Chelae
{{Short description|Pincer-like organ terminating certain limbs of some arthropods}}
{{Other uses}}
File:fiddler crab.jpg, and other members of the family Ocypodidae, have chelae of different sizes: a large left chela and a small right chela.]]
A chela ({{IPAc-en|ˈ|k|iː|l|ə}}){{spaced en dash}}also called a claw, nipper, or pincer{{spaced en dash}}is a pincer-shaped organ at the end of certain limbs of some arthropods.{{cite web |url=http://crustacea.nhm.org/glossary/define.html?termID=159 |title=Chela |work=Crustacea glossary |publisher=Natural History Museum of Los Angeles County |first=Dean|last=Pentcheff |access-date=November 28, 2011 |archive-date=August 16, 2016 |archive-url=https://web.archive.org/web/20160816231312/http://crustacea.nhm.org/glossary/define.html?termID=159 |url-status=dead}} The name comes from Ancient Greek {{wikt-lang|grc|χηλή}}, through Neo-Latin {{wikt-lang|la|chela}}. The plural form is chelae.{{cite book |first1=Gordon|last1=Gordh |first2=David|last2=Headrick |year=2003 |title=A Dictionary of Entomology |publisher=CAB International |isbn=978-0-85199-655-4 |page=182 |url=https://books.google.com/books?id=d0XSwMJLDg4C&pg=PA182}} Legs bearing a chela are called chelipeds.{{cite web |url=http://crustacea.nhm.org/glossary/define.html?term=Cheliped |title=Cheliped |work=Crustacea glossary |publisher=Natural History Museum of Los Angeles County |author=Dean Pentcheff |access-date=November 28, 2011 |archive-date=April 26, 2012 |archive-url=https://web.archive.org/web/20120426005924/http://crustacea.nhm.org/glossary/define.html?term=Cheliped |url-status=dead }} Another name is claw because most chelae are curved and have a sharp point like a claw.
File:20220411 arthropod chela mechanics en.gif chela mechanics.]]
Chelae can be present at the tips of arthropod legs as well as their pedipalps. Chelae are distinct from spider chelicerae in that they do not contain venomous glands and cannot distribute venom.
Uses
Chelae have a wide variety of uses, but most commonly they are used for handling their prey and for defense. These uses are often reflected in the morphology of the chelae. For instance, some species, such as the members of the families Ocypodidae and Alpheidae show asymmetry between their paired claws.{{Cite journal |last=Read |first=A. T. |last2=Govind |first2=C. K. |date=1997-11-01 |title=Regeneration and sex-biased transformation of the sexually dimorphic pincer claw in adult snapping shrimps |url=https://onlinelibrary.wiley.com/doi/10.1002/(SICI)1097-010X(19971101)279:43.0.CO;2-N |journal=The Journal of Experimental Zoology |language=en |volume=279 |issue=4 |pages=356–366 |doi=10.1002/(SICI)1097-010X(19971101)279:4<356::AID-JEZ5>3.0.CO;2-N|url-access=subscription }} Possessing one enlarged chela used for defensive and courtship purposes and a smaller chela for shearing and feeding. For some species, this asymmetry between chelae may be a sexually dimorphic trait. whereas in others, like many species of scorpions, it is not.{{Cite journal |last=Van Der Meijden |first=A. |last2=Herrel |first2=A. |last3=Summers |first3=A. |date=20 March 2010 |title=Comparison of chela size and pincer force in scorpions; getting a first grip |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.2009.00628.x |journal=Journal of Zoology |language=en |volume=280 |issue=4 |pages=319–325 |doi=10.1111/j.1469-7998.2009.00628.x |issn=0952-8369|url-access=subscription }} An example of specialization of these asymmetrical chelae can be seen in the Alpheus heterochaelis, the bigclaw snapping shrimp. The enlarged snapping claws of these shrimp are capable of snapping shut with such force to shoot a jet of water and create a loud popping noise, which they use to deter predators and other members of their species.
In scorpion species, the chelae are often used to grab hold of prey and then further subdue them by injecting them with the venom from their stingers, although some species rely solely on the chelae to subdue their prey. Scorpions also use their chelae for defense by using them to shield and protect their bodies. For scorpions, the chelae are formed at the end of the pedipalps and covered in sensory hairs that they use in a similar manner to insect antennae.
Further uses of chelae include digging, burrowing, and climbing. Chelae also play an important role in many species mating rituals, such as to communicate and attract prospective mates, wherein species with asymmetrical chelae use their enlarged chela as a display to attract mates. Chelae are also used in the act of mating, where the male species will often use them to hold onto the female during the act.
See also
References
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