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Secernentea are the main class of nematodes, characterised by numerous caudal papillae and an excretory system possessing lateral canals. Like all nematodes, they have no circulatory or respiratory system. The Secernentea contain several significant parasitic species among the Rhabditia and Spiruria. ''Caenorhabditis elegans'', the famous laboratory animal, is one of the many harmless members of the Rhabditia. ==Systematics== Subclasses and orders of Secernentea are:〔Tree of Life Web Project (ToL) (2002): (Nematoda ). Version of January 1, 2002. Retrieved November 2, 2008.〕 * Subclass Rhabditia (paraphyletic?) * * Rhabditida * * Strongylida * Subclass Spiruria * * Ascaridida * * Camallanida (sometimes included in Spirurida) * * Drilonematida (sometimes included in Spirurida) * * Oxyurida (= Rhabdiasida) * * Rhigonematida (formerly in Tylenchia) * * Spirurida * Subclass Diplogasteria (may belong in Rhabditia) * * Diplogasterida * Subclass Tylenchia (may belong in Rhabditia) * * Aphelenchida * * Tylenchida Some families traditionally considered to be Rhabditida seem to be closer to the Tylenchida. If the Tylenchia are to be maintained as separate, they probably will be included therein. These are also called as Phasmidians as they have the phasmids which are the posterior glandulo sensory and excretory structure.〔 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「Secernentea」の詳細全文を読む スポンサード リンク
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