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metameric segmentation

A Dictionary of Zoology | 1999 | | Copyright

metameric segmentation The repetition of organs and tissues at intervals along the body of an animal, thus dividing the body into a linear series of similar parts or segments (metameres). It is most strikingly seen in Annelida. Essentially, metameric segmentation is an internal, mesodermal phenomenon, the body musculature and coelom being the primary segmental divisions; this internal segmentation imposes a corresponding segmentation on the nerves, blood vessels, and excretory organs. In some metameric animals the segmentation is visible externally but in others (e.g. Chordata) external segmentation has been lost and internal segmentation is best seen in the embryo. Metameric segmentation is thought to have arisen as an adaptation to more efficient locomotion.

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MICHAEL ALLABY. "metameric segmentation." A Dictionary of Zoology. 1999. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

MICHAEL ALLABY. "metameric segmentation." A Dictionary of Zoology. 1999. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O8-metamericsegmentation.html

MICHAEL ALLABY. "metameric segmentation." A Dictionary of Zoology. 1999. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O8-metamericsegmentation.html

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metameric segmentation

A Dictionary of Biology | 2004 | Copyright

metameric segmentation (metamerism; segmentation) The division of an animal's body (except at the head region – see cephalization) into a number of compartments (segments or metameres) each containing the same organs. Metameric segmentation is most strongly marked in annelid worms (e.g. earthworms), in which the muscles, blood vessels, nerves, etc. are repeated in each segment. In these animals the segmentation is obvious both externally and internally. It also occurs internally in arthropods and in the embryonic development of all vertebrates, in which it is confined to parts of the muscular, skeletal, and nervous systems and does not show externally.

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"metameric segmentation." A Dictionary of Biology. 2004. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

"metameric segmentation." A Dictionary of Biology. 2004. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O6-metamericsegmentation.html

"metameric segmentation." A Dictionary of Biology. 2004. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-metamericsegmentation.html

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metameric segmentation

A Dictionary of Earth Sciences | 1999 | | Copyright

metameric segmentation The repetition of organs and tissues at intervals along the body of an animal.

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AILSA ALLABY and MICHAEL ALLABY. "metameric segmentation." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>.

AILSA ALLABY and MICHAEL ALLABY. "metameric segmentation." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O13-metamericsegmentation.html

AILSA ALLABY and MICHAEL ALLABY. "metameric segmentation." A Dictionary of Earth Sciences. 1999. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-metamericsegmentation.html

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