In the deep sea, the lives of cephalopods — the group including squid, octopus, and nautilus species — remain deeply mysterious. That mystery can spark some fear, like when imagining a fight between the titans of the dark water.
But sometimes, the weird world of the ocean's depth is actually just adorable.
The image of a baby octopus riding on top of a jellyfish recently went viral on Twitter after it was shared by Rebecca Helm, an assistant professor at the University of North Carolina, Asheville. Its popularity is for obvious reasons: It's cute, it's weird; and it's likely exactly what you need right now.
Besides being a stunning display of quirky nature, there's a scientific reason this adorable rodeo takes place.
Researchers in Portugal describe a similar observation in the Atlantic Ocean, near Terceira Island, in a 2017 study published in the journal Marine Biodiversity. The paper describes a seven-armed octopus, Haliphron atlanticus, who hitched a ride on a jellyfish near the ocean's surface.
The octopus seemed to be in control of its living vehicle, the researchers write. It actually steered the jellyfish, using it for protection by turning the jelly's tentacles toward the divers photographing the phenomenon.
"The interaction between the octopod and divers, namely by rotating the jelly towards what we presume to be a perceived threat, supports a potential defensive use of the hijacked jelly," the scientists explain. "Thus, we argue that the octopod seems to be using the jelly to protect itself."
Using jellyfish stingers as an attack shield isn't the only way seven-armed octopuses benefit from jellyfish; they also eat jellies. But that doesn't seem to be what's happening here, the researchers explain. If it were only looking for a snack, the octopus would have taken a bite and moved on.
Therefore, it is "unlikely that the footage recorded refers exclusively to a predatory event," the researchers say, "because of the unwillingness of the octopod to release the jelly."
Protection and prey — Besides seven-armed octopuses, other species have been known to catch a ride on a jellyfish, as well as other ocean floaties.
"Female Argonauts have been observed hitching-a-ride on jellyfishes, attached to floating seaweed, or attached to each other forming a 'cephalo-chain' of up to 20 to 30 individuals," writes Bennice, who runs social media accounts under the alter-ego Octo Girl.
Here's a video of a paper nautilus riding a jellyfish through the dark ocean — clearly not its first rodeo:
The blanket octopus, Tremoctopus violaceus, gets a bit more creative — and decidedly less adorable — with its use of jellyfish for protection. It uses jellyfish tentacles as weapons, researchers reported in a 1963 paper published in Science.
Male and small female blanket octopuses carry around fragments of tentacles from Physalia physalis, aka the dreaded Portuguese Man-of-War, Bennice says. The stinging tentacles don't bother the octopus, which holds fragments with its first two pairs of arms.
In addition to defense, the tentacle-wielding habit may help the octopus capture, food, too. That may seem like a far cry from being a floating nursery, but who are we to try to limit the capabilities of a jellyfish.