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Evisceration is a method of autotomy involving the ejection of internal organs used by animals as a defensive strategy. Sea cucumbers (Holothuroidea) eject parts of the gut in order to scare and defend against potential predators such as crabs and fish. The organs are regenerated in a few days by cells in the interior of the sea cucumber.〔(【引用サイトリンク】title=Learn about sea cucumbers; Defences and predators )〕 ==Description== When stressed, the sea cucumber faces away from the attacker and contracts its body wall muscles sharply. This causes the wall of the cloaca to tear and the anus to gape. The evisceration process in ''Eupentacta quinquesemita'' proceeds as follows: (taken from 〔〔Byrne, M., (1985). Evisceration behaviour and the seasonal incidence of evisceration in the Holothurian ''Eupentacta quinquestemita'' (Selenka). Ophelia, 24: 75-90〕〔Byrne, M., (2001). The morphology of autotomy structures in the sea cucumber ''Eupentacta quinquesemita'' before and during evisceration" ''Journal of Experimental Biology'' 204: 849-863 ()〕) :1. Three main structures weaken over a period of about 1-3 minutes, become soft and transparent, and eventually separate from their attachments. These are the basal part of the tentacles, the attachment points of the introvert retractor muscles to the longitudinal muscles (there are 10 of these), and the junction of intestine and cloaca. The softening is a state-transformation of the collagen components in the tissue. :2. Parts eviscerated include the gut, associated heamal vessels, tentacles, and introvert (the dexterous anterior extensible portion of the body wall). The gut tears away from the mesenteries that suspend it within the coelomic cavity. :3. Most of the gonad stays behind. Only strands of gonad tangled in the gut are eviscerated. The paired respiratory trees and cloaca also remain (although they may be expelled in other species) :4. The introvert changes from being firm and opaque to being soft and translucent. The body-wall muscles contract and the increased pressure forces coelomic fluid and viscera into the introvert. It enlarges like a balloon and soon ruptures, expelling the fluid and viscera. :5. This takes about 20 minutes, with final detachment of the tentacles and introvert sometimes taking as long as 12 hours. :6. The anterior rupture seals, at first by muscular contraction and then by healing as a plug of connective-tissue. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Evisceration (autotomy)」の詳細全文を読む スポンサード リンク
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