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: Aging white lion euthanized at Ohio zoo

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

A vegetarian carnivorous plant

Dec 19, 2014

Carnivorous plants catch and digest tiny animals in order and derive benefits for their nutrition. Interestingly the trend towards vegetarianism seems to overcome carnivorous plants as well. The aquatic carnivorous bladderwort, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.