The gulper eel (Eurypharynx pelecanoides) is a strange-looking deep-sea fish with a mouth that can balloon to huge sizes to gobble down prey.
Discovered in 1882, these elusive animals are rarely seen by humans. Yet, some researchers on deep-sea expeditions have been lucky enough to catch a glimpse of this baffling creature as it contorts itself into strange shapes.
Its ability to stretch its mouth wide enough to hold lots of food is the reason for both its common names: the gulper eel, or the pelican eel.
What are gulper eels?
Also known as pelican eels, these deep-sea fish have a huge mouth which stretches, just like a balloon or a pelican’s bill, so they can guzzle down large amounts of food.
In one viral video, scientists onboard the EV Nautilus research vessel are exploring the Papahānaumokuākea Marine National Monument (a sanctuary off Hawaiʻi) when they come across one of these strange critters. Thanks to its bizarre appearance, it takes the experts a minute or two before they identify the muppet-like creature as a gulper eel. They gasp and giggle as they watch the animal’s astounding shape-shifting abilities as it twists and buckles its swollen mouth like a balloon artist.
When their mouth isn’t inflated like this, they have an eel-like long, thin body that wiggles through the water as they move along. They are black in colour, sometimes with a white line down their dorsal fin and the tip of their tail has a red or pink bioluminescent glow.
Where are gulper eels found?
These strange animals are found between 500 and 3,000 metres deep in tropical and temperate waters around the world. These ocean depths – made up of the mesopelagic (twilight) and bathypelagic (midnight) zones – are dark and cold. Little to no sunlight makes it this far down in the ocean and creatures have had to adapt to survive in this alien world where food is scarce.
Below 1,000m, the only light available is created by bioluminescent animals – and the gulper eel is one of them. Its tail can glow pink or red, which might be a way of luring prey towards it.
How do gulper eels eat?
Gulper eels are famous for their ability to devour large prey with their unusual mouths. Their lower jaw is around a quarter of the length of their entire body and it has a hinge to allow it to extend even wider.
But that’s not all. Like a pelican, these oceanic oddballs can stretch their mouth to vast sizes to scoop up a morsel to eat. When they do this, they also take in a whole mouthful of water which is filtered out by their gills. This spectacular show has been caught on camera by deep-sea explorers who were amazed by the ballooned individual.
Food is hard to come by in the deep ocean so this could help the pelican eel guzzle down a large animal, like a squid, or a whole school of shrimp or other small crustaceans. It even allows them to consumer prey bigger than themselves, like a snake.
How do gulper eels swim?
Not very well. Gulper eels don’t have scales, pelvic fins or a swim bladder (an organ that helps fish adjust their buoyancy) so they are not strong swimmers. They move through the water by undulating their slim tail.
What makes them unusual compared to other deep-sea creatures?
With their tiny eyes peering out into the deep, dark ocean, gulper eels can’t see prey easily. This is unusual for deep-sea animals which often have huge, haunting eyes to take in as much light around them so they can see in the dark.
Another way gulper eels differ from several other deep-sea species is that they don’t migrate to the surface – where food is more plentiful – to eat. This could be because they’re not very good swimmers. Instead, they stay in the depths where food is scarce.
Why does their tail glow?
Their bad vision and poor swimming skills means gulper eels need another way of finding food. Rather than relying on seeing prey and chasing after it, they bring their meal to them. The tip of their tail can glow like a pink or red lure and this little beacon helps maximise their chances of getting a snack because prey swimming nearby sees the light and are attracted towards it.
How do gulper eels reproduce?
Like the other aspects of deep-sea organisms, not much is known about the species reproduction. However, experts believe that finding a mate is an important part of gulper eels’ lives.
When males become sexually mature, their olfactory organs grow larger to improve their sense of smell. This is because they rely on scent to find a female to mate with.
They put everything they have into finding a mate, so much so that their teeth fall out. And once they track her down, their story is nearly at an end – scientists believe gulper eels die shortly after mating.
Are gulper eels endangered?
IUCN Red List of Threatened Species lists gulper eels as a species of least concern. However, their current population trends are unknown.
A gulper eel’s special features
- A large mouth that can balloon to swallow huge prey
- Hinged jaw
- Several rows of teeth
- Tiny eyes
- Long, thin body
- Black colouring
- Glowing tail tip
Gulper eel facts at a glance
- Gulper eel facts at a glance
- Scientific family name: Eurypharyngidae
- Nicknames: Pelican eel, Umbrella-mouth gulper
- Length: Up to around 80cm
- Average lifespan: Unknown
- Weight: Unknown
- Depth: 500 to 3,000m
Main image: Gulper eel (Eurypharynx pelecanoides)
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