Chuck Bednar for redOrbit.com – @BednarChuck
Researchers have created a detailed kinematic analysis of how an octopus coordinates its arms while crawling, demonstrating for the first time how these cephalopods use a unique method of motor control to move in any direction relative to its body orientation.
Their findings, published Thursday in the journal Current Biology, indicate that octopuses use locomotion strategies that are unlike those found in other animals, and that this is probably due to the soft, bilaterally symmetrical bodies that required efficient control without a skeleton.
The research, which was led by scientists at The Hebrew University of Jerusalem, builds upon previous work at the institution focusing on goal-directed arm movements such as reaching for a target or fetching food to the mouth. It is the first study to examine the larger, overall question of how an octopus manages to coordinate their eight long, flexible arms while moving.
How the creature of the depths evolved those slimy legs
The cephalopods likely evolved from animals more similar in nature to clams, with a protective outer shell and nearly no discernible movement, the authors said. As it evolved, the octopus lost their heavy protective shells, becoming both more maneuverable and more vulnerable. They had to move faster than other mollusks in order to compensate for the lack of a shell.
As they evolved long, slender arms, octopuses also gained improved vision, a brain that was both large and well developed, and the ability to use color to camouflage themselves. While this made them successful predators, the mechanisms they used to control their bodies remained unclear.
The Hebrew University of Jerusalem team reviewed videos of the creatures, frame-by-frame, as they moved and make several new discoveries. For one thing, even though an octopus has a body that is bilaterally symmetrical, it can actually crawl in any direction relative to its orientation. Its body orientation and crawling direction are controlled independent of each other.
Furthermore, they found that the octopus’s crawling appears to lack rhythmical patterns in limb coordination. They also demonstrate that this unusual maneuverability is derived from the radial symmetry of their arms around the body, that the arms create crawling thrust through a push-by-elongation mechanism, and that it chooses which arms to activate to move in a specific direction.
The findings provide evidence supporting what is known as the Embodied Organization concept, the researchers explained. In the traditional view, motor-control strategies are devised in order to fit the body. Under Embodied Organization, however, the control and the body evolve together in the context of their environment, indicating that a creature’s optimal behavior is achieved as a result of the optimization of interactions between body, brain, and environment.
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