Meeting Abstract
Fish produce context-specific sounds during social communication, but it is not known how the acoustic behaviors and auditory systems in fishes have evolved in noisy coral reef environments. Butterflyfishes (family Chaetodontidae) are speciose and prominent members of coral reefs and show a diversity of close affiliative social behaviors. At least two sound production mechanisms exist in the bannerfish clade, and additional mechanisms in the Chaetodon clade which is distinguished by anterior swim bladder horns and the laterophysic connection (LC). Some Chaetodon species share the head bob acoustic behavior with the bannerfishes, which along with other sounds in the 100–1000 Hz spectrum, are likely adequate to stimulate the ear, swim bladder or LC of a receiver fish. In contrast, only Chaetodon species produced the tail slap sound, which involves a 1–30 Hz infrasound pulse that can stimulate the receiver’s ear or lateral line at close distances, but not the swim bladder or LC. Chaetodon species are more sensitive to sound intensities from 100-1000 Hz than the forcepsfish, Forcipiger flavissimus (which lacks swim bladder horns and LC), and also have an extended hearing range up to 2000 Hz that are due to their divergent sensitivity to sound pressure mediated by the swim bladder horns. Coral reef ambient noise levels in the hearing spectrum of Chaetodon vary in amplitude and frequency with depth at their territory locations in the field, and appear to differentially degrade the transmission of sound types used by Chaetodon for communication. Thus both the close social affiliations common among butterflyfishes and the evolution of the swim bladder horns in Chaetodon facilitate their short-range acoustic communication.
