Meeting Abstract

S5.1  Jan. 5  Cnidarian milestones in metazoan evolution BOERO, Ferdinando*; SCHIERWATER, Bernd; PIRAINO, Stefano; DiSTeBA , University Lecce, Italy; ITZ, Ecology & Evolution, Hannover, Germany; DiSTeBA , University Lecce, Italy boero@unile.it

Cnidaria (characterized by the presence of cnidocysts) contain most of the characters considered as milestones of Metazoan evolution. It is suggested that nervous cells, bilateral symmetry, eyes, statocysts, chitinous skeleton, calcium-based skeleton, metamery, and apoptotic pathways first emerged in the Cnidaria and that this group led to the array of diversity, known as the Cambrian explosion, that represents the main animal phyla of the present. Some authors even suggest that the origin of the coelom and mesoderm date back to the Cnidaria. The hypothesis of homology of the above traits throughout the animal kingdom is testable by the identification of their genetic determinants. Morphological homology is to be supported by genetic homology. Such tests are being made, and in most cases they support homology of morphological traits. The milestone of metazoan evolution might have been the loss of cnidocysts in some (or even one) cnidarian species, leading to further development of some of the traits that are all present in what is possibly the founding phylum of Metazoan diversity.