Clownfish sounds were first recorded in 1930, but how the sounds were made remained elusive until now.
While lots of fish make noise, most do so using muscles attached to their swim bladders.
(Related: "Herring Break Wind to Communicate, Study Suggests" [November 10, 2003].)
Fine said the clownfish sound-making mechanism is a so-called exaptation, an adaptation that changes function.
"We know very little about the evolution of sound production in fish," he said.
"Here we have a system that is presumably part of a feeding mechanism that was co-opted to being a sound-producing mechanism. It shifted from one function to another."
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