Scientists Uncover the Secret behind the Incredible Control of the Octopus Arm

A fortuitous laboratory accident has led researchers to uncover the mechanism behind octopuses’ impressive arm control, revealing a segmented nervous system that gives these eight-armed creatures precise control over their movements.

The groundbreaking study from the University of Chicago, published in Nature Communications, demonstrates that octopus arms have a complex nervous system organized like a corrugated pipe, with distinct segments working in harmony to facilitate their smooth and graceful movements.

Discovering the Unexpected

The breakthrough occurred when graduate students Cassady Olson and Grace Schulz encountered difficulties while trying to examine thin cross-sections of octopus arms under a microscope. As a result, they switched to viewing lengthwise strips, which unexpectedly led to a significant discovery.

“From a modeling perspective, segmenting the long, flexible arm would be the most effective way to control it,” explains Olson. “There must be communication between the segments to ensure coordinated movements.”

A Neural Network in Each Arm

Each octopus arm contains more neurons than its brain, concentrated in a large nerve cord that runs along the length of the arm. The researchers found that these neurons are arranged in distinct columns separated by gaps where nerves and blood vessels extend to nearby muscles.

This segmented arrangement creates what the researchers refer to as “suckerotopy” – a spatial map that aids in controlling the numerous independently moving suckers that allow octopuses to interact with their environment through touch.

An Evolutionary Innovation

“For dynamic movement control, organizing the nervous system in this manner is highly advantageous,” notes Clifton Ragsdale, PhD, Professor of Neurobiology and senior author of the study. “We believe this feature evolved specifically in soft-bodied cephalopods with suckers to facilitate worm-like movements.”

Diverging Paths of Cephalopods

The research team also studied squid, which diverged from octopuses over 270 million years ago. They observed that squid tentacle clubs, used for capturing prey, exhibit the same segmented structure, while the sucker-less stalks do not. This suggests that segmented nerve cords evolved to control appendages with suckers.

“Organisms with sucker-laden appendages requiring worm-like movement necessitate a specific type of nervous system,” explains Ragsdale. “Different cephalopods have developed segmented structures tailored to their unique environments and the evolutionary pressures they have faced over millions of years.”