26 January 2010

Whales and Bats Share Echolocation-Related Gene

Toothed whales and bats share the same gene:

The echolocation abilities of bats and whales, though different in their details, rely on the same changes to the same gene - Prestin. These changes have produced such similar proteins that if you drew a family tree based on their amino acid sequences, bats and toothed whales would end up in the same tight-knit group, to the exclusion of other bats and whales that don't use sonar.

This is one of the most dramatic examples yet of 'convergent evolution', where different groups of living things have independently evolved similar behaviours or body parts in response to similar evolutionary pressures.


At first, it might seem strange to see such strong convergence at the genetic level. After all, bats and toothed whales echolocate very differently. Bats create their sonar pulses using their voicebox while whales pass air through their nasal bones. Bats send their calls through air and whales send their through water. A single gene can't have accounted for these differences in production.

Instead, Prestin's role is in detecting the rebounding echoes. It is activated in the "outer hair cells" of the ear, which allow mammals to hear high frequencies. In echolocating species, these cells are shorter and stiffer than normal, making them exquisitely sensitive to the ultrasonic frequencies used in echolocation. Li thinks that the Prestin changes might have helped to tune the outer hair cells of echolocators to high-pitched noises.

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