Spend a few minutes watching the graceful dance of an octopus on the prowl and you’ll quickly appreciate their talent for making their arms flow like a living liquid.
It’s one thing to marvel at their flexibility. To really get a grip on their motor skills, researchers from the Marine Biological Laboratory in Massachusetts put ten specimens in their own specially sectioned tanks to film every twitch of their limbs.
All up, 120 minutes of footage collected over several months contained a total of 16,563 arm deformations from 10 octopuses, providing plenty of examples of just about every kind of bend, clockwise twist, anti-clockwise turn, contraction and elongation imaginable.
We can easily assume the octopus ranks high among animals for dexterity, outperforming similar boneless movements found in worm torsos, elephant trunks, and even our own twisting tongues.
But in science, assumptions are for chumps. Hard data matter, and surprisingly nobody had actually mapped the precise movements of an octopus’s arms.
We already have a good sense of octopus anatomy and physiology. Each arm is essentially a cord of nerves extending down from its own unique brain centre, giving limbs an ability to reflexively make individual decisions based on its unique sensory system.
In fact, two-thirds of an octopus’s neurons are spread out through its eight arms this way, meaning there is more ‘brain’ in its limbs than in any one central place. Densely packed transverse muscles surround each arm’s axial nerve chord, which is linked to a wrapping of longitudinal muscles with fibres that run lengthwise down the limb.
Slanted strips of oblique muscle fibre are interspersed with these longitudinal muscles, angled in two directions to provide torsion in clockwise and anticlockwise directions. Lastly, there is yet another layer of muscle on top, with its meatiest part towards the
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