A new model for underwater noise research in larval fishes: Biomedical and ecological implications

In humans, excessive noise exposure from occupational or recreational sources causes permanent hearing loss. Similarly, exposure to underwater anthropogenic noise can cause hearing loss in aquatic organisms, including fish. While fish can recover from noise-induced hearing loss, underwater noise exposure can cause behavioral changes that reduce organismal fitness. In all vertebrates, acoustic trauma can cause damage to sensory hair cells. To better study the effects of noise on hair cells, we have developed a noise exposure system that uses broadband sound to damage hair cells of the inner ear and lateral line of larval zebrafish. Acoustic over-exposure kills hair cells in an intensity- and time-dependent manner, with maximum hair cell damage observed 72 hours after noise exposure. This time course is consistent with mammalian studies, where hair cell death occurs days to weeks after noise exposure. Other features of acoustic trauma are also conserved between zebrafish and mammals, including activation of apoptotic signaling cascades and changes in hair cell-afferent synapses. These studies demonstrate that larval zebrafish are a tractable new model for studies of noise-induced hair cell death. However, our acoustic trauma system could also be used in other species, allowing for new studies of underwater noise in larval fishes.