MARSH, A.G.; Univ. of Delaware, Lewes: Transcriptome profiling in individual larvae of the polychaete Streblospio benedicti: interindividual variance between planktotrophic and lecithotrophic development

Understanding the range of physiological phenotypes in a cohort of embryos or larvae is crucial to understanding the lifespan, dispersal potential, and recruitment success of the early life history stages of a species. We all tacitly recognize the large biological variation that exists among individual embryos of a cohort, even at the level of maternal investment in individual eggs; no propagules are identical. In this study, a novel kinetic assay has been employed to profile the transcriptome pool complexity in individual larvae of S. benedicti. Using a nano-scale synthesis strategy, the mRNA pool in single embryos or larvae can be amplified into cDNA for quantitative characterization in a high-throughput kinetic reannealing (Cot-like) assay using a 96-well format. This assay generates 30 nucleic-acid pool-complexity estimates at 1 &degC temperature increments for each well resulting in 2,880 kinetic regressions per run. Measuring transcriptome complexity on 8 individual planktotrophic and 8 individual lecithotrophic larvae (with 4 duplicate assays for each individual) reveals: 1) a more complex gene expression profile in planktotrophic larvae; 2) a lower level of interindividual variation in expression patterns in lecithotrophic larvae; and 3) a convergence in total cumulative complexity between the two larval types. Although differences in gene expression patterns are more likely due to physiological differences between feeding and non-feeding larval types in these late-stage individuals, we now have the tools to begin to work back towards early embryonic stages to assess the degree of expression differentiation between these developmental modes at the level of individual embryos.