Editing Crab (section)

== 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]]

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 }}</ref> This is because female crabs brood fertilised eggs on their [[pleopod]]s.