Seeing into the world of hearing

Bush-crickets possess miniature-scale ears in their forelegs. Despite their size and location however, they have similar techniques for hearing sounds as those of a mammal; from sound capturing and sound transformation to frequency analysis.

Fascinating new research into this system by scientists in the School of Life Sciences at the University of Lincoln, UK, now paves the way for major advancements in hearing research using non-invasive methods.

The crystal bush-cricket Phlugis Poecila

Published today (Wednesday 3rd May 2017) in Royal Society Open Science, the new study has found that the transparent cuticles which surround the ears of some bush-crickets could offer a window into the natural operation of a frequency analyser which works under similar biophysical principles as the mammalian cochlea. The research found that it is possible to pass harmless laser beams through the cuticle of live bush-crickets to accurately record the biophysical activity of the inner ear – something that is challenging to achieve in the mammalian cochlea. This work therefore offers a potential new insect model for hearing research.

Fabio Sarria-S, a PhD student funded by the School of Life Sciences at Lincoln, who conducted the research, said: Bush-crickets exhibit a highly sophisticated hearing system that includes analogous hearing steps also shown by other animals, such as mammals: an outer, middle and inner ear. Although we recognise that many more questions need to be answered before the two systems can be seen as equivalent, both can be compared in a broad sense.”

This new finding could lead to new directions in hearing research, with non-invasive investigations into the workings of a bush-cricket ear having the potential to teach us about analogous process occurring in the mammalian cochlea.

The research was sponsored by the School of Life Sciences and supported by the Leverhulme Trust research grant awarded to Fabio’s supervisor, Dr Fernando Montealegre-Z.

Dr Montealegre-Z, a leading entomologist, explained: “We are delighted that our work could enable us to learn much more about the inner workings of the bush-cricket ear, which is quite unique among the ears of other insects. The equivalent inner ear component of the bush-cricket is simpler than that of mammals, and so learning about its natural function using non-invasive approaches has the potential to teach us about how complex auditory processes occur on a micro-scale.

“The fact that we can now take measurements from inside the ears of bush-crickets will open doors for advanced hearing research in the future. Until now, scientists have lacked an easy, non-invasive approach to directly access the complex auditory processes occurring within the bush-cricket ear – we hope that our research constitutes the first step for a non-invasive approach to hearing.”

The transparent cuticle of the bush-cricket effectively allows the scientists to see inside the ear and measure inner auditory activity, with no surgical intervention or manipulation of the hearing organ required.

The researchers believe that this study may now open avenues of research to help answer fundamental questions in auditory mechanics, and could provide insights into the evolution of acoustic perception, the likes of which cannot be attained by only investigating mammalian models.

The full paper is available to read online.

 

Paper caption: The crystal bush-cricket Phlugis poecila, a predatory Neotropical species found in the lowland rainforest of Colombia, constitutes the cornerstone of this research. The inset expands a close up view of the ear in the right foreleg, showing the mechanoreceptors through highly transparent cuticle. Picture taken by Fabio Sarria-S.