Pizer, M.*; Wray, G.A.: The Evolution and Development of Left-Right Asymmetry in Echinoderms

Echinoderms have a bilaterally symmetrical larva that becomes left-right asymmetric when adult structures begin to develop. These structures form primarily on the left side of the larva, eventually producing a pentaradially symmetrical adult. This unusual symmetry transition is one of the most distinctive characteristics of the phylum and plays a central role in many theories of echinoderm origins. We are using a variety of approaches to investigate the evolution and development of left-right asymmetry and metamorphosis in echinoderms. The first of these approaches involves determining the fates of cells in the left and right larval coelomic sacs in a variety of echinoderm groups. Comparison of the degree of left-right asymmetry between different classes of echinoderms suggests how this feature has evolved within the phylum. The second approach uses molecular developmental techniques to investigate the mechanistic basis of left-right asymmetry in echinoids. The study of the developmental mechanisms of the unique symmetry characteristics of echinoderms has important implications for the evolution of these features in echinoderms and in deuterostomes.