SICB Division of Comparative Biomechanics (DCB)

DCB Researchers Database Entry

Billie Swalla

Evolution and Development of the Chordates
My laboratory uses a multidisciplinary approach to understanding the evolution of chordates. We have ongoing projects in the lab focused on understand the phylogenetic relationships within and between the tunicates and the hemichordates. Our current Deuterostome Phylogeny is shown here in picture form. Because phylogenetic analyses suggest that enteropneust worms may be basal hemichordates, we are studying a complex of Saccoglossus worms in the Pacific Northwest in an effort to understand the evolution of the chordate body plan. We are specifically focusing on the nature of the hemichordate cartilage matrix (see above, left), how it develops, and it's composition. On the other hand, phylogenies also suggest that the tunicate ancestor was likely to be colonial, so we are studying the evolution of coloniality in the tunicates. We are comparing the development of colonial, social and solitary tunicates, shown above. We are hoping that our knowledge of the evolution and development of the extant animals may give us insight into the forces that allowed the evolution of the unique chordate body plan.