Meeting Abstract
50.10 Jan. 6 Semicircular Canal Morphology as Evidence of Locomotor Behavior in Amniotes GEORGI, Justin A; Stony Brook University, Stony Brook justin.georgi@hsc.stonybrook.edu
The vestibular system is a critical component of the neural control of locomotion in vertebrates. In the vestibule, macular endorgans transduce linear movements of the head and the semicircular ducts transduce the rotational movements. Integrated in the cerebellum with visual and proprioceptive inputs, the vestibular signals provide vital information about movement relative to the environment, and drive stabilization reflexes. The semicircular ducts leave distinct canals through the bones of the posterior braincase. These bony semicircular canals preserve some of the morphologies that determine the functional parameters of the semicircular ducts: e.g. response time, signal gain and frequency range. Thus, the semicircular canals represent the function of a neurological system via discrete bony correlates. Therefore, since the semicircular ducts should have morphologies that attune the system parameters to specific qualities and modes of locomotion and since some of these morphologies can be determined by examination of the semicircular canals, it has been hypothesized that there are correlations between semicircular canal morphology and locomotion. Semicircular canals represent a possible way, independent of post-cranial morphology, to verify hypotheses about locomotion in extinct vertebrates. To test this hypothesis, the semicircular canals of a broad array of amniotes were examined using Computed Tomography (CT). Shape analysis of the semicircular canals in carnivorans, turtles, varanids and crocodilians shows that despite phylogenetic shape differences, there is a consistent pattern of shape change that correlates with the terrestrial to aquatic locomotor transition. This pattern is most observable in the anterior semicircular canal where the maximum distance of the canal from the utricle is reduced in aquatic taxa.
