A Mechanistic Model for the Evolution of the Vertebrate Head Skeleton

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Vertebrates evolved from small filter-feeding worms around a half-billion years ago. The vertebrate subphylum has since become one of the most widespread animal groups, giving rise to a stunning diversity of species, including humans. One of the keys to vertebrate success is the robust and highly adaptable vertebrate head skeleton. Despite the central role of the head skeleton in vertebrate evolution very little is known about how it first formed. This project uses modern molecular methods to address this long-standing and previously intractable question by analyzing the genetic mechanisms underlying skeletal development in three key species. The first animal, amphioxus, is an invertebrate regarded as a 'living fossil' highly similar to the worm-like ancestor of the vertebrates. While previously thought to lack a vertebrate-type skeletal tissue, we have found exciting evidence that such tissue may form during its larval phase. The second, the lamprey, is a living representative of the most ancient vertebrate group, the agnathans. The third, the African clawed frog, is an easily accessible model vertebrate with a head skeleton similar to our own. By the novel application of modern molecular methods to the embryos and larvae of these animals, we are elucidating the genetic and developmental changes driving the evolution of the vertebrate head. In the process, the work provides training for a postdoctoral scholar, graduate, and several undergraduate students, as well as hands-on research experiences for high school students. The project also provides an opportunity for undergraduates to participate directly in novel basic research through an upper division lab course. Finally, the results of the work will be incorporated into the curriculum of a large general biology course and widely disseminated to the public through a traveling exhibit at the University of Colorado Museum of Natural History.