UCLA

Bats are highly agile animals by virtue of their flight and echolocation behaviors, and they are acknowledged to be “spatiotemporal integration specialists.” In order to avoid obstacles, scavenge food, and capture prey, bats must be able to navigate a three-dimensional space. In flight, bats must perform high speed navigation through obstacles using a blend of sensory modalities including vision and echolocation. While some bat species exhibit structural adaptations to their cochleae as an adaptation to the demands of echolocation, there is an absence architectural adaptation of the vestibular labyrinth that would accommodate the increased demands for high frequency head movement coding associated with agile movement. The present study tested the hypothesis that there may exist cellular adaptations within the vestibular epithelia consistent with increased capability for high fidelity head movement coding. This was accomplished using immunohistochemical analyses focusing primarily in the striolae of the utricles of Rousettus aegyptiacus and Mus musculus, regions bounded by the presence of calretinin (Calb2) positive calyces. Hair cell counts revealed increased proportions of type I hair cells (hair cells surrounded by calyces) in Rousettus when compared to Mus (72.6% � 3.5% and 57.2% � 2.7%, respectively, p<10-5). Additionally, Rousettus exhibits increases in the proportion of complex calyces in the striola when compared to Mus. Ocm, a calcium binding protein expressed in vestibular hair cells, is also observed to have expanded expression in Rousettus and Mus both in the striola as well as the extrastriolar regions. These novel findings indicate that vestibular epithelia of Rousettus exhibit cellular adaptations over Mus that are consistent with increases in head movement coding capability associated with agile movement in flight.