Fish
Green Moray Eel
Gymnothorax funebris · also called green moray, olive-green moray
The green moray is the big, watchful eel of Atlantic and Caribbean reefs — a metre or two of muscle wedged into a hole, jaw working steadily, watching everything that swims past. Its “green” is a trick of mucus, and hidden in its throat is one of the strangest feeding mechanisms of any vertebrate.
Overview
Green morays live on reefs, rocky ledges, seagrass beds, and shipwrecks in the warm western Atlantic and Caribbean, from the shallows to around 40 metres. Each eel occupies a den — a crevice or hole with one or more openings — and stays there through the day with just its head protruding, emerging at night to hunt across the reef. They are solitary and territorial, though several may share a large reef structure.
Body and colour
A green moray has the classic moray shape: a long, laterally flattened, scaleless body with the dorsal fin running its full length and no paired fins. It is coated in a thick layer of toxic yellow-tinged mucus that protects against parasites and disease and helps it slide through rough coral. Over the eel’s actual brown skin, that yellow mucus reads as a solid green — the reason for the name.
The two sets of jaws
The green moray hunts fish, octopus, and crustaceans, largely by smell and by night. Its most remarkable feature is a second pair of jaws deep in the throat, the pharyngeal jaws. Most fish capture prey by opening the mouth fast to create a suction that pulls water and food in — but a moray hunting in a tight reef hole has no room to do this. Instead, once its outer jaws grip the prey, the pharyngeal jaws thrust forward into the mouth, clamp on, and haul the food back into the throat. It is a mechanical solution to swallowing without suction, and it lets morays take surprisingly large prey.
Reproduction
Green morays spawn in open water, the eggs and larvae joining the plankton. Moray larvae, called leptocephali, are transparent, leaf-shaped, and drift for months before settling to the reef and transforming into tiny eels. Little is known about green moray courtship in the wild.
Green morays and people
The species is common and listed as Least Concern. It is not an important food fish — the flesh can carry ciguatera toxin — but it is a favourite of reef divers and a fixture of public aquariums. Its fearsome reputation is largely undeserved: bites are defensive or feeding accidents, almost always linked to people feeding or harassing the eels, and a green moray left in its hole is no threat.
Green Moray Eel: common questions
Why does a moray eel constantly open and close its mouth?
It is breathing, not threatening. Moray eels have small, rounded gill openings and cannot pump water over their gills as efficiently as most fish by flexing the gill covers, so they hold the mouth open and rhythmically gape to force a current of water across the gills. To a diver it can look menacing, but a moray showing its teeth in this way is usually just respiring while resting in its hole.
What are a moray eel's second jaws?
Morays have pharyngeal jaws — a second, tooth-bearing jaw set located in the throat. In most fish these are used only to manipulate food already in the mouth, but in morays they are highly mobile and can be launched forward into the mouth cavity to grab prey and drag it back toward the gut. This lets a moray swallow large or struggling prey in the confined space of a reef crevice, where it cannot create suction the way an open-water fish does. It is the closest thing in nature to the creature in the film "Alien."
Is the green moray actually green?
No. Its skin is a drab brown or grey-blue. The eel secretes a thick, yellowish mucus over its whole body — a protective layer against parasites, abrasion, and infection — and the yellow tint over the darker skin combines optically to look uniformly green. Strip the mucus away and the eel is brown.
Are green moray eels dangerous?
Not to a diver who leaves them alone. Green morays are shy and spend the day wedged in reef holes with only the head showing. Bites happen when people try to hand-feed them, reach into crevices, or corner them — the backward-angled teeth make a moray bite hard to pull free, and the wounds tear and can become infected. Left undisturbed, the eel simply watches and gapes.