The animal often rumored to possess nine separate brains is the octopus. This description is not literally accurate but serves as an intriguing simplification of one of the most unique nervous systems in the animal kingdom. The reality is that the creature’s neurology is highly decentralized, an arrangement that grants it astonishing capabilities and distributed intelligence. This structure allows the animal to manage its eight complex limbs with a level of coordination unlike almost any other organism.
The Animal with the Decentralized Nervous System
The octopus has a single, central brain encased in a cartilaginous capsule in its head. This brain is donut-shaped, a necessity because it wraps around the animal’s esophagus, which is part of the digestive tract. The central brain handles tasks like vision, complex decision-making, and overall body coordination.
The source of the “nine brains” concept lies in the eight large clusters of nerve cells, known as ganglia, located at the base of each arm. Each arm possesses its own ganglion, acting as a control center for that specific limb.
Approximately two-thirds of the octopus’s total 500 million neurons are distributed throughout these eight arm ganglia and the nerve cords that run down the length of each limb. This distribution allows the arms to process information and initiate actions locally, separating the octopus nervous system from the centralized structures found in vertebrates.
How the Nine-Part System Controls the Arms
The decentralized nervous system creates a functional split between the central brain and the arms, giving the limbs a remarkable degree of semi-autonomy. The main brain issues high-level commands, such as “move toward that shelter” or “reach for that crab.” The intricate motor execution required to fulfill the command is then delegated to the arm’s own ganglion.
This allows the arm to handle complex movements, like navigating around obstacles or manipulating objects, without requiring constant direction from the central brain. The arms can even communicate with each other via a neural ring, bypassing the central processing unit for local coordination. This enables the arms to work together seamlessly during locomotion or when handling prey.
Each arm is equipped with chemoreceptors on its hundreds of suckers, allowing it to “taste” and “touch” its environment simultaneously. This sensory information is processed by the arm’s ganglion, which can then initiate a grasping or tasting action independently. The semi-autonomous nature is so pronounced that a severed arm can continue to react to stimuli and even attempt to move a captured food item toward the mouth.
Exceptional Octopod Characteristics
Beyond its unique neural architecture, the octopus possesses other unusual biological traits. Its circulatory system operates with three hearts. Two, called branchial hearts, are dedicated to pumping blood through the gills to pick up oxygen. The third heart, the systemic heart, circulates the oxygenated blood to the rest of the body.
The systemic heart temporarily stops beating when the animal swims, which is why octopuses often prefer to crawl along the ocean floor rather than swim long distances, as swimming can quickly tire them out.
Furthermore, the animal’s blood is a striking blue color, not red like that of mammals. This is due to the use of hemocyanin, a copper-based protein, to transport oxygen, rather than the iron-based hemoglobin found in human blood. Hemocyanin is more efficient at carrying oxygen in the cold, low-oxygen environments of the deep ocean.
The octopus is also a master of instantaneous camouflage, powered by thousands of specialized pigment sacs in its skin called chromatophores. Through muscle contractions controlled by its nervous system, the animal can instantly change its color and the texture of its skin to perfectly match its surroundings. This rapid disguise is a primary defense mechanism, allowing the soft-bodied creature to blend into complex backgrounds quickly.