HERNANDEZ, LP; George Washington University: Zebrafish: A model system for investigating the generation of novel feeding mechanisms

Most research using zebrafish exploits the enormous conservation seen within vertebrate embryogenesis and early larval development. Such conserved processes allow easy extrapolation regarding biomedical implications. Yet in ignoring what makes zebrafish different, we are overlooking the utility of the zebrafish as a model organism for investigating the origin of morphological novelty. While comparative anatomists often ignore this unassuming fish, it possesses a number of interesting and poorly investigated feeding adaptations, including both a unique means of premaxillary protrusion as well as a unique pharyngeal jaw mechanism. Thus, such novelties exist not only in the morphological features used to procure prey, but also in those structures used in processing prey. Functional morphologists have long examined the functional significance of premaxillary protrusion, yet their work has focused largely on the mechanics of feeding in adult perciforms. The highly speciose Cypriniformes possess a novel median bony element, the kinethmoid, which allows for a different mechanism of premaxillary protrusion. We have examined the development and function of this important feeding innovation. Interestingly, even in closely related species there exists functionally relevant variation in kinethmoid structure. Moreover, while pharyngeal jaw development has been described within the Cichlidae, little work exists examining the development of the novel pharyngeal jaw structure within the Cyprinidae. Given that the Cyprinidae lack oral jaw teeth, there must exist significant selection for efficient pharyngeal jaw processing in these species. Understanding the function and development of these two feeding adaptations may add considerably to our knowledge of the development and evolution of morphological innovations.