcinus vernalis]]'' (Portunidae), ''[[Carpilius maculatus]]'' (Carpiliidae); '''Bottom row:''' ''[[Gecarcinus quadratus]]'' (Gecarcinidae), ''[[Grapsus grapsus]]'' (Grapsidae), ''[[Ocypode ceratophthalmus]]'' (Ocypodidae).
| image_upright     = 1.2
| display_parents   = 2
| taxon             = Brachyura
| authority         = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]
| subdivision_ranks = Sections and subsections
| subdivision_ref   = <ref name="DeGrave">{{cite journal |last1=De Grave |first1=Sammy |last2=Pentcheff |first2=N. Dean |last3=Ahyong |first3=Shane T. |display-authors=etal |date=2009-09-15 |title=A Classification of Living and Fossil Genera of Decapod Crustaceans |url=http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf |journal=[[Raffles Bulletin of Zoology]] |volume=Suppl. 21 |pages=1–109 |access-date=2024-01-03 |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>
| subdivision       = * [[Dromiacea]]
* [[Raninoida]]
* [[Cyclodorippoida]]
* [[Eubrachyura]]
** [[Heterotremata]]
** [[Thoracotremata]]
}}
'''Brachyura''' (from [[Ancient Greek]] βραχύς (''brakhús''), meaning "short",<ref>{{cite web |url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dbraxu%2Fs |title=βραχύς |author1=Henry George Liddell |author2=Robert Scott |work=A Greek–English Lexicon |publisher=[[Perseus Digital Library]] |access-date=2010-05-24}}</ref> and οὐρά (''ourá''), meaning "tail"<ref>{{cite web |url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dou%29ra%2F |title=οὐρά |author1=Henry George Liddell |author2=Robert Scott |work=A Greek–English Lexicon |publisher=[[Perseus Digital Library]] |access-date=2010-05-24}}</ref>), is an [[infraorder]] of [[decapod]] [[crustacean]]s comprising the '''true crabs'''. They typically have a very short projecting [[tail]]-like [[abdomen#Arthropoda|abdomen]], usually hidden entirely under the [[Thorax (arthropod anatomy)|thorax]]. Their [[exoskeleton]] is often [[Sclerotization|thickened and hard]]. They generally have [[Arthropod leg|five pairs of legs]], and they have "[[Pincers (tool)|pincer]]s" or "[[claw]]s" on the ends of the frontmost pair, scientifically termed the ''[[chelae]]''. They are present in all the world's oceans, [[Freshwater crab|in freshwater]], and [[Terrestrial crab|on land]], often hiding themselves in small crevices or [[burrowing]] into [[sediment]]. True crabs are [[omnivore]]s, feeding on a variety of food, including a significant proportion of [[Algae eater|algae]], as well as [[Detritivore|detritus]] and other [[invertebrate]]s. [[Crab meat|True crabs are widely consumed]] by humans as [[food]], with over 1.5 million tonnes [[Crab fisheries|caught]] annually.

True crabs first appeared in the [[fossil record]] during the [[Jurassic]] period, around 200 million years ago, achieving great diversity by the [[Cretaceous]] period; around 7,000 extant species in 96 families are known. The true crabs are the largest of the [[crab]] decapod groups with [[carcinised]] body forms. Smaller groups include the [[porcelain crab]]s, [[king crab]]s, and [[hairy stone crab]]s which have [[Convergent evolution|independently evolved similar forms]] and lifestyles.<ref name="Keiler 2014">{{cite journal |author1=Jonas Keiler |author2=Stefan Richter |author3=Christian S. Wirkner |year=2014 |title=Evolutionary morphology of the organ systems in squat lobsters and porcelain crabs (Crustacea: Decapoda: Anomala): an insight into carcinization |journal=[[Journal of Morphology]] |volume=276 |issue=1 |pages=1–21 |doi=10.1002/jmor.20311 |pmid=25156549 |bibcode=2015JMorp.276....1K |s2cid=26260996 }}</ref>

==Description==

[[File:Gecarcinus quadratus (Nosara).jpg|thumb|left|''[[Gecarcinus quadratus]]'', a [[land crab]] from [[Central America]]]]

Brachyuran crabs are generally covered with a thick [[exoskeleton]], composed primarily of highly mineralized [[chitin]].<ref>{{cite journal |author1=F. Boßelmann |author2=P. Romano |author3=H. Fabritius |author4=D. Raabe |author5=M. Epple |date=October 25, 2007 |title=The composition of the exoskeleton of two crustacea: The American lobster Homarus americanus and the edible crab ''Cancer pagurus'' |journal=[[Thermochimica Acta]] |volume=463 |issue=1–2 |pages=65–68 |doi=10.1016/j.tca.2007.07.018|bibcode=2007TcAc..463...65B }}</ref><ref>{{cite journal |author1=P. Chen |author2=A.Y. Lin |author3=J. McKittrick |author4=M.A. Meyers |date=May 2008 |title=Structure and mechanical properties of crab exoskeletons |journal=[[Acta Biomaterialia]] |volume=4 |issue=3 |pages=587–596 |doi=10.1016/j.actbio.2007.12.010|pmid=18299257 }}</ref> Behind their pair of [[chelae]] (claws) are six walking legs and then two swimming legs. The crab [[breathing|breathes]] through [[gills]] on its underside; gills must be at least moist to work.

True crabs vary in size from the [[pea crab]], a few millimeters wide,<ref>{{cite web |last1=Baker |first1=Nick |title=Pea crabs guide: what they are and their lifecycle |url=https://www.discoverwildlife.com/animal-facts/insects-invertebrates/pea-crabs-guide |website=Discover Wildlife |access-date=4 November 2025 |date=1 February 2023}}</ref> to the [[Japanese spider crab]], with a leg span up to {{convert|4|m|ft|abbr=on}}.<ref>{{cite web |url=http://na.oceana.org/en/explore/creatures/japanese-spider-crab |title=Japanese spider crab ''Macrocheira kaempferi'' |publisher=[[Oceana (non-profit group)|Oceana North America]] |access-date=2009-01-02 |archive-url=https://web.archive.org/web/20091114041143/http://na.oceana.org/en/explore/creatures/japanese-spider-crab |archive-date=2009-11-14 }}</ref> Several other groups of crustaceans with similar appearances – such as [[king crab]]s and [[porcelain crab]]s have [[convergently evolved]] similar features to true crabs, making them good examples of [[carcinisation]].<ref>{{cite journal |author=Borradaile, L.A. |title=Crustacea. Part II. Porcellanopagurus: an instance of carcinization |journal=British Antarctic ("Terra Nova") Expedition, 1910. Natural History Report. Zoology|year=1916 |volume=3 |number=3 |pages=111–126}}</ref><ref>{{cite journal |author1=Martin, J.W. |author2=Abele, L.G. |title=Phylogenetic relationships of the genus ''Aegla'' (Decapoda: Anomura: Aeglidae), with comments on anomuran phylogeny |journal=Journal of Crustacean Biology |year=1986 |volume=6 |number=3 |pages=576–612 |doi=10.1163/193724086X00406 |bibcode=1986JCBio...6..576. }}</ref><ref>{{cite journal |author1=McLaughlin, P.A. |author2=Lemaitre, R. |title=Carcinization in the Anomura - fact or fiction? I. Evidence from adult morphology|journal=Contributions to Zoology |year=1997 |volume=67 |number=2 |pages=79–123 |doi=10.1163/18759866-06702001|doi-access=free}}</ref><ref>{{cite journal |author=Scholtz, G. |title=Evolution of crabs - history and deconstruction of a prime example of convergence|journal=Contributions to Zoology |year=2014|volume=83|number=2|pages=87–105 |doi=10.1163/18759866-08302001 |doi-access=free}}</ref>

==Environment==

True crabs are found in all of the world's oceans, as well as in [[fresh water]] and on [[Land crab|land]], particularly in [[tropical]] regions. About 850 [[species]] are [[freshwater crabs]].<ref>{{cite journal |author1=Richard von Sternberg |author2=Neil Cumberlidge |year=2001 |title=On the heterotreme-thoracotreme distinction in the Eubrachyura De Saint Laurent, 1980 (Decapoda: Brachyura) |journal=[[Crustaceana]] |volume=74 |pages=321–338 |doi=10.1163/156854001300104417 |issue=4 |bibcode=2001Crust..74..321V |url=http://decapoda.nhm.org/pdfs/11802/11802.pdf |citeseerx=10.1.1.493.6718 }}</ref>

== Sexual differences ==

[[File:Pachygrapsus marmoratus male female.png|thumb|left|The underside of a male (top) and a female (bottom) individual of ''[[Pachygrapsus marmoratus]]'', showing the difference in shape of the abdomen]]

Brachyuran crabs often show marked [[sexual dimorphism]]. Males often have larger [[Chelae|claws]],<ref>{{cite web |url=http://www.sms.si.edu/irLspec/Pachyg_transv.htm |title=''Pachygrapsus transversus'' |publisher=[[Smithsonian Institution]] |access-date=2010-01-20 |author=L. H. Sweat |date=August 21, 2009}}</ref> a tendency that is particularly pronounced in the [[fiddler crab]]s of the genus ''Uca'' ([[Ocypodidae]]). In fiddler crabs, males have one greatly enlarged claw used for communication, particularly for attracting a mate.<ref>{{cite journal |doi=10.1016/j.anbehav.2007.09.004 |author1=Martin J. How |author2=Jan M. Hemmi |author3=Jochen Zeil |author4=Richard Peters |url=http://richard.eriophora.com.au/pubs/pdf/HowHemmiZeilPeters-07.pdf |title=Claw waving display changes with receiver distance in fiddler crabs, ''Uca perplexa'' |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |volume=75 |issue=3 |pages=1015–1022 |year=2008|s2cid=44197123 }}</ref> Another conspicuous difference is the form of the pleon ([[Abdomen#Arthropoda|abdomen]]); in most male crabs, this is narrow and triangular in form, while females have a broader, rounded abdomen.<ref>{{cite journal |title=Post-larval development and sexual dimorphism of the spider crab ''Maja brachydactyla'' (Brachyura: Majidae) |author1=Guillermo Guerao |author2=Guiomar Rotllant |journal=[[Scientia Marina]] |volume=73 |issue=4 |year=2009 |pages=797–808 |doi=10.3989/scimar.2009.73n4797 |url=http://digital.csic.es/bitstream/10261/19120/3/1148.pdf |archive-url=https://web.archive.org/web/20100326165537/http://digital.csic.es/bitstream/10261/19120/3/1148.pdf |archive-date=2010-03-26 |url-status=live|doi-access=free |bibcode=2009ScMar..73..797G }}</ref> This is because female crabs brood fertilised eggs on their [[pleopod]]s.

==Life cycle==

[[File:Crab (Pachygrapsus marmoratus) on Istrian coast (Adriatic sea).jpg|thumb|Crab (''[[Pachygrapsus marmoratus]]'') on Istrian coast, [[Adriatic Sea]]]]

True crabs attract a mate through chemical ([[pheromone]]s), visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic species, while [[terrestrial crab|terrestrial]] and semiterrestrial crabs often use visual signals, such as [[fiddler crab]] males waving their large claws to attract females. The vast number of brachyuran crabs have [[internal fertilisation]] and mate belly-to-belly. For many aquatic species, mating takes place just after the female has moulted and is still soft. Females can store the [[sperm]] for a long time before using it to fertilise their [[ovum|eggs]]. When fertilisation has taken place, the eggs are released onto the female's abdomen, below the tail flap, secured with a sticky material. In this location, they are protected during embryonic development. Females carrying eggs are called "berried" since the eggs resemble round berries.

When development is complete, the female releases the newly hatched [[crustacean larvae|larvae]] into the water, where they are part of the [[plankton]]. The release is often timed with the [[tide|tidal]] and light/dark [[diel cycle|diurnal cycle]].<ref>{{Cite journal|last=Forward|first=Jr., Richard B.|date=1987-09-01|title=Larval Release Rhythms of Decapod Crustaceans: An Overview|url=https://www.ingentaconnect.com/content/umrsmas/bullmar/1987/00000041/00000002/art00006|journal=Bulletin of Marine Science|volume=41|issue=2|pages=165–176}}</ref><ref>{{Cite journal|last1=Ricardo|first1=Gerard F.|last2=Davis|first2=Andrew R.|last3=Knott|first3=Nathan A.|last4=Minchinton|first4=Todd E.|date=2014-04-01|title=Diel and tidal cycles regulate larval dynamics in salt marshes and mangrove forests|journal=Marine Biology|language=en|volume=161|issue=4|pages=769–784|doi=10.1007/s00227-013-2376-4|bibcode=2014MarBi.161..769R |s2cid=84260279|issn=1432-1793}}</ref> The free-swimming tiny [[Zoea|zoea larvae]] can float and take advantage of water currents. They have a spine, which probably reduces the rate of predation by larger animals. The zoea of most species must find food, but some crabs provide enough [[Egg yolk|yolk]] in the eggs that the larval stages can continue to live off the yolk.

[[File:Xantho poressa 2009 G1.jpg|thumb|Female crab ''[[Xantho poressa]]'' at spawning time in the [[Black Sea]], carrying eggs under her abdomen]]

[[File:Grapsus tenuicrustatus - hawaii - 2015-11-01.webm|thumb|A ''[[Grapsus tenuicrustatus]]'' climbing up a rock in [[Hawaii]]]]

Each species has a particular number of zoeal stages, separated by [[Ecdysis|moults]], before they change into a [[megalopa]] stage, which resembles an adult crab, except for having the abdomen (tail) sticking out behind. After one more moult, the crab is a [[Juvenile (organism)|juvenile]], living on the bottom rather than floating in the water. This last moult, from megalopa to juvenile, is critical, and it must take place in a habitat that is suitable for the juvenile to survive.<ref name="Weis">{{cite book |author=Judith S. Weis |year=2012 |title=Walking Sideways: The Remarkable World of Crabs |publisher=[[Cornell University Press]] |location=Ithaca, NY |isbn=978-0-8014-5050-1 |oclc=794640315}}</ref>{{rp|63–77}}

Most terrestrial crabs must [[Animal migration|migrate]] down to the ocean to release their larvae; in some cases, this entails very extensive migrations. After living for a short time as larvae in the ocean, the juveniles must do this migration in reverse. In many tropical areas with land crabs, these migrations often result in considerable [[roadkill]] of migrating crabs.<ref name="Weis"/>{{rp|113–114}}

Once crabs have become juveniles, they still have to keep moulting many more times to become adults. They are covered with a hard shell, which would otherwise prevent growth. The moult cycle is coordinated by [[hormone]]s. When preparing for moult, the old shell is softened and partly eroded away, while the rudimentary beginnings of a new shell form under it. At the time of moulting, the crab takes in a lot of water to expand and crack open the old shell at a line of weakness along the back edge of the [[carapace]]. The crab must then extract all of itself – including its legs, [[Arthropod mouthparts|mouthparts]], [[eyestalk]]s, and even the lining of the front and back of the digestive tract – from the old shell. This is a difficult process that takes many hours, and if a crab gets stuck, it will die. After freeing itself from the old shell (now called an [[exuvia]]), the crab is extremely soft and hides until its new shell has hardened. While the new shell is still soft, the crab can expand it to make room for future growth.<ref name="Weis" />{{rp|78–79}}

==Behaviour==

[[File:Carpilius convexus is consuming Heterocentrotus trigonarius in Hawaii.jpg|left|thumb|''[[Carpilius convexus]]'' consuming ''[[Heterocentrotus trigonarius]]'' in Hawaii]]

True crabs typically walk sideways<ref name="Sleinis">{{cite journal |title=Locomotion in a forward walking crab |author1=Sally Sleinis |author2=Gerald E. Silvey |journal=Journal of Comparative Physiology A |volume=136 |issue=4 |year=1980 |doi=10.1007/BF00657350 |pages=301–312|s2cid=33455459 }}</ref> (hence the term [[wikt:crabwise|crabwise]]), because of the articulation of the legs which makes a sidelong gait more efficient.<ref name="Vidal-Gadea">{{cite journal |title=Skeletal adaptations for forward and sideways walking in three species of decapod crustaceans |author1=A. G. Vidal-Gadea |author2=M.D. Rinehart |author3=J.H. Belanger |journal=[[Arthropod Structure & Development]] |volume=37 |issue=2 |date=March 2008 |pmid= 18089130 |pages=179–194 |doi=10.1016/j.asd.2007.06.002|bibcode=2008ArtSD..37...95V }}</ref> Some crabs walk forward or backward, including [[Raninidae|raninids]],<ref>{{cite web |title=Spanner crab ''Ranina ranina'' |url=http://www.dpi.nsw.gov.au/fisheries/recreational/saltwater/sw-species/spanner-crab |publisher=[[New South Wales Department of Primary Industries]] |access-date=2009-01-04 |year=2005 |work=Fishing and Aquaculture}}</ref> ''[[Libinia emarginata]]''<ref>{{cite journal |title=Muscular anatomy of the legs of the forward walking crab, ''Libinia emarginata'' (Decapoda, Brachyura, Majoidea) |author1=A. G. Vidal-Gadea |author2=J. H. Belanger |journal=[[Arthropod Structure & Development]] |volume=38 |issue=3 |year=2009 |pmid=19166968 |pages=179–194 |doi=10.1016/j.asd.2008.12.002|bibcode=2009ArtSD..38..179V }}</ref> and ''[[Mictyris platycheles]]''.<ref name="Sleinis"/> Some crabs, like the [[Portunidae]] and [[Matutidae]], are also capable of swimming,<ref name="Ng">{{cite journal|journal=[[Raffles Bulletin of Zoology]] |year=2008 |volume=17 |pages=1–286 |title=Systema Brachyurorum: Part I. An annotated checklist of extant Brachyuran crabs of the world |author=Peter K. L. Ng, [[Danièle Guinot]] & Peter J. F. Davie |url=http://rmbr.nus.edu.sg/rbz/biblio/s17/s17rbz.pdf |archive-url=https://web.archive.org/web/20110606061453/http://rmbr.nus.edu.sg/rbz/biblio/s17/s17rbz.pdf |archive-date=2011-06-06 }}</ref> the [[Portunidae]] especially so as their last pair of walking legs are flattened into swimming paddles.<ref name="Weis" />{{rp|96}}

Brachyuran crabs are mostly active animals with complex behaviour patterns such as communicating by drumming or waving their [[Chela (organ)|pincers]]. Crabs tend to be aggressive toward one another, and males often fight to gain access to females.<ref>{{cite book |chapter=Crab (animal) |title=Encarta |year=2005 |publisher=[[Microsoft]]|title-link=Encarta }}</ref> On rocky [[shore|seashores]], where nearly all caves and crevices are occupied, crabs may also fight over hiding holes.<ref>{{cite book |title=The Miles Kelly Book of Life |location=[[Great Bardfield]], [[Essex]] |publisher=[[Miles Kelly Publishing]] |year=2006 |page=512 |isbn=978-1-84236-715-5}}</ref> [[Fiddler crab]]s (genus ''Uca'') dig burrows in sand or mud, which they use for resting, hiding, and mating, and to defend against intruders.<ref name="Weis"/>{{rp|28–29, 99}}

True crabs are [[omnivore]]s, feeding primarily on [[alga]]e,<ref>{{cite journal |doi=10.1080/00288330.1993.9516571 |title=Natural diet of the crab ''Notomithrax ursus'' (Brachyura, Majidae) at Oaro, South Island, New Zealand |author=Chris M. C. Woods |journal=[[New Zealand Journal of Marine and Freshwater Research]] |year=1993 |volume=27 |pages=309–315 |issue=3 |bibcode=1993NZJMF..27..309W |doi-access=free }}</ref> and taking any other food, including [[mollusc]]s, [[worm]]s, other [[crustacean]]s, [[fungi]], [[bacteria]], and [[detritus]], depending on their availability and the crab species. For many crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest [[fitness (biology)|fitness]].<ref>{{cite journal |author=Robin Kennish |year=1996 |title=Diet composition influences the fitness of the herbivorous crab ''Grapsus albolineatus'' |journal=[[Oecologia]] |volume=105 |issue=1 |pages=22–29 |doi=10.1007/BF00328787|pmid=28307118 |bibcode=1996Oecol.105...22K |s2cid=24146814 }}</ref><ref>{{cite journal |title=Diet choice in an omnivorous salt-marsh crab: different food types, body size, and habitat complexity |author1=Tracy L. Buck |author2=Greg A. Breed |author3=Steven C. Pennings |author4=Margo E. Chase |author5=Martin Zimmer |author6=Thomas H. Carefoot |journal=[[Journal of Experimental Marine Biology and Ecology]] |year=2003 |volume=292 |issue=1 |pages=103–116 |doi=10.1016/S0022-0981(03)00146-1|bibcode=2003JEMBE.292..103B }}</ref> Some species are more specialised in their diets, based in plankton, clams or fish.<ref name="Weis"/>{{rp|85}} Some crabs, such as members of [[Pinnotheridae]], live on or inside animals such as [[Bivalvia|bivalves]], either being [[Commensalism|commensal]] (benign) or [[Parasitism|parasitic]] on their host.<ref>{{Cite journal |last1=de Gier |first1=Werner |last2=Becker |first2=Carola |date=2020-11-16 |title=A Review of the Ecomorphology of Pinnotherine Pea Crabs (Brachyura: Pinnotheridae), with an Updated List of Symbiont-Host Associations |journal=Diversity |language=en |volume=12 |issue=11 |page=431 |doi=10.3390/d12110431 |doi-access=free |bibcode=2020Diver..12..431D |issn=1424-2818}}</ref>

True crabs work together to provide food and protection for their family, and during mating season to find a comfortable spot for the female to release her eggs.<ref>{{cite journal |author=[[Danièle Guinot]] & J.–M. Bouchard |year=1998 |title=Evolution of the abdominal holding systems of brachyuran crabs (Crustacea, Decapoda, Brachyura) |journal=[[Zoosystema]] |volume=20 |issue=4 |pages=613–694 |doi=10.5962/p.268908 |url=http://www.mnhn.fr/publication/zoosyst/z98n4a4.html |format=[[Portable Document Format|PDF]] |archive-url=https://web.archive.org/web/20061118171555/http://www.mnhn.fr/publication/zoosyst/z98n4a4.html |archive-date=2006-11-18 }}</ref>

==Evolution==

[[File:Eocarcinus reconstructon.jpg|thumb|upright|Reconstruction of ''[[Eocarcinus]]'', the earliest known crab]]

The earliest unambiguous brachyuran [[fossil]]s date from the [[Early Jurassic]], with the oldest being ''[[Eocarcinus]]'' from the early [[Pliensbachian]] of Britain, which likely represents a [[Stem-group|stem-group lineage]], as it lacks several key morphological features that define modern crabs.<ref>{{Cite journal|last=Scholtz|first=Gerhard|date=November 2020|title=Eocarcinus praecursor Withers, 1932 (Malacostraca, Decapoda, Meiura) is a stem group brachyuran|journal=Arthropod Structure & Development |language=en |volume=59 |article-number=100991 |doi=10.1016/j.asd.2020.100991 |pmid=32891896 |doi-access=free|bibcode=2020ArtSD..5900991S }}</ref><ref>{{cite journal |author1=Carrie E. Schweitzer |author2=Rodney M. Feldmann |year=2010 |title=The oldest Brachyura (Decapoda: Homolodromioidea: Glaessneropsoidea) known to date (Jurassic) |journal=[[Journal of Crustacean Biology]] |volume=30 |issue=2 |pages=251–256 |doi=10.1651/09-3231.1|doi-access=free |bibcode=2010JCBio..30..251F }}</ref> Most Jurassic crabs are only known from [[Dorsal (anatomy)|dorsal]] (top half of the body) [[carapace]]s, making it difficult to determine their relationships.<ref>{{Cite journal |last=Guinot |first=Danièle |date=2019-11-14 |title=New hypotheses concerning the earliest brachyurans (Crustacea, Decapoda, Brachyura)|journal=Geodiversitas|volume=41|issue=1|page=747|doi=10.5252/geodiversitas2019v41a22|issn=1280-9659|doi-access=free|bibcode=2019Geodv..41..747G }}</ref> Crabs [[Evolutionary radiation|radiated]] in the [[Late Jurassic]], corresponding with an increase in reef habitats, though they would decline at the end of the Jurassic as the result of the decline of reef ecosystems. Crabs increased in diversity through the Cretaceous and represented the dominant group of [[Decapoda|decapods]] by the end of the period.<ref>{{Cite journal|last1=Klompmaker|first1=A. A.|last2=Schweitzer|first2=C. E.|last3=Feldmann|first3=R. M.|last4=Kowalewski|first4=M.|date=2013-11-01|title=The influence of reefs on the rise of Mesozoic marine crustaceans|url=https://pubs.geoscienceworld.org/geology/article/41/11/1179-1182/131064|journal=Geology|language=en|volume=41|issue=11|pages=1179–1182|doi=10.1130/G34768.1|bibcode=2013Geo....41.1179K|issn=0091-7613|url-access=subscription}}</ref>

The [[infraorder]] Brachyura belongs to the group [[Reptantia]], which consists of the walking/crawling decapods ([[lobsters]] and crabs).  Brachyura is the [[sister clade]] to the infraorder [[Anomura]], which contains the hermit crabs and relatives.  The [[cladogram]] below shows Brachyura's placement within the larger [[order (biology)|order]] [[Decapoda]], from analysis by Wolfe ''et al.'', 2019.<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. |title=A phylogenomic framework, evolutionary timeline and genomic resources for comparative studies of decapod crustaceans |journal=Proceedings of the Royal Society B | date=24 April 2019 |volume=286 |issue=1901 |doi=10.1098/rspb.2019.0079 |pmid=31014217 |pmc=6501934 |doi-access=free }}</ref>

{{Decapoda cladogram}}

Brachyura is separated into several sections, with the [[basal (phylogenetics)|basal]] [[Dromiacea]] diverging the earliest in the evolutionary history, around the [[Late Triassic]] or [[Early Jurassic]].  The group consisting of [[Raninoida]] and [[Cyclodorippoida]] split off next, during the [[Jurassic]] period.  The remaining [[clade]] [[Eubrachyura]] then divided during the [[Cretaceous]] period into [[Heterotremata]] and [[Thoracotremata]].
A summary of the high-level internal relationships within Brachyura can be shown in the [[cladogram]] below:<ref name="Ling">{{cite journal |title=Evolutionary History of True Crabs (Crustacea: Decapoda: Brachyura) and the Origin of Freshwater Crabs |author1=Ling Ming Tsang |author2=Christoph D. Schubart |author3=Shane T. Ahyong |author4=Joelle C.Y. Lai |author5=Eugene Y.C. Au |author6=Tin-Yam Chan |author7=Peter K.L. Ng |author8=Ka Hou Chu |journal=[[Molecular Biology and Evolution]] |publisher=[[Oxford University Press ]]|volume=31 |issue=5 |year=2014 |pages=1173–1187 |doi=10.1093/molbev/msu068 |pmid=24520090 |doi-access=free}}</ref><ref name="Wolfe2019" />
{{clade| style=font-size:85%; line-height:85%
|label1='''Brachyura'''
|1={{clade
 |1=[[Dromiacea]]
 |2={{clade
  |1={{clade
   |1=[[Raninoida]]
   |2=[[Cyclodorippoida]] }}
  |label2=[[Eubrachyura]]
  |2={{clade
   |1=[[Heterotremata]]
   |2=[[Thoracotremata]] }} }} }} }}

There is a no consensus on the relationships of the subsequent [[superfamily (taxonomy)|superfamilies]] and [[family (biology)|families]].  The proposed [[cladogram]] below is from analysis by Tsang ''et al'', 2014:<ref name="Ling" />
{{clade| style=font-size:85%; line-height:85%
|label1='''Brachyura'''
|1={{clade
 |label1=[[Dromiacea]]
 |1={{clade
  |label1=[[Dromioidea]]
  |1={{clade
   |1=[[Dromiidae]] (may be paraphyletic)
   |2=[[Dynomenidae]] }}
  |label2=[[Homoloidea]]
  |2={{clade
   |1=[[Homolidae]] (paraphyletic)
   |2=[[Latreilliidae]] }} }}
 |2={{clade
  |1={{clade
   |label1=[[Raninoida]]
   |1=[[Raninidae]]
   |label2=[[Cyclodorippoida]]
   |2={{clade
    |1=[[Cyclodorippidae]]
    |2=[[Cymonomidae]] }} }}
  |label2=[[Eubrachyura]]
  |2={{clade
   |label1=[[Heterotremata]]
   |1={{clade
    |label1=Freshwater crabs
    |1={{clade
     |label1=[[Potamoidea]] |sublabel1=(Old World freshwater crabs)
     |1={{clade
      |1=[[Potamonautidae]]
      |2={{clade
       |1=[[Potamidae]]
       |2=[[Gecarcinucidae]] }} }}
     |label2=Pseudothelphusoidea |sublabel2=(New World freshwater crabs)
     |2=[[Pseudothelphusidae]] }}
    |2=&nbsp; |state2=none
    |3={{clade
     |1={{clade
      |1={{clade
       |1=[[Trichodactylidae]] (freshwater crabs)
       |2=[[Orithyiidae]] }}
      |2={{clade
       |1={{clade
        |1=[[Belliidae]]
        |2=[[Chasmocarcinidae]] }}
       |2=[[Retroplumidae]] }} }}
     |2={{clade
      |1={{clade
       |1={{clade
        |label1=[[Dorippoidea]]
        |1={{clade
         |1=[[Ethusidae]]
         |2=[[Dorippidae]] }}
        |2=[[Leucosiidae]] }}
       |2={{clade
        |label1=[[Majoidea]]
        |1={{clade
         |1=[[Inachidae]]
         |2={{clade
          |1=[[Epialtidae]] (paraphyletic)
          |2=[[Majidae]] / [[Mithracidae]] }} }}
        |2=[[Corystidae]] }} }}
      |2={{clade
       |1={{clade
        |1=[[Euryplacidae]]
        |2=[[Matutidae]] }}
       |2={{clade
        |1={{clade
         |1={{clade
          |1=[[Calappidae]]
          |2={{clade
           |1={{clade
            |1=[[Parthenopidae]]
            |2=[[Cancridae]] }}
           |2={{clade
            |1=[[Carpiliidae]]
            |2={{clade
             |1=[[Aethridae]]
             |2=''[[Pseudocarcinus]]'' of [[Menippidae]] }} }} }} }}
         |2={{clade
          |1=''[[Menippe (crab)|Menippe]]'' of [[Menippidae]]
          |2={{clade
           |1=[[Polybiidae]]
           |2=[[Portunidae]] }} }} }}
        |2={{clade
         |label1=[[Pilumnoidea]]
         |1={{clade
          |1=[[Tanaochelidae]]
          |2={{clade
           |1=[[Galenidae]]
           |2=[[Pilumnidae]] }} }}
         |2={{clade
          |1={{clade
           |1={{clade
            |1=[[Mathildellidae]]
            |2={{clade
             |1=[[Eriphiidae]]
             |2={{clade
              |1=[[Oziidae]]
              |2=[[Vultocinidae]] }} }} }}
           |2=[[Trapeziidae]] }}
          |2={{clade
           |1=[[Goneplacidae]]
           |2={{clade
            |1=[[Scalopidiidae]]
            |label2=[[Xanthoidea]]
            |2={{clade
             |1=[[Xanthidae]] (paraphyletic)
             |2=[[Panopeidae]] }} }} }} }} }} }} }} }} }} }}
   |label2=[[Thoracotremata]]
   |2={{clade
    |1={{clade
     |1=[[Pinnotheridae]]
     |2=[[Dotillidae]] }}
    |2={{clade
     |1=[[Percnidae]]
     |2={{clade
      |1={{clade
       |1=[[Xenograpsidae]]
       |2=[[Cryptochiridae]] }}
      |2={{clade
       |1={{clade
        |1=[[Ocypodidae]]
        |2={{clade
         |1=[[Glyptograpsidae]]
         |2=[[Grapsidae]] }} }}
       |2={{clade
        |1={{clade
         |1={{clade
          |1=[[Plagusiidae]]
          |2=[[Gecarcinidae]] }}
         |2=[[Sesarmidae]] }}
        |2={{clade
         |1=[[Mictyridae]]
         |2={{clade
          |1=[[Varunidae]]
          |2=[[Macrophthalmidae]]
}} }} }} }} }} }} }} }} }} }} }}

==Classification==

The [[infraorder]] Brachyura contains approximately 7,000 species in 98 [[family (biology)|families]],<ref name="Ling" /><ref name="Ng" /> as many as the remainder of the [[Decapoda]].<ref name="Martin & Davis">{{cite book |url=http://atiniui.nhm.org/pdfs/3839/3839.pdf |title=An Updated Classification of the Recent Crustacea |author1=Joel W. Martin |author2=George E. Davis |year=2001 |page=132 |publisher=[[Natural History Museum of Los Angeles County]] |access-date=2009-12-14 |archive-date=2013-05-12 |archive-url=https://web.archive.org/web/20130512091254/http://atiniui.nhm.org/pdfs/3839/3839.pdf }}</ref> The evolution of crabs is characterized by an increasingly robust body, and a reduction in the [[Abdomen#Arthropoda|abdomen]]. Although many other groups have undergone similar processes, [[carcinisation]] is most advanced in crabs. The [[telson]] is no longer functional in crabs, and the [[uropod]]s are absent, having probably evolved into small devices for holding the reduced abdomen tight against the [[Sternum (arthropod)|sternum]].

In most decapods, the [[gonopore]]s (sexual openings) are found on the legs. Since crabs use their first two pairs of [[pleopod]]s (abdominal appendages) for sperm transfer, this arrangement has changed. As the male abdomen evolved into a slimmer shape, the gonopores have moved toward the midline, away from the legs, and onto the sternum.<ref>{{cite journal |author=M. de Saint Laurent |year=1980 |title=Sur la classification et la phylogénie des Crustacés Décapodes Brachyoures. II. Heterotremata et Thoracotremata Guinot, 1977 |journal=[[Comptes rendus de l'Académie des sciences]] |volume=t. 290 |pages=1317–1320}}</ref> A similar change occurred, independently, with the female gonopores. The movement of the female gonopore to the sternum defines the [[clade]] [[Eubrachyura]], and the later change in the position of the male gonopore defines the [[Thoracotremata]]. It is still a subject of debate whether a [[Monophyly|monophyletic group]] is formed by those crabs where the female, but not male, gonopores are situated on the sternum.<ref name="Martin & Davis" />

===Families===

Numbers of extant and extinct (†) species are given in brackets.<ref name="DeGrave" /> The superfamily [[Eocarcinoidea]], containing ''[[Eocarcinus]]'' and ''[[Platykotta]]'', was formerly thought to contain the oldest crabs; it is now considered part of the [[Anomura]].<ref name="Chablais">{{cite journal |author1=Jérôme Chablais |author2=Rodney M. Feldmann |author3=Carrie E. Schweitzer |year=2011 |title=A new Triassic decapod, ''Platykotta akaina'', from the Arabian shelf of the northern United Arab Emirates: earliest occurrence of the Anomura |journal=[[Paläontologische Zeitschrift]] |volume=85 |issue=1 |pages=93–102 |doi=10.1007/s12542-010-0080-y |bibcode=2011PalZ...85...93C |s2cid=5612385 |url=http://decapoda.nhm.org/pdfs/31744/31744.pdf |archive-url=https://web.archive.org/web/20120319132343/http://decapoda.nhm.org/pdfs/31744/31744.pdf |archive-date=2012-03-19 |url-status=live }}</ref>

{{Multiple image
| direction         = vertical
| align             = right
| width             = 220
| header            = Examples of different crab sections
| image1            = Dromia personata.jpg
| caption1          = ''[[Dromia personata]]'' ([[Dromiacea]]: [[Dromiidae]])
| image2            = Ranina ranina.jpg
| caption2          = ''[[Ranina ranina]]'' ([[Raninoida]]: [[Raninidae]])
| image3            = Corystes cassivelaunus.jpg
| caption3          = ''[[Corystes cassivelaunus]]'' ([[Heterotremata]]: [[Corystidae]])
| image4            = Ocypode quadrata.jpg
| caption4          = ''[[Ocypode quadrata]]'' ([[Thoracotremata]]: [[Ocypodidae]])
| image5            = Goneplax rhomboides 2.jpg
| caption5          = ''[[Goneplax rhomboides]]''
}}

* '''Section †[[Callichimaeroida]]'''
** †[[Callichimaeroidea]] (1†)<ref>{{cite journal |last1=Luque |first1=J. |last2=Feldmann |first2=R. M. |last3=Vernygora |first3=O. |last4=Schweitzer |first4=C. E. |last5=Cameron |first5=C. B. |last6=Kerr |first6=K. A. |last7=Vega |first7=F. J. |last8=Duque |first8=A. |last9=Strange |first9=M. |last10=Palmer |first10=A. R. |last11=Jaramillo |first11=C. |title=Exceptional preservation of mid-Cretaceous marine arthropods and the evolution of novel forms via heterochrony |journal=Science Advances |date=24 April 2019 |volume=5 |issue=4 |article-number=eaav3875 |doi=10.1126/sciadv.aav3875|pmid=31032408 |pmc=6482010 |bibcode=2019SciA....5.3875L }}</ref>
* '''Section [[Dromiacea]]'''
** †[[Dakoticancroidea]] (6†)
** [[Dromioidea]] (147, 85†)
** [[Glaessneropsoidea]] (45†)
** [[Homolodromioidea]] (24, 107†)
** [[Homoloidea]] (73, 49†)
* '''Section [[Raninoida]]''' (46, 196†)
* '''Section [[Cyclodorippoida]]''' (99, 27†)
* '''Section [[Eubrachyura]]'''
** '''Subsection [[Heterotremata]]'''
*** [[Aethroidea]] (37, 44†)
*** [[Bellioidea]] (7)
*** [[Bythograeoidea]] (14)
*** [[Calappoidea]] (101, 71†)
*** [[Cancroidea]] (57, 81†)
*** [[Carpilioidea]] (4, 104†)
*** [[Cheiragonoidea]] (3, 13†)
*** [[Corystoidea]] (10, 5†)
*** †[[Componocancroidea]] (1†)
*** [[Dairoidea]] (4, 8†)
*** [[Dorippoidea]] (101, 73†)
*** [[Eriphioidea]] (67, 14†)
*** [[Gecarcinucoidea]] (349)
*** [[Goneplacoidea]] (182, 94†)
*** [[Hexapodoidea]] (21, 25†)
*** [[Leucosioidea]] (488, 113†)
*** [[Majoidea]] (980, 89†)
*** [[Orithyioidea]] (1)
*** [[Palicoidea]] (63, 6†)
*** [[Parthenopoidea]] (144, 36†)
*** [[Pilumnoidea]] (405, 47†)
*** [[Portunoidea]] (455, 200†)
*** [[Potamoidea]] (662, 8†)
*** [[Pseudothelphusoidea]] (276)
*** [[Pseudozioidea]] (22, 6†)
*** [[Retroplumoidea]] (10, 27†)
*** [[Trapezioidea]] (58, 10†)
*** [[Trichodactyloidea]] (50)
*** [[Xanthoidea]] (736, 134†)<ref name="Mendoza2022">{{cite journal |title=A comprehensive molecular phylogeny of the brachyuran crab superfamily Xanthoidea provides novel insights into its systematics and evolutionary history |author1=Jose C.E. Mendoza |author2=Kin Onn Chan |author3= Joelle C.Y. Lai |author4=Brent P. Thoma |author5=Paul F. Clark |author6=Danièle Guinot |author7=Darryl L. Felder |author8=Peter K.L. Ng |journal=[[Molecular Phylogenetics and Evolution]] |volume=177 |year=2022 |article-number=107627 |doi=10.1016/j.ympev.2022.107627 |pmid=36096461 |doi-access=free|bibcode=2022MolPE.17707627M }}</ref>
** '''Subsection [[Thoracotremata]]'''<ref name="Tsang2022">{{cite journal |title=Molecular phylogeny of Thoracotremata crabs (Decapoda, Brachyura): Toward adopting monophyletic superfamilies, invasion history into terrestrial habitats and multiple origins of symbiosis |author1=Chandler T.T. Tsang |author2=Christoph D. Schubart |author3=Ka Hou Chu |author4=Peter K.L. Ng |author5=Ling Ming Tsang |journal=[[Molecular Phylogenetics and Evolution]] |volume=177 |year=2022 |article-number=107596 |doi=10.1016/j.ympev.2022.107596 |pmid=35914646 |doi-access=free|bibcode=2022MolPE.17707596T }}</ref>
*** [[Cryptochiroidea]] (46)
*** [[Grapsoidea]] (493, 28†)
*** [[Ocypodoidea]] (304, 14†)
*** [[Pinnotheroidea]] (304, 13†)

21st century studies have found the following [[superfamily (taxonomy)|superfamilies]] and [[family (biology)|families]] to not be [[monophyletic]], but rather [[paraphyletic]] or [[polyphyletic]]:<ref name="Ling"/><ref name="Wolfe2019"/><ref name="Tsang2022"/><ref name="Mendoza2022"/>

* The [[Thoracotremata]] superfamily [[Grapsoidea]] is polyphyletic
* The [[Thoracotremata]] superfamily [[Ocypodoidea]] is polyphyletic
* The [[Heterotremata]] superfamily [[Calappoidea]] is polyphyletic
* The [[Heterotremata]] superfamily [[Eriphioidea]] is polyphyletic
* The [[Heterotremata]] superfamily [[Goneplacoidea]] is polyphyletic
* The [[Heterotremata]] superfamily [[Potamoidea]] is paraphyletic with respect to [[Gecarcinucoidea]], which is resolved by placing [[Gecarcinucidae]] within [[Potamoidea]]
* The [[Majoidea]] families [[Epialtidae]], [[Mithracidae]] and [[Majidae]] are polyphyletic with respect to each other
* The [[Dromioidea]] family [[Dromiidae]] may be paraphyletic with respect to [[Dynomenidae]]
* The [[Homoloidea]] family [[Homolidae]] is paraphyletic with respect to [[Latreilliidae]]
* The [[Xanthoidea]] family [[Xanthidae]] is paraphyletic with respect to [[Panopeidae]]

==Human consumption==

===Fisheries===

[[File:The Lobster Pot - a shellfish company from Wales - 2016.webm|thumb|right|A short video on catching and exporting shellfish in [[Wales]] ]]

{{Main|Crab fisheries}}

True crabs make up 20% of all marine [[crustacean]]s caught, farmed, and consumed worldwide, amounting to 1.5&nbsp;million [[tonne]]s annually. One species, ''[[Portunus trituberculatus]]'', accounts for one-fifth of that total. Other commercially important [[taxon|taxa]] include ''[[Portunus pelagicus]]'', several species in the genus ''[[Chionoecetes]]'', the blue crab (''[[Callinectes sapidus]]''), [[Charybdis (crab)|''Charybdis'' spp.]], ''[[Edible crab|Cancer pagurus]]'', the [[Dungeness crab]] (''Metacarcinus magister''), and ''[[Scylla serrata]]'', each of which yields more than 20,000&nbsp;tonnes annually.<ref>{{cite web |title=Global Capture Production 1950–2004 |url=http://www.fao.org/figis/servlet/TabLandArea?tb_ds=Capture&tb_mode=TABLE&tb_act=SELECT&tb_grp=COUNTRY |archive-url=https://web.archive.org/web/20160123085332/http://www.fao.org/figis/servlet/TabLandArea?tb_ds=Capture&tb_mode=TABLE&tb_act=SELECT&tb_grp=COUNTRY |archive-date=2016-01-23 |access-date=2006-08-26 |publisher=[[Food and Agriculture Organization]]}}</ref>

In some species, meat is harvested by manually twisting and [[Declawing of crabs|pulling off]] one or both claws and returning the live crab to the water in the knowledge that it may survive and regenerate the claws.<ref>{{cite web |title=Stone Crabs FAQs |url=http://www.myfwc.com/research/saltwater/crustaceans-marine-arthropods/stone-crabs/faq/ |archive-url=https://web.archive.org/web/20170621061113/http://www.myfwc.com/research/saltwater/crustaceans-marine-arthropods/stone-crabs/faq/ |archive-date=2017-06-21 |access-date=2012-09-23}}</ref><ref>{{cite journal |author1=Lynsey Patterson |author2=Jaimie T.A. Dick |author3=Robert W. Elwood |date=January 2009 |title=Claw removal and feeding ability in the edible crab, ''Cancer Pagurus'': implications for fishery practice |journal=[[Applied Animal Behaviour Science]] |volume=116 |issue=2 |pages=302–305 |doi=10.1016/j.applanim.2008.08.007}}</ref><ref>{{cite web |author=[[Queen's University, Belfast]] |date=October 10, 2007 |title=Declawing crabs may lead to their death |url=https://www.sciencedaily.com/releases/2007/10/071007210836.htm |access-date=2012-09-21 |website=[[Science Daily]]}}</ref>

===Crabs as food===
{{refimprove section|date=November 2025}}

{{Cookbook|Crab}}

{{see also|Crab meat|List of crab dishes}}

[[File:Crabmasala.jpg|thumb|right|Crab [[masala (spice)|masala]] from [[Karnataka]], [[India]]|alt=Photo of cooked crab in bowl of soup]]

Crabs are prepared and eaten as a dish in many different ways all over the world. Some species can be eaten whole, including the shell, as [[soft-shell crab]]s; with other species, just the claws or legs are eaten. The latter is particularly common for larger crabs, such as the [[snow crab]]. In many cultures, the [[roe]] of the female crab is also eaten, which usually appears orange or yellow in fertile crabs. This is popular in Southeast Asian cultures, some Mediterranean and Northern European cultures, and on the East, [[Chesapeake Bay|Chesapeake]], and Gulf Coasts of the United States.

In some regions, spices improve the culinary experience. In [[Southeast Asia]] and the [[Indosphere]], [[spice mix|masala]] crab and [[chilli crab]] are examples of heavily spiced dishes. In the Chesapeake Bay region, blue crab is often steamed with [[Old Bay Seasoning]]. Alaskan king crab or snow crab legs are usually simply boiled and served with garlic or lemon butter.

[[File:Kobako crab sushi (32301286552).jpg|thumb|[[Sushi]] with crab meat and eggs]]

For the British dish [[dressed crab]], the [[crab meat]] is extracted and placed inside the hard shell. One American way to prepare crab meat is by extracting it and adding varying amounts of binders, such as egg white, cracker meal, mayonnaise, or mustard, creating a [[crab cake]].  Crabs can also be made into a [[bisque (food)|bisque]], a global dish of French origin which in its authentic form includes in the broth the pulverized shells of the shellfish from which it is made.

[[Crab stick|Imitation crab]], also called [[surimi]], is made from minced fish meat that is crafted and colored to resemble crab meat. While it is sometimes disdained among some elements of the culinary industry as an unacceptably low-quality substitute for real crab, this does not hinder its popularity, especially as a sushi ingredient in Japan and South Korea, and in home cooking, where cost is often a chief concern.<ref name="New York Times">Daniel P. Puzo (February 14, 1985) [https://www.latimes.com/archives/la-xpm-1985-02-14-fo-2740-story.html Imitation Crab Draws Criticisms]. ''Los Angeles Times''</ref> Indeed, surimi is an important source of protein in most East and Southeast Asian cultures, appearing in staple ingredients such as fish balls and fish cake.

==Cultural influences==

[[File:A crab divination pot in Kapsiki.jpg|thumb|upright|A [[Nggàm|crab divination pot]] in Kapsiki, North Cameroon.]]

Both the [[constellation]] [[Cancer (constellation)|Cancer]] and the [[astrological sign]] [[Cancer (astrology)|Cancer]] are named after the crab, and depicted as a crab. [[William Parsons, 3rd Earl of Rosse]] drew the [[Crab Nebula]] in 1848 and noticed its similarity to the animal; the [[Crab Pulsar]] lies at the centre of the nebula.<ref>{{cite book |author=B. B. Rossi |year=1969 |title=The Crab Nebula: Ancient History and Recent Discoveries |publisher=Center for Space Research, [[Massachusetts Institute of Technology]] |id=CSR-P-69-27 |url=https://ntrs.nasa.gov/search.jsp?R=19700008151}}</ref> The [[Moche (culture)|Moche]] people of ancient [[Peru]] worshipped nature, especially the sea,<ref>{{cite book |author=Elizabeth Benson |title=The Mochica: A Culture of Peru |location=New York, NY |publisher=[[Praeger Press]] |year=1972 |isbn=978-0-500-72001-1}}</ref> and often depicted crabs in their art.<ref>{{cite book |author1=Katherine Berrin |author2=Larco Museum |title=The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera |location=New York |publisher=[[Thames and Hudson]] |year=1997 |page=216 |isbn=978-0-500-01802-6}}</ref> In [[Greek mythology]], [[Karkinos]] was a crab that came to the aid of the [[Lernaean Hydra]] as it battled [[Heracles]]. One of [[Rudyard Kipling]]'s ''[[Just So Stories]]'', ''The Crab that Played with the Sea'', tells the story of a gigantic crab who made the waters of the sea go up and down, like the tides.<ref>{{cite book|last1=Kipling|first1=Rudyard|title=Just So Stories|date=1902|publisher=Macmillan|url=http://etc.usf.edu/lit2go/79/just-so-stories/1297/the-crab-that-played-with-the-sea/|chapter=The Crab that Played with the Sea}}</ref> In [[Malay people|Malay]] mythology (as related by [[Hugh Clifford (colonial administrator)|Hugh Clifford]] to [[Walter William Skeat (anthropologist)|Walter William Skeat]]), ocean tides are believed to be caused by water rushing in and out of a hole in the Navel of the Seas (''Pusat Tasek''), where "there sits a gigantic crab which twice a day gets out in order to search for food".<ref>{{Cite book|title=Malay Magic|last=Skeat|first=Walter William|publisher=Macmillan and Co., Limited|year=1900|location=London|pages=1–15|chapter=Chapter 1: Nature|chapter-url=https://www.gutenberg.org/files/47873/47873-h/47873-h.htm#s1.2}}</ref>{{Rp|7–8}}

The [[Kapsiki people]] of North Cameroon use the way crabs handle objects for [[divination]].<ref>Zeitlyn, David. 1987. Mambila Divination. Cambridge Anthropology 12 (1):21-51. NB: this also appeared as a chapter in Zeitlyn's PhD which is online: [https://www.repository.cam.ac.uk/handle/1810/237240 Mambila Traditional Religion], and in a revised form in: Zeitlyn, David. 1994. Sua in Somié. Mambila Traditional Religion. Vol. 41, Collectanea Instituti Anthropos. Sankt Augustin: Academia Verlag</ref><ref>David Zeitlyn. 2020. Mambila Divination: Framing Questions, Constructing Answers (Routledge Studies in Anthropology) London: Routledge. {{ISBN|9780367199500}}</ref>

The term ''[[crab mentality]]'' is derived from a type of detrimental social behavior observed in crabs.<ref>{{cite web |last1=Henry |first1=Elizabeth |title=FAQ: Crab Theory |url=https://libguides.gallaudet.edu/crab-theory |website=LibGuides }}</ref>

== Notes ==

{{notelist}}

==References==

{{Reflist|30em}}

{{Decapoda}}
{{Brachyura|state=expanded}}
{{commercial fish topics}}
{{Edible crustaceans}}
{{Portal bar|Crustaceans}}
{{Taxonbar|from=Q40802}}
{{Authority control}}

[[Category:Crabs| ]]
[[Category:Articles containing video clips]]
[[Category:Commercial crustaceans]]
[[Category:Edible crustaceans]]
[[Category:Extant Jurassic first appearances]]