EXTREME FEEDING: BLUE whales' gluttonous gobbling of fishy fluids

Marine mammal boffins are less baffled by blue whales, having discovered that stretchy nerves allow the beasts to gobble the gallons upon gallons of water and food they are famous for guzzling.

In a paper with the pleasantly explicit title "Stretchy nerves are an essential component of the extreme feeding mechanism of rorqual whales" published on Monday in Current Biology, a Canadian research team has revealed how a class of whales, which includes Blues and Humpbacks, are able to engage in its distinctive "lunge feeding" activity.

Lunge feeding is a unique and extreme predation technique in which an enormous amount of water is swallowed - along with the food swimming in it - and then expelled through filter-like baleens which snag the whales' aquatic apéritifs.

The biomechanics of this feeding method, which requires the whale to first gain enough momentum that the to-be-swallowed volume of water will force its elastic throat to fold, have long fascinated scientists.

The Canadian research team had trekked to Iceland to investigate the biomechanics of "lunge feeding" and sought to examine the more extraordinary anatomical qualities of whales' muscles, including the separate right and left jawbones which allow the animal to open its mouth to 3m in width.

Talking to the BBC, Professor Vogl credits co-author Robert Shadwick with the "serendipitous discovery" of an extraordinarily elastic nerve in rorqual whales.

"We were looking at the muscle in the floor of the mouth and there were these long white cords," Prof Vogl told the BBC. "Bob picked one up - about 3ft of it - grabbed each end and stretched it. He looked at me and said, 'Hey, look at this!'

"We thought it was a blood vessel." said the University of British Columbia boffins.

The stretchiness of the long white cord was unusual, and its elasticity in returning to its original size piqued the scientists' interest. When the team cut it open, however, it was evidently not a blood vessel as it was not hollow. Instead, they found a yellowish core running through its middle.

"I realised this was a nerve, and it was very different from any other nerve I've ever seen," Professor Vogl told the Beeb.

Nerves are not typically stretchy and will usually be of enough length to cover the muscle extensions - however the extraordinary extensions capable of the "lunge feeding" rorqual whales has contributed to the development of these elastic nerves. Examining the yellowish core under a microscope, the scientists were able to assess how nervous fibres were wound tightly about a central core which itself unfolded as the cable stretched.

The thicker, white layer insulating the nervous core, however, is composed of a protein called elastin, which is found in many mammals. "[The whales have] used building blocks that are present in other animals but they've used them in different ways to produce this stretchy nerve," Dr Vogl explained.

The Beeb was also in touch with Dr Guy Berwick, a neuroscientist at the University of Aberdeen in Scotland, who stated his expertise with nerves and muscles.

"Nerves are generally really quite fragile things; they're quite well protected and they don't withstand stretch well at all." said Berwick, adding that "This looks like a really neat trick to get around that problem, which the whale obviously needs to do because its mouth inflates so much." ®