Why octopuses don't get into a tangle

Unlike humans, octopuses don’t have a constant awareness of their arms’ locations. Their walnut-sized brain simply cannot keep track of what their eight arms are doing. So how come they don’t get all tangled up?

It’s a mystery that has long baffled scientists, but it seems researchers in Jerusalem may have found the answer.

The arms themselves control their own movement. If you chop of an octopus arm, it will keep on moving for more than an hour, grabbing and latching onto things with its suckers.

Researchers at the Hebrew University of Jerusalem placed various amputated octopus limbs in water to see what would happen. The tests showed that the arms would not latch on to other severed limbs. The only time an amputated arm grabbed hold of another was when the skin had been peeled off.

“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,” said neuroscientist Guy Levy.

The test seems to suggest that there is a chemical detection capacity built into the rims of the suckers to recognise octopus skin and inhibit attachment – a useful trait bearing in mind that the sea creature is cannibalistic.

“Maybe an octopus would want 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,” said Guy Levy.

Researchers hope this self-recognition mechanism will help develop bio-inspired robots, that could be used for medical procedures or in search and rescue missions that require flexible movement and a need to distinguish between different surfaces.