Meeting Abstract
The Phylum Echinodermata is ancestrally indirect developing via a feeding larva lacking a skeleton, and evolved to include both direct and indirect developing species. Larvae are bilaterally symmetrical with a ciliary band dividing oral and aboral ectoderm territories. The classes Echinoidea and Ophiuroidea develop via feeding pluteus larvae with underlying calcified skeletons. These pluteus larvae likely arose independently; evolving the skeleton and overlying arm ectoderm from pre-existing adults. This evolution involved reorganization and co-option of numerous genes in the production of pluteus arms. The research pursued here aims to understand the evolution and development of pluteus arms by beginning to dissect regulatory controls involved in their development. The expression patterns of the arm-associated genes carbonic anhydrase, msp130, and tetraspanin were analyzed using whole mount in situ hybridization. The expression patterns for these genes were compared between direct and indirect developing species of sea urchins. Additionally, expression patterns were determined in indirect developing species by interfering with signaling pathways in early development that perturbed pluteus arms. Following developmental perturbation, changes in marker gene expression were assessed and the following questions were answered, how do expression patterns of marker genes change when normal development is disrupted? Do their region(s) of expression expand, contract, disappear, or remain unchanged? What does a change in their expression reveal about the evolution of developmental regulation? This study in conjunction with existing knowledge of ancient gene pathways shed light on the evolution of axial regulation and development in echinoderms.
