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. ... Metameric segmentation is thought to have arisen as an adaptation to more efficient locomotion.

Why annelid are called Metamerically segmented?

Metamerism is first seen in annelids in animal kingdom. ... In annelids the metameric segmentation is both external and internal. The body is divided into a number of segments which contain all body organs repeatedly but the alimentary canal is long and straight tube extending through all the segments.

Are annelids Metamerically segmented?

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.