裸海蝶（學名：Clione limacina），俗稱海天使，生活在北冰洋及南冰洋水深350米處。它們最初被描述為翼足目的一種[2]。
亞種
分佈
裸海蝶分佈在寒冷海域：除南極裸海蝶（英语：Clione antarctica）只見於南極海域以外，其餘兩個亞種分佈於由北冰洋至北卡羅萊納州、阿拉斯加、加拿大及北歐的北大西洋[1]及北太平洋[3][4]。裸海蝶有時會在北歐的海岸積聚成群。
型態描述
在北半球的兩個亞種在體長上有分別[3]：在北方棲息的亞種在較冷水溫的環境棲息，成熟時體長約3 cm（1.2英寸），最長可達7～8.5 cm（2.8～3.3英寸）[3][5]。 而在南方棲息的亚种則只長1.2 cm（0.47英寸）[3]。 最長的可達4公分[6]。
這個翼足目物種在神經生物學的範疇曾被深入研究過。
生態
裸海蝶生活在表層帶及中层带[1]。
食性
裸海蝶幾乎只以蟠虎螺（有殼翼足亞目的螔螺屬物種為食，例如：蟠虎螺（Limacina helicina（英语：Limacina helicina））及後彎螔螺（Limacina retroversa（英语：Limacina retroversa））[3][7]。牠們進食的過程有點特別：牠們的口器（buccal apparatus）有三對叫作口錐（buccal cones）的觸手狀部分。牠們利用這些口錐抓緊蟠虎螺的殼。當獵物的殼口面向其齒舌時，裸海蝶會用其幾丁質的鉤捉住獵物，將之從殼中抽出及吞下[8][9]。
根據一份以138隻裸海蝶作研究對象的文獻，這些裸海蝶處於一個沒有成年螔螺屬物種的環境一段時間。當這些裸海蝶被解剖後，當中有24隻的胃裡還殘留有端足類、另外3隻殘留有calanoid（英语：calanoid）[5]。在這段臨時轉變食物環境的情況下，裸海蝶可不進食一段時期而不至於餓死[5]，儘管裸海蝶其實可以在沒有食物的情況下生存達一年之久[10]。在這種特殊的假死狀態下，實驗室內研究個體的其體長也會從原來平均22.4毫米的體長縮減至只有12毫米長[10]。
The earliest 幼体 stages of C. limacina feed on 浮游植物, but from the later laval stage this changes to Limacina.[5] The development of these two species is parallel and small C. limacina feed on Limacina of a similar size, while large C. limacina avoid small Limacina (including its larvae).[5]
Life cycle
In 斯瓦尔巴, the 生物生命週期 of C. limacina appears to be at least 2 years.[3] It is a hermaphrodite and observations suggest this is 雌雄間性.[5] It breeds during the spring and summer, and the eggs are about 0.12 mm（4.7 thou）.[5]
Clione limacina is a prey of planktonic feeders, such as the 鬚鯨小目s,[3] which historically led to sailors naming it "whale-food".[11]
Some fishes are also its predators.[3] For example, the Chum Salmon, 大麻哈鱼, is a major predator of sea angels.[12]
參考文獻
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^ 1.0 1.1 1.2 Gofas, Serge. Clione limacina (Phipps, 1774). World Register of Marine Species. [2018-10-31].
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^ Spitzbergiscbe oder grönlandische Reisebeschreibung [斯皮茨堡及格陵蘭遊記]. : p. 189, p1. P. fig. f. （德语）. 引文格式1维护：冗余文本 (link)
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^ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Böer, M.; Gannefors, C.; Kattner, G.; Graeve, M.; Hop, H.; Falk-Petersen, S. "The Arctic pteropod Clione limacina: seasonal lipid dynamics and life-strategy". Marine Biology. 2005, 147 (3): 707–717. doi:10.1007/s00227-005-1607-8 （英语）.
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^ Mileikovsky S.A. (1970) Breeding and larval distribution of the pteropod Clione limacina in the North Atlantic, Subarctic and North Pacific Oceans. Marine Biology 6(4): 317–334.
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^ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Kallevik, I.H.F. Alternative prey choice in the pteropod Clione limacina (Gastropoda) studied by DNA-based methods (PDF). Biology Field of study - Arctic Marine Ecology and Resource Biology. Bio-3950 (60 ECT). The University Center in Svalbard. 2013 （英语）.
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^ Welch, J. J. "The “Island Rule” and Deep-Sea Gastropods: Re-Examining the Evidence". PLoS ONE. 2010, 5 (1). doi:10.1371/journal.pone.0008776.
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^ Lalli, C. M.; Gilmer, R. W. Pelagic Snails. The biology of holoplanktonic gastropod molluscs.. Stanford, California. (USA): Stanford University Press. 1989: 188 （英语）.
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^ Hermans C. O. & Satterlie R. A. (1992). "Fast-strike feeding behavior in a pteropod mollusk, Clione limacina Phipps". The Biological Bulletin, Marine Biological Laboratory（英语：Marine Biological Laboratory）, 182: 1–7.
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^ Vortsepneva, E.V.; Tzetlin, A.B,. New Data on the Fine Structure of hooks in Clione limacina (Gastropoda, Opistobranchia) and Diversity of the Jaw Apparatus in Gastropods. Zoologicheskii Zhurnal. March 2014, 93 (3): 466–478 [2015-05-01]. doi:10.7868/S0044513414030179 （英语）.
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^ 10.0 10.1 Böer, M.; Graeve, M.; Kattner, G. Exceptional long-term starvation ability and sites of lipid storage of the Arctic pteropod Clione limacina". Polar Biology. 2006, 30 (5): 571–580. doi:10.1007/s00300-006-0214-6 （英语）.
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^ Gosse, Philip Henry. Mollusca. Natural History. Society for Promoting Christian Knowledge. 1854: 72.
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^ Takashi, Makoa; Takashi, Kuwahara; Masanoa, Narita. Carotenoids of Sea Angels Clione limacina and Paedoclione doliiformis from the Perspective of the Food Chain. Marine Drugs. March 2014, 12 (3): 1–11 [22 April 2015]. doi:10.3390/md12031460.
