Meeting Abstract

P2.40  Monday, Jan. 5  Untangling the palatal organ: Investigating the embryological origin of a novel structure OBERG, F.*; HERNANDEZ, L. P.; George Washington University, Washington, DC 20052 phernand@gwu.edu

Exploiting the conserved developmental mechanisms seen in vertebrates, the zebrafish has become a popular model organism within the field of biomedical research. Yet, by ignoring what makes this cypriniform fish unique we are overlooking a powerful model organism for investigating the origin and development of morphological novelty. The trophic diversity that characterizes cypriniform fishes includes a unique feeding mechanism whereby small food particles often encountered in benthic feeding are extracted. The structure that plays a key role in separating edible from inedible prey items during benthic feeding is the palatal organ. Located in the anterior pharyngeal roof, the palatal organ is a muscular cushion composed of a highly disorganized tangle of differently sized muscle fibers covered by an epithelium studded with mucous cells. During feeding the palatal organ secretes mucus to entrap food and the muscles work to entrap and move the food along to the pharyngeal teeth. Functionally, and indeed even in histological sections the palatal organ strongly resembles a small mammalian tongue. There is little, if any, data addressing either the embryological origin of this muscular organ or the ontogenetic stage at which it first develops. Here we describe the ontogeny of the palatal organ in several ontogenetic stages of the zebrafish. The palatal organ, while less well-developed in zebrafish than in other cypriniforms, is apparent from very early larval stages. Moreover, the combination of muscle fiber types seen in the adult may reflect the complex embryological origin of this organ. Identifying the developmental mechanisms responsible for the origin of this feeding adaptation may enhance our understanding of how functional novelties arise and evolve.