Meeting Abstract
Gastropods exhibit enormous extant diversity and have a rich fossil record, making them fertile ground for testing evolutionary theories. The regular coiling of the gastropod shell has made it a tractable shape to quantify, but some questions raised aren’t answerable by morphology alone. What determines occupied morphospace (shapes of shells seen) compared to all possible morphospace? Why has the macroevolutionary shift from coiled shells to limpet-like shells occurred so often, when the reverse is so rare? Advances in genomics, developmental techniques, transgenics, mathematical modeling, and microCT scanning can be used with non-traditional model systems to crack open these old issues. Crepidula fornicata, the slipper-shell snail, is a model caenogastropod that has been instrumental in our understanding of spiral cleavage, but the majority of its molecular resources extend only through early morphogenesis (largely pre-shell stages). Potential shell patterning genes, including well-conserved Hox genes and signaling molecules, cannot be found in existing caenogastropod transcriptomes, which holds back our understanding of shell development and evolution. To facilitate the study of shell patterning and the developmental basis of shell shape, we used Illumina HiSeq technology to sequence the transcriptome of pre-metamorphosis Crepidula larval stages from early shell secretion, two post-metamorphosis shell stages, and the mantle edge (shell secreting organ) of adult Crepidula. Our transcriptome and subsequent in situ hybridization revealed that some putative shell patterning genes are expressed at the right time and place to be participating in shell development, for instance the signaling molecule dpp is asymmetrically expressed in the direction of shell coiling in the shell gland. Preliminary functional assessments of the roles of these genes will be reported, including the phenotypic effects of inhibiting dpp activity, which produced a more straightened shell phenotype.
