Octopus Arms

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It’s common knowledge that octopuses have eight arms, but lesser known facts are that they use their arms to propel through water, walk on the sea floor, hunt and trap prey and even groom themselves.

Each nerve bundle at the base of each arm serves as that appendage’s “brain,” according to octopus expert Julie Gee, aquarist at the Georgia Aquarium. “An octopus does not have think through every muscle contraction in order to reach out and grab something, instead they will send the command to move to the arm, and the arms “brain” takes care of the details.”

“In vertebrates – or animals with a backbone – the skeleton is used for muscles to work/push against in order to move their bodies,” Julie explained to me during a recent visit to the world’s largest aquarium in Atlanta. “In invertebrates  – like crabs or insects – they use a shell or exoskeleton to push against and to move. Octopuses do not have any sort of internal skeleton or external skeleton, so they flex small regions of their limbs which become rigid enough for the rest of the arm to move against. Thus the arm is able to bend, flex, extend and contract in an infinite number of directions.”

An octopus is extremely coordinated in the independent moving, gripping and twisting of each arm. And if an octopus loses its arm, it can slowly regrow another one in its place. 

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This wide range of movement allows an octopus to walk in a specific direction with its “back” arms while exploring the seafloor with its “front” arms. And while they can move about using a water jet propulsion system, Julie shared that octopuses more commonly walk as means of ocean travel.

Learn more about the octopus species through this National Geographic fact sheet.

Caught in the Act: Cannibal Octopus airs on Nat Geo Wild Wednesday September 1 9P et/pt.

Photo Credits: Jodi Kendall