A recent study led by University of Western Ontario researchers using 3-D imaging has uncovered exactly how bats are able to ‘see’ their surroundings.
The results of the research will appear this week in the journal Nature, entitled “A Bony Connection Signals Laryngeal Echolocation in Bats.”
With echolocation, animals emit sounds and then listen to the reflected echoes of those sounds to form images of their surroundings in their brains. The research team at Western used state-of-the-art micro-computed tomography systems at Robarts Research Institute to collect detailed 3-D scans of the internal anatomy of 26 different bats, representing 11 different evolutionary lineages.
Schulich School of Medicine & Dentistry PhD candidate David McErlain and Robarts Research Institute scientist David Holdsworth are among researchers using 3-D imaging to better understand how bats echolocate.
The bats were provided on loan by Judith Eger, senior curator of mammalogy at the Royal Ontario Museum.
“It’s a new model for this type of research where we will be able to take advantage of large collections that exist at Western and other institutions and go back over them non-destructively and image them and look for subtle details we hadn’t noticed before,” says Robarts’ imaging scientist David Holdsworth.
This means researchers can examine “anything you would like to look at but not destroy,” he adds.
By examining the bats without having to dissect them, this technique allowed researchers to identify a bone – called the stylohyal bone – that connects the larynx to the bones that surround and support the eardrum in bats.
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.
This newly identified bone is unique to bats that use larynx to produce echolocation signals, allowing researchers to distinguish them from bats that echolocate using tongue clicks.
The discovery adds new information about the timing and origin of flight, and echolocation in the early evolution of bats.
“This discovery may change the way that researchers interpret previous observations from the fossil record of bats,” says biology professor Brock Fenton, an expert on bats who led the study.
“These new results give researchers working with fresh or fossil material an independent anatomical characteristic to distinguish laryngeally-echolocating bats from all other bats.”
The investigation involved a multi-disciplinary and international collaboration between imaging scientists, biophysicists, biologists, physiologists, and neuroscientists at five different institutions.
This study gave researchers a previously unavailable look at “just what’s happening inside a bat,” says Fenton.
The next stage in the study is looking at the voice boxes of bats. “We are finding an overwhelming diversity of voice box structure, probably much more than we expected,” he says.
Students also played a major role in the study.
The joint first authors are Western graduate Nina Veselka, who worked on the study during her fourth-year in biology, and Schulich School of Medicine & Dentistry PhD candidate David McErlain; co-author Kirsty Brain is a student at the University of Cambridge.
“This research provides a unique and exciting approach for the future study of bats,” says McErlain, whose research focus is on using novel medical imaging techniques in the study of bone and joint diseases, such as osteoarthritis. “Through the use of medical imaging technology, any small animal species can be fully explored in 3-D without the need for dissection or other destructive techniques.
“As a student, it is wonderful to publish your work within the scientific community, but, to be recognized in the world’s leading scientific journal is truly astonishing. It has been an overwhelmingly positive experience to work on such an interesting and rewarding collaboration with some of the world’s leading scientists in these fields.”
The idea for the study came from radiologist, Rethy Chhem, who brought together biologists and imaging scientists at Western to apply non-destructive imaging to a basic biological research question.
Scientists Matthew Mason at the University of Cambridge and Paul Faure at McMaster University provided additional expertise in mammalian physiology and neurobiology to carry out the research.
The small-animal micro-CT used in the study has implications for clinicians and biophysicists working with animal models to identify and correct hearing impairments in humans.
In the future, this type of “virtual dissection” could be used to study the micro-anatomy of many other species of small animals or insects. The ability to create 3-D computer displays of internal structures is likely to lead to the next generation of virtual or online museums where researchers can study internal anatomy remotely and without dissecting the specimen.
Funding for the research was provided by the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada, the Royal Ontario Museum and ROM Governors Fund, Canada Foundation for Innovation and Ontario Innovation Trust.