Meeting Abstract

23.6  Saturday, Jan. 4 14:30  Development and Growth of the Medullary Cavity in the Rostrum of Paddlefish (Polyodon spathula) ROBERTSON, J.; Westminster College, New Wilmington, PA robertjc@westminster.edu

The rostrum is not present in newly hatched paddlefish, but soon grows to about one-third the total body length of juvenile fish, and is known to have electroreceptive and mechanosensory functions. This work focuses on a major internal structural feature of the rostrum, the adipose-filled medullary cavity. This cone-shaped cavity is formed within the hyaline cartilage core of the rostrum. Widest adjacent to the braincase and tapering toward the tip of the rostrum, the cavity can extend more than half the rostrum length. To better understand formation, growth and function of the rostrum and medullary cavity, cavity volume was compared to rostrum length and total body length in groups of size-matched juvenile paddlefish. Medullary cavity volume was modeled as a simple cone. Mid-sagittal sections of each rostrum were imaged, and cavity length and width measurements were obtained by image analysis. Results show significant differences in ratios of cavity volume:rostrum length and cavity volume:body length between the groups. In early development the medullary cavity increases in size rapidly, later the rate of cavity volume increase slows relative to body and rostrum growth. Determining the pattern of growth of the medullary cavity contributes to understanding of the development and functions of the rostrum and the biology of paddlefish.