MICHEL MARTIN, HOST:
The octopus is a striking creature. Their most defining feature, of course, is their eight arms. A new study of octopuses has now documented exactly how those eight arms are used in the wild. Scientists wanted to know if different arms take on different jobs. NPR's Nell Greenfieldboyce reports.
NELL GREENFIELDBOYCE, BYLINE: Octopus arms have been observed in the lab, but Roger Hanlon says, in the past, descriptions of what the arms can do generally haven't been that detailed.
ROGER HANLON: Most people have just made some really, really crude drawings and just say, oh, it can bend here, and it does a little of this.
GREENFIELDBOYCE: Hanlon's with the Marine Biological Laboratory in Woods Hole, Massachusetts.
HANLON: There were some hints that left and right arms did something a little bit different.
GREENFIELDBOYCE: He wondered about that. He's gone on lots of underwater dives over the years. So have his colleagues. And they've collected a whole bunch of videos of octopuses going about their days. They decided to use the videos to create a complete catalog of all the ways that wild octopuses use their arms to achieve their various goals.
HANLON: Whether it's feeding or excavation or whatever, we can then tease that apart and see what the arm actions are to achieve that.
GREENFIELDBOYCE: In the journal Scientific Reports, they describe how every octopus arm can extend, retract or bend anywhere along its length.
HANLON: And it can twist clockwise or counterclockwise, and it can do that along the full length of every one of the eight arms.
GREENFIELDBOYCE: He says, basically, the arms all seem to be capable of doing everything.
HANLON: We didn't see specialization. It just did not show up.
GREENFIELDBOYCE: And arms on both sides of the body are used equally, although octopuses tend to rely on their front arms for exploration and their rear arms for moving around. Dominic Sivitilli is an octopus researcher with the University of Washington. He wasn't part of this team. He says it's impressive to do this kind of study with octopuses out in nature rather than in a tank.
DOMINIC SIVITILLI: In the wild, it's a lot more complicated, right? There's a lot more chemicals. There's a lot more sharp things. There's predators. There's prey.
GREENFIELDBOYCE: He says this is a step towards having a standard system for describing octopus arm activity, one that could help everything from training AI to track octopus behaviors to designing new kinds of robots with soft, flexible arms. Nell Greenfieldboyce, NPR News.
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