Bat study turns evolutionary history on its ear

Bat study turns evolutionary history on its ear
Wednesday 10 March 2021

An international team studying the development of bats has helped answer a decades-old question, providing new evidence of the clever way they get around at night. 

Most bats use a technique called echolocation to navigate the night sky, using high-pitched sound to determine the location of objects. 

According to co-author Dr Laura Wilson from The Australian National University (ANU), fruit bats are the only family of bats not capable of navigation using their voice box - despite being closely related to bats that can. 

Instead, they use their large eyes and sense of smell to get around. 

"Some evolutionary biologists take this to mean that fruit bats have lost the sophisticated echolocation capability of their relatives, which evolved once in an ancient bat and was inherited by other bat species," Dr Wilson said. 

"Others think that fruit bats never acquired these capabilities in the first place, meaning that sophisticated echolocation evolved multiple times. 

"Our study took a different approach by focusing on early development of the ear and throat bones."  

The research group collected hundreds of embryos of bats from all over the world and used new technology that allowed them to study microscopic soft tissue structures.  

"If you try to imagine a bat embryo's size, we are talking about millimetres, so examining their anatomy at this scale is extremely difficult," Dr Camilo López-Aguirre a lead author of the study from UNSW said.  

"Using dice-CT - a tool for high-resolution 3D imaging of soft tissue - allowed us to see these tiny structures and trace their development." 

The team compared fruit bats to sophisticated echolocating bats, as well as non-echolocating mammals such as shrews, and found something striking.  

Fruit bats were indistinguishable from non-echolocating mammals in all aspects of their ear bone development, while the two major groups of sophisticated echolocators showed different patterns of development, suggesting they evolved their sonar independently.  

"The developmental evidence pointed towards multiple origins of echolocation," Dr Wilson said. 

Dr Wilson says while the discovery advances our understanding of these "enigmatic" mammals, research is far from over.   

"Echolocation is a remarkable feat that innovations in engineering systems have yet to match. There's a lot we still don't know about how it evolved and how it works," Dr Wilson said.  

Dr Wilson's research lab is continuing to investigate how bats function. 

The research team also included biologists from The University of New South Wales, as well as City University of Hong Kong, the University of Tokyo and Vietnam Academy of Science and Technology. 

The study has been published in the journal Current Biology.

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Updated:  10 March 2021/Responsible Officer:  Head of School/Page Contact:  CASS Marketing & Communications