Meeting Abstract

90.4  Wednesday, Jan. 7  Development of a functional complex: Ontogeny of the zebrafish pharyngeal jaw apparatus O’QUIN, C.T.*; HERNANDEZ, L.P.; The George Washington University; The George Washington University ctoquin@gwu.edu

The pharyngeal jaw apparatus of teleosts has long been of interest to both functional and descriptive morphologists alike. However, little to no work has been done to understand how this functional complex comes together during ontogeny. Fortunately, we have the opportunity to examine this by use of the popular model cypriniform, Danio rerio. Cypriniforms (cyprinids, balitorids, catostomids, and cobitids) posses a number of morphological novelties associated with their pharyngeal jaw apparatus (PJA). These include: (1) a muscular sling controlling movement of the lower pharyngeal jaws; (2) loss of the upper pharyngeal jaws; and (3) a pharyngeal pad on the basioccipital that has taken the place of the upper pharyngeal jaws. The cypriniform muscular sling originates on the neurocranium and inserts on ceratobranchial 5, and serves to adduct the pharyngeal jaws against a horny pad on the basioccipital. Here we present developmental data of musculoskeletal structures ranging from larvae to adult zebrafish. Morphological analyses following clearing and staining, histological processing, and immunohistochemistry revealed that the muscles of the PJA develop in larvae as early as 4 days post fertilization. However, some bony elements (epi- and pharyngobranchials) do not form until the fish is 4.4 mm in length, at which point larvae are approximately two weeks of age. These findings suggest that the musculature of the pharyngeal sling is established early on in development, well before the fish is feeding. As a result, we are provided with an understanding of how a functionally important trophic structure forms during ontogeny.