The hundreds of suckers lining an octopus’s tentacles will stick to most anything, but not the octopus itself, proving that octopuses evolved an ingenious way to avoid tying themselves up in knots.
Researchers at the Hebrew University in Jerusalem have discovered that a chemical signal in the cephalopod’s skin prevents the chances of dangerous self-adhesion. Without the active agent that the researchers have yet to specifically identify, the flexible animals would quickly wind up in a tangle. However, their ability to remain unknotted is a sure sign of the octopus’s superior intelligence and self-awareness.
”We were surprised that nobody before us had noticed this very robust and easy-to-detect phenomena,” said researcher Dr. Guy Levy, who carried out the research with co-author Dr. Nir Nesher in the Department of Neurobiology at the Hebrew University’s Alexander Silberman Institute of Life Sciences. ”We were entirely surprised by the brilliant and simple solution of the octopus to this potentially very complicated problem.”
Solving the mystery of untangled tentacles
According to a number of studies, it has been proven that octopuses lack accurate knowledge about the position of their arms and given the clingy nature of their suckers, the question of how they avoided tangling themselves in knots was a previously unresolved puzzle.
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Tests showed that amputated octopus arms, which remain highly active for an hour after separation, never grabbed hold of octopus skin nor did they attach themselves to lab dishes covered with octopus skin or skin extract, while they did grab onto skinned octopus arms. Even more remarkable, live octopuses seem able to override the avoidance mechanism at will. They will, for instance, grab on to an amputated arm, especially if it is not one of their own.
Professor Binyamin Hochner, Principle Investigator in the Hebrew University’s Octopus Research Group, has focused his research for years on octopuses flexible arms and body motor control. He explains that there is a good reason that octopuses move their arms in different ways than other animals and even humans do, “Our motor control system is based on a rather fixed representation of the motor and sensory systems in the brain in a format of maps that have body part coordinates. Using such maps would have been tremendously difficult for the octopus, and maybe even impossible.”
Rest assured: self-strangulation won’t do the octopus in
The researchers wrote in the journal “Current Biology” that, ”The results so far show, and for the first time, that the skin of the octopus prevents octopus arms from attaching to each other or to themselves in a reflexive manner. 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.”
Besides shaking us all of the unfounded worry of octopus death by self-strangulation, this discovery could help researchers design bio-inspired ”soft” robots. Levy and his team have shared their findings with colleagues working on the European STIFF-FLOP project, which aims to develop a flexible surgical manipulator in the shape of an octopus arm. “Soft robots have advantages in that they can reshape their body,” said Dr. Nesher. “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.”
Photo: Anja Osenberg