The discovery of a tiny, seemingly insignificant bone connecting the larynx to the bones that surround and support the eardrum in bats doesn't sound like a big deal to most people, but to Paul Faure, McMaster's "Bat Man" and co-author of a study that appeared last week in Nature, this finding will change the way scientists study echolocation.

Echolocation is an active form of orientation used by some mammals (e.g. bats and whales) and a few birds. The animals emit sounds and then listen to reflected echoes of their sounds to form images in their brain of objects in the environment.

Faure was part of an international research team that used a relatively new imaging technology - micro-computed tomography - to collect detailed 3D scans of the internal anatomy of 26 bat species from 11 different evolutionary lineages. This non-destructive technique allowed the researchers to identify a bony connection between the larynx and the ear that was unique to bats that used laryngeal echolocation. Some bats use their larynx to generate echolocation (biosonar) signals, allowing them to operate at night; other bats use tongue clicks to achieve the same purpose. The team's discovery makes it possible to distinguish bats that produce echolocation signals with the larynx from bats that do not echolocate and from bats that echolocate with tongue clicks.

"This work is an important step forward in echolocation research," says Faure, assistant professor in the Department of Psychology, Neuroscience & Behaviour. "For years, scientists have been searching for a mechanism that would allow echolocating animals to a have a neural representation of their outgoing biosonar sounds for future comparison with reflected echoes of the sounds, and this anatomical discovery may be that mechanism."

What also excites Faure is that the discovery adds new information to the ongoing debate about the timing and origin of flight and echolocation in the early evolution of bats. Moreover, the work may have significance for clinicians and biophysicists working with animal models to identify and correct hearing impairments in humans.

The investigation involved a multi-disciplinary collaboration between imaging scientists, biophysicists, biologists, physiologists, and neuroscientists from the University of Western Ontario and the Robarts Research Institute, the Royal Ontario Museum, the University of Cambridge, and McMaster University.

Funding for the research was provided by the Canadian Institutes of Heath Research, the Natural Sciences and Engineering Research Council of Canada, the Royal Ontario Museum, the Canada Foundation for Innovation, and the Ontario Innovation Trust.

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