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We believe that the flight and echolocation behaviors displayed by the Egyptian fruit bat (Rousettus aegyptiacus) may translate to more precise head movement coding in response to their unique sensorimotor demands. While there is evidence for a relationship between locomotive behaviors and structural adaptations in the bony labyrinth of birds and mammals, none exist in the bat’s bony labyrinth. The present study determines whether cellular adaptations that translate to increased capability for high fidelity head movement coding exist in the crista central zone of Rousettus. This was accomplished using immunohistochemical techniques comparing hair cell and afferent phenotypes within crista central zone of Rousettus and the mouse (Mus musculus). Central zone hair cell counts revealed an increased fraction of type I hair cells in Rousettus. Additionally, Rousettus exhibits increases in the proportion of higher order complex calyces within the central zone. The calcium binding protein OCM is also observed to have expression that is restricted to type I hair cells in the central zone of Rousettus, unlike in Mus where it is also expressed in type II hair cells. KCNQ4, a low-voltage activated potassium channel, exhibits a positive association with CALB2 expression in the central zone of both Rousettus and Mus, which suggests that their association may contribute to the unique response characteristics of calyx-only afferents that project to the central zone. These findings provide evidence that the crista epithelia of Rousettus exhibits cellular adaptations that are consistent with enhanced head movement coding that may serve to be advantageous to their unique behavioral niche.

We believe that the flight and echolocation behaviors displayed by the Egyptian fruit bat (Rousettus aegyptiacus) may translate to more precise head movement coding in response to their unique sensorimotor demands. While there is evidence for a relationship between locomotive behaviors and structural adaptations in the bony labyrinth of birds and mammals, none exist in the bat’s bony labyrinth. The present study determines whether cellular adaptations that translate to increased capability for high fidelity head movement coding exist in the crista central zone of Rousettus. This was accomplished using immunohistochemical techniques comparing hair cell and afferent phenotypes within crista central zone of Rousettus and the mouse (Mus musculus). Central zone hair cell counts revealed an increased fraction of type I hair cells in Rousettus. Additionally, Rousettus exhibits increases in the proportion of higher order complex calyces within the central zone. The calcium binding protein OCM is also observed to have expression that is restricted to type I hair cells in the central zone of Rousettus, unlike in Mus where it is also expressed in type II hair cells. KCNQ4, a low-voltage activated potassium channel, exhibits a positive association with CALB2 expression in the central zone of both Rousettus and Mus, which suggests that their association may contribute to the unique response characteristics of calyx-only afferents that project to the central zone. These findings provide evidence that the crista epithelia of Rousettus exhibits cellular adaptations that are consistent with enhanced head movement coding that may serve to be advantageous to their unique behavioral niche.