The Relevance of the Inner Ear and Lateral Line System for Sound Localization in Fish

Abstract

A long standing question in the field of neuroethology is how do fish localize sound? Fish are capable of detecting acoustic information through both an auditory system, the otolithic inner ear, and a mechanosensory system, the lateral line. Both systems are sensory hair cell based and exhibit directional sensitivity responses. Although the fundamental “auditory” anatomy is well characterized in fish, the physiological mechanism of how each system specifically aids in sound source detection is unknown. Using interaural time delays (ITDs) between sensory organs is the well characterized mechanism for terrestrial species sound localization; however, due to the rapid speed of sound underwater and the close proximity of otolithic organs in fish, using ITDs to localize sound is problematic. Alternatively, the conserved lateral line system in fish contains sensory organs located around the entire body, posing a potential sensory system capable of ITDs sufficient for sound localization. The inner ear also plays a dual role functioning in both the auditory and vestibular system, which further questions its potential for acute sound localization during self-induced movements, such as swimming and ventilation. Therefore, the lateral line system may provide additional information about the direction and distance of a sound source that the inner ear in fish cannot.