Meeting Abstract

29.6  Monday, Jan. 4  Central Nervous System Development and Regeneration in Hemichordates LUTTRELL, S.; BENGTSSON, B.C.; SWALLA, B.J.*; University of Washington bjswalla@u.washington.edu

Hemichordates share several characteristics with chordates, a Hox-specified A-P axis, pharyngeal gill slits, a dorsal central nervous system (CNS) and an embryonic postanal tail in some species. Ptychoderids are the more complex of the motile hemichordates and their planktonic larvae share many similarities with echinoderm larvae. We describe here developmental, morphological and molecular characteristics that distinguish ptychoderid hemichordates, such as Ptychodera flava from harrimanid hemichordates, such as Saccoglossus kowalevskii. We show dramatic differences in the development of the larvae and CNS. An additional interesting property of the ptychoderid hemichordates is their amazing capacity to regenerate. We have been comparing the development of the central nervous system in ptychoderid hemichordates during metamorphosis and regeneration. Surprisingly, development of the CNS appears to be similar and is dependent on the dorsal vessel, suggesting that there may be some signaling properties in the dorsal vessel. We suggest that ptychoderid hemichordate worms are more likely to represent the hemichordate ancestor than saccoglossid worms. These results have important implications for the evolution of chordates and central nervous system evolution.