Meeting Abstract

P2.48  Monday, Jan. 5  Poecilogony as a window on larval evolution: Comparative analyses of gut development in Streblospio benedicti (Spionidae, Annelida) MCHUGH, D.*; SCHULT, N.; PERNET, B.; Colgate University; Colgate University; California State University, Long Beach dmchugh@mail.colgate.edu

As a poecilogonous species, Streblospio benedicti (Spionidae, Annelida) provides an excellent opportunity to explore evolutionary transitions in larval developmental modes in marine invertebrates. Within a single population, females of S. benedicti produce either larvae that develop from large, yolky eggs (100-200 um) and spend only a few hours or days in the plankton without any need to feed, or larvae that develop from small eggs (60-70 um) and spend days to weeks feeding in the plankton before metamorphosis. In comparative analyses of morphogenesis and gene expression patterns, we are assessing similarities and differences between the two contrasting larval developmental modes. Because one of the key traits that differs between the two larval types is the timing of formation of a functional gut, we are focusing on gut development. Using phalloidin labeling and immunohistochemical techniques, we identify comparable developmental stages in the two larval types and reconstruct gut development for these stages. For genes involved in gut patterning (foxA, hedgehog, Tbox6), we use quantitative PCR to record transcript levels and in situ hybridization to document the patterns of expression at specific developmental stages in both larval types. This work is bringing us closer to explaining the evolution of larval diversity in marine invertebrates.