SEAVER, Elaine C; PAULSON, Dave A; IRVINE, Steve Q; MARTINDALE, Mark Q: Variation in Segment Formation in Polychaetes and its Relationship to Life History Characteristics

There is a great deal of spatial and temporal variation in the way polychaetes generate their adult segmented body plan, associated primarily with changes in life history. We are interested in whether these variations reflect fundamentally distinct developmental mechanisms of generating segments. We have examined several species that have distinct body plans, degrees of tagmatization, direct vs. indirect development etc. utilizing both molecular segmentation markers such as engrailed, and characterizing the nature of the growth zone at the cellular level. From examination of species in 3 different orders, it appears that 1/ the segment-polarity gene en does not have an expression pattern consistent with it having a role in segmentation and 2/ there is variation at the cellular level in how segments are generated. Increasing our understanding of the variation of segment formation within the polychaetes will allow for more accurate comparison with other segmented taxa.