gulper eel

Class Osteichthyes
Subclass Actinopterygii
Order Anguilliformes
Family Saccopharyngidae
Genus Eurypharynx
species E. pelecanoides

Also known as the umbrellamouth eel, the gulper eel lives on or near the ocean floor at depths of 1500-3000 metres. It prefers warm or temperate waters and is found in all oceans of this kind around the world, quite an achievement for a creature that is basically just a big bag that can swim. With tiny, almost useless eyes, it relies on its sense of smell and touch, picking up waterborne scents and vibrations.

Gulper eels have long, flaccid bodies (2-6 feet) without very much muscle, consisting mostly of an enormous distensible stomach which, like that of many deep ocean creatures, is capable of containing and digesting prey as large or even larger than the eel itself. The gulper eel also has a huge, slack-jawed mouth with very small teeth, and its hunting style is simply to swim up to and engulf its food, which consists mostly of plankton, shrimp, and occasionally larger fish. When the eel is finished digesting its meal, lacking another opening to its digestive tract, it just opens its mouth and lets the remains drift out.

The gulper eel, like many deep sea predators, uses a bioluminescent lure to attract its prey - the tip of its bony tail glows red in the dark, and it waves it gently to imitate the movements of a small fish. A curiosity of this eel is that many specimens which have been caught in fishermen's nets have one or more knots in their tail. The same phenomenon has been seen in moray eels, but since the gulper eel has virtually no muscle in its tail, it's not clear how exactly these knots could have been made, except possibly by a giant squid intent on confusing marine biologists.