Cnidaria

Abstract

Cnidaria is a large animal phylum comprising mostly marine, with few species that have adapted to freshwater environments. Molecular phylogenies place the Cnidaria as a sister group to the Bilateria. The sister group relationship between Cnidaria and Bilateria is very robust and puts this phylum in a strategic position for the understanding of the evolution of key bilaterian features, such as the third germ layer (the mesoderm), the central nervous system, and bilaterality. We will give a short historical account and then highlight recent advances in the field of evolution and development from a variety of cnidarian model systems.