The laterophysic connection: A novel specialization thought to enhance sound pressure sensitivity in butterflyfishes (Chaetodontidae, Chaetodon)

Abstract

Morphological specializations that enhance sound reception have been described among fishes, but sources of behaviorally-significant sound stimuli and sound transduction mechanisms are known for very few bony fishes. Butterflyfishes in the genus Chaetodon have a unique sensory specialization, the laterophysic connection (LC), defined anterior swim bladder extensions (horns) in association with medial openings in the lateral line canals of the cranial supracleithral bones. The LC is hypothesized to enhance sensitivity of both the lateral line and ear to sound pressure. Variation in LC morphology among species is defined by variation in soft tissues and is thought to be functionally significant. Preliminary field studies demonstrate that C. multicinctus produces sounds during agonistic interactions, thus providing a source of potentially relevant sound stimuli. Presence of an inflated swim bladder in close proximity to well-developed supracleithral openings in pelagic tholichthys stage individuals (15 mm SL) and horn development at the end of the tholichthys stage (25–29 mm SL) in C. ocellatus suggests that sound may also play an important role in the early life history of Chaetodon. [Work supported by the NSF IBN-9603896 to J.F.W.]