Slashdot Mirror
Some Moray Eels Have Two Sets of Jaws
mikesd81 writes that the Mercury News reports that scientists at UC Davis have discovered that some eels have an extra set of jaws deep in their throats that launch forward into their mouths to help pull prey in. "'It looks like a funny pair of forceps with curved sharp teeth,' said evolutionary biologist Rita Mehta, lead author of the research, which appears Thursday in Nature. Before the discovery, scientists thought that all aquatic predators swallowed their prey using suction. By dropping the lower jaw and creating a flow of water into their mouths, they draw in the prey. The two species of moray eels studied by Mehta and Wainwright are the first examples of an alternative feeding method. Instead of sucking, one of these eels bites its prey with its primary set of teeth. It then draws the second set of teeth into its mouth by contracting long muscles. The secondary jaws clamp down on the prey, allowing the eel to move its primary jaws forward in a gulping motion to take in more of the prey. The two sets of jaws take turns until the whole animal has been swallowed." mikesd81 adds a link to a YouTube video of an eel eating, noting "If you look closely right around 34 seconds you can see what looks like the other set of jaws chewing."
From the original source of information and in the Journal Nature's News, these jaws are definitely not for chewing. If you look at the images of x-rays you will see that these are more 'hooks' or teeth than jaws.
In the rest of the articles, they talk about this mearly being the method by which the eel pulls the food down or holds on to it. I don't believe any fish (or snakes for that matter) really 'chew' their food.
I think what you are seeing in that video is the extra skin around the inner part of the mouth billow out as the animal attempts to suck the food in (which as mentioned, most fish do). I don't know a lot about eels so I can't verify that the eel in that video is a moray eel much less one of the kinds that have that kind of device to ingest food. There's over 200 species of moray eels so I guess it would be futile to try and verify it. Still an interesting video but I predict you would see that kind of action when any fish feeds.
My work here is dung.
One reason: the alien queen in Aliens (and Aliens 2 3 4) exhibited this type of anatomy. Of course in the movie the inner set of jaws were for biting chewing and drooling ...
IANMB but it seems unlikely.
Those eels have two distinct sets of jaws with associated muscles, but the sharks only have one set with several layers of teeth (new one are grown all the time on one side of the jaw and push the older ones until they fall).
Yup, http://en.wikipedia.org/wiki/Xenomorph_(Alien)
Witty Comment Here
Halfway down on the left side: "Watch the Moray Eel"
y Id=14194579
http://www.npr.org/templates/story/story.php?stor
Interesting idea, but prolly not. Sharks and rays are a completely different brand of creatures than the moray eels, which belong to the bony fishes. Sharks, which are cartilaginous fishes, are also far older.
Both the summary and part of the article are written to erroneously imply that the jaws were just discovered... But what was actually discovered (and is newsworthy) is the function of those jaws.
Virtually all fish have two sets of jaws - oral jaws and pharyngeal jaws, also known as the pharyngeal mill. The pharyngeal mill is normally used for crushing and grinding hard foods, such as crustaceans, but morays have evolved the ability to use them to grab prey held in the oral jaws and pull it into the oesaphagus. There's a good interview here: http://www.practicalfishkeeping.co.uk/pfk/pages/it em.php?news=1367