Octopuses Have Nine Brains and Blue Blood

Octopuses have nine brains working together to control their complex bodies. One central brain sits between the eyes and coordinates overall behavior, while each of the eight arms has its own mini brain that controls movement and processes sensory information independently. About two thirds of an octopus's 500 million neurons are located in these arm brains rather than the central brain, making octopuses one of the most neurologically unusual creatures on Earth.

How the Nine Brains Work Together

The central brain handles high level functions like visual processing, decision making, and learning. It coordinates the overall behavior and tells the arms what general task to accomplish. However, the arm brains handle the details of movement without waiting for instructions from the central brain. When an octopus reaches for food, the central brain sends a simple command like reach toward that object. The arm brain then figures out exactly how to move, which muscles to contract, and how to navigate around obstacles. This distributed intelligence allows octopuses to accomplish complex tasks quickly because the central brain does not need to micromanage every movement.

Arms That Think for Themselves

Each arm brain contains about 40 million neurons that process touch, taste, and movement information. Octopus arms can taste what they touch using chemical receptors in their suckers, allowing them to identify food without using their eyes. The arm brains process this sensory information and make simple decisions independently. A severed octopus arm can continue moving, reacting to stimuli, and even reaching for food for several hours after separation from the body. The detached arm still tries to bring food to where the mouth would be, demonstrating that basic behaviors are programmed into the arm brain itself.

Blue Blood and Three Hearts

Octopuses also have blue blood powered by three hearts. Their blood uses hemocyanin instead of hemoglobin to carry oxygen. Hemocyanin contains copper rather than iron, giving oxygenated blood a blue color instead of red. This copper based system works better in cold, low oxygen environments where many octopuses live. Two of the three hearts pump blood to the gills where it picks up oxygen. The third heart pumps oxygenated blue blood throughout the body. Interestingly, the main heart stops beating when the octopus swims, which is why octopuses prefer to crawl along the ocean floor rather than swim.

Remarkable Intelligence

Despite being invertebrates, octopuses demonstrate intelligence rivaling some mammals. They solve complex puzzles, navigate mazes, use tools, and remember solutions for months. Octopuses recognize individual humans and show different behaviors toward people they like versus dislike. They can open childproof jars by watching and learning the twisting motion required. In laboratories, octopuses escape their tanks, travel across floors to other tanks to eat fish, and then return to their own tanks before morning. They also exhibit playful behavior, which scientists associate with higher intelligence.

Distributed Nervous System Advantages

The distributed nervous system provides octopuses with several advantages. Processing sensory information in the arms reduces the workload on the central brain, allowing faster reaction times. An octopus can explore eight different areas simultaneously because each arm operates independently. The arm brains handle routine tasks like maintaining grip and adjusting sucker positions, freeing the central brain to focus on navigation and decision making. This parallel processing allows octopuses to accomplish multiple complex tasks simultaneously that would overwhelm a centralized nervous system.

Short Lives Despite High Intelligence

Despite their remarkable intelligence and complex nervous system, most octopuses live only 1 to 5 years depending on species. The giant Pacific octopus has the longest lifespan at about 5 years, while smaller species survive just 1 or 2 years. All octopuses die shortly after reproducing. Females stop eating after laying eggs and spend weeks or months guarding them until hatching. The female dies soon after the eggs hatch. Males die within months of mating. This reproductive strategy means octopuses cannot teach their offspring, yet they develop sophisticated problem solving abilities through individual learning during their brief lives.