Introducing the brain: octopus nervous system (Introduction)

by David Turell , Thursday, January 16, 2025, 18:23 (6 days ago) @ David Turell

Each leg has a massive system while the brain is small:

https://www.sciencedaily.com/releases/2025/01/250115125422.htm

'New research has revealed that the nervous system circuitry that controls arm movement in octopuses is segmented, giving these extraordinary creatures precise control across all eight arms and hundreds of suckers to explore their environment, grasp objects, and capture prey.

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"Each octopus arm has a massive nervous system, with more neurons combined across the eight arms than in the animal's brain. These neurons are concentrated in a large axial nerve cord (ANC), which snakes back and forth as it travels down the arm, every bend forming an enlargement over each sucker.

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"Using cellular markers and imaging tools to trace the structure and connections from the ANC, they saw that neuronal cell bodies were packed into columns that formed segments, like a corrugated pipe. These segments are separated by gaps called septa, where nerves and blood vessels exit to nearby muscles. Nerves from multiple segments connect to different regions of muscles, suggesting the segments work together to control movement.

"'Thinking about this from a modeling perspective, the best way to set up a control system for this very long, flexible arm would be to divide it into segments," Olson said. "There has to be some sort of communication between the segments, which you can imagine would help smooth out the movements."

"Nerves for the suckers also exited from the ANC through these septa, systematically connecting to the outer edge of each sucker. This indicates that the nervous system sets up a spatial, or topographical, map of each sucker. Octopuses can move and change the shape of their suckers independently. The suckers are also packed with sensory receptors that allow the octopus to taste and smell things that they touch -- like combining a hand with a tongue and a nose. The researchers believe the "suckeroptopy," as they called the map, facilitates this complex sensory-motor ability.

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"Using the same process to study long strips of the squid tentacles, Olson saw that the ANC in the stalks with no suckers are not segmented, but the clubs at the end are segmented the same way as the octopus. This suggests that a segmented ANC is specifically built for controlling any type of dexterous, sucker-laden appendage in cephalopods. The squid tentacle clubs have fewer segments per sucker, however, likely because they do not use the suckers for sensation the same way octopuses do. Squid rely more on their vision to hunt in the open water, whereas octopuses prowl the ocean floor and use their sensitive arms as tools for exploration.

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"While octopuses and squid diverged from each other more than 270 million years ago, the commonalities in how they control parts of their appendages with suckers -- and differences in the parts that don't -- show how evolution always manages to find the best solution."

Comment: amazing muscle/nerve complexity fitted exactly to need. Think of the thousands of mutations needed. Not by chance but by design.