Specialization for underwater hearing by the tympanic middle ear of the turtle

Mar 21, 2012

A group of biologists from Denmark and the US led by Jakob Christensen-Dalsgaard, University of Southern Denmark, and Catherine Carr, University of Maryland, have shown that the turtle ear is specialized for underwater hearing.

The new discovery is published in March 21, Special features of the turtle ear – a large, air-filled and a movable tympanic disk increase its sensitivity for underwater sound. Laser measurements of disk vibrations in response to underwater sound show up to 100-fold larger vibrations of the disk than the surrounding water, most likely because the air volume resonates in an underwater sound field and drives the tympanic disk.

The tympanic middle ear is often seen as an adaptation to hearing in air, but the turtle tympanic ear is an anomaly here, because turtles are generally 100-fold less sensitive than other animals with eardrums, like mammals, birds and reptiles.

However, turtles are amphibious animals, and anatomical and biophysical studies by a group of from Denmark and the US have shown that the ear of the red-eared slider is specialized for underwater rather than airborne sound.

CT scans, laser measurements from the ear under water and auditory evoked responses showed that the turtle ear was more sensitive for underwater than for airborne sound. The sensitivity is caused by the air filled middle ear. Resonance in the air cavity lined by the tympanic disc drives the disc and amplifies its vibrations up to 100 fold under water.

What the turtle is using its sensitive underwater hearing for is unknown. However, the sensitive hearing can be used for prey capture, predator avoidance and navigation under water. An alternative possibility is that communicate by underwater sound. Underwater sound communication is unknown in the red-eared slider, but has recently been described in two other turtle species.

Explore further: Two new species of yellow-shouldered bats endemic to the Neotropics

Provided by University of Southern Denmark

not rated yet
add to favorites email to friend print save as pdf

Related Stories

Were our tetrapod ancestors deaf?

Nov 08, 2010

A research group led by Jakob Christensen-Dalsgaard, University of Southern Denmark, have shown that the closest living relatives of the tetrapods, the lungfish, are insensitive to sound pressure, but sensitive ...

Common musk turtle breathes through its tongue

May 21, 2010

(PhysOrg.com) -- The North American common musk turtle (Sternotherus odoratus) is a pretty ordinary sort of turtle except for one thing newly discovered by Austrian scientists: it can breathe through its tongue, ...

Lasers generate underwater sound

Sep 04, 2009

Scientists at the Naval Research Laboratory (NRL) are developing a new technology for use in underwater acoustics. The new technology uses flashes of laser light to remotely create underwater sound. The new ...

Teaching about hearing can save young people's ears

Mar 05, 2012

Many adolescents frequently expose their ears to loud sounds, for example from portable music players. Some of them may think that 'the doctor said that my hearing is good, so I guess I can handle the loud volume'. A new ...

Recommended for you

Biologists help solve fungi mysteries

23 minutes ago

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

More vets turn to prosthetics to help legless pets

3 hours ago

A 9-month-old boxer pup named Duncan barreled down a beach in Oregon, running full tilt on soft sand into YouTube history and showing more than 4 million viewers that he can revel in a good romp despite lacking ...

Chimpanzees prefer firm, stable beds

13 hours ago

Chimpanzees may select a certain type of wood, Ugandan Ironwood, over other options for its firm, stable, and resilient properties to make their bed, according to a study published April 16, 2014 in the open-access ...

User comments : 0

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

More vets turn to prosthetics to help legless pets

A 9-month-old boxer pup named Duncan barreled down a beach in Oregon, running full tilt on soft sand into YouTube history and showing more than 4 million viewers that he can revel in a good romp despite lacking ...

Robotics goes micro-scale

(Phys.org) —The development of light-driven 'micro-robots' that can autonomously investigate and manipulate the nano-scale environment in a microscope comes a step closer, thanks to new research from the ...