Tucked into its coral lair just off the coast of the Canary Islands, a fangtooth moray eel (Enchelycore anatina) lies in wait. While the eel’s menacing stare may strike fear into the heart of an underwater photographer, it’s the teeth of this top-level predator that really make an impression—and those are just the teeth we can see.

The fangtooth moray displays some of the most impressive teeth in the moray eel family, a group made up of some 200 toothy species. Its gaping mouth is rimmed with dagger-sharp, glass-like teeth that can measure more than 2 centimeters (almost 1 inch) in length—significantly longer than those of most morays. For obvious reasons, these are the teeth that have drawn interest from divers and photographers. Scientists, however, have focused their attention on the moray eel’s hidden weapon: a second set of jaws and teeth that enables the animal to swallow large prey in tight quarters.

Moray eels are well-adapted to life on the reef, often slinking through crevices and holes in pursuit of prey. This requires specialized adaptions: a narrow, streamlined head and serpentine body. But the physical traits that make this way of life possible can present serious challenges.

Most fish use suction to help them swallow. After latching onto an animal it wants to eat, a fish quickly opens its jaws wide to create a vacuum that pulls the prey from the mouth into the throat. With little room for such maneuvers in the tight spaces they haunt, moray eels have evolved a different solution. The moment an eel grabs a large fish, squid, or octopus with its outer jaws, a second set of jaws deep inside the eel’s throat lunges forward and sinks its curved teeth into the prey. It’s only when this inner jaw retracts, pulling the meal into the eel’s body, that the outer jaw loosens its hold. With adaptations like these, it’s no wonder this group of fishes is among the most successful in the sea.