Gulper Eels: Order Saccopharyngiformes

Besides the angler-fish, the fish best known as deep sea "monsters" are the gulper eels of the order Saccopharyngiformes. While they may look a lot like eels, they are not true eels. The most notable differences have to do with physical differences of their internal organs.

Why are gulper eels not eels?

Fish in the order are very closely related to the true eels in the order Anguilliformes, yet they are classified in their own order. The following characteristics help make them unique.

They lack several bones including the symplectic bone, some ribs and the opercle.
They have no scales, pelvic fins or a swim bladder
The myomeres (muscle segments) are V-shaped instead of W-shapped as in most other fish.
The lateral line doesn't have pores. Instead it has elevated tubules.

What do gulper eels eat?

Gulper eels, snipe eels, pelican eels and swallowers are deep sea fish that typically eat copepods, shrimp, and plankton. Gulper eel mouths are typically very large compared to the animal. This allows them to eat fish and other deep sea animals that are relatively very large. Often, gulper eels will open their mouth and swim at their prey, capturing them as if their mouth was a net.

Gulper eels catch their prey, not by being fast, but as sit and wait predators. They often attract prey through bioluminescent organs at the tip of its tail.

Classification

There are 29 species of fish in the order Saccopharyngiformes. They are grouped into the following four families.

Cyematidae (Bobtail Snipe Eels)

There are only two species of bobtail snipe eels. These small elongated fishes only grow to about 6 inches long. They live in the deep bathypelagic zone (from the edge of light penetration to about 16,000 feet).

Cyema atrum - White bobtail snipe eel
Neocyema erythrosoma - Red bobtail snipe eel

Eurypharyngidae (Pelican Eel)

This family has one species, Eurypharynx pelecanoides, the pelican eel. Sometimes it is known as the umbrella mouth gulper. This eel has a mouth larger than its body allowing it to eat prey that are larger than it. Yet, most still just eat small crustaceans. It grows to 3.3 feet long.

Eurypharynx pelecanoides - Pelican eel

Monognathidae

The family Monognathidae derives from the greek - monos (one) and gnathos (jaw). This is in reference to the general large size of their mouths. The fins are greatly reduced in this family. The dorsal and anal fins lack bony supports and the pectoral fins are missing. Of particular interest is the fang in the snout. This fang is connect to glands. There are 15 species.

Monognathus ahlstromi - Paddletail onejaw
Monognathus berteli
Monognathus bertini
Monognathus boehlkei
Monognathus bruuni
Monognathus herringi
Monognathus isaacsi
Monognathus jesperseni
Monognathus jesse
Monognathus nigeli
Monognathus ozawai
Monognathus rajui
Monognathus rosenblatti
Monognathus smithi
Monognathus taningi

Saccophayngidae (Swallowers, Gulper eels)

The name for this family comes from the Latin - saccus meaning "sack" and Greek - pharynx (part of the neck and throat). These eels are generally black and can reach about 6.5 feet long. Their tails have a luminous bulp-shaped organ.