June 2 - The octopus has eight, sucker-lined arms that can grab almost anything, even when the arms have been severed from the body. But, as the limbs act independently of the animal's brain, how does the animal avoid tying itself up in knots?Scientists at Hebrew University say they have discovered the answer hidden in the creature's skin. Jim Drury has more.
It's a mystery that's long baffled scientists - how does an octopus prevent its eight arms from becoming entangled, when each limb behaves independently of the other seven and the animal's brain ? Neuroscientists Guy Levy and Nir Nesher say they have the answer - chemoreceptors on the rim of each sucker which sense molecules in the skin, inhibiting the grabbing reflex. Octopus arms are autonomous. When severed, they can move for up to an hour. The Hebrew University of Jerusalem researchers placed various amputated limbs in water to see what would happen. The tests showed that removed arms wouldn't suck on other severed limbs, unless the skin had been removed, says Levy. SOUNDBITE (English) GUY LEVY, NEUROSCIENTIST AT THE HEBREW UNIVERSITY OF JERUSALEM, DEPARTMENT OF NEUROBIOLOGY, SAYING: "We saw that the amputated arm grabbed the flesh, the peeled arm, as any other item, but when we stretched the skin over plastic discs, the amputated arm didn't grab it. The sucker simply won't respond to the skin." But it will respond to the skin of another octopus. This suggests the octopus's brain can distinguish its own limbs, a useful trait bearing in mind that the sea creature is cannibalistic. SOUNDBITE (English) GUY LEVY, NEUROSCIENTIST AT THE HEBREW UNIVERSITY OF JERUSALEM, DEPARTMENT OF NEUROBIOLOGY, SAYING: "An octopus would want maybe to grab the skin of another octopus in order to catch it and eat it, but it doesn't want its own arms to grab each other. so this is a magnificent and brilliant solution of nature, to a potentially very complicated problem. The octopus, instead of having to calculate and compute when and where its arms touch each other, it seems simply avoids grabbing each other ahead of time in the first place." Levy says this self-recognition mechanism could help develop bio-inspired robots - useful for medical procedures or search and rescue missions that require flexible movements and a need to distinguish between different surfaces. The pair are now examining which specific molecules allow the octopus to recognise its own skin....and prevent it getting in a twist.