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FROM BITE TO BELLY How does a 12-foot-long eel move food down its throat? Sliding rear jaws. After the front jaws bite, the rear ones slide up and grab the prey. As those retract, the front jaws release. The eel then juts its head forward, which aids in the swallowing process.
Pulsing mouth, vacant stare, snakelike body: The moray eel truly suggests alien origins. But there’s more. Back behind this giant reef fish’s already toothy maw looms a second set of jaws, which launch from the throat, grab prey from the front teeth, then retreat into the dark tunnel of the eel’s esophagus. It’s the stuff of science fiction. But to scientists studying this unique morphology, it’s a brilliant feeding mechanism for such an elongated creature.
Unlike most bony fishes, morays don’t seem to generate enough suction to help in swallowing, says Rita Mehta of the University of California at Davis. Instead, the novel dual-jaw arrangement, which she and colleagues recently examined with high-speed video, allows the animals to both restrain and transport big prey—the most efficient nourishment for big animals—down the long throat. This is the first report of such a mechanism in a vertebrate. Though on a different branch of the evolutionary tree, snakes have a related system, a set of ratcheting jaws that grip and maneuver food into the gullet. Says Mehta, “It’s a wonderful example of convergence”—when distant organisms facing the same problem develop similar solutions. —Jennifer S. Holland
Art: Raúl Martín
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Mar 4, 2009 10PM #
You might also be interested in presenting an examination of the alimentary canal of the parrot fish: it has so-called "pharyngeal jaws" behind its mouth which grind the coral on which it feeds, it has no stomach, and larger individuals can defecate up to a ton of 'sand' annually.
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