The moray eel is a slender, reef-dwelling fish native to the nooks and crannies of subtropical and temperate seas. While they are voracious eaters, they are not great swimmers due to their lack of a pectoral fin. Instead they lurk almost motionless in rocky crevices, often with just their heads peeking out, waiting for a meal to swim by.
Most other bony fish have developed a method of slurping up prey by very rapidly opening their mouths to create an area of negative pressure directly in front of them. This quickly draws water – and any unsuspecting victim – back into the mouth cavity. While fish that bite also use suction to get food from their mouths into their throats, the moray eel doesn’t. In fact, few fish consume their food in as impressive – or terrifying – a manner as the moray eel.
Because they live in tight crevices, the suction method wouldn’t work for a moray because the head has no space to expand into. And besides, the eel’s prey is generally too large to really be affected by the suction technique. Instead, morays are the only known species of vertebrate to possess two pairs of jaws. It sounds like some kind of special-effects monster from the Alien movies, but the moray eel has a second set of raptorial jaws in its pharynx: the pharyngeal jaws. These gnashers located behind the eel’s skull lurch forward after the fish has taken the initial bite and grab at the victim, drawing it back down into the throat so the eel can swallow it.
It’s thought that these movable second jaws are a result of adaptation to suit the confined spaces these fish tend to inhabit in reef environments.