Evolution of Shell Loss in Opisthobranch Gastropods: Sea Hares (Opisthobranchia, Anaspidea) as a Model System

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A fundamental question in comparative biology is whether similar morphological structures are homologous or non-homologous, i.e., homoplastic. The rapidly growing field of evolutionary developmental genetics (evo-devo) now provides the tools to address whether the developmental processes involved in the formation of homologous anatomical features are also homologous at the molecular level. Sea slugs (Mollusca,Gastropoda, Opisthobranchia) are an ideal model to address these questions because of rampant morphological homoplasy (i.e. convergences, reversals and parallelisms). The goal of this project will be to use a group of sea slugs, the sea hares (Opisthobranchia, Anaspidea), Aplysia californica and Bursatella leachii in particular, to develop a new model system to study developmental homoplasy. To accomplish this goal, three specific aims of this project will be to: 1) improve the phylogeny of the anaspidean clade by using complete mitochondrial genome data, 2) produce Expressed Sequenced Tags (ESTs) from shell forming tissue from A. californica (reduced adult shell) and B. leachii (absent adult shell), and 3) examine spatial and temporal gene expression of genes involved in the formation of the shell in these species in comparison to fully shelled gastropods. A collaboration will also be done with Dr. Jeffrey Boore at the Joint Genome Institute (JGI) on the mitochondrial genomics of sea hares. Furthermore, a collaboration will be conducted with Dr. Patrick Walsh and Dr. Alice Hudder at the University of Miami in cDNA library construction and EST annotation of both species. In addition, Dr. Bernard Degnan at the University of Queensland will be trained to develop skills in developmental biology. Degnan's work on the abalone Haliotis anisina, a gastropod snail with a fully developed shell, will be a suitable comparative system. Finally, the Aplysia Resource Facility at the University of Miami will provide material for the necessary developmental stages for the purpose of this project.The intellectual merit of this proposal resides in its integrated approach to address the evolution of homoplasy at different levels of organization. This project will be the first attempt to look at the relationship between morphological homoplasy and the underlying developmental pathways that produce homoplastic features in opisthobranch gastropods. The outcome of this research will open the field of developmental genetics for opisthobranch biologists. The suite of evolutionary, genomic and developmental data that will result from this project should also benefit a larger scientific community.Broader implications of this project include the training of underrepresented minorities at the University of California, Merced. UC Merced is the tenth and newest UC campus opening in Fall, 2005. Part of the mission of the university is to offer higher education and research opportunities to the disadvantaged Central Valley communities. A large percentage of this year's incoming student body is from ethnic minorities (i.e. Hispanic and Asian). Being a funded and productive scientist provides a role model to minority students who wish to start careers in biological sciences. Finally, by collaborating with the California Academy of Sciences in order to bring some of their K-12 educational programs to the Central Valley, evolutionary and developmental knowledge will be disseminated to younger students.