View source for Autotomy

{{Short description|Self-amputation}}
{{Distinguish|Autonomy}}
[[File:White-headed dwarf gecko.jpg|thumb|A [[white-headed dwarf gecko]] with tail lost due to autotomy]]
'''Autotomy''' (from the [[Greek language|Greek]] ''auto-'', "self-" and ''tome'', "severing", [[wikt:αὐτοτομία|αὐτοτομία]]) or 'self-amputation', is the behaviour whereby an animal sheds or discards an [[appendage]],<ref>(2000). The American Heritage Dictionary of the English Language: Fourth Edition.</ref> usually as a [[self-preservation|self-defense]] mechanism to elude a [[predation|predator's]] grasp or to distract the predator and thereby allow escape. Some animals are able to [[regeneration (biology)|regenerate]] the lost body part later. Autotomy is thought to have evolved independently at least nine times.<ref>{{cite journal |last1=Emberts |first1=Z. |last2=Escalante |first2=I. |last3=Bateman |first3=P. W. |year=2019 |title=The ecology and evolution of autotomy |journal=Biological Reviews |volume=94 |issue=6 |pages=1881–1896 |doi=10.1111/brv.12539 |pmid=31240822 |s2cid=195660712}}</ref> The term was coined in 1883 by [[Léon Fredericq|Leon Fredericq]].<ref>{{cite journal |last=Fredericq |first=Leon |year=1883 |title=Sur l'autotomie ou mutilation par voie reflexe comme moyen de defense chez les animaux |trans-title=On autotomy or reflex mutilation as a means of defence in animals |url=https://orbi.uliege.be/bitstream/2268/128727/1/autotomie.pdf |journal=Archives de Zoologie Expérimentale et Générale |series=2 |volume=1 |pages=414–426 |language=fr}}</ref>
==Vertebrates==
===Reptiles and amphibians===
[[File:Lizard tail autotomy.JPG |thumb |A lizard tail shed by autotomy]]
[[File:Severed skink tail.webm |thumb |An autotomised skink tail exhibiting continued movement]]
[[File:Marbled Gecko (Christinus marmoratus) post-autotomy.jpg |thumb |The conspicuous change in the tail pattern of this [[Christinus marmoratus |marbled gecko]] indicates regeneration after autotomy. |alt=lizard with abrupt change in tail pattern]]
Some [[lizard]]s,<ref>{{cite journal |last1=Congdon |first1=J.D. |last2=Vitt |first2=L.J. |last3=King |first3=W.W. |year=1974 |title=Geckos: adaptive significance and energetics of tail autotomy |journal=Science |volume=184 |issue=4144 |pages=1379–1380 |doi=10.1126/science.184.4144.1379 |pmid=4833262 |bibcode=1974Sci...184.1379C |s2cid=21997926}}</ref><ref>Bellairs, A.D.; Bryant, S.V., (1985). Autotomy and regeneration in reptiles. In: ''Biology of the Reptilia.'' Vol. 15. C. Gans; F. Billet (eds.). John Wiley and Sons, New York. pp. 301–410</ref> [[salamander]]s<ref>{{cite journal |last1=Maiorana |first1=V.C. |year=1977 |title=Tail autotomy, functional conflicts and their resolution by a salamander |journal=Nature |volume=265 |issue=5594 |pages=533–535 |doi=10.1038/265533a0 |bibcode=1977Natur.265..533M |s2cid=4219251 }}</ref><ref>{{cite journal |last1=Ducey |first1=P.K. |last2=Brodie |first2=E.D. |last3=Baness |first3=E.A. |year=1993 |title=Salamander tail autotomy and snake predation: role of antipredator behavior and toxicity for three neotropical ''Bolitoglossa'' (Caudata: Plethodontidae) |journal=Biotropica |volume=25 |issue=3 |pages=344–349 |doi=10.2307/2388793 |jstor=2388793 |bibcode=1993Biotr..25..344D }}</ref><ref>{{cite journal |last1=Marvin |first1=A.G. |year=2010 |title=Effect of caudal autotomy on aquatic and terrestrial locomotor performance in two Desmognathine salamander species |url=http://www.cnah.org/pdf_files/1881.pdf |journal=Copeia |volume=2010 |issue= 3 |pages=468–474 |doi=10.1643/cp-09-188 |s2cid=84584258 |url-status=dead |archive-url=https://web.archive.org/web/20131202222203/http://www.cnah.org/pdf_files/1881.pdf |archive-date=2013-12-02 }}</ref> and [[tuatara]]<ref>Cree, A. (2002). Tuatara. In: Halliday, Tim and Adler, Kraig (eds.), ''The New Encyclopedia Of Reptiles and Amphibians''. Oxford University Press, Oxford, pp. 210–211. {{ISBN |0-19-852507-9}}</ref> when caught by the tail will shed part of it in attempting to escape. In many species the detached tail will continue to wriggle,<ref name="Higham et al">{{Cite journal |last1=Higham |first1=Timothy E. |last2=Russell |first2=Anthony P. |date=2010 |title=Flip, flop and fly: modulated motor control and highly variable movement patterns of autotomized gecko tails |journal=Biology Letters |volume=6 |issue=1 |pages=70–73 |doi=10.1098/rsbl.2009.0577 |pmid=19740891 |pmc=2817253}}</ref> creating a deceptive sense of continued struggle, and distracting the predator's attention from the fleeing prey animal. In addition, many species of lizards, such as ''[[Plestiodon fasciatus]]'', ''[[Cordylosaurus subtessellatus]]'', ''[[Holaspis guentheri]]'', ''[[Phelsuma barbouri]]'', and ''[[Ameiva wetmorei]]'', have elaborately colored blue tails which have been shown to divert predatory attacks toward the tail and away from the body and head.<ref>{{cite journal |last1=Watson |first1=C. M. |last2=Roelke |first2=C. E. |last3=Pasichnyk |first3=P. N. |last4=Cox |first4=C. L. |year=2012 |title=The fitness consequences of the autotomous blue tail in lizards: an empirical test of predator response using clay models |journal=Zoology |volume=115 |issue=5 |pages=339–344 |doi=10.1016/j.zool.2012.04.001 |pmid=22938695 |bibcode=2012Zool..115..339W }}</ref> Depending upon the species, the animal may be able to partially [[Regeneration (biology) |regenerate]] its tail, typically over a period of weeks or months. Though functional, the new tail section often is shorter and will contain [[cartilage]] rather than regenerated vertebrae of [[bone]],<ref>{{Cite news |url=https://www.thehindu.com/sci-tech/the-lost-tail-that-wags-research-tales/article26556212.ece |title=The lost tail that wags research tales |last1=Balasubramanian |first1=D. |date=2019-03-17 |work=The Hindu |access-date=2019-03-25 |language=en-IN |issn=0971-751X}}</ref><ref>{{Cite journal |last1=Bely |first1=Alexandra E. |date=2010-10-01 |title=Evolutionary Loss of Animal Regeneration: Pattern and Process |url=https://academic.oup.com/icb/article/50/4/515/653177 |journal=Integrative and Comparative Biology |language=en |volume=50 |issue=4 |pages=515–527 |doi=10.1093/icb/icq118 |pmid=21558220 |issn=1540-7063 |doi-access=free}}</ref> and in color and texture the [[skin]] of the regenerated organ generally differs distinctly from its original appearance. However, some salamanders can regenerate a morphologically complete and identical tail.<ref>{{Cite journal |last1=Scadding |first1=S.R. |date=1977 |title=Phylogenic Distribution of Limb Regeneration Capacity in Adult Amphibia |journal=Journal of Experimental Zoology |volume=202 |issue=1 |pages=57–67 |doi=10.1002/jez.1402020108|bibcode=1977JEZ...202...57S }}</ref> Some reptiles, such as the [[Western fence lizard]], develop split or branched tails after autotomy.<ref>{{Cite journal |last1=Baum |first1=Timothy J. |last2=Kaiser |first2=Hinrich |date=2024-07-06 |title=Tail furcations in lizards: a revised summary and the second report of tail duplication in the Western Fence Lizard, Sceloporus occidentalis Baird & Girard, 1852 |url=https://www.biotaxa.org/hn/article/view/85433 |journal=Herpetology Notes |volume=17 |pages=459–475 |issn=2071-5773}}</ref>
====Mechanism====
The technical term for this ability to drop the tail is 'caudal autotomy'. In most lizards that sacrifice the tail in this manner, breakage occurs only when the tail is grasped with sufficient force, but some animals, such as some species of geckos, can perform true autotomy, throwing off the tail when sufficiently stressed, such as when attacked by ants.<ref name= "Wrose">Rose, Walter; The Reptiles and Amphibians of Southern Africa; Pub: Maskew Miller, 1950</ref>
Caudal autotomy in lizards takes two forms. In the first form, called intervertebral autotomy, the tail breaks between the [[vertebra]]e. The second form of caudal autotomy is intravertebral autotomy, in which there are zones of weakness, fracture planes across each vertebra in the mid-part of the tail. In this second type of autotomy the lizard contracts a muscle to fracture a vertebra, rather than break the tail between two vertebrae.<ref name=":1">{{cite journal |last2=Fleming |first2=P.A. |year=2009 |title=To cut a long tail short: a review of lizard caudal autotomy studies carried out over the last 20 years |url=http://ftp.eebweb.arizona.edu/courses/Ecol483_583/Bateman%20and%20Fleming%202009.pdf |journal=Journal of Zoology |volume=277 |pages=1–14 |doi=10.1111/j.1469-7998.2008.00484.x |last1=Bateman |first1=P.W.}}</ref> [[Sphincter]] muscles in the tail then contract around the [[caudal artery]] to minimize bleeding.<ref>{{Cite journal |last1=Gilbert |first1=Emily A. B. |last2=Payne |first2=Samantha L. |last3=Vickaryous |first3=Matthew K. |date=November 2013 |title=The Anatomy and Histology of Caudal Autotomy and Regeneration in Lizards |journal=Physiological and Biochemical Zoology |volume=86 |issue=6 |pages=631–644 |doi=10.1086/673889 |pmid=24241061 |s2cid=8962045 |issn=1522-2152}}</ref> Another adaptation associated with intravertebral autotomy is that skin flaps fold over the wound at the site of autotomy to readily seal the wound, which can minimize infection at the autotomy site.<ref>{{cite journal |last1=Gilbert |first1=E. A. B. |last2=Payne |first2=S. L. |last3=Vickaryous |first3=M. K. |year=2013 |title=The anatomy and histology of caudal autotomy and regeneration in lizards |journal=Physiological and Biochemical Zoology |volume=86 |issue=6 |pages=631–644 |doi=10.1086/673889 |pmid=24241061 |s2cid=8962045 }}</ref> Caudal autotomy is prevalent among lizards; it has been recorded in 13 of approximately 20 families.<ref>{{Cite journal |last1=Clause |first1=Amanda R. |last2=Capaldi |first2=Elizabeth A. |date=2006-12-01 |title=Caudal autotomy and regeneration in lizards |journal=Journal of Experimental Zoology Part A: Comparative Experimental Biology |volume=305A |issue=12 |pages=965–973 |doi=10.1002/jez.a.346 |pmid=17068798 |issn=1552-499X|doi-access=free |bibcode=2006JEZA..305..965C }}</ref>
====Effectiveness and costs====
Caudal autotomy is present as an anti-predator tactic but is also present in species that have high rates of intraspecific competition and aggression. The ''[[Agama agama]]'' lizard fights by using its tail as a whip against other conspecifics. It can autotomize its tail but this is met with a social cost - tail loss decreases social standing and mating ability. For example, ''[[Uta stansburiana]]'' suffers reduced social status following caudal autotomy, while ''[[Iberolacerta monticola]]'' experiences reduced mating success. Among ''[[Coleonyx brevis]]'', smaller eggs or no eggs at all are produced after the tail is lost.<ref name=VittCaldwell>{{cite book |title=Herpetology: An Introductory Biology of Amphibians and Reptiles |edition=4th |first1=Laurie J. |last1=Vitt |first2=Janalee P. |last2=Caldwell |publisher=Academic Press |year=2014 |pages=340}}</ref> However, the regenerated tail in ''[[Agama agama]]'' takes on a new club-like shape providing the male with a better fighting weapon, such that autotomy and regeneration work together to increase the lizard's ability to survive and reproduce.<ref>{{Cite journal |last1=Gans |first1=Carl |last2=Harris |first2=Vernon A. |date=1964-09-10 |title=The Anatomy of the Rainbow Lizard Agama agama L. |journal=Copeia |volume=1964 |issue=3 |pages=597 |doi=10.2307/1441541 |issn=0045-8511 |jstor=1441541}}</ref><ref>{{Cite journal |last1=Arnold |first1=E.N. |date=February 1984 |title=Evolutionary aspects of tail shedding in lizards and their relatives |journal=Journal of Natural History |volume=18 |issue=1 |pages=127–169 |doi=10.1080/00222938400770131 |bibcode=1984JNatH..18..127A |issn=0022-2933}}</ref><ref>{{Cite journal |last1=Bateman |first1=P. W. |last2=Fleming |first2=P. A. |s2cid=43627684 |date=January 2009 |title=To cut a long tail short: a review of lizard caudal autotomy studies carried out over the last 20 years |journal=Journal of Zoology |volume=277 |issue=1 |pages=1–14 |doi=10.1111/j.1469-7998.2008.00484.x |issn=0952-8369}}</ref> There are also examples in which salamanders will attack the tails of conspecifics in order to establish social dominance and decrease the fitness of competitors.<ref>{{cite journal |last1=Jaeger |first1=R. G. |year=1981 |title=Dear enemy recognition and the costs of aggression between salamanders |journal=American Naturalist |volume=117 |issue=6 |pages=962–974 |doi=10.1086/283780 |s2cid=83564728 }}</ref>
Despite this mechanism's effectiveness, it is costly, and is employed only after other defenses have failed.<ref name=":2">{{Cite journal |last1=Arnold |first1=E. N. |date=1984-02-01 |title=Evolutionary aspects of tail shedding in lizards and their relatives |journal=Journal of Natural History |volume=18 |issue=1 |pages=127–169 |doi=10.1080/00222938400770131 |bibcode=1984JNatH..18..127A |issn=0022-2933}}</ref><ref name=":3">{{Cite journal |last1=Brock |first1=Kinsey M. |last2=Bednekoff |first2=Peter A. |last3=Pafilis |first3=Panayiotis |last4=Foufopoulos |first4=Johannes |date=2015-01-01 |title=Evolution of antipredator behavior in an island lizard species, Podarcis erhardii (Reptilia: Lacertidae): The sum of all fears? |journal=Evolution |volume=69 |issue=1 |pages=216–231 |doi=10.1111/evo.12555 |issn=1558-5646 |pmid=25346210 |url=https://deepblue.lib.umich.edu/bitstream/2027.42/110598/1/evo12555.pdf |hdl=2027.42/110598 |s2cid=6203357 |hdl-access=free}}</ref> One cost is to the immune system: tail loss results in a weakened immune system which allows for mites and other harmful organisms to have a larger negative impact on individuals and reduce their health and lifespan.<ref>{{Cite journal |last1=Argaez |first1=Víctor |last2=Solano-Zavaleta |first2=Israel |last3=Zúñiga-Vega |first3=J. Jaime |date=2018-04-24 |title=Another potential cost of tail autotomy: tail loss may result in high ectoparasite loads in Sceloporus lizards |journal=Amphibia-Reptilia |volume=39 |issue=2 |pages=191–202 |doi=10.1163/15685381-17000156 |s2cid=90793506 |issn=0173-5373}}</ref> Since the tail plays a significant role in locomotion and energy storage of fat deposits,<ref name=":1" /><ref name=":3" /> it is too valuable to be dropped haphazardly. Many species have evolved specific behaviors after autotomy, such as decreased activity, to compensate for negative consequences such as depleted energy resources.<ref name="Cooper 2003">{{cite journal |last1=Cooper |first1=W.E. |year=2003 |title=Shifted balance of risk and cost after autotomy affects use of cover, escape, activity, and foraging in the Keeled Earless Lizard (''Holbrookia propinqua'') |journal=Behavioral Ecology and Sociobiology |volume=54 |issue=2 |pages=179–187 |jstor=25063251 |doi=10.1007/s00265-003-0619-y |bibcode=2003BEcoS..54..179C |s2cid=26292254 }}</ref> Some such lizards, in which the tail is a major storage organ for accumulating reserves, will return to a dropped tail after the threat has passed, and will eat it to recover part of the sacrificed supplies.<ref>{{cite journal |year=1971 |title=Strategy of Tail-Autotomy in Ground Skink, ''Lygosoma laterale'' |journal=Journal of Experimental Zoology |volume=176 |issue=3 |pages=295–302 |doi=10.1002/jez.1401760305 |pmid=5548871 |last1=Clark |first1=DR|bibcode=1971JEZ...176..295C }}</ref> Conversely, some species have been observed to attack rivals and grab their tails, which they eat after their opponents flee.<ref>Durrell, Gerald. My Family and Other Animals. Penguin Books 1987. {{ISBN |978-0140103113}}</ref>
There are also adaptations that help mitigate the cost of autotomy, as seen in the highly toxic salamander, ''[[Bolitoglossa rostrata]]'', in which the individual will delay autotomy until the predator moves its jaws up the tail or holds on for a long time, allowing the salamander to retain its tail when toxicity alone can ward off predators.<ref>{{cite journal |last1=Ducey |first1=P. K. |last2=Brodie |first2=E. D. |last3=Baness |first3=E. A. |year=1993 |title=Salamander tail autotomy and snake predation - role of antipredator behavior and toxicity for 3 neotropical ''Bolitoglossa'' (Caudata, Plethodontidae) |journal=Biotropica |volume=25 |issue=3 |pages=344–349 |doi=10.2307/2388793 |jstor=2388793 |bibcode=1993Biotr..25..344D }}</ref> Regeneration is one of the highest priorities after autotomy, in order to optimize locomotor performance and recoup reproductive fitness. While regenerating their tails, caudal autotomy is restored at an energetic cost that often hinders body growth or intraspecies interactions.<ref name=":2" /><ref name=":4">{{Cite journal |last1=Bely |first1=Alexandra E. |last2=Nyberg |first2=Kevin G. |date=2010-03-01 |title=Evolution of animal regeneration: re-emergence of a field |journal=Trends in Ecology & Evolution |volume=25 |issue=3 |pages=161–170 |doi=10.1016/j.tree.2009.08.005 |pmid=19800144|bibcode=2010TEcoE..25..161B }}</ref>
==== Autotomy in the fossil record ====
Fossils of reptiles possessing the ability to autotomize that are not within the lizard family have been found that date back to the [[Pennsylvanian (geology) |Late Carboniferous]] and [[Cisuralian |Early Permian]], belonging to the groups [[Recumbirostra]] and [[Captorhinidae]].<ref>{{Cite journal |last1=van der Vos |first1=W. |last2=Witzmann |first2=F. |last3=Fröbisch |first3=N. B. |date=2017-11-16 |title=Tail regeneration in the Paleozoic tetrapod Microbrachis pelikani and comparison with extant salamanders and squamates |journal=Journal of Zoology |volume=304 |issue=1 |pages=34–44 |doi=10.1111/jzo.12516 |issn=0952-8369}}</ref><ref>{{Cite journal |last1=LeBlanc |first1=A. R. H. |last2=MacDougall |first2=M. J. |last3=Haridy |first3=Y. |last4=Scott |first4=D. |last5=Reisz |first5=R. R. |date=2018-03-05 |title=Caudal autotomy as anti-predatory behaviour in Palaeozoic reptiles |journal=Scientific Reports |volume=8 |issue=1 |pages=3328 |doi=10.1038/s41598-018-21526-3 |pmid=29507301 |pmc=5838224 |bibcode=2018NatSR...8.3328L |issn=2045-2322}}</ref> Two [[Squamata |squamate]] species from the Jurassic period, ''[[Eichstaettisaurus |Eichstaettisaurus schroederi]]'' and ''[[Ardeosaurus |Ardeosaurus digitatellus]]'', were identified as having intervertebral autotomy planes, and these species were placed in the squamate taxonomy as being an ancestor of current existing geckos.<ref>{{Cite journal |last1=Simões |first1=Tiago R. |last2=Caldwell |first2=Michael W. |last3=Nydam |first3=Randall L. |last4=Jiménez-Huidobro |first4=Paulina |date=September 2016 |title=Osteology, phylogeny, and functional morphology of two Jurassic lizard species and the early evolution of scansoriality in geckoes |journal=Zoological Journal of the Linnean Society |doi=10.1111/zoj.12487 |issn=0024-4082}}</ref>
===Mammals===
At least two species of African [[spiny mouse|spiny mice]], ''[[Acomys kempi]]'' and ''[[Acomys percivali]]'', are capable of autotomic release of skin, e.g. upon being captured by a predator. They are the first mammals known to do so.<ref name="seifert2012">{{Cite journal |last1 = Seifert |first1 = A. W. |last2 = Kiama |first2 = S. G. |last3 = Seifert |first3 = M. G. |last4 = Goheen |first4 = J. R. |last5 = Palmer |first5 = T. M. |last6 = Maden |first6 = M. |doi = 10.1038/nature11499 |title = Skin shedding and tissue regeneration in African spiny mice (''Acomys'') |journal = Nature |volume = 489 |issue = 7417 |pages = 561–565 |year = 2012 |pmid =  23018966|pmc =3480082 |bibcode = 2012Natur.489..561S }}</ref> They can completely regenerate the autotomically released or otherwise damaged skin tissue — regrowing hair follicles, skin, sweat glands, fur and cartilage with little or no scarring.<ref>{{cite news |first1=Zoe |last1=Cormier |url= http://www.nature.com/news/african-spiny-mice-can-regrow-lost-skin-1.11488#/ref-link-1|title= African spiny mice can regrow lost skin |publisher= [[Nature (journal)|Nature]] |date=2012-09-26 |access-date= 2012-09-27}}</ref> These and other species of [[rodent]] are also known to exhibit a so-called "false caudal autotomy," whereby the skin on the tail slides off with minimal force, leaving only the bare vertebral structure.<ref name="ShargalRath-WolfsonKronfeld1999">{{cite journal |last1 = Shargal |first1 = Eyal |last2 = Rath-Wolfson |first2 = Lea |last3 = Kronfeld |first3 = Noga |last4 = Dayan |first4 = Tamar |title = Ecological and histological aspects of tail loss in spiny mice (Rodentia: ''Muridae'', ''Acomys'') with a review of its occurrence in rodents |journal = Journal of Zoology |date = October 1999 |volume = 249 |issue = 2 |pages = 187–193 |issn = 0952-8369 |eissn = 1469-7998 |doi = 10.1111/j.1469-7998.1999.tb00757.x |pmid = |url = }}</ref> Examples of species possessing this ability are [[cotton rat]]s (''Sigmodon hispidus''), [[eastern chipmunk]]s (''Tamias striatus''), and [[common degu|degu]] (''Octodon degus'').<ref name="HosotaniNakamuraIchii2021">{{cite journal |last1 = Hosotani |first1 = Marina |last2 = Nakamura |first2 = Teppei |last3 = Ichii |first3 = Osamu |last4 = Irie |first4 = Takao |last5 = Sunden |first5 = Yuji |last6 = Elewa |first6 = Yaser Hosny Ali |last7 = Watanabe |first7 = Takafumi |last8 = Ueda |first8 = Hiromi |last9 = Mishima |first9 = Takashi |last10 = Kon |first10 = Yasuhiro |title = Unique histological features of the tail skin of cotton rat (Sigmodon hispidus) related to caudal autotomy |journal = Biology Open |date = 15 February 2021 |volume = 10 |issue = 2 |eissn = 2046-6390 |doi = 10.1242/bio.058230 |pmid = 33563609 |pmc = 7904004 |url = }}</ref>
==Invertebrates==
Over 200 species of invertebrates are capable of using autotomy as an avoidance or protective behaviour.<ref name=":4" /><ref name="Fleming et al., 2007">{{cite journal |last1 = Fleming |first1 = P.A. |last2 = Muller |first2 = D. |last3 = Bateman |first3 = P.W. |year = 2007 |title = Leave it all behind: a taxonomic perspective of autotomy in invertebrates |journal = Biological Reviews |volume = 82 |issue = 3|pages = 481–510 |doi = 10.1111/j.1469-185X.2007.00020.x |pmid = 17624964 |s2cid = 20401676 }}</ref> These animals can voluntarily shed appendages when necessary for survival. Autotomy can occur in response to chemical, thermal and electrical stimulation, but is perhaps most frequently a response to mechanical stimulation during capture by a predator. Autotomy serves either to improve the chances of escape or to reduce further damage occurring to the remainder of the animal such as the spread of a chemical toxin after being stung.
===Molluscs===
Autotomy occurs in some species of octopus for survival and for reproduction: the specialized reproductive arm (the [[hectocotylus]]) detaches from the male during mating and remains within the female's [[mantle (mollusc)|mantle]] cavity.
Species of (land) slugs in the genus ''[[Prophysaon]]'' can self-amputate a portion of their tail.<ref name="Donnel et al., 2009">McDonnel, R.J., Paine, T.D. and Gormally, M.J., (2009). [http://anrcatalog.ucdavis.edu/Items/8336.aspx Slugs: A Guide to the Invasive and Native Fauna of California] {{Web archive |url=https://web.archive.org/web/20110704191903/http://anrcatalog.ucdavis.edu/Items/8336.aspx |date=2011-07-04 }}. 21 pp., {{ISBN|978-1-60107-564-2}}, page 9.</ref> There is known autotomy of the tail of sea snail ''[[Oxynoe panamensis]]'' under persistent mechanical irritation.<ref name="Lewin 1970">{{cite journal |last1 = Lewin |first1 = R. A. |year = 1970 |title = Toxin secretion and tail autotomy by irritated ''Oxynoe panamensis'' (Opisthobranchiata: Sacoglossa)". |url = https://scholarspace.manoa.hawaii.edu/bitstream/10125/4096/1/v24n3-356-358.pdf |journal = [[Pacific Science]] |volume = 24 |pages = 356–358 }}</ref>
Some [[sea slugs]] exhibit autotomy. Both ''[[Discodoris lilacina]]'' and ''[[Berthella martensi]]'' will often drop their entire mantle skirt when handled, leading to [[Discodoris lilacina]] also being called ''Discodoris fragilis''. The members of ''[[Phyllodesmium]]'' will drop a large number of their [[cerata]] each, on the tip having a large sticky gland that secretes a sticky substance.<ref>{{cite web |title=Autotomy |url=http://www.seaslugforum.net/factsheet.cfm?base=defauto |work=The Sea Slug Forum |author=Rudman, W.B. |date=October 14, 1998 |url-status=dead |archive-url=https://web.archive.org/web/20100615000625/http://seaslugforum.net/factsheet.cfm?base=defauto |archive-date=2010-06-15 }}</ref> Young specimens of two [[Elysia (gastropod)|Elysia]] species, ''[[Elysia atroviridis|E. atroviridis]]'' and ''[[Elysia marginata|E. marginata]]'', can regenerate their whole [[Parasitism|parasitised]] body from their head which may have evolved as a defence-mechanism against internal parasites. These sea slugs are known to be able to conduct [[photosynthesis]] via incorporating chloroplasts from [[alga]]l food into their cells which they use to survive after separation from their digestive system.<ref>{{cite web |url=https://www.livescience.com/decapitated-sea-slugs-regrow-entire-body.html |title=This sea slug can chop off its head and grow an entire new body, twice |last=Baker |first=Harry |date=2021-03-08 |website=[[Live Science]] |access-date=2021-03-09 }}</ref><ref>{{cite journal |last1=Mitoh |first1=Sayaka |last2=Yusa |first2=Yoichi |title=Extreme autotomy and whole-body regeneration in photosynthetic sea slugs |journal=Current Biology |date=8 March 2021 |volume=31 |issue=5 |pages=R233–R234 |doi=10.1016/j.cub.2021.01.014 |pmid=33689716 |s2cid=232145105 |language=English |issn=0960-9822 |doi-access=free |bibcode=2021CBio...31.R233M |hdl=10935/5590 |hdl-access=free }}</ref>
===Crustaceans===
Autotomic [[Florida stone crab|stone crabs]] are used as a self-replenishing source of food by humans, particularly in Florida. Harvesting is accomplished by removing one or both claws from the live animal and returning it to the ocean where it can regrow the lost limb(s).<ref name="NOAA.gov FishWatch">''[http://www.nmfs.noaa.gov/fishwatch/species/stone_crab.htm Gulf and Florida Stone Crabs]''</ref>  However, under experimental conditions, but using commercially accepted techniques, 47% of stone crabs that had both claws removed died after declawing, and 28% of single claw amputees died; 76% of the casualties died within 24 hours of declawing.<ref name="Davis et al., (1978)">{{cite book |author1=Gary E. Davis |author2=Douglas S. Baughman |author3=James D. Chapman |author4=Donald MacArthur |author5=Alan C. Pierce |year=1978 |url=http://ufdcimages.uflib.ufl.edu/FI/44/44/00/02/00001/FI44440002.pdf |title=Mortality associated with declawing stone crabs, ''Menippe mercenaria'' |publisher=US National Park Service |id=Report T-522}}</ref> The occurrence of regenerated claws in the fishery harvest is low; one study indicates less than 10%,<ref name="Davis et al., (1978)" /> and a more recent study indicates only 13% have regenerated claws.<ref name="Florida_2006">{{cite web |url=http://myfwc.com/research/saltwater/stock-assessments/invertebrate/2006-stone-crab/ |title=The 2006 Stock Assessment Update for the Stone Crab, ''Menippe'' spp., Fishery in Florida |publisher=Florida Fish and Wildlife Conservation Commission |access-date=23 September 2012}}</ref>
(See [[Declawing of crabs]])
Post-harvest leg autotomy can be problematic in some crab and lobster fisheries, and often occurs if these crustaceans are exposed to freshwater or hypersaline water in the form of dried salt on sorting trays.<ref name="Davidson and Hosking 2004">Davidson, G.W. and Hosking, W.W. (2004) ''[http://frdc.com.au/research/Documents/Final_reports/2000-251-DLD.PDF Development of a Method for Alleviating Leg Loss During Post-harvest Handling of Rock Lobsters] {{Webarchive|url=https://web.archive.org/web/20160305064527/http://frdc.com.au/research/Documents/Final_reports/2000-251-DLD.PDF |date=2016-03-05 }}''. 104 pp.</ref> The autotomy reflex in crustaceans has been proposed as an example of natural behaviour that raises questions concerning assertions on whether crustaceans can "feel pain", which may be based on definitions of "pain" that are flawed for lack of any falsifiable test, either to establish or deny the meaningfulness of the concept in this context.<ref name="Rose et al. 2012">{{cite journal |last1 = Rose |first1 = JD |last2 = Arlinghaus |first2 = R |last3 = Cooke |first3 = SJ |last4 = Diggles |first4 = BK |last5 = Sawynok |first5 = W |last6 = Stevens |first6 = ED|author-link7=Clive Wynne |last7 = Wynne |first7 = CDL |s2cid = 43948913 |year = 2012 |title = Can fish really feel pain? |journal = Fish and Fisheries |volume = 15|pages = 97–133|doi = 10.1111/faf.12010 }}</ref>
===Spiders===
[[File:Fishing spider autotomy.jpg|thumb|A [[fishing spider]] with two limbs missing]]
Under natural conditions, orb-weaving spiders ([[Argiope (spider)|''Argiope'']] spp.) undergo autotomy if they are stung in a leg by wasps or bees.<ref>{{Cite journal|last1=Eisner|first1=T.|last2=Camazine|first2=S.|date=1983-06-01|title=Spider leg autotomy induced by prey venom injection: An adaptive response to "pain"?|journal=Proceedings of the National Academy of Sciences|volume=80|issue=11|pages=3382–3385|doi=10.1073/pnas.80.11.3382|pmid=16593325|pmc=394047|bibcode=1983PNAS...80.3382E|issn=0027-8424|doi-access=free}}</ref> Under experimental conditions, when spiders are injected in the leg with bee or wasp venom, they shed this appendage. But, if they are injected with only saline, they rarely autotomize the leg, indicating it is not the physical injection or the ingress of fluid that necessarily causes autotomy. In addition, spiders injected with venom components which cause injected humans to report pain ([[serotonin]], [[histamine]], [[phospholipase A2]] and [[melittin]]) autotomize the leg, but if the injections contain venom components which do not cause pain to humans, autotomy does not occur.<ref name="Eisner and Camazine, 1983">{{cite journal |last1 = Eisner |first1 = T. |last2 = Camazine |first2 = S. |year = 1983 |title = Spider leg autotomy induced by prey venom injection: an adaptive response to 'pain'? |journal = Proceedings of the National Academy of Sciences of the United States of America |volume = 80 |issue = 11|pages = 3382–3385 |doi=10.1073/pnas.80.11.3382|pmid = 16593325 |pmc = 394047 |bibcode = 1983PNAS...80.3382E |doi-access = free }}</ref>
In spiders, autotomy can also play a role in mating. The male of ''[[Nephilengys malabarensis]]'' from Southeast Asia breaks off his [[pedipalp]] when transferring sperm and plugs the female's genital opening, after which the palp keeps pumping. This helps the male to avoid [[sexual cannibalism]] and if escape succeeds, the male goes on to guard the female from competitors.<ref>{{cite news |last=Yong |first=Ed |date=2012-02-01 |title=Spiders dodge cannibalism through remote copulation |work=[[Nature (journal)|Nature News]] |doi=10.1038/nature.2012.9939}}</ref>
===Bees and wasps===
Sometimes when honey bees (genus ''[[Apis (genus)|Apis]]'') [[sting (biology)|sting]] a victim, the barbed stinger remains embedded. As the bee tears itself loose, the stinger takes with it the entire distal segment of the bee's abdomen, along with a nerve [[ganglion]], various muscles, a [[venom sac]], and the end of the bee's digestive tract.<ref>Snodgrass, R.E. (1956). ''The Anatomy of the Honey Bee.'' Ithaca, New York: Cornell University Press.</ref><ref>{{cite journal|url=http://www.beekeeping.com/articles/us/bee_stings.htm|title=Removing bee stings|author =Visscher, P.K.|author2 =Vetter, R.S.|author3 =Camazine, S.|journal=Lancet|volume=348|issue=9023|pages=301–2|name-list-style=amp|access-date=April 23, 2013|pmid=8709689|year=1996|doi=10.1016/s0140-6736(96)01367-0|s2cid=43667134}}</ref>
This massive abdominal rupture kills the bee.<ref>{{cite web|url=http://earthsky.org/earth/why-do-bees-die-after-they-sting-you|title=Why do honeybees die after they sting you?|date=23 June 2011|access-date=April 23, 2013}}</ref> Although it is widely believed that a [[worker bee|worker]] honey bee can sting only once, this is a partial misconception: although the [[stinger]] is barbed so that it lodges in the victim's [[skin]], tearing loose from the bee's [[abdomen]] and leading to its death, this only happens if the skin of the victim is sufficiently thick, such as a mammal's.<ref name="how bees work">[http://science.howstuffworks.com/zoology/insects-arachnids/bee2.htm How Bees Work] – ''howstuffworks.com.'' Retrieved 23 April 2013.</ref> The sting of a queen honey bee has no barbs, however, and does not autotomize.<ref>{{cite web|url=http://www.asktheexterminator.com/bees/Bee_Stings.shtml|title=Bee stings|author=Steinau, R.|year=2011|access-date=April 23, 2013|archive-date=December 5, 2016|archive-url=https://web.archive.org/web/20161205225014/http://asktheexterminator.com/bees/Bee_Stings.shtml/|url-status=dead}}</ref> All species of true honey bees have this form of stinger autotomy. No other stinging insect have the sting apparatus modified this way, though some may have barbed stings.  Two wasp species that use sting autotomy as a defense mechanism are ''[[Polybia rejecta]] ''and ''[[Synoeca surinama]].''<ref>{{Cite journal|title = Sting Autotomy, a defensive mechanism in certain social Hymenoptera|last1 = Hermann|first1 = Henry|date = 1971|journal = Insectes Sociaux|doi =10.1007/bf02223116 |volume=18 |issue = 2|pages=111–120|s2cid = 42293043}}</ref>''  ''
The endophallus and cornua portions of the [[Drone (bee)#Mating and the drone reproductive organ|genitalia of male honey bees]] ([[Drone (bee)|drones]]) also autotomize during copulation, and form a [[mating plug]], which must be removed by the genitalia of subsequent drones if they are also to mate with the same queen.<ref>{{cite journal |last1 = Collins |first1 = A.M. |last2 = Caperna |first2 = T.J. |last3 = Williams |first3 = V. |last4 = Garrett |first4 = W.M. |last5 = Evans |first5 = J.D. |year = 2006 |title = Proteomic analyses of male contributions to honey bee sperm storage and mating |journal = Insect Molecular Biology |volume = 15 |issue = 5|pages = 541–549 |doi=10.1111/j.1365-2583.2006.00674.x|pmid = 17069630 |pmc = 1847503 }}</ref> The drones die within minutes of mating.
===Echinoderms===
[[Evisceration (autotomy)|Evisceration]], the ejection of the internal organs of [[Holothuroidea|sea cucumbers]] when stressed, is also a form of autotomy, and they regenerate the organ(s) lost.<ref>{{cite journal |title=Biomechanics of adhesion in sea cucumber cuvierian tubules (Echinodermata, Holothuroidea) |journal=Integrative and Comparative Biology |date=2002-12-01 |author1=Patrick Flammang |author2=Jerome Ribesse |author3=Michel Jangoux |doi=10.1093/icb/42.6.1107 |pmid=21680394 |volume=42 |issue=6 |pages=1107–15|doi-access=free }}</ref>
Some [[starfish]] shed their arms.<ref name=Byrne>{{cite book|author1=O'Hara, Timothy |author2=Byrne, Maria |title=Australian Echinoderms: Biology, Ecology and Evolution |url=https://books.google.com/books?id=EtkqDwAAQBAJ&pg=PA282 |year=2017 |publisher=Csiro Publishing |isbn=978-1-4863-0763-0 |pages=282–285}}</ref> The arm itself may even be able to regrow into a new starfish.<ref name=Edmondson1935>{{cite journal|last1=Edmondson|first1=C. H. |title=Autotomy and regeneration of Hawaiian starfishes |journal=Bishop Museum Occasional Papers |year=1935 |volume=11 |issue=8 |pages=3–20 |url=http://hbs.bishopmuseum.org/pubs-online/pdf/op11-8.pdf}}</ref>
==See also==
* [[Ainhum]]
* [[Anti-predator adaptation]]
* [[Autoamputation]]
* [[Evisceration (autotomy)]]
* [[Amputation#Self-amputation|Self-amputation]]
==References==
{{reflist|28em}}
==Further reading==
* {{cite journal |last1 = Pakarinen |first1 = E |year = 1994 |title = Autotomy in arionid and limacid slugs |url = http://mollus.oxfordjournals.org/cgi/content/abstract/60/1/19 |journal = Journal of Molluscan Studies |volume = 60 |issue = 1|pages = 19–23 |doi=10.1093/mollus/60.1.19|ref=none}}
* [http://www.seaslugforum.net/find/defauto Autotomy in sea gastropod]
== External links ==
* {{wiktionary-inline}}
*[https://www.journals.uchicago.edu/journals/pbz/caudal-autonomy-collection ''Physiological and Biochemical Zoology'' Focused Collection: Caudal Autotomy and Regeneration in Lizards: Patterns, Costs, and Benefits]
{{Ethology}}
[[Category:Animal anatomy]]
[[Category:Antipredator adaptations]]
[[Category:Types of amputation]]
[[Category:Ethology]]
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