BIRD, N.C.*; HERNANDEZ, L.P.; George Washington Univ.; George Washington Univ.: The Weberian apparatus: Development and evolution of a morphological novelty

Understanding the relationship between genes and morphology is a major motivation driving the field of Evo-Devo. In order to connect genes to skeletal morphology, a detailed documentation of normal development and anatomy must be combined with molecular techniques and genetic manipulation. Use of the zebrafish affords the potential for such a synthesis. The availability of varied phenotypic mutants, many linked to single genes, as well as the presence of morphological novelties make the zebrafish an ideal candidate to study morphological change. One novelty, the Weberian apparatus, is a highly modified region of the anterior vertebral column. It serves as a physical connection between the swim bladder and the inner ear, allowing for acute hearing. Homologies within the Weberian apparatus are still intensely debated. This lack of agreement is due, at least in part, to the contribution of multiple basal elements into a single new element. Identification of genes important to the formation of this novel structure may supply additional data allowing us to assess homologies within the Weberian apparatus. We are documenting the expression patterns of key genes prior to and during Weberian apparatus development in wildtype and mutant zebrafish. Future directions include comparisons of zebrafish gene expression to those in phylogenetically appropriate taxa (other ostariophysans and key outgroups). Manipulation of development (activating and repressing Weberian apparatus development) is also a future goal. The emerging patterns, when combined with previous studies of zebrafish development, will yield insights into the mechanisms that drove the evolution of this structure.