The amazing transformation of gulper eels

The gulper eel is an elusive creature of the deep which we know very little about. But incredible footage from a deep sea rover shows the surprising and remarkable behaviour which gives it its name.

inflated gulper eel
A fully inflated gulper eel that appears to have more in common with a balloon than a fish

Also known as the pelican eel and umbrella-mouth gulper, these strange creatures from the deep are capable of a truly incredible feat. Much like some snakes they can unhinge their jaws to consume prey much larger than themselves. But unlike their serpentine cousins these fish can accomplish a much more spectacular and rapid transformation. They can inflate and deflate their bodies from a slim eel-like fish to a giant balloon in a matter of seconds. Not a lot is known about these elusive animals who have been confusing scientists for years. However recent footage from a deep sea rover has given us our best look yet at what they are truly capable of. It highlights the importance of deep sea exploration because there is still so much we don’t know about this part of the ocean.

Caught in the act

The footage in question was captured by a deep sea rover belonging to Nautilus, an ocean exploration company owned by Dr Robert Ballard. They were studying unmapped seamounts in the Papahānaumokuākea Marine National Monument near Hawaii. It shows an inflated juvenile gulper eel, Eurypharynx pelecanoides, performing what could be described as fluid acrobatics before rapidly changing back to its original size and shape and swimming off into the dark. It was filmed at the depth of about a mile below the surface and features commentary from scientists on board the ship. Check out the video (via National Geographic) below and make sure you have your sound on!

 

Surprising scientists

As you can tell from the commentary by the Nautilus scientists this a very rare and relatively undocumented behaviour by the gulper eel. It’s also not the first time gulper eels have confused researchers. Due to its rarity and strange physiology it has previously been described as five different species despite there being no evidence there is more than one species of gulper. It also has several unique features such as a protruding lateral line and the ability to tie their tails in a knot for no apparent reason. Little is known about their reproduction except that the male’s olfactory systems, responsible for smell, are amplified during sexual maturity. Some researchers aren’t even convinced the behaviour in the video is a feeding mechanism and may instead be a defensive behaviour much like puffer fish.

What we do know

So there’s lots more to learn about these bizarre creatures but what do we actually know about them?

gulper eel specimen
A deceased gulper eel caught as bycatch in the North Atlantic

Well for starts they’re not really eels at all. They lack the pelvic fins, swim bladders, and scales necessary to qualify as eels and are instead what is known as ray-finned fish. They have a proportionately large head and a loosely hinged lower jaw capable of detaching and opening up to consume fish much larger than themselves. They push out water through their gills to deflate back to their original size which can be up to three feet long in fully grown adults. Gulpers have very undeveloped eyes and cannot see anything more than faint light changes above them. It is therefore assumed they use sound to navigate although there is little evidence to support this. Their tails also have a lure at the end that glows pink and has been known to give off bright red flashes to entice prey species. This may seem like a lot of knowledge for something that lives so deep but in reality we know very little particularly about behaviours, population levels and conservation threats of the species.

Mysteries of the deep

What is so exciting about this video, apart from the incredible transformation of the gulper eel, is that it highlights how many strange an amazing creatures live in the depths of the ocean that we know so little about. It is often said that we know more about the surface of the moon than the bottom of our oceans and for good reason. The dark waters of the deep oceans are perhaps the last properly unexplored areas on Earth. Yet when we have ventured there we have found an incredible array of fascinating alien-like animals which capture the world’s imagination. Who knows what else we could discover if we were to properly explore down there.


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