Meeting Abstract

P2.73  Saturday, Jan. 5  A Preliminary Comparative Study of Vascular Corrosion Casts of the Spiral Intestine of Select Acipenseriformes and Elasmobranchs LASH, J/L*; SHERMAN, R/L; Nova Southeastern University, Dania Beach; Nova Southeastern University, Fort Lauderdale lash@nova.edu

In members of Families Urotrygonidae (sub-Class Elasmobranchii) and Acipenseriformes, the body cavity encloses an extensive reproductive system and large liver, constraining the available space for the alimentary canal. The digestive system of these organisms have evolved a spiral intestine to compensate for the limited space. Whether it has evolved secondarily or is a conserved trait is unknown, and the evolutionary relationship between these species is still debated (Hymann, 1992). Current phylogenetic placement argues for two hypotheses regarding the relationship of Actinopterygii and Chondryichthyes 1) Actinopterygii and Sarcopterygii are sister taxa, and both share a common ancestor to Chondryicthyes, or 2) Actinopterygii and Chondryicthyes are sister taxa (Martin, 2001). This preliminary study uses vascular corrosion casting techniques to compare the spiral intestine vasculature of the Siberian sturgeon (Acipensiformes, Acipenser baerii), North American Paddlefish (Acipensiformes, Polydon spathula) and yellow stingray (Elasmobranchii, Urobatis jamaicensis). Future studies using vascular corrosion casting and SEM analysis will focus on branching and arteriole and venule patterns and capillary bed characterizations throughout the mucosa, submucosa, muscularis, and serosa, while histology studies will examine the vasculature through various tissue types, connective, epithelial and muscular, and gross dissection will examine the variation of valvular folds between species. Results from this research will offer a greater understanding of the functional morphology and phylogenetic connections between these two diverse groups of fishes.