Meeting Abstract

P3.17  Saturday, Jan. 5  Ontogeny of the pharyngeal jaw apparatus in the zebrafish O’QUIN, C.T.*; OBERG, F.L.; HERNANDEZ, L.P.; George Washington University; George Washington University; George Washington University ctoquin@gwu.edu

Cypriniforms (cyprinids, balitorids, catostomids, and cobitids) are an interesting group of fishes in that they posses a number of morphological novelties to the 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. While previous studies have examined the adult function of the PJA, little attention has been paid to the ontogeny of this unique structure. This is an unfortunate omission given that the pharyngeal morphology of cypriniforms may be convergent with the pharyngeal sling of other species. Before we can assess whether they are indeed convergent we need to understand early development of this novelty. Using a popular cypriniform model organism, Danio rerio, we examined the PJA from a developmental perspective, with emphasis on the development of the musculature. Here we present developmental data of musculoskeletal structures going from larvae to adults. Morphological analyses using both clearing and staining 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 if there is an interdependent developmental relationship between the muscles and skeleton of the pharyngeal jaw apparatus, the muscles may be playing a role in the proper development of the adjacent skeletal elements.