The hundreds of suckers on an octopus’ eight arms can stick to just about anything except for the animal itself, as a chemical produced by the octopus’ skin prevents its suckers from latching on to each other, according to a new study conducted by researchers from the Hebrew University of Jerusalem.
The study, published Thursday in the journal Current Biology, revealed that the special chemical helps the octopus to avoid being tangled up in its own suckers, even as the animal’s brain is unaware of what its eight arms are doing, and is expected to contribute to the field of robotics.
“We were surprised that nobody before us had noticed this very robust and easy-to-detect phenomena,” Guy Levy of the Hebrew University of Jerusalem and the study’s co-author, said in a statement. “We were entirely surprised by the brilliant and simple solution of the octopus to this potentially very complicated problem.”
Unlike humans and other animals, an octopus does not know where its arms are. While the human brain uses a mapping method to coordinate body parts, it is hard to envisage a similar mechanism to function in the octopus brain because of its long and flexible arms, the study said.
Octopuses’ “arms have an infinite number of degrees of freedom. Therefore, using such maps would have been tremendously difficult for the octopus, and maybe even impossible,” Binyamin Hochner, a co-author of the study, said in the statement.
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To determine how an octopus avoids tying itself up in knots without being aware of where its arms are all the time, researchers observed the behavior of amputated octopus arms, which remain active for an hour after separation from the animal's main body. The scientists' observations showed that the arms never grabbed octopus skin but they grabbed a skinned octopus arm. The researchers also found that the octopus arms did not grab petri dishes covered with octopus skin.
“The drastic reduction in the response to the skin crude extract suggests that a specific chemical signal in the skin mediates the inhibition of sucker grabbing,” the researchers wrote in the study.
When the scientists offered the amputated arm to live octopuses, the creatures either treated the limb like food, did not touch the arm at all, or stuck one end in their mouth and carried it around, suggesting that some kind self-recognition mechanism prevents the suckers from attaching to octopus skin, National Geographic reported.
Researchers believe that the new findings could help scientists incorporate this self-avoidance strategy to build better robots.
"Soft robots have advantages [in] that they can reshape their body," Nir Nesher, a co-author, said. "This is especially advantageous in unfamiliar environments with many obstacles that can be bypassed only by flexible manipulators, such as the internal human body environment."