In a study published in 2007 in Science Daily, moray eels' are noted as having "alien" jaws. Describing anatomy as "alien" is always a bit spooky, but the description isn't nearly as scary as it is when you understand exactly what the eels' jaws do.
As the study out of University of California Berkeley explains, the eel "seizes" the prey in its jaws, and then a second set of jaws in the back of the animal's throat comes forward into the mouth and takes the food back through the esophagus.
It is ... pretty horrifying. But, anatomically and scientifically speaking, it's kind of cool, too.
As Rita Mehta, one of the experts quoted in the study says, this feed mechanism is an "amazing innovation for feeding behavior for fishes in general."
The notable anatomy of eels was discovered with the assistance of high-speed cameras and X-rays. The combination resulted in records of how eels feed, as well as anatomical details that explain how the eels' bones move.
While the eels' outer jaws have teeth and are easy to see, the other "pharyngeal" jaws have larger, curved teeth (again, horrifying) that come forward to move the food through the eels' body.
They never come out far enough to go beyond the eels' outer teeth, though, meaning that they stay relatively hidden.
It also means that the eel can grab its prey while also securing it. The benefit of having a lot of teeth.
Moray Eel Eats Octopus www.youtube.com
Mehta also noted in the study that this interesting eels' mechanism results from its elongated body shape, much like the way a snake has to separate its jaw to get food to move through its long, narrow body. There has to be something that propels the food through its body, and for the eel, the second jaw works to make that happen.
The discovery of the second jaw also means that research will take place around how exactly the eel evolved this way, which will likely provide more information about how eels differentiated themselves from other fish (most of which use suction to eat, rather than two sets of jaws).