Moray eelMuraenidae

A moray has a second set of jaws, and they are not in its mouth. They sit back in the throat, and when the eel bites, they slide forward into the mouth cavity, take hold of whatever is being gripped there and drag it back down. No other vertebrate is known to feed this way, and it exists because of where a moray lives. Most fish swallow by suction: the mouth opens fast and a slug of water carries the prey inward. An animal wedged in a hole in the reef cannot pull that off, so the throat jaws do the transporting instead. The mechanism was only described in 2007.

The body handles anything too big to swallow. A moray with a grip on something large ties itself into a knot, works the knot down its own length until it comes up against the prey, and uses its coils as a brace to twist a piece off. Run the other way, the same trick levers the eel out of a hold.

The open mouth is not a threat display. A moray has none of the stiff gill covers other fish flare to drive water across the gills, only a small round opening on each side, so it pumps by working its jaws, continuously, whether or not you are there. It hunts by smell rather than sight, which is the part worth carrying with you: bites happen when hands go into holes and when people feed them, and the teeth rake backward, so an eel that has taken hold of something is not built to let go of it.

Thirty-one species are listed for this sea, from the giant moray at three meters to snake morays no thicker than a pencil that live inside rubble and are almost never seen whole. Most of them hunt at night, which is why a reef that looks like it holds two morays holds many more.