The purpose of this study is to understand the evolution and diversification of a complex of basioccipital and pharyngeal structures that are important for feeding in cypriniform fishes with special reference to Catostomidae. Fishes in the family Catostomidae are a diverse group inhabiting temperate lotic and lacustrine waters of North America and East Asia. The palatal organ is a muscular pad that forms the roof of the pharynx in catostomids and some cyprinids and functions in separating food items from inorganic debris during feeding. The basioccipital bone forms the postero-ventral part of the neurocranium and part of the skeletal base of the palatal organ. Palatal organ and basioccipital bone morphology is variable among cypriniform families and statistically significant variation exists among catostomids. Subfamily Cycleptinae has the shortest, narrowest, and thinnest palatal organ of all the subfamilies. Subfamily Ictiobinae has the thickest and widest palatal organ. Generally, the shape and size of the palatal organ in Catostominae is intermediate between the other subfamilies. Catostomids possess a ventral and posterior pharyngeal process of the basioccipital bone that is expanded into a fenestrated lattice of bony struts. The pharyngeal process is not fenestrated in cyprinids; however, its ventral portion is modified in to the masticatory plate for attachment of the chewing pad. Only catostomids and cyprinids possess a chewing pad. The chewing pad is lunate in catostomids and generally ovoid in cyprinids. A synonymy of terms used to describe the palatal organ and chewing pad of Cypriniformes is provided. Phylogenetic analysis of mitochondrial and nuclear genes resolve Catostomidae as a monophyletic group with two major clades. Of the two major clades, one comprises Catostominae and the other includes a basal Cycleptinae sister to Myxocyprininae plus Ictiobinae. The sister group of Catostomidae is uncertain because of low bootstrap support at the base of the cypriniform tree. Ancestral character state reconstruction determines that the palatal organs of Catostomidae and Cyprinidae are not homologous. The ancestor of Catostomidae had a palatal organ, fenestrated pharyngeal process, and was probably a large-bodied fish with an inferior or subterminal mouth that occupied benthic habitats / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_23591 |
| Date | January 2010 |
| Contributors | Doosey, Michael H (Author), Mayden, Richard L (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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