SEAVER, Elaine C.; KANESHIGE, Lori M.; MAKAGON, Maja B.; SCHWAB, Rachel L.; University of Hawaii; University of Hawaii; University of Hawaii; University of Hawaii: The expression of �segmentation� genes in polychaete annelids

Historically, annelids and arthropods were thought to share a common segmented ancestor. Spatio-temporal patterns of gene expression of genes underlying the segmentation process may be conserved if segmentation has a common origin between these two phyla. To address this possibility, we have analyzed expression patterns of a number of arthropod segmentation genes of the segment polarity and pair-rule class such as eve , paired, runt, wg, hh, and en in polychaete larvae by whole mount in situ hybridization. Several developmental stages corresponding to segment formation were analyzed in three different polychaete annelids: Capitella, Chaetopterus, and Hydroides. Each species has a distinct body plan, degree of tagmatization, and life history. These species also show morphological and temporal differences in segment formation. We observe variability in expression patterns among the species and our results do not obviously support a shared molecular mechanism of segment formation between annelids and arthropods.