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''Opuntia'' is a genus in the cactus family, Cactaceae. The most common culinary species is the Indian fig opuntia (''O. ficus-indica''). Most culinary uses of the term "prickly pear" refer to this species. Prickly pears are also known as ''tuna'' (fruit), ''sabra'', ''nopal'' (paddle, plural ''nopales'') from the Nahuatl word ''nōpalli'' for the pads, or nostle, from the Nahuatl word ''nōchtli'' for the fruit; or paddle cactus. The genus is named for the Ancient Greek city of Opus, where, according to Theophrastus, an edible plant grew which could be propagated by rooting its leaves. == Description == Prickly pears typically grow with flat, rounded cladodes (also called platyclades) armed with two kinds of spines; large, smooth, fixed spines and small, hairlike prickles called glochids, that easily penetrate skin and detach from the plant. Many types of prickly pears grow into dense, tangled structures. In the Galapagos Islands, six different species are found: ''O. echios'', ''O. galapageia'', ''O. helleri'', ''O. insularis'', ''O. saxicola'', and ''O. megasperma''. These species are divided into 14 different varieties; most of these are confined to one or a few islands. For this reason, they have been described as "an excellent example of adaptive radiation".〔Fitter, Fitter, and Hosking, Wildlife of the Galapagos (2000)〕 On the whole, islands with tall, trunked varieties have giant tortoises, and islands lacking tortoises have low or prostrate forms of ''Opuntia''. Prickly pears are a prime source of food for the common giant tortoises in the Galapagos islands so they are important in the food web. Charles Darwin was the first to note that these cacti have thigmotactic anthers: when the anthers are touched, they curl over, depositing their pollen. This movement can be seen by gently poking the anthers of an open ''Opuntia'' flower. The same trait has evolved convergently in other cacti (e.g. ''Lophophora''). 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「Opuntia」の詳細全文を読む スポンサード リンク
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