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《《Building an evolutionary innovation》.pdf

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ARTICLE IN PRESS ZOOLOGY Zoology 112 (2009) 97–112 www.elsevier.de/zool Building an evolutionary innovation: Differential growth in the modified vertebral elements of the zebrafish Weberian apparatus Nathan C. Bird, L. Patricia Hernandez Department of Biological Sciences, George Washington University, Lisner Hall, Room 340, 2023 G Street NW, Washington, DC 20052, USA Received 31 October 2007; received in revised form 17 May 2008; accepted 22 May 2008 Abstract The Weberian apparatus, a complex assemblage of greatly modified vertebral elements, significantly enhances hearing within Otophysi. Ultimately we are interested in investigating the genetic mechanisms responsible for the origin, development and morphological diversification of these vertebral elements in the Weberian apparatus of otophysan fishes. However, a necessary first step involves identifying changes in growth of this region as compared with the vertebrae from which these modified elements purportedly derive. Using an ontogenetic series of the zebrafish, Danio rerio, we collected growth data for specific elements within the Weberian apparatus, including neural arches, ribs, and parapophyses. These data are compared to both serially homologous structures in posterior thoracic vertebrae (which act as internal controls) and vertebral elements from the same axial levels in three other non- otophysan teleosts. Significant differences in growth rate were found among serially homologous structures, as well as at equivalent axial levels in different species. Uniform changes in growth rates (in whic
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