Meeting Abstract
The dramatic rostrum of the paddlefish (Polyodon spathula) begins to grow several weeks after hatching, and within a period of several more weeks, this extension of the cranium has grown to represent one-third of the total body length of the juvenile fish. This remarkable positive allometric growth pattern coincides with elaboration of large numbers of well-described electrosensory ampullae on the rostrum surface. Paddlefish use electrosensation in prey (plankton) acquisition and in navigating their environment. We quantified changes in rostrum ampullae number during juvenile development in order to better appreciate sensory development in this species. Rostrums of five size classes of juvenile paddlefish were imaged by fluorescence microscopy and dorsal rostrum ampullary pores were counted using an image analysis program. Results indicate: 1) rostrum ampullae exhibit bilateral symmetry, and; 2) the number of ampullae does increase dramatically as juvenile fish grow and the rostrum extends. Growth of the rostrum provides a structural basis for increasing ampullary numbers, and more ampullae likely contribute to enhanced electrosensory capacity. In development, as ampullae are added, they must be integrated into the sensory transmission and processing systems. Therefore, the increase seen in rostrum ampullary numbers suggests that paddlefish may provide an interesting model for investigating vertebrate sensory plasticity and integration.
