'Alien' jaws help moray eels feed

Moray eels have a unique way of feeding reminiscent of a science fiction thriller, researchers at UC Davis have discovered. After seizing prey in its jaws, a second set of jaws located in the moray's throat reaches forward into the mouth, grabs the food and carries it back to the esophagus for swallowing.

"This is really an amazing innovation for feeding behavior for fishes in general," said Rita Mehta, a postdoctoral researcher in the Section of Evolution and Ecology at UC Davis.

The research is published in the Sept. 6 issue of the journal Nature.

The research shows the amazing diversity possible among living things, even in something as fundamental as feeding, Mehta said.

The researcher used a high-speed digital camera to film eels feeding in the laboratory, and was able to capture the rapid movement of these secondary pharyngeal jaws. She also used X-ray and other imaging equipment at the UC Davis School of Veterinary Medicine to work out how the jaws could move.

More than 200 species of moray eels are found in tropical waters worldwide, often living in holes in rocks and coral reefs. In the wild, they can reach 10 feet in length.

Most fish feed by suction. When it comes upon food or prey, the fish rapidly expands its mouth cavity, sucking in water and the food with it. Some fish feed by overtaking prey with their mouth open or grabbing it in their jaws, but most of those fish then use suction to move the food from the mouth to the esophagus.

But moray eels have little ability to generate suction through their mouths, Mehta found. Instead, they first grasp food with their powerful, toothsome outer jaws. Then the pharyngeal jaws, armed with large, curved teeth, reach forward and seize it. At the same time, the outer jaws release the prey and the pharyngeal jaws bring it back for swallowing. The whole process takes just fractions of a second.

Other fish are known to have pharyngeal jaws that can grind or crush food, but "nothing this spectacular," said Peter Wainwright, professor of evolution and ecology at UC Davis and co-author with Mehta on the paper. Only the moray eel seems to have a second, mobile set of jaws that can reach forward and grab prey.

At rest, the pharyngeal jaws sit behind the eel's skull. When they reach forward, they move almost the length of the animal's skull, but do not protrude beyond the powerful outer jaws. The arrangement means that if the eel can sink in a few teeth to hold its prey, it can secure its meal with the pharyngeal jaws, the researchers note.

Mehta compared the eels to snakes, which also have to fit large food items through a relatively narrow mouth into a long, thin body. Snakes solve the problem by "ratcheting:" they can separate the left and right sides of their jaw, and hold onto the food with one side while they work the other side of the mouth round it.

Mehta and Wainwright are now investigating how the morays' extraordinary jaws evolved. Other species of eel, such as the American eel Anguilla, feed by suction. Moray eels may have evolved other methods as a result of hunting in confined spaces, where they could not rapidly expand their heads to create suction.

"Eels are an amazingly diverse and bizarre group of fishes, and not very well known," Wainwright said.

Source: University of California - Davis

Related stories:

Giant flying reptiles preferred to walk
New research into gigantic flying reptiles has found that they weren’t all gull-like predators grabbing fish from the water but that some were strongly adapted for life on the ground.
When following the leader can lead into the jaws of death
For animals that live in social groups, and that includes humans, blindly following a leader could place them in danger. To avoid this, animals have developed simple but effective behaviour to follow where at least a few of them dare to tread – rather than follow a single group member.
You are what you eat? Maybe not for ancient man
New findings suggest that the ancient human “cousin” known as the “Nutcracker Man” wasn’t regularly eating anything like nuts after all.
Unveiling the underwater ways of the white shark
It's hard to study a creature when you only catch fleeting glimpses of it. Up until recently, that was one of the big stumbling blocks for marine biologists and ecologists, but advances in electronic tracking technology have allowed them to peer farther across, and deeper under, the surface of the oceans than ever before.
Chimps dig up clues to human past?
One of the keys enabling the earliest human ancestors to trade a forest home for more open country may have been the ability to gather underground foods. Now a team of scientists reports for the first time that in Tanzania our closest living relatives, chimpanzees, are using sticks and pieces of bark to dig for edible roots, tubers and bulbs.
Rare albino ratfish has eerie, silvery sheen
A ghostly, mutant ratfish caught off Whidbey Island in Washington state is the only completely albino fish ever seen by both the curator of the University of Washington's 7.2 million-specimen fish collection and a fish and wildlife biologist with more than 20 years of sampling fish in Puget Sound.
Exciting New Kenyan Fossils Challenge Established Views on Early Evolution of Our Genus Homo
Two new fossils, described this week in the journal Nature, cast fresh light on a little understood and important period of human prehistory at the dawn of our own genus, Homo.
Did pterosaurs feed by skimming?
Scientists at the University of Sheffield, collaborating with colleagues at the Universities of Portsmouth and Reading, have taken a step back in time and provided a new insight into the lifestyle of a prehistoric flying reptile.

News discussion:

General Science news