Clione limacina
Introduction '''''Clione limacina''''', known as the '''naked sea butterfly''', '''sea angel''', and '''common clione''', is a sea angel (pelagic sea slug) found from the surface to greater than  depth. It lives in the Arctic Ocean and cold regions of the North Atlantic Ocean. It was first described by Friderich Martens in 1676 and became the first gymnosomatous (without a shell) "pteropod" to be described.
Subspecies * ''Clione limacina australis'' (Bruguière, 1792)* ''Clione limacina limacina'' (Phipps, 1774)
Distribution ''Clione limacina'' is found in cold waters of the Arctic Ocean and North Atlantic Ocean, ranging south at least to the Sargasso Sea. There are three other species in the genus, which formerly were included in ''C. limacina'' (either as subspecies, variants or subpopulations). These are ''C. elegantissima'' of the cold North Pacific (at least north to the Gulf of Alaska; the Beaufort Sea is inhabited by ''C. limacina''), ''C. okhotensis'' of the Okhotsk Sea (where it overlaps with ''C. elegantissima''), and ''C. antarctica'' of Antarctic waters. ''Clione limacina''
Description There are two subspecies that differentiate in body length. The northern subspecies lives in colder water, matures at  and can reach a size of . This makes it by far the largest sea angel. In comparison, the size of the southern subspecies is , ''C. elegantissima'' is up to , ''C. okhotensis'' up to , and ''C. antarctica'' up to .The neurobiology of this pteropod has been studied in detail.
Ecology ''Clione limacina'' inhabits both the epipelagic and mesopelagic regions of the water column.=== Feeding habits ===Adults feed in a predator-prey relationship almost exclusively on the sea butterflies of the genus ''Limacina'': on ''Limacina helicina'' and on ''Limacina retroversa''. The feeding process of ''Clione limacina'' is somewhat extraordinary. The buccal ("mouth") apparatus consists of three pairs of buccal cones. These tentacles grab the shell of ''Limacina helicina''. When the prey is in the right position, with its shell opening facing the radula of ''Clione limacina'', it then grasps the prey with its chitinous hooks, everted from hook sacs. Then it extracts the body completely out of its shell and swallows it whole.Adult ''Limacina'' are absent for much of the year, leaving ''C. limacina'' without access to their main food source. A study of 138 ''C. limacina'' during a period without adult ''Limacina'' found that the stomachs of 24 contained remains of amphipods and 3 contained remains of calanoids. This temporary prey change may allow them to survive in periods of starvation, although the species can survive for one year without food. Under such exceptional starvation in the laboratory the length of slugs have decreased on average from .The earliest larvae stages of ''C. limacina'' feed on phytoplankton, but from the later laval stage this changes to ''Limacina''. The development of these two species is parallel and small ''C. limacina'' feed on ''Limacina'' of a size, while large ''C. limacina'' avoid small ''Limacina'' (including its larvae).=== Life cycle ===In Svalbard, the life cycle of  ''C. limacina'' appears to be at least 2 years. It is a hermaphrodite and observations suggest this is simultaneous. It breeds during the spring and summer, and the eggs are about . ''Clione limacina'' is a prey of planktonic feeders, such as the baleen whales, which historically led to sailors naming it "whale-food". Some fishes are also its predators. For example, the Chum Salmon, ''Oncorhynchus keta'', is a major predator of sea angels.
Cultural significance While sea angels are relatively obscure in Western countries, they are extremely well-known in Japanese culture. As a result, two creatures from the Pokémon franchise, Manaphy and Phione, are based on the clione.
References This article incorporates CC-BY-SA-3.0 text from the reference
Further reading * http://www.seaslugforum.net/factsheet/cliolima accessed 5 January 2010*  Boas J. E. V. (1888). "Spolia Atlantica. Bidrag til Pteropodernes. Morfologi og Systematik samt til Kundskaben om deres geografiski Udbredelse". ''Det Kongelige Danske videnskabernes selskabs skrifter''. København, serie 6, number 4: 1–231.Pages  162–166.Plate 7, figure 101–103. * Abbott, R.T. (1974). ''American Seashells''. 2nd ed. Van Nostrand Reinhold: New York, NY (USA). 663 pp* Backeljau, T. (1986). ''Lijst van de recente mariene mollusken van België List of the recent marine molluscs of Belgium.'' Koninklijk Belgisch Instituut voor Natuurwetenschappen: Brussels, Belgium. 106 pp. * Conover R. J. & Lalli C. M. (1972). "Feeding and growth in ''Clione limacina'' (Phipps), a pteropod mollusc". ''Journal of Experimental Marine Biology and Ecology'' '''9'''(3): 279–302..* Falk-Petersen S., Sargent J. R., Kwasniewski S., Gulliksen B. & Millar R.-M. (2001). "Lipids and fatty acids in ''Clione limacina'' and ''Limacina helicina'' in Svalbard waters and the Arctic Ocean: trophic implications". ''Polar Biology'' '''24'''(3): 163–170..* Gilmer R. W. & Lalli C. M. (1990). "Bipolar variation in ''Clione'', a gymnosomatous pteropod". ''Am. Malacol. Union Bull.'' '''8'''(1): 67–75. * Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). ''European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification''. Collection Patrimoines Naturels, 50: pp. 180–213* Gosliner T. (1987). ''Nudibranchs of southern Africa: A guide to Opisthobranch molluscs of southern Africa''. Sea Challengers, Monterey. * Gosner, K.L. 1971. ''Guide to identification of marine and estuarine invertebrates: Cape Hatteras to the Bay of Fundy.'' John Wiley & Sons, Inc. 693 p. * Hermans C. O. & Satterlie R. A. (1992). "Fast-Strike Feeding Behaviour in a Pteropod Mollusk, ''Clione limacina'' Phipps". ''The Biological Bulletin'', Marine Biological Laboratory, '''182''':  1–7. * Linkletter, L.E. 1977. ''A checklist of marine fauna and flora of the Bay of Fundy''. Huntsman Marine Laboratory, St. Andrews, N.B. 68 p.* Morton J. E. (1958). "Observations on the gymnosomatous pteropod ''Clione limacina'' (Phipps)". ''Journal of the Marine Biological Association of the United Kingdom'' '''37''': 287–297. * Muller, Y. (2004). ''Faune et flore du littoral du Nord, du Pas-de-Calais et de la Belgique: inventaire. Coastal fauna and flora of the Nord, Pas-de-Calais and Belgium: inventory''. Commission Régionale de Biologie Région Nord Pas-de-Calais: France. 307 pp. * Thomas, M.L.H. (ed.). 1983. ''Marine and coastal systems of the Quoddy Region, New Brunswick''. Canadian Special Publication of Fisheries and Aquatic Sciences 64.306 p. * Trott, T.J. 2004. ''Cobscook Bay inventory: a historical checklist of marine invertebrates spanning 162 years''. Northeastern Naturalist (Special Issue 2): 261–324. * * Turgeon, D. D., et al. 1998. ''Common and scientific names of aquatic invertebrates of the United States and Canada''. American Fisheries Society Special Publication 26
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