As much as we struggle to avoid tripping on cracks in the sidewalk while fumbling with our smart phones, life would seem to be twice as difficult for the eight-legged octopus. The brains of cephalopods like Octopus vulgaris are considerably simpler than humans’, yet they seem to have no trouble keeping track of their many flexible appendages. To figure out how, researchers conducted a frame-by-frame analysis of videos of octopuses as they crawled over objects. The secret behind the animal’s dexterity comes from the radial symmetry of its legs, the team reports online today in Current Biology. An octopus moves by placing its limbs on the ground and then elongating them. As a leg stretches, it propels the main body away from where the leg touches the surface. Because octopus legs are evenly spaced around the body, choosing a direction is as simple as choosing which legs to stretch: to move right, elongate the legs on the left; to move forward, elongate the legs in the back. Furthermore, videos like the one above in which the green arrow marks body direction and the blue arrow indicates crawling direction, showed that octopuses are able to change direction without adjusting the orientation of their body, suggesting that these abilities are controlled independently in the brain. The team also discovered that octopus movement doesn’t follow a rhythmic pattern. This contrasts sharply with movement strategies found in other animals—like humans and even insects—that rely on neural networks that intentionally impart rhythm to their movement. The researchers assert that their results support the idea that movement strategies, body plans, the environment, and central nervous system architecture all evolve together and are intimately intertwined—a concept known as embodied organization that is influencing the design and programming of bioinspired robots.
(Video credit: Levy et al./Current Biology 2015)