Octopus as a comparative model for understanding the neural control of limb movement and limb-based behaviors

Octopuses provide a model system for examining the neural control of limbs. Octopus arms serve in a wide range of limb functions, but their arms' neural anatomy, muscle, and connective tissue structures are strikingly different from those of other model taxa, arthropods, and vertebrates. Unlike those groups, octopus arms contain true nerve cords with diverse neuron populations. Nerve cords of different arms connect to one another at their bases. For the arms' large axial nerve cord, signals pass from one arm to other arms through a connecting nerve ring. While the connection of the arm nervous system to the brain is necessary for behaviors such as locomotion; arm movements can be triggered with naturalistic mechanosensory input to an arm. What we know about biological systems shapes our imagination of the possible; understanding the octopus arm neural control expands how we conceive of limb systems operating in animals and inspires engineered devices.