Eel Species with Protruding Throat Jaw

Researchers studying one species of moray eels have uncovered a deadly secret that helps the fish to swallow their prey. Like the creatures from the sci-fi movie Alien, these eels have a second, extendable pair of jaws — encrusted with sharp teeth — that thrusts forward to ensnare their prey.

High-speed videos and X-ray photos show how the second jaws, called pharyngeal jaws, lie in wait inside the throat (top of picture), and then extend forwards into the mouth to grab prey that has been captured by the eel's main teeth (bottom of picture). The morsel is then drawn into the eel's esophagus.

This helps the eels (Muraena retifera) to be deadly hunters, despite the fact that, unlike many other predatory fish, they cannot generate strong suction forces inside the mouth cavity to capture a meal. Zoologists had previously been puzzled as to how moray eels, which live on coral reefs and rocky shorelines all over the world, keep hold of their prey long enough to swallow it. Unlike the movie creatures, however, these moray eels cannot extend their second set of jaws out beyond their first.

Many fish species have extra jaws in their throats, which can function to filter food from water or to grind prey when swallowing. But the eel's extendable jaws are the first throat jaws known to be adapted to help catch prey, rather than simply to help swallow it.

Be sure to check out the video of the jaws in action: