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Metamerism

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Definition

noun

The condition of possessing or forming a linear series of body segments


Supplement

Metamerism is a condition in which an organism forms or possesses a linear series of body segments. For example, in animals, metamerism is exhibited by earthworms. Their body is divided into segments or metameres. Metamerism is also observed in vertebrates particularly during the early embryonic stages of development. The developmental period in which the embryo forms metameres (therefore exhibiting metamerism) is referred to as metametry. The strict serial succession of metameres is particularly called homonymous metametry. It can be further grouped into true metamerism and pseudometamerism. In true metamerism, the segments work together for the whole organism whereas in pseudometamerism each of the repeating segments may act independently from each other. An example of true metamerism is that of earthworms whereas an example of pseudometamerism is that of tapeworms. In contrast to homonymous metametry, the condition in which metameres are grouped together for a similar task is referred to as heteronomous metametry. Insects exhibit this type of metametry. Certain insects have discernible five metameres in its head portion, three metameres in the thorax, and eleven metameres in the abdomen.


Also called:

  • metameric segmentation

See also: