Dr. Nathan Bird

My research focuses on the development and evolution of the vertebrate skeletal system. In particular, I am interested in how novel structures and key innovations evolve in vertebrates. Using cypriniform fishes (minnows, loaches, etc.) as an evolutionary model, and the zebrafish (Danio rerio) as a developmental model, my lab is investigating the evolution and development of the Weberian apparatus, a novel modification of the vertebral column that allows for enhanced hearing in these fishes. Two complimentary major research projects are being used to elucidate the morphological diversity of the Weberian apparatus as well as the genetic mechanisms regulating its development.
First, a large scale project documenting the ontogenetic development of the Weberian apparatus across cypriniform taxa is ongoing (Bird and Hernandez 2007, 2008). This project utilizes primarily classic methods to document skeletal development, including whole mount clearing and staining as well as histological analysis of sectioned material to document the timing and growth of the Weberian apparatus. These classic methods are supplemented with more modern methods to document morphology, such as 3-D micro-CT reconstruction on preserved specimens. In addition to looking at the changes in bone size and shape, we are also documenting the parallel changes in ligaments, musculature, swim bladder, and inner ear to gain a system-wide understanding of sensory evolution (See Bird and Webb 2014, Webb et al 2014 for similar work on another sensory system, the mechanosensory lateral line).

Second, a long-term study on the developmental regulation of Weberian apparatus development is underway (Bird and Hernandez, unpublished). Initial work on this project is focusing on identifying the critical genetic players involved in Weberian apparatus development. Using the zebrafish, we are employing in situ hybridization and immunohistochemistry (Bird et al. 2011) to determine the regulatory system in both space and time. This fundamental work will expand to include two additional projects. First, once the pattern of genetic regulation is known for the zebrafish, we can compare it to ancestral gene expression patterns in fishes without a Weberian apparatus, to gain an evolutionary perspective on the changes in genetic regulation during morphological evolution. Second, using known zebrafish mutants as well as transgenic zebrafish (see Windner et al. 2012 for examples), we are manipulating gene expression to disrupt Weberian apparatus development and documenting the morphological and functional consequences of regulatory changes. Previous analysis (Bird and Hernandez, unpublished) has revealed deviations in normal zebrafish development can result in morphological phenocopies of other cypriniform species.