Bizarre Pelican Eel Can Eat Prey Larger Than Own Body Thanks to Giant Mouth

The deep sea is filled with all manner of weird and wonderful creatures. Among them is a bizarre eel species with a giant mouth that has a remarkable resemblance to a pelican's beak. Dubbed the pelican eel and known scientifically as Eurypharynx pelecanoides, this mysterious fish lives in the deep ocean in tropical and temperate regions around the world, although not near the bottom, instead preferring depths between 500 and 3,000 meters (1,640 to 9,842 feet), according to the Woods Hole Oceanographic Institution. Joel Llopiz, a fisheries oceanographer and larval fish ecologist at Woods Hole, told Newsweek the most interesting aspect of this species is its relatively huge, expandable, scoop-like mouth that opens 90 degrees. This enables the eel to swallow prey larger than its own body. (The pelican eel also has a very stretchable stomach that can accommodate relatively large amounts of food.) When the pelican eel spots potential food, it inflates its mouth drastically like a balloon, creating a giant pouch that acts like a net, which it can use to gobble up meals like small crustaceans, squid or even seaweed. The huge mouth, which can make up around a quarter of the fish's body length, is a particularly helpful adaptation when you are feeding in an environment with relatively few options for meals, according to Llopiz. "If you encounter something when you're in the deep ocean, and you don't generally encounter many things, you would want to be able to eat it. A good way to ensure this is to have a huge mouth, which it clearly has evolved to have," Llopiz said. "[The mouth] allows pelican eels to feed on a large variety of prey types, giving them options in a generally food-poor environment," he said.

While this creature, which can grow to lengths of more than 3 feet, was originally named after the pelican, it is now sometimes referred to by other names, such as gulper eel, pelican gulper or umbrella-mouth gulper, a reference to its amazing mouth-expanding abilities. But there is some confusion about what exactly a gulper eel is, according to Llopiz. He said, "When most people, and even fish scientists, hear "gulper eel," they are probably thinking of what is actually the pelican eel—Eurypharynx pelecanoides," which is the only species in its animal family. But he points out that there is a different eel species, Saccopharynx ampullaceus, that also has the accepted common name of "gulper eel." Other features that characterize the pelican eel are its tiny eyes and a bioluminescent organ at the tip of its tail. It is not entirely clear what this bioluminescent organ, which produces pink light or occasional red flashes, does, but it might help the eel to attract prey. This would be helpful, given that the pelican eel is not the most effective swimmer. Also, it cannot rely on sight, given its small eyes, unlike some other deep-sea creatures. "They are likely at the mercy of ocean currents drifting around the world, hanging out at their preferred depths and temperatures," Llopiz said. Not much is known about the life of the pelican eel, but it appears to spend much of its time searching for a mate. When the males reach sexual maturity, they grow larger olfactory organs, which help them detect the scent of females. Intriguingly, the males also lose their tiny teeth around this time, potentially because the body of the fish is diverting all its energy into reproduction. Researchers think these eels die soon after mating.

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With its hard-to-access deep-sea habitat, the pelican eel is rarely seen by people, but it is not immune to threats from human activity. Among these threats is climate change, which is affecting the amount of food reaching deep-sea habitats as well as their temperatures, Llopiz said. Another threat the eels may face in the future is fishing, according to the researcher. "Humans are generally not fishing the deep water column ecosystems in the open ocean yet," he said. "However, because of the globally large amount of biomass that occurs there, it may one day become financially viable to fish these waters, especially as our coastal waters become more and more overfished."