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The common periwinkle or winkle (''Littorina littorea'') is a species of small edible sea snail, a marine gastropod mollusc that has gills and an operculum, and is classified within the family Littorinidae, the periwinkles.〔Reid, David G.; Gofas, S. (2011). Littorina littorea (Linnaeus, 1758). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=140262 on 2011-05-16〕 This is a robust intertidal species with a dark and sometimes banded shell. It is native to the rocky shores of the northeastern, and introduced to the northwestern, Atlantic Ocean. == Description == The shell is broadly ovate, thick, and sharply pointed except when eroded.〔 The shell contains six to seven whorls with some fine threads and wrinkles. The color is variable from grayish to gray-brown, often with dark spiral bands.〔 The base of the columella is white.〔 The shell lacks an umbilicus. The white outer lip is sometimes checkered with brown patches. The inside of the shell has a chocolate-brown color. The width of the shell ranges from 10 to 12 mm at maturity,〔 with an average length of 16–38 mm.〔 Shell height can reach up to 30 mm,〔(Common periwinkle ) at marlin.ac.uk retrieved 16.10.2008〕 43 mm〔Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". ''PLoS ONE'' 5(1): e8776. .〕 or 52 mm.〔 As a result of its robust nature, ''Littorina littorea'' can be highly variable in phenotype with several different morphs present. Its phenotypic variations may be indicative of a speciation event, as opposed to phenotypic plasticity. This is of particular importance to evolutionary biology, as it presents the possible opportunity to view a transitional phase in the evolutionary life of an organism.〔Grahame J. (1975). "Spawning in ''Littorina littorea'' (L.) (Gastropoda: Prosobranchiata)". ''Journal of experimental marine Biology and Ecology'' 18: 185-196.〕 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「Common periwinkle」の詳細全文を読む スポンサード リンク
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