Octopuses have a lot of arms, with which they can do a lot of things. They can unscrew jars and steal cameras and even create watertight vacuum seals with their suckers. That's partly because octopus arms basically have minds of their own, and experience a great deal of highly dextrous control reflexively, without needing to consult the brain.
Guy Levy, a doctoral candidate at Hebrew University in Jerusalem, was wondering why, then, octopus arms don't get tangled -- so he set out to determine how the animals keep their arms apart. His research, published on Thursday in the research journal Current Biology, found that octopuses know better than to attack their own arms, but only when they have skin. The solution, it seems, is simple: the marine animals secrete a certain chemical from the skin that indicates to the receptors in the arm that it should avoid contact, if possible.
The researchers also found that octopuses behave more oddly when interacting with their own arms, to which they appear to be especially sensitive, but not to other octopuses' arms -- in fact, they're more likely to consider them food. This isn't entirely abnormal, as octopuses are known to eat one another. But it does imply a certain level of self-recognition that had not been confirmed before -- making the study just one more example of how bright these incredible sea creatures are.