Meeting Abstract

P2.80  Thursday, Jan. 5  The Development of the Visual System in the Polyodon spathula KEMER, K.M.*; FURIMSKY, M.M.; Westminster College, PA; Westminster College, PA kemerkm@wclive.westminster.edu

The paddlefish, Polyodon spathula, is a primitive cartilaginous fish that lives primarily in the Mississippi river system in the United States. These economically important fish are thriving over some parts of their historical range, but their numbers have been slowly declining in many areas due to human activities and they are already extirpated in parts of the U.S. and Canada. Strong efforts are, however, being made to re-introduce this species to its original native waters, including rivers in western Pennsylvania. Paddlefish are the largest species of freshwater fish in the United States and are distinguished by their elongated snout, the rostrum, and their heterocercal tail. The rostrum is a sensory organ which uses electroreception to locate zooplankton in the deep murky water which is their preferred habitat. The visual system, however, remains a key part of the paddlefish’s ability to sense its environment. Following hatching, paddlefish rely solely on their eyes for prey detection until the rostrum begins to develop. In the fully developed eyes, the photoreceptor layer of the retina contains a higher percentage of rods than cones, allowing the paddlefish to see easily in the dimly lit water. Since very little is known about paddlefish development and anatomy, the purpose of this study was to use a histological approach to describe visual system development and ocular structure in these prehistoric animals. The results of this study will be presented.