The Moray Eels And Their Amazing Pharyngeal Jaws

Moray eels’ heads are too narrow to swallow their prey. For this reason, they have a second pair of jaws located in the throat, called the pharyngeal jaws.
Moray eels and their amazing pharyngeal jaws

All species of the muraenidae family are known by the name moray eels. All share an eel-shaped appearance, meaning a long, cylindrical body. Currently, about 200 species are known, distributed in 16 genera.

The largest, exceptionally large species can reach four meters in length: Strophidon satura . These fish live in rocky cavities and are carnivores. In fact, they are accurate hunters thanks to their keen sense of smell.

Undeservedly, these beautiful creatures have earned a reputation for being aggressive, as they often open their mouths and show their teeth. However, this is because they need to force water in, as their gills are very small.

Where do moray eels live?

The distribution of this fish family is cosmopolitan. Moray eels live at depths ranging from the surface to 100 meters.

They are known to spend most of their time hidden in crevices and small caves. The greatest richness of moray species is located, in particular, in regions where there are coral reefs, in warm waters.

Thus, morays inhabit tropical, subtropical and temperate seas. Although many species of moray eels can be found in brackish waters,  few marine species penetrate freshwater.

How to recognize moray eels?

As we mentioned before, their bodies are elongated. In addition, other characteristics are: the absence of paired fins and the presence of smooth, thick and scaleless skin. They also have a very narrow opercular slit, usually a simple orifice.

A brownish or blackish purple skin color is common, but  tropical species often have a light or bright pattern. This pattern, in some species, repeats itself inside the mouth.

These fish have an angular body, robust and slightly compressed laterally, especially on the back. The short, massive head stands out, with a rounded profile that has between one and three lateral pores.

A hallmark of a diverse group of eels  is their large mouths with numerous  long, pointed teeth.

Are they as fierce as they look?

It is a popular idea that moray eels are particularly aggressive fish, mainly because of their appearance. In fact, they  only attack in self-defense when they feel threatened.

In fact, moray eels hide from humans in crevices and would rather flee than attack. Many attacks come from the disturbance in their lair, to which they react strongly.

It is fair to point out that the attacks also occur in the context of a tourist activity that feeds moray eels, on diving expeditions.

It is interesting to know that moray eels have little vision and, to eat, depend mainly on their sense of smell, which makes it difficult to distinguish between a person’s fingers and food. This activity was banned in some places, such  as the Great Barrier Reef.

Something little known is that the skin of moray eels, as they do not have scales, tends to be prey to parasites. For this reason, some moray eels can get used to the presence of divers, trying to rub their bodies against them and even seeking caresses.

Are moray eels poisonous?

Although moray eels are hunted for food in some places, some species produce toxins. The toxin they have is ciguatera, which resists being destroyed by cooking.

Ciguatera comes from the metabolism of another toxin, maitotoxin, produced by a dinoflagellate ( Gambierdiscus toxicus ) that is part of zooplankton.

Once the dinoflagellate is ingested by the fish, the precursor toxin is metabolized and the resulting substance  accumulates at higher trophic levels.

According to experts, this mechanism could be an evolutionary response to threats from potential predators. Interestingly, in some species, the toxin is secreted in your skin’s protective mucus.

The amazing pharyngeal jaw of moray eels

In moray eels, the mouth space is deep, covered by numerous teeth. In addition to the normal teeth that fish have on the edge of the jaw,  many species of moray eels have the so-called pharyngeal jaw.

These pharyngeal jaws do not have a bony base, as they are supported only by muscle ligaments. It is interesting to know that they are very similar to teeth and oral jaws.

When feeding,  moray eels advance these jaws into the oral cavity, where they cling to their prey  and carry it down their throat.


Moray eels are carnivorous and act as opportunistic predators. They feed mainly on small fish, octopus, squid, cuttlefish and crustaceans. In addition, they themselves have few predators, including groupers, barracudas and sea snakes.

On reefs, it has been observed that coral groupers ( Plectropomus pessuliferus ) can associate with giant morays for hunting. This collaborative strategy allows moray eels to remove prey from locations that are not accessible to groupers.

Conservation status and ecological role

There are studies suggesting that moray eels of the genus  Gymnothorax spp . they can act as natural predators of invasive lionfish species. There are no major known threats to the Muraenidae family on a global scale.

However, the modification taking place in their coral reef habitat may be contributing to their population decline.

Conservation status and ecological role

In this sense, many species of morays are considered species of lesser concern. On the other hand, the production of toxins is not a general characteristic of all species and some are hunted for human consumption.

However, its commercial exploitation is small. Therefore, there are no specific conservation measures to protect these species.

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