Not a True Eel

Most of us are familiar with eels, snake-like fish with elongated bodies. There are different types of eels found in both freshwater and seawater. The gulper eel is an eel-like fish usually found in deep seas. It is not a true eel and is not related to the order of true eels, Anguilliformes. Gulper eels belong to the order Saccopharyngiformes and family Eurypharyngidae. In fact, the gulper eel (Eurypharynx pelecanoides) is the single member of the genus Eurypharynx.

A gulper eel, showing its enormous hinged jaw and long slender body
The gulper eel's enormous loosely hinged jaw is wider than its body, one of the most striking features of any deep-sea creature.

Where It Lives

Gulper eels are deep-sea creatures found in tropical and temperate oceans. These fish are usually found at a depth of around 3,000 to 26,200 feet. Occasionally, they travel to the surface and may sometimes shift to rivers, as they find it difficult to locate food in their natural habitat.

Body and Appearance

Gulper eels look like true eels because they share the same snake-like body shape. But there are key differences. Unlike true eels, they have long and thin tails that help them move through the water. In fact, the tail of the gulper eel is so long that it sometimes gets knotted. Gulper eels have almost no pectoral fins and are blackish or dark green in color.

The most striking feature is the loosely hinged mouth, very big and very wide. This enormous mouth is bigger in proportion to its body than almost any other fish. The lower jaw has a big pouch-like structure where prey can be deposited. It is because of this pouch that the fish is also called the pelican eel. Its other nickname, umbrella mouth gulper, also comes from that giant mouth.

Interesting Facts

The following are some of the most amazing facts about the umbrella mouth gulper eel.

  • They have big mouths wide enough to swallow large prey. In fact, the length of the jaws is almost one-fourth of their body length.
  • Even the stomach of the gulper eel is stretchable and can hold a large amount of food. However, this fish feeds on small crustaceans in spite of having a big mouth and a stretchable stomach.
  • Even though gulper eels have big mouths, their teeth are small. This shows they are not built to prey on large animals. Apart from crustaceans, gulper eel diet includes fish, seaweed, and cephalopods such as squids and octopus.
  • The mouth acts like a net: the eel swims into large groups of small fish and shrimp with its mouth wide open. The open mouth fills with food as well as water, and the water is slowly released through the gill slits.
  • The eyes of this deep-sea creature are very small. Experts believe their eyes are meant for detecting light rather than forming images.

Frequently Asked Questions

Is a gulper eel a true eel?

No, it is not related to the order of true eels, Anguilliformes. It belongs to the order Saccopharyngiformes.

How deep does the gulper eel live?

Around 3,000 to 26,200 feet below the surface in tropical and temperate oceans.

Why is it called a pelican eel?

Its lower jaw has a large pouch-like structure where prey is deposited, just like a pelican's throat pouch.

What does the gulper eel eat?

Mainly small crustaceans, but also fish, shrimp, seaweed, and cephalopods such as squids and octopus.

What is bioluminescence?

It is the ability of a living organism to produce and emit its own light through a chemical reaction.

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The Glowing Tail

This fish has a tiny light-producing organ at the tip of its tail. This organ, called a photophore, has numerous tentacles and glows pink through bioluminescence. It can also produce red flashes occasionally.

A bioluminescent pink glow from the photophore at the tip of a gulper eel's tail in the dark deep sea
The photophore at the tip of the gulper eel's tail glows pink and can flash red, a living lure in the darkness of the deep ocean.

These red flashes are used to attract prey. The eel keeps its tail tip near its wide open mouth so it can swallow fish and other organisms that move toward the light source.

Reproduction and Lifespan

Mature males have bigger eyes and better-developed olfactory organs compared to females, who do not change much as they become sexually mature. Males use these olfactory organs to sense the pheromones released by females. It is also said that after reproduction, gulper eels die.

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A Saccopharyngiformes fish (the order to which gulper eels belong) photographed in the deep sea
A member of the order Saccopharyngiformes, the same deep-sea order as the gulper eel. These fish are rarely seen because they live so far below the surface.