Somite compartments in anamniotes.

Somites are a common feature of the phylotypic stage of embryos of all higher chordates. In amniote species like mouse and chick, somite development has been the subject of intense research over many decades, giving insight into the morphological and molecular processes leading to somite compartmentalization and subsequent differentiation. In anamniotes, somite development is much less understood. Except for recent data from zebrafish, and morphological studies in Xenopus, very little is known about the formation of somite compartments and the differentiation of somite derivatives in anamniotes. Here, we give a brief overview on the development of myotome, sclerotome and dermomyotome in various anamniote organisms, and point out the different mechanisms of somite development between anamniotes and the established amniote model systems.