With a twitch of a muscle, the Chinese concave-eared torrent frog brushes off the sounds of thundering rivers, focusing on the one thing that really matters: the siren song of the opposite sex.
The males of this rare species are the only animal known to be able to turn a deaf ear to distracting noises while enhancing the calls of their own kind, according to a study published last week in the Proceedings of the National Academy of Science.
When the frog is calling for a mate, a piece of cartilage in its eustachian tubes – the canals that connect the ears with the mouth – largely blocks out distracting low-frequency sounds like rushing water. Scientists hope their discovery may lead to improved hearing aids.
“This probably is the only example we know of in the animal kingdom with this unusual adaptation,” said Albert Feng, professor of molecular and integrative physiology at the University of Illinois at Urbana-Champaign and a study lead author.
Dr. Feng and his colleagues were measuring how the frog’s unusually thin eardrum responded to different sounds when the eardrum stopped vibrating.
Shining a flashlight into its eustachian tubes, “we saw something, a dark shadow through this transparent eardrum,” he said.
The team found that a muscle in the frog’s head pulls a piece of cartilage and a curtain of tissue into the tube, “almost like an accordion or shower curtain,” Dr. Feng said.
Without its special adaptation, a frog might never hear a mate above the din.
“I’m thinking of making use of some of this mechanism to help us to develop better hearing aids,” which could gracefully handle noisy environments, Dr. Feng said.