Octopi create temporary human-like arm-joints to feed

Few things are more flexible than the noodly octopus arm; it has a nearly infinite number of degrees of freedom. But when it comes time to eat? Apparently octopi pull a neat trick — they initiate muscular contractions that create temporary “joints” that limit their arms’ range of movement, so that they move oddly like … human arms.

The scientists reported their findings in the recent issue of Current Biology, and a report on MSNBC describes it thusly:

Researchers recorded muscle activity in octopus limbs, and found that an arm generates two waves of muscle contractions that propagate toward each other. When the waves collide, they form a part-time joint.

This process occurs three times, forming a shoulder where the arm meets the body, a wrist where the suckers have grasped their food, and an “elbow” somewhere in between. The elbow typically exhibits the most movement during food retrieval.

The researchers say this is a remarkably simple and apparently optimal mechanism for adjusting the length of arm segments according to where the food item is grasped along the arm.

(Thanks to Yishay Mor for this one!)

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I'm Clive Thompson, the author of Smarter Than You Think: How Technology is Changing Our Minds for the Better (Penguin Press). You can order the book now at Amazon, Barnes and Noble, Powells, Indiebound, or through your local bookstore! I'm also a contributing writer for the New York Times Magazine and a columnist for Wired magazine. Email is here or ping me via the antiquated form of AOL IM (pomeranian99).

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