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How did whales get so big? New research suggests a unique organ

Ben Anderson

New research on an unusual organ in the jaws of rorqual whales -- better known as filter-feeding whales -- offers new insight into how such a large mammal is able to subsist on such a small diet.

Of course, "small" when it come to whales means the size of the food, not the quantity. Indeed, many rorqual whales -- which include humpbacks, the endangered fin whales, and the blue whale, largest animal on earth -- can consume several tons of krill every day, using their baleen.

The secret to their success is something called "lunge-feeding," in which they open their massive jaws, exposing the baleen and filling their mouths with immense quantities of water -- tens of thousands of gallons -- and anything edible therein.

According to the New York Times, the unique feeding process is the result of an organ in the whales' lower jaw, which allows for an expansion of the accordion-like jaws, filling with water like the pouch of a pelican's beak before pushing the water back out and retaining the food left behind.

A new report published in the journal Nature says that the organ is crucial to coordinate the physiological processes behind filter feeding. According to the BBC, previous scientists had possibly dismissed the organ as being nothing more than a fluid filled sac. One scientist who helped author the new study referred to the organ as little more than a "gelatinous mass."

The research was conducted on dead fin and minke whales caught by Icelandic whalers.

Whales are able to expand their jaws to contain such huge amounts of water because their lower jaw isn't fused -- in the way humans' jaws are. Instead, there are two separate bones, with the newly-discovered organ located at the front tip of the mouth in the gap between the bones.

So how does the organ work? According to the Los Angeles Times:

(The organ) is composed of connective tissue with protrusions that contain nerves, and is suspended in a gel-like material. The evidence indicates that the sensory organ responds to jaw rotation when the whale opens and closes its mouth and when the whale's throat pleats expand as it takes in water.

"This odd arrangement of tissues didn't make much sense to us at first, but then we realized that that this organ was perfectly placed, anatomically, to coordinate a lunge because the soft structure is pinched by tips of the jaws and deforms through the course of a lunge," (study author Nick) Pyenson said. "This deformation is registered by nerves inside the organ, informing the gulping whale about its gigantic jaws, which must close before prey escape."

The result, Pyenson said, is a controlled lunge where the whale adapts to the way the water fills its mouth, rather than just a blind lunge that ends when the whale's mouth is full.

The finding is particularly unique since humans -- scientists, whalers, and subsistence hunters alike -- have been butchering and dissecting whales for years, and no one has noticed the amazing organ before. 

Read much more about the new discovery at the New York Times, the Los Angeles Times and the BBC.