Metameric segmentation is true segmentation in which external segmentation corresponds to the internal segmentation and the body is divided into a number of segments. Animals which belong to phyla Annelida and Arthropoda exhibit metameric segmentation. Metameric segmentation is the characteristic of Annelida and Arthropod.
What is metameric segmentation?
An architectural body plan in some animals in which the similar body segments and organ systems are serially repeated one after another is called metameric segmentation or metamerism. Similar body segments are called metamers or somites. The animals that exhibit such features called metamerically segmented. Structurally each meta-mere or somite is constructed or designed on the basis of some fundamental plan and basically possesses a part of almost all the body systems.
Occurrence of Metamerism
Metamerism is first observed in annelids in the animal kingdom. Every single segment mainly contains appendages, muscles, nerves, blood vessels, excretory organs and a pair of coelomic sacs that are repeated in almost all segments. It is also seen in kinorhynchs, arthropods and most chordates.