How does an octopus control all eight arms at once?
Octopuses would be unique for their body plan alone, with a highly developed brain, large eyes, bilaterally symmetrical body and eight distinctive radially symmetrical, flexible arms. Scientists have long struggled to understand exactly how these marine organisms are able to coordinate their eight long arms at once during locomotion, until recently.
A paper, published in the journal Current Biology earlier this week, reported that octopuses are now even more unique, with individuals using locomotion strategies that are not found in any other animal in order to coordinate.
Researchers from the Hebrew University of Jerusalem examined videos, frame by frame, of octopuses in action and a remarkable discovery was found. Regardless of its bilaterally symmetrical body, which means their left and right sides are mirror images of each other, the octopus can actually crawl in any direction relative to the orientation of its body. In other words, octopuses do not have to turn their bodies in order to change direction.
According to the study, octopuses move not by pulling or pushing in one direction, but rather by allocating different arms for different directions. Individuals move by shortening and then elongating its arms, which creates a pushing thrust. Choosing a direction is as simple as choosing which legs to stretch i.e. to move right, elongate the legs on the left; to move forward, elongate the legs in the back. This manoeuvrability contrasts to any known animal locomotion as octopus crawling lacks any apparent rhythmical patterns in limb coordination.
Octopuses have a unique motor control strategy, which is activated by the central brain as opposed to autonomous motor programmes in the peripheral nervous system of the arms, which allows these instantaneous movements. The findings support the Embodied Organization concept which states that motor control strategies, body plans, the environment and central nervous systems all evolved together. This is likely to have arisen as a consequence of its evolutionary history. Their locomotory abilities may have evolved quickly to compensate for a lack of shell.
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