Why don’t an octopus’s arms become hopelessly entangled? Their appendages can move with seemingly infinite freedom, forming far more postures and positions than their brains could possibly keep tabs on. The key, according to a study published online today in Current Biology, is chemicals in their skin. By examining amputated octopus arms (don’t worry, they grow back) of the common octopus (Octopus vulgaris, shown), researchers have found that the creature’s suckers don’t latch on to its own arms the way they snare everything else. Petri dishes coated with intact octopus skin became “immune” to the zombie arms. The same occurred if the skin was ground up into a mush and spread over the petri dish, implying that a special substance in the skin is responsible for repelling the suckers. That’s important because octopuses have been known to dine on their comrades. So somehow a chemical in their skin not only keeps them from tangling themselves up, but it also prevents them from eating themselves alive.