The find, outlined in this week’s Nature, is the first described case of a vertebrate using a second set of jaws to restrain and move prey.

But having two jaws is not unusual. Most other fish have them, with the second set generally remaining in the throat where it helps to grind and pulverize prey before sending it down the esophagus. Fish with this anatomy usually first secure their prey through suction, similar to a person slurping down a raw oyster.

The moray eel takes that basic design to a surprising new level.

"The second set of jaws in a moray eel reaches up from within the throat cavity into the oral jaws and grabs the prey," lead author Rita Mehta told Discovery News.

"Once the prey has been grabbed, the jaws move the prey into the esophagus," added Mehta, a biologist at the University of California at Davis.

The double jaw allows the eels to capture and eat large, slippery squid, octopuses and fish.

"The prey items are swallowed dead or alive, depending upon the strength of the initial bite during prey capture," Mehta said.

For the study, she and co-author Peter Wainwright studied moray eel anatomy and recorded the eels using cinefluoroscopy, an X-ray imaging technique that can produce moving, two-dimensional images. They also captured moray eels in action with high-speed video.

Since the second set of jaws launches forward very quickly, its movement was only then made evident.

Moray eels are long, skinny bony fishes that usually inhabit, and hide out in, confined spaces such as coral crevices and shallow reefs. Without much space to work, it would be hard for the eels to build up sufficient suction the way other fish do.

The researchers suggest that over time, the eels must have evolved their second set of jaws, which look like thin, clawed forceps, to resolve the problem of eating slippery, squirming food in a confined space without limbs for holding and the ability to suck.

Although moray eels and snakes are not closely related, the two groups share similar body plans. Snakes don’t have the eels’ dramatic double-jawed eating method, but they too can swallow large, moving prey without arms.

Snakes achieve this with alternating ratcheting movements of the left and right sides of their upper jaws. The process remarkably allows them to advance their heads over prey that may be much fatter than the snake.

Mark Westneat, curator of zoology at the Field Museum of Natural History in Chicago, told Discovery News he was fascinated by the moray eel findings.

"When I first saw the videos, I said, ‘Oh wow — look at that!’; it was the most interesting and surprising thing in vertebrate feeding I have seen in several years," Westneat said.

"The discovery opens up an interesting track of research into the structure and function of eel feeding — there are over 600 eel species!" he added.

Via: Discovery Channel