The deep-sea octopus Haliphron atlanticus is so elusive that marine biologists have seen it just three times in as many decades. Now, new footage has finally confirmed what this strange creature eats – and the clip is shaking up what we know about finding food in the murky depths.

Scientists with the Monterey Bay Research Institute (MBARI) and GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany spotted the seven-armed octopus during a recent dive off California's coast. Amazed by the sighting, the team watched on as H. atlanticus began to eat the egg yolk jellyfish (Phacellophora camtschatica) clutched between its arms. 

Tucking into a gelatinous meal is the norm for many creatures: sea turtles, Mola mola and other large fish all have a fondness for gooey prey. But scientists had assumed that in the deep sea, where food is scarce, jellyfish meals weren't nutritious enough to warrant the effort it takes to find them. 

MBARI team member Steve Haddock suspects that while jellies might be lacking in nutritive benefits, they do make up for it in abundance and mass. In other words, they're less a high-calorie hamburger and more an all-you-can-eat salad bar.

What's more, the Haliphron octopus seemed to target the digestive tract of the jellyfish, which would allow it to gain access to any nutrients in the food the jelly itself had eaten.

To make sure the sighting wasn't an anomaly, the team looked into the bellies of five dead octopus specimens, and all of them contained at least traces of gelatinous prey. Three contained jellyfish, while the others held a salp and siphonophore (a colonial jellyfish doppleganger), respectively.

"Haddock feels the general sentiment surrounding gelatinous diets in oceanic food webs has been unappreciated and underestimated," says MBARI. 

Want more seven-armed action? H. atlanticus was also seen last year when it cruised past an underwater camera in the Philippines! Learn more about the species here.

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Top header image: John Kroll/Flickr