Meeting Abstract
Hox genes constitute an essential and ubiquitous mechanism in the construction of the animal body. Despite the diversity in bilaterian body plans, every member of this clade utilizes these key genes in patterning the anteroposterior axis, with one potential exception – radial echinoderms. As adults, members of Echinodermata are characterized by a highly derived radial body plan, however, most species develop indirectly, beginning their lives as bilateral larvae that undergo a radical metamorphosis into a radial adult. A broad understanding of echinoderm development is still lacking, and it is unknown how classically bilateral patterning genes like Hox are involved in setting up these very different life stages. To resolve this, in situ hybridizations of four Hox genes present in the bat star, Patiria miniata in its larval stages were performed. P. miniata exhibits indirect development, and is an excellent model in which to characterize the usage of conventional AP axis patterning genes to compare with that of bilateral organisms. Hox expression was observed in larval forms in a collinear fashion analogous to the expression patterns in other animals. These results suggest that, despite a greatly divergent radial body plan, echinoderms use many of the same developmental mechanisms found in bilateral organisms to pattern their larval stages prior to metamorphosis. This research represents the beginning of studies on Hox genes in asteroids, and provides evidence for rethinking our assumptions about the evolutionary transition from bilateral to radial symmetry in early echinoderms.
