Hearing in plethodontid salamanders: A review

The ability to detect airborne sound using a pressure-transducing tympanic ear has evolved several times over the course of vertebrate history, suggesting that hearing is an advantageous modality and an informative model for sensory evolution. Amphibian hearing is especially interesting because these animals must negotiate water to land transitions. Salamanders are good animal models for the study of hearing, not only because they have a wide range of ear morphologies, but also because they have evolved extratympanic pathways for sound and vibration transmission. Here we suggest that sufficient extratympanic hearing in salamanders and reduced reliance on vocal communication has relaxed selection on the auditory system and allowed for the structural diversity of the salamander ear. Unique among salamanders is the family Plethodontidae, which is not only the most speciose and ecologically diverse family of salamanders, but also possesses a highly derived ear with great inter-specific variation. In this review, we provide an overview of historical and current research on acoustic behavior, auditory anatomy, evolution, and physiology. We highlight plethodontid salamanders as an informative model for study of extratympanic function and auditory evolution.