Science has found that baleen whales have an unusual bungee-tongue

A humpback whale tail breaches off Sydney Heads. Cameron Spencer/Getty Images

A unique type of nerve has been found in the mouths of rorqual whales which can stretch to more than double their length and help them sift the sea for their food.

Canadian and US scientists say the stretchy nerves support a unique and extreme feeding strategy, where the whales open their mouths and lunge while their tongues invert and their mouths fill like giant water balloons full of floating prey.

Those prey are concentrated by slowly expelling the water through the sieve-like baleen plates. The volume of water brought in with a single gulp can exceed the volume of the whale itself.

Rorqual whales represent the largest group among baleen whales weighing 40 tonnes to 80 tonnes.

Rorqual whales. Image: Vogl et al./Current Biology 2015

“Rorqual whales attained large body size with the evolution of a bulk filter feeding mechanism based on engulfing huge volumes of prey-laden water,” says A. Wayne Vogl of the University of British Columbia.

Vogl and his team made the nerve discovery after a member of the lab picked up a dull white cord-like structure and stretched it. Vogl recalls him saying something like: “Wow, look at this.”

They realised that it was a nerve but it was unlike any they’d seen before. The nerves of other species are generally surrounded by a thin collagen wall and any stretch can pull and damage the nerves.

The nerve fibres are packaged inside a central core. A thick and stretchy outer wall, full of elastin fibres like elastic bands, surrounds the nerve core.

The findings are reported in the journal Current Biology.

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