Dolphin and bat sonar share DNA design

The sonar sense of dolphins and bats evolved independently in very different environments but is similar at the genetic and molecular level in both species, scientists say.

The sonar sense of dolphins and bats evolved independently in very different environments but is similar at the genetic and molecular level in both species, scientists say.

The bottlenose dolphin, related to toothed whales like the orca, uses echolocation to track prey more than 100 metres away. ((Rich Pedroncelli/Associated Press))

Researchers in China, the U.S. and the U.K. say echolocation — the ability to emit pulses of high-frequency sound and interpret their echoes — in bats and toothed whales is essentially the same.

The researchers said it's an unusual case of an independently evolved characteristic having the same genetic and molecular basis.

"The seemingly different echolocation abilities that evolved independently in whales and bats have a similar underlying molecular mechanism," said Jianzhi George Zhang of the University of Michigan, in a statement.

In both toothed whales, including dolphins, and in bats, a protein called prestin, located in specialized hair cells in the inner ear, plays an important role in echolocation.

The protein acts as an amplifier, allowing the hair cells to vibrate in response to sound waves at certain frequencies.

DNA databases reveal identical genetic changes

Researchers used DNA databases to find the gene that holds the code for prestin in 26 mammal species, including two toothed whales and 13 species of bat, 10 of which have the echolocation ability.

They found that in both bats and dolphins, the same genetic changes accompanied the evolution of echolocation.

The endangered grey bat relies on echolocation to find its insect prey. ((Kevin Pieper, Baxter Bulletin/Associated Press))

"The natural world is full of examples of species that have evolved similar characteristics independently, such as the tusks of elephants and walruses," said Stephen Rossiter of Queen Mary, University of London. "However, it is generally assumed that most of these so-called convergent traits have arisen by different genes or different mutations."

"Our study shows that a complex trait — echolocation — has in fact evolved by identical genetic changes in bats and dolphins," Rossiter said.

Despite this basic similarity, bats and dolphins have very different abilities because of their very different environments, Zhang said. Bats can find prey a few metres in front of them, while dolphins can use echolocation for ranges of 100 metres and beyond.

"The speed of sound in air is about one-fifth that in water, making the information transfer during sonar transmission much slower for bats than for whales," said Zhang.

Two related studies on the topic appear this week in the journal Current Biology.