Under the circus tent of the ocean, octopuses play the role of contortionists and escape artists, packing themselves itself into spaces too tiny to believe.
For aquarium professionals and lab scientists, it’s a challenge to contain these animals known for their intelligence and dexterity. But to roboticist Wenci Xin of the National University of Singapore, octopuses’ skill makes them a model worth mimicking. That’s because he wants to design better robots for search-and-rescue operations, which can navigate tight and unpredictable spaces inside collapsed buildings and other settings. Right now, such robots are typically long and narrow. Xin dreams instead of robots that are squishy and flexible: octopuslike instead of snakelike, so to speak.
So he and his colleagues set about studying how octopuses accomplish their astonishing feats. The results, published Thursday in the Journal of Experimental Biology, show that some of these cephalopods use a specific step-by-step process to cram themselves into tight crevices and that they can tailor the approach to specific circumstances.
Xin and his colleagues tested juveniles of two species, common and Mayan octopuses, in a few scenarios. The researchers designed a thin, clear, plastic partition with an adjustable hole in its center, which blocked off part of a tank. They studied whether the octopuses stayed put or tried to move through the hole once the partition was placed in the tank. If an octopus seemed interested in the hole but unwilling to move through it, or if it started moving frantically, it got a respite from the tests.
When researchers presented a smaller common octopus with a relatively large hole, it moved through with a smooth, three-step process. First, it used one arm to scout out the opening the way humans feel for a light switch in the dark. Then it stuck a few more arms through. Finally, it pushed those arms against the far side of the barrier surrounding the hole as leverage to pull the rest of its body through the opening.
The four Mayan octopuses the researchers tested used a similar approach when confronted with a larger hole. But when faced with a squeeze, they declined to feel it out.
Meanwhile, when the scientists presented two larger common octopuses with a comparatively small hole, they used more or less the same strategy as the smaller one, although the process of pulling through their final arms and their head were more distinct steps instead of one smooth operation.
Both Xin and Trevor Wardill, a neuroethologist at the University of Minnesota who was not involved in the new research, said that differences in personality and the types of obstacles that octopuses face in their natural environment may explain the different strategies of the two species that were tested. Other kinds of octopuses may have their own approaches to squeezing through tight spaces.
Wardill said he had suggested this line of inquiry to a colleague in the past because of how striking the behavior is. “It’s well known that they do this, but it’s actually very poorly studied,” he said.
Xin is eager to get to work engineering robots that mimic the approach of the animals he and his team have studied. He’s intrigued by both the malleable form of octopus and its ability to smoothly direct eight limbs by breaking complex movements into discrete actions using a decentralized brain spread between its arms and body.
There’s more work to do to unpack these animals’ biology, Wardill said, adding that he is curious how octopus bodies withstand the stresses of these contortions.
“That level of brain distortion for a normal vertebrate would be like a massive concussion — you’d be really spaced out for a very long time, if not dead,” Wardill said. But the octopuses appear unfazed, he said. “It’s really remarkable that they carry on about their daily business.”
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