Insects Found To Have Similar Hearing System To That Of Dolphins
December 14, 2012

Insects Found To Have Similar Hearing System To That Of Dolphins

April Flowers for - Your Universe Online

Scientists have discovered a hearing system component previously thought to be unique to toothed whales — such as dolphins — in insects.

The team, comprised of scientists from the School of Biological Sciences at the University of Auckland, with colleagues from Plant & Food Research in New Zealand, and engineers from the University of Strathclyde in Glasgow, Scotland, is challenging ideas about how a large group of insects, including crickets and katydids, hear. This investigation revealed the unexpected similarity to toothed whale hearing.

The team found that the iconic New Zealand insect, the weta, relies on a unique lipid to hear the world around them. Lipids are compounds that include oils and fats. The results of this study have recently been published in the journal PLoS ONE.

Dr James Windmill, of the University of Strathclyde's Centre for Ultrasonic Engineering, said, "As engineers we are particularly interested in how sound interacts with certain materials and how it travels to and from a source. These findings help us to improve our fundamental knowledge and could inspire new systems in ultrasound technologies like biomedical and non-destructive testing."

"The discovery is interesting as previously only toothed whales were known to use this hearing system component, the lipid. There are many similarities in the use of lipids to amplify the sounds and help both animal groups to hear. We don't know why animals who are so far apart in evolutionary terms have this similarity, but it opens up the possibility that others may use the same system component," said Windmill in a statement.

It was already known that the insects hear through the mechanism of sound being transmitted through a liquid-filled cavity to reach the hearing organs. Until this latest study, however, it was assumed that the liquid was simply the insect equivalent of blood.

The team found, instead, that the liquid was a lipid of a new chemical class. The role of the lipid, the team believes, is to transmit the sound efficiently between compartments of the ear. It might also amplify quiet sounds.

Dr Kate Lomas from the University of Auckland, added, "In the weta, as in other members of the Ensiferan group which includes katydids and crickets, sound is detected by ear drums on the front legs."

The scientists discovered a tiny organ in the insects' ears, which they named the olivarius after Dr Lomas' son Ollie, using new tissue analysis and three-dimensional imaging techniques. The olivarius appears to be responsible for producing the critical lipid.

Dr Lomas notes, "The ear is surprisingly delicate so we had to modify how we looked at its structure and in doing so we discovered this tiny organ."

The team used the Auckland tree weta for their testing, but they believe that the same method of hearing is likely used by other members of its biological class, including crickets and katydids.