Range: Marine waters worldwide Habitat: Deep marine waters Size: Up to 3 feet (0.9m) in diameter; Arms more than 30 feet (9m) long Diet: Plankton, fish, and more Threats: Unknown Life span: Unknown

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Today on Animal Fact Files we’re going to be looking at Stygiomedusa gigantea. If you like learning facts about animals then subscribe to this channel so you can stay up to date on all the new content. This gigantic jellyfish of the deep was suggested by twitter user @JethroReading. He’s a cool dude and has a pretty great collection of writing on his blog if you want to check him out. He has a novel as well - we’ll put links in the description!

Before this suggestion I was not privy to the Stygiomedusa gigantea which is actually not very surprising. Since their discovery in the first decade of the 1900s, the entire scientific community has only observed these enigmatic creatures just over 100 times. That’s a little less than once per year on average. What’s crazy is it’s actually considered to be one of the largest invertebrate predators living the ocean. Like, seriously, these things are huge!

Its bell, or the dome-shaped part of its body, can reach 3 feet (0.9m) in diameter and it’s arms: more than 30 feet (9m) in length. You’d think with a body that size these jellyfish would be easier to spot. Plus, they’ve been documented in every ocean in the world with the exception of the Arctic. So what gives, why can’t we find them?

Well, one contributing factor could be how well camouflaged they are. They come in a murky red-brown to purplish-red tint. Red light has the least amount of energy on our visible spectrum and thus it is unable to reach deep into the ocean. Animals that appear red on the visible light spectrum will actually show up closer to black in deeper water because there is no red light for them to reflect. This makes blending in for red colored deep-sea creatures easy and is why a lot of them would appear red in visible light.

It also seems that Stygiomedusa gigantea prefer deep water. They’ve been observed anywhere from 1,400 feet (425m) to 4,000 feet (1,200m) and possibly deeper. And it’s not like we can just hold our breath and dive that far down. As of this recording the deepest a human had dived was just over 1,000 feet (300m) and that’s still 400 feet above the Stygiomedusa gigantea’s depth range. We have to use ROVs (remotely operated vechicles) in order to observe these jellyfish and according to rovworld.com, there are around 400 working class ROVs being used. What’s more, most of them are being used by oil and gas companies, not exploration for crazy gigantic jellyfish. Their camouflage as well as where they prefer to live could be contributing factors as to why stygiomedusa gigantea have been observed so infrequently in the past century.

Even though they are jellyfish they actually don’t have tentacles so they don’t sting in order to catch a meal. It’s guessed that their long oral arms are used to entangle anything edible that may come near including plankton and small fish. Yes, oral arms - that’s what they’re called. Some even call them mouth arms. Not tentacles. Mouth arms. Mmm. On the bright side, because they’re so huge, it’s believed that they probably do not have many if any predators roaming in the depths. Of course, there is still a lot of ocean for us to explore, who knows what we’re missing down there!

With so few sightings, there’s not been much opportunity for research into these ghostly jellies. Their mating habits and life cycle are still a mystery though it has been suggested that they may be vivparious or in other words give birth to live young. We do know that they have formed a symbiotic relationship with a small fish called Thalassobathia pelagica. It would seem that these small, deep-sea dwelling fish have learned to live within the bell and arms of the Stygiomedusa gigantea in a wonderful relationship where they get to eat all the Stygiomedusa gigantea’s leftovers. Again I say, mmm. Because these fish have formed this relationship with the jellyfish, they have been seen in waters where they otherwise have never been observed.

Thanks again to @JethroReading for shedding some light on this mysterious creature of the deep. For more facts on Stygiomedusa gigantea check out the links in the description. If you know of an amazing animal we should cover let us know in the comments. As always, thank you for watching and be sure to give a thumbs up for more Animal Fact Files.