Despite lacking a rigid skeleton, octopuses have a remarkable coordinated locomotion. Using high-speed cameras, a group at the Hebrew University of Jerusalem found the octopus achieves this by precisely and independently moving one or more of its eight legs to crawl its body, even when its facing a different direction. Moreover, there is no discernible rhythm or pattern to this undulating leg movement, making the octopus unique in this respect. It’s controlled chaos, and only the octopus itself completely knows how it pulls all this off.
One leg at a time
“Octopuses use unique locomotion strategies that are different from those found in other animals,” researcher Binyamin Hochner said in a recent release. “This is most likely due to their soft molluscan body that led to the evolution of ‘strange’ morphology, enabling efficient locomotion control without a rigid skeleton.”
Hochner and colleague Guy Levy investigated what makes the octopus so efficient and agile. Analyzing the animal frame by frame, the two found that by shortening or lengthening its arms, the octopus crawled about. That’s not much of a secret, but what’s important is that each arm pushes the animal in only one direction, and this is independent of the direction the body is facing. Having arms with literally a mind of their own, does help a lot in this situation.
“So the octopus only has to decide which arm to use for the pushing – it doesn’t need to decide which direction this arm will push,” explained Dr Levy.
“[It has] found a very simple solution to a potentially complicated problem – it just has to pick which arm to recruit.”
This is likely a consequence of its evolutionary history, being forced to adapt quickly because its lost shell.
“During evolution, octopuses lost their heavy protective shells and became more maneuverable on the one hand, but also more vulnerable on the other hand,” explained Guy Levy, co-author of the study which appeared in Current Biology. “Their locomotory abilities evolved to be much faster than those of typical molluscs, probably to compensate for the lack of shell.”
Next, the researchers plan on revealing the octopuses’ neural circuits that allow it to use its arms in such a way. Since its arms are completely flexible with no joints, this insight might prove extremely valuable to engineers who might want to design octopus-like robots. Such bots might be useful in search-rescue operations. Speaking of the octopuses’ arms, have you ever wondered how it never gets tangled? The same team, Levy and Hochner, found that the octopus uses a chemical mechanism to attach its sticky arms to surfaces. This peculiar mechanism has a sort of on-off switch, so when the animals need to stick together and cling, like when mating for instance, the mechanism is activated, but otherwise its off so its arms never stitch to one another and become tangled. To make it even more interesting, some species are master camouflagers, or can withstand freezing temperatures in the Antarctic despite their blue blood. For sure, octopuses are among the most intriguing animals out there, and I have a feeling we’re only beginning to scratch the surface.
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