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Octopus movement control is unique

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The orientation of an octopus’ body and crawling direction are independently controlled/Levy et al./Current Biology 2015

From ScienceDaily:

“Octopuses use unique locomotion strategies that are different from those found in other animals,” says Binyamin Hochner of The Hebrew University of Jerusalem. “This is most likely due to their soft molluscan body that led to the evolution of ‘strange’ morphology, enabling efficient locomotion control without a rigid skeleton.”

Odd, isn’t it, how entirely different, very complex systems can just happen to evolve randomly in a universe dominated by mere agglomerations of lifeless material.

After poring over videos of octopuses in action, frame by frame, the researchers made several surprising discoveries, as reported in the new study. Despite its bilaterally symmetrical body, the octopus can crawl in any direction relative to its body orientation. The orientation of its body and crawling direction are independently controlled, and its crawling lacks any apparent rhythmical patterns in limb coordination.

The findings lend support to what’s known as the Embodied Organization concept. In the traditional view, motor-control strategies are devised to fit the body. But, the researchers say, under Embodied Organization, the control and the body evolve together in lockstep within the context of the environment with which those bodies interact.

“This concept, which is borrowed from robotics, argues that the optimal behavior of an autonomous robot or an animal is achieved as a result of the optimization of the reciprocal and dynamical interactions between the brain, body, and the constantly changing environment, thus leading to optimal adaptation of the system, as a whole, to its ecological niche,” Levy says. “Another important virtue of this type of organization is that every level, including the physical properties and the morphology, contribute to the control of the emerging behavior–and not only the brain, as we tend to think.”

And robotics happens without design, right?

Keep talkin’, Darwin, keep talkin’ …

Here’s the summary:

To cope with the exceptional computational complexity that is involved in the control of its hyper-redundant arms [ 1 ], the octopus has adopted unique motor control strategies in which the central brain activates rather autonomous motor programs in the elaborated peripheral nervous system of the arms [ 2, 3 ]. How octopuses coordinate their eight long and flexible arms in locomotion is still unknown. Here, we present the first detailed kinematic analysis of octopus arm coordination in crawling. The results are surprising in several respects: (1) despite its bilaterally symmetrical body, the octopus can crawl in any direction relative to its body orientation; (2) body and crawling orientation are monotonically and independently controlled; and (3) contrasting known animal locomotion, octopus crawling lacks any apparent rhythmical patterns in limb coordination, suggesting a unique non-rhythmical output of the octopus central controller. We show that this uncommon maneuverability is derived from the radial symmetry of the arms around the body and the simple pushing-by-elongation mechanism by which the arms create the crawling thrust. These two together enable a mechanism whereby the central controller chooses in a moment-to-moment fashion which arms to recruit for pushing the body in an instantaneous direction. Our findings suggest that the soft molluscan body has affected in an embodied way [ 4, 5 ] the emergence of the adaptive motor behavior of the octopus. – Levy et al. Arm Coordination in Octopus Crawling Involves Unique Motor Control Strategies. Current Biology, 2015 DOI: 10.1016/j.cub.2015.02.064 (paywall)

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