Meeting Abstract
We aim to elucidate the developmental principles that govern the evolution of animal body plans. The phylum Tardigrada is part of the superphylum Panarthropoda, which also includes the phyla Euarthropoda and Onychophora. Understanding the origin of the tardigrade body plan is critical for illuminating the evolution of panarthropod body plans more generally. Here we present results of our recent studies of anteroposterior patterning genes, which reveal two important aspects of tardigrade body plan evolution. First, our results suggest that tardigrades have lost a relatively large portion of the anteroposterior body axis. This result supports a model in which the ancestor of Panarthropoda was a relatively elongate animal, rather than a compact animal like a tardigrade. Second, our recent results suggest that tardigrades possess a unipartite brain, rather than a tripartite brain like euarthropods. This conclusion supports a model in which a tripartite brain organization is a synapomorphy of Euarthropoda, while the ancestor of tardigrades and euarthropods possessed a unipartite brain. We present additional ways in which developmental studies of tardigrades could illuminate the evolution of panarthropod body plans.
