Can you believe living creatures hearing from their mouth? Weird use of body parts if different organism is not new. We know about urchin that can eat with its anus and a tadpole that can see through its tail. And now, in the latest discovery of a surprising use for body parts is about a frog that can hear through its mouth.
This had been a mystery that how one of the world’s smallest frogs-Gardiner’s Seychelles frog- can hear without an ear. Scientists had thought that the Gardiner’s Seychelles frog-which at 11 millimeters named as the tiniest in the world—was deaf because it doesn’t have a middle ear, a critical component of hearing that’s found most land animals.
But now scientists have discovered that these frogs can hear sounds because they use their mouth cavity and tissue to transmit sound to their inner ears.
Most frogs do not possess an outer ear like humans, but a middle ear with an eardrum located directly on the surface of the head. Incoming sound waves make the eardrum vibrate, and the eardrum delivers these vibrations using ossicles to the inner ear where hair cells translate them into electric signals sent to the brain.
“However, we know of a frog species that croaks like other frogs but do not have tympanic middle ears to listen to each other. This seems to be a contradiction,” said lead author Renaud Boistel from the University of Poitiers in France.
To verify whether Gardiner’s frogs actually use sound to communicate with each other, the researchers set up loudspeakers in their natural habitat and broadcast pre-recorded frog songs. This caused male frogs present in the rainforest to answer, proving that they were able to hear the sound from the loudspeakers, the researchers said.
As these animals are tiny, the researchers used X-ray images of the soft tissue and the bony parts with micrometric resolution to determine which body parts contribute to sound propagation. And to their surprise they found that neither the pulmonary system nor the muscles of these frogs “contribute significantly” to the transmission of sound to the inner ears. Numerical simulations helped investigate the third hypothesis, that the sound was received through the frogs’ heads. These simulations confirmed that the mouth acts as a resonator, or amplifier, for the frequencies emitted by this species.
“The combination of a mouth cavity and bone conduction allows Gardiner’s frogs to perceive sound effectively without use of a tympanic middle ear,” Boistel said.