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Jaws 2: not the sequel but moray eel sci-fi

Bienvenidos! A south-of-the-border argus moray eel (Muraena argus) recently arrived in the La Jolla submarine canyon. Be it a vacationer, immigrant or lost soul, the eel is squatting in the premade den of a male sheephead fish. Though the sheephead acts agitated as a result of the attention his roommate has garnered, the eel seems to be taking the scores of camera-toting divers calmly in stride.

We do have a local moray, the California moray eel (Gymnothorax mordax), but it’s really more like a naturalized citizen. Our moray does not reproduce in Southern California waters, possibly because the water is too cold. Eggs hatched off Baja California develop into larvae that drift for up to a year. Currents carry some north, where they settle in U.S. waters. Though California and argus eels are similar in overall look, the argus has one distinction that’s a real eye opener: striking 24K gold eyes punctuated with dark pupils. In contrast, a California moray sports watery blue eyes. Other disparities between the two are more subtle. The argus eel’s body is gray-brown splattered with tiny, white dots, a black splotch covers the gill openings and the head sprouts prominent, tubular nostrils. The California moray has a light- to dark-brown or greenish body and stubby nostrils.

To breathe, most fish simply close and open their gill flaps, which forces oxygen-rich water over the gills. Breathing in gill-flap-toting fish is essentially unnoticeable to divers. Since a moray doesn’t come with gill covers, the mouth must constantly open and close to flush water over the gills, inadvertently giving the wrong impression to humans. The eel’s open mouth and intimidating dental work look in position to attack; the closed mouth, puffed-cheek stance looks like the moray is holding its breath until it turns blue.

Moving on to take-out, most bony fish approach food or prey by expanding the mouth to take in both water and the food. This creates negative pressure to suction in the repast while the excess water leaves through the gills. The food is then sucked back to the second set of jaws and teeth situated deep in the throat, which then split, slice, tear or crush food as it goes down the gullet.

A moray eel doesn’t have the luxury of suction because it can’t open its mouth wide enough to create the negative pressure needed to get the food to the secondary jaws and teeth. Instead, it feeds in a way so ingenious, it smacks of science fiction. The feeding sequence begins when a moray snags prey with its clearly adept front jaws. Now comes the sci-fi part. The secondary jaws, moving independently from the front jaws, spring forward and seize the prey, dragging it back toward the throat for swallowing. When these jaws lunge forward, they cover nearly the length of the animal’s skull but don’t overlap the front jaws. Put another way, if the moray can sink in a few teeth to hold its prey, the back jaws will surge forward and seal the meal deal. Even if you blink, you’ll miss the entire process because it takes just fractions of a second. When not in feeding mode, the back jaws sit benignly behind the eel’s skull.

A moray has a kindred spirit in terrestrial snakes because both demonstrate how a physical strategy evolved to allow long, skinny animals to consume whole prey that are big and fat. But snakes use a side-to-side ratcheting mechanism to swallow prey, which is physiologically different from the eel’s front-to-back use of mobile second jaws — the first described case for a vertebrate. Whereas much is understood about the ecology of snakes, we are mostly in the dark about morays. How morays evolved, how often they feed, what they eat and how large is their prey are only some unknowns yet to be discovered. What we do know is that both jaws have sharp teeth covered with bacteria. A bite can be doubly painful and become infected. Though morays aren’t aggressive unless disturbed or frightened, savvy divers do not tempt fate by inserting hands into crevices.

I have a diving update: The argus moray eel has gone missing! Personal choice or foul play? Diving continues to monitor the situation.


— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Send comments to