Watch as Octopus Eats Jellyfish, Then Clings to It as Likely Weapon

The deep sea is an environment so mysterious that even studying what animals eat can be a challenging task.

That's why scientists were baffled when a large, rarely seen octopus known as the Haliphron atlanticus was spotted clutching an egg-yolk jellyfish in its arms. Scientists were able to see the female octopus's behavior when a camera on a remotely operated vehicle zoomed toward the creature, revealing the jellyfish clutched under the animal's cage-like underbelly.

The footage was filmed 1,240 feet below the surface of the ocean in Monterey Submarine Canyon. It's existence far below sea means that much of its population size, geographic distribution, and potential threats are largely unknown.

Egg-yolk jellyfish are not known to be packed with nutrients, a fact that baffled scientists upon first observation. It's believed that the H. atlanticus, which can grow up to 13 feet and weigh as much as 165 pounds, has a slow metabolism. So while the jellyfish's gelatinous top might not have been rich in nutrients, the biomass from the remainder of its body likely sustains the large cephalopod.

As to why H. atlanticus held on to its prey after feeding, Steven Haddock, a senior scientist with the Monterey Bay Aquarium Research Institute, believes this may have been done for defense.

H. atlanticus's large size makes it adept at easily carrying a jelly as a tool. By using its beak, H. atlanicus can suck the nutrients out of a jellyfish cavity while leaving its unencumbered legs to swim.

Jellyfish tentacles are still capable of stinging even after death. Researchers postulate that given the way the octopus is letting the tentacles drag behind it, the animal may be wielding the stinging cells for defense or to catch more prey.

Haddock co-wrote a paper on the strange behavior with Henk-Jan Hoving of GEOMAR Helmholtz Centre for Ocean Research Kiel, which they published in the journal Nature . They examined the stomach contents of five additional specimens and found jellyfish and other gelatinous zooplankton. Their paper confirmed that the interaction was the first known sighting of H. atlanticus feeding on this surprising choice of prey.

H. atlanticus is commonly referred to as a "seven-armed" octopus but in fact has eight legs, keeping one tucked into a space under its eye. The majority of what scientists know about this deep-sea creature comes from corpses drudged up in trawl nets.

Understanding the habits and characteristics of a cephalopod that lives in a region inhospitable to human life has been a challenge for scientists. The footage, filmed by a remotely operated vehicle from the Monterey Bay Aquarium Research Institute, was only the third time H. atlanticus had been spotted in the wild.

While this was the first time an H. atlanticus octopus had been observed exhibiting this type of behavior, it's not the first time an octopus has been known to wield a jellyfish to its advantage.

Male blanket octopuses, which are immune to the stings of Portuguese man o' war, have been observed wielding them like weapons as a form of defense, and football octopuses have been found residing inside salps, a similarly gelatinous sea creature.