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Eyestalk ablation is the removal of one (unilateral) or both (bilateral) eyestalks from a crustacean. It is routinely practiced on female shrimps (or prawns) in almost every marine shrimp maturation or reproduction facility in the world, both research and commercial. The aim of ablation under these circumstances is to stimulate the female shrimp to develop mature ovaries and spawn.〔http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0024427〕 Most captive conditions for shrimp cause inhibitions in females that prevent them from developing mature ovaries. Even in conditions where a given species will develop ovaries and spawn in captivity, use of eyestalk ablation increases total egg production and increases the percentage of females in a given population that will participate in reproduction. Once females have been subjected to eyestalk ablation, complete ovarian development often ensues within as little as 3 to 10 days. The most commonly accepted theory of why eye ablation reduces this inhibition is that a gonad inhibitory hormone (GIH) is produced in the neurosecretory complexes in the eyestalk. This hormone occurs in nature in the non-breeding season and is absent or present only in low concentrations during the breeding season. The reluctance of most shrimp to routinely develop mature ovaries in captivity is a function of elevated levels of GIH, and eyestalk ablation lowers the high haemolymph titer of GIH. The effect of eyestalk ablation is not on a single hormone such as GIH, but rather affects several physiological processes. Besides the GIH evidence, another hypothesis suggests that eyestalk ablation also reduces light intensity and thereby induces ovarian maturation. In the banana prawn (''Fenneropenaeus merguiensis'', syn. ''Penaeus merguiensis''), dim light favours ovarian maturation and spawning. The exact mechanism of eyestalk ablation on the ovarian maturation is not conclusive.〔 It has been reported that in the tiger prawn (''Penaeus monodon''), the eyestalks fully regenerate in less than 6 months. ==Effects== There are several direct and indirect effects of eye ablation in female shrimps, including;〔(【引用サイトリンク】title=Unilateral eye ablation )〕 *increases total egg production by producing more frequent spawnings, but not larger spawns *moult cycle duration is shorter *increases mortality *deteriorates female condition *in some instances, produces lower hatch rate of eggs *leads to changes in ovarian colour *increases energetic demands *leads to eventual loss in egg quality 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「Eyestalk ablation」の詳細全文を読む スポンサード リンク
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