Meeting Abstract
The amphibian ear is highly sensitive to both air and water-borne sound energy and substrate-borne vibration. In anurans, auditory sensitivity on land is facilitated by an impedance matching tympanic middle ear. Salamanders lack many of the structural adaptations that enhance perception of airborne sound, including the tympanum and the middle ear cavity. However, early anatomical work has revealed much structural diversity in the salamander auditory system. The function of this diversity remains unresolved, but may have significant implications for hearing abilities across species. In this study, we use a comparative morphometric approach to explore the relationship between structural variation in the otic region, phylogenetic relatedness, and ecological diversification in salamanders. We contrast cave-adapted lineages with closely related terrestrial and aquatic surface species in order to sample species that experience variation in the physical constraints imposed by the environment on their sensory systems. We hypothesize that cave-related auditory variation will include structural changes to the otic region to support increased sensitivity to acoustic energy (in the form of sound and vibration), including hypertrophy of the inner ear organs and/or greater coupling of otic structures to the fluid of the inner ear. Preliminary results reveal trends in otic variation among cave-adapted lineages of salamanders, including an enlargement of the perilymphatic foramina, which may have physiological consequences for the fluid pressure relief pathway of the inner ear, and for potential directionality of the coupled ears.
