Meeting Abstract
Due to its critical role in sensing motion, the vestibular system of the vertebrate inner ear is expected to undergo evolutionary changes concomitant with major shifts in locomotor mode. While previous comparative studies have examined the relationship between inner ear morphology and locomotor performance across taxa, the potential link through ontogeny, such as the onset of flight, has been seldom addressed. To examine ontogenetic changes in inner ear anatomy, we used high-resolution computed tomography (CT) imaging on postnatal developmental series of alligators and chickens, two model archosaurs with disparate locomotor mode. We employed a high-dimensional 3-D geometric morphometric (GM) approach to (1) test the difference in ontogenetic trajectories of semicircular canal (SCC) shape, and (2) compare the disparity between taxa and individual SCCs. The results indicate that alligators and chickens exhibit distinct ontogenetic modes for SCCs and display contrasting pattern of ontogenetic disparity across SCCs. Semicircular canals show greater overall disparity in chickens than in alligator. Chickens exhibit similarly high disparity in both the anterior and lateral SCCs whereas alligators exhibit the greatest disparity in the posterior SCC. Notably, chickens show a different ontogenetic trajectory 1-2 weeks after hatching, which may correspond to the onset of limited flying capability. Through synthesis of micro-CT imaging and GM methods, this study provides important insight into the potential link between ontogenetic changes in locomotor mode and inner ear anatomy.
