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Scientists have often pondered over how the eight-armed octopus avoids getting tangled around itself. This mystery was particularly perplexing given that each tentacle is lined with hundreds of suckers that are strong enough to stick to almost anything. Also, unlike animals with rigid skeletons, the mollusks have no idea where their arms are at any given moment.
Now some researchers from Israel's Hebrew University of Jerusalem may have finally solved the puzzle. They believe that whenever the octopuses sense their own skin, they release a chemical signal that temporarily disables the suckers.
The team of scientists led by the University's neurobiologist Nir Nesher, were first tipped off to this well-kept secret, when they noticed that the suckers on amputated octopus arms, which remain active for up to an hour after being severed and even try pick up food for a phantom mouth, never stick onto their own or the amputated arm of any other octopus. Curious, they conducted a lab experiment using twenty one amputated arms that were still active. Sure enough, none tried to grasp the other.
However when they removed the skin from a couple of the arms, the suckers on the others immediately came alive and reached out for them. This led the researchers to suspect that the octopus released a tactile or chemical signal, which automatically shut down the suckers, whenever it sensed one of its own hands.
To verify their theory, the researchers conducted a second laboratory experiment whereby they coated two Petri dishes - One with octopus skin extract and the other with a fish skin extract. They then tested each with octopus amputated arms that were still active. What they discovered was that the force required to separate the amputated arm from the Petri dish coated with the octopus skin extract was twenty times weaker than that needed to separate it from the one containing the fish skin extract.
Nesher and his team then took the experiment one step further by offering live octopuses, the amputated arms. The results were mixed. In some cases, the octopus grabbed them just like they would any other prey, while in others, they ignored them completely. Upon analyzing the results, the researchers discovered that the cannibalistic animals had avoided the amputated arms that had once belonged to them, but happily grabbed onto the ones from other members of its own species.
The findings from all these experiments has led the team who published their research in the scientific journal Current Biology on April 24th, to conclude that octopuses have a general tendency not to grip their own skin. However when necessary, its brain can override that reflex, something that happens when the animal decides to prey off a member of its own species. Nesher believes the findings will help scientists engineer better soft-bodied robots - Ones that can function efficiently without getting tangled around themselves.
This is the not the first time the Octopi has impressed scientists. These highly intelligent cephalopods with razor sharp memories have been known to create shelters from coconut shells, maneuver through mazes and even, try escape from their tanks!
Resources: animals.i09.com, nationalgeo.com