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Thursday, September 6, 2007

Moray eels' hidden jaws pack second bite.

Moray eels, those snake-like predators that lurk in coral reefs, use a second set of jaws to pull prey back into their throats with deadly efficiency, researchers said on Wednesday.

Biologists have known for some time that moray eels have a second set of jaws, known as pharyngeal jaws, as do many other bony fish. But until now, biologists had never seen them put to such unique use.

"They spotted this outrageous behavior of the pharyngeal jaw thrusting way forward into the mouth, which was not suspected before," said Mark Westneat, who studies feeding mechanisms of coral reef fishes at the Field Museum of Natural History in Chicago.

"The surprise and interest was the extent of the movement, and how it grasped the prey and yanked it back into the throat," Westneat, who wrote a commentary on the findings, said in a telephone interview.

"It's one of these great 'Oh wow' stories in basic biology."

Rita Mehta and colleagues at the University of California Davis discovered the moray's special feeding ability through high-speed digital cameras, that captured the second jaw as it jutted forward while feeding.

Mehta, whose study appears in the journal Nature, said the jaws allow the eels to swallow large prey.

Mehta had set out to understand the purpose of this second set of jaws in moray eels, a diverse group of some 200 species.


She and UC Davis Professor Peter Wainwright used X-ray and other imaging equipment from the university's veterinary school to work out how the jaws could move.

It turns out the moray accomplishes its oral gymnastics by elongating the jaw muscle, allowing the second set of jaws -- armed with large curved teeth -- to bite into the prey.

When not in use, the moray's extra set of jaws rest behind the eel's skull. When in use, they move almost the length of the animal's skull.

"What this enables moray eels to do is to grip their prey at all times," Mehta said. "It's definitely a good predator."

Of the roughly 30,000 species of fish, most devour their prey by means of suction, or as in the case of sharks, by biting off large chunks.

Mehta and Wainwright suspect moray eels may have evolved this fierce feeding method through hunting in tight spaces, such as the crevices of coral reefs.

In the wild, moray eels can reach 10 feet in length.

They are now looking into how the moray's jaws evolved. Other species of eel, such as the American eel Anguilla, feed by suction.

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