Meeting Abstract

P1-150   -   Effect of continuous, intraspecific variation in larval size and chaetal investment on the settlement competence of the poecilogonous annelid Streblospio benedicti Gilligan, CP*; Rockman, MV; Center for Genomics and Systems Biology, Department of Biology, New York University; Center for Genomics and Systems Biology, Department of Biology, New York University cpg324@nyu.edu http://www.ecoevogilligan.com

The recurrent evolution of derived lecithotrophy from ancestral planktotrophy observed within multiple clades of marine invertebrates involves both an increase in larval size as well as qualitative changes in larval form; the acquisition of lecithotrophy seemingly necessitates the diminution of larval anatomical complexity. The observation of perfectly correlated larval syndromes— stereotypically complex planktotrophs and simple lecithitrophs— gives the impression that these shifts in trophic mode may be driven by natural selection. Presumably, it is energetically costly for a morph, which spends little to no time in the dangers of the pelagic zone, to produce unneeded defenses or swimming structures. However, it is also possible that through bypassing planktonic development, lecithotrophs are able to accumulate, at no cost, mutations in genes that underpin traits that are essential for life in the plankton, but not in the benthos. In order to test the hypothesis that investment in planktotrophic traits across increasing larval size imposes a fitness cost (upon which selection acts), it is essential to first quantify the relationship between variation in size and anatomy on a tractably measured fitness component, such as settlement competence. These analyses, moreover, should be performed intraspecifically, to avoid the confounding effects of speciation. Streblospio benedicti is an abundant marine annelid that harbors heritable, intraspecific variation in developmental mode, enabling different genotypes to produce planktotrophic or lecithotrophic larvae— a condition known as poecilogony. Leveraging this natural variation, I have created crosses that vary continuously in both size and chaetal characteristics. Using these phenotypically diverse larvae will allow me to experimentally interrogate the functional interaction among larval anatomical structures, size, and fitness.