How Octopuses Move So Weirdly

The octopus's coordinated, eight-legged groove could inspire soft robotics.

|
Apr 17 2015, 1:50pm

​Octopus vulgaris, the same kind as used in the study. Image: ​​Morten Brekkevold/Flickr

With their bulbous, squishy heads and eight super-bendy arms, octopuses are really radical-looking invertebrates. They also have a mouth attached to the centre point of their arms, and a killer underwater crawl. But what lets the octopus move so fluidly, when it's got no backbone to keep everything together?

It's a question that's intrigued scientists from the ​Octopus Group at The Hebrew University of Jerusalem. Set on solving the mystery through a frame-by-frame analysis of a video capturing an octopus in motion, they recently​ published their find​ings in the journal Current Biology.

"Octopuses use unique locomotion strategies that are different from those found in other animals," said Binyamin Hochner of The Hebrew University of Jerusalem in a press statement. He pointed out that this was thanks to an evolution in their soft molluscan bodies, which enabled an "efficient locomotion control" even though they had no "rigid skeleton."

Video: Levy et al./Current Biology 2015

Thanks to its unique motor control strategies, the octopus's central brain activates autonomous motor programs in each of its eight arms. This means that each of the arms can move independently of the other arms, giving the octopus its wacky, out-of-sync groove. What's also cool is that, according to the researchers, the octopus can "change their crawl direction while maintaining a fixed body orientation."

The octopus's flexy-crawl came down, they said, to the "radially symmetrical distribution" of its eight arms. This means that each arm is arranged around the octopus's mouth in a circle with a 45 degree angle between each arm. "The animal need only choose which arms to activate in order to determine the direction of locomotion," stated study co-author and lab manager Guy Levy.

Octopuses are thought to have evolved from sea creatures like clams, who have a protective shell, but little movement. As octopuses evolved, they lost their heavy outer shells and gained speedier movements in the process. "Their locomotory abilities evolved to be much faster than those of typical molluscs, probably to compensate for their lack of shell," said Levy.

The octopus's dexterous movements and knack for camouflage have provided useful fodder for engineers. In 2014, scientists at the University of Illinois developed high-tech materials that mimicked the octopus's camouflage abilities. 

This time round, the growing soft robotics scene could expand on the findings to develop sophisticated stretchable electronics that mimic the octopus's flexibility and shape-shifting qualities. In a report for the BBC, Levy stated, "people want to build soft robots for medical purposes and rescue operations," adding that an octopus's flexible body movements could inspire soft robotics that could easily squeeze through small spaces to access people trapped in buildings, for example.

Next up, Levy and Hochner want to demystify the neural circuits which underpin the octopus's crawl. The robots may soon be getting some octopus-inspired super-flexy, sucker arms.