Octopuses are among the strangest animals on Earth. They have three hearts, blue blood, arms that can think independently, and the ability to change color, texture, and even shape in an instant.
Scientists consider octopuses the most intelligent invertebrates on the planet. Found in every ocean and at nearly every depth, these animals challenge what we think intelligence, consciousness, and survival look like in the natural world.
The octopus facts below explore how octopuses think, how their bodies work, and why their short lives are so extraordinary.
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Octopus Intelligence and Behavior
Octopuses can recognize individual humans
Research shows that octopuses are capable of remembering and recognizing individual people. In laboratory settings, they have been observed reacting differently to familiar handlers than to strangers, suggesting long-term memory and individual recognition.[3]
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Octopuses use tools and solve problems
Like dolphins, crows, and chimpanzees, octopuses belong to a small group of animals known to use tools. They have been observed carrying coconut shells for shelter, manipulating objects to escape enclosures, and solving complex puzzles.
One famous octopus named Otto repeatedly threw rocks and sprayed water at a light above his aquarium until it short-circuited.[3]
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Octopus arms can think independently
Nearly two-thirds of an octopus’s neurons are located in its arms rather than its central brain. This allows each arm to respond to stimuli and perform complex actions independently, even without direct input from the brain.[3]
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Octopus Anatomy and Biology
Octopuses have three hearts and blue blood
Octopuses have three hearts: two pump blood to the gills, and one pumps blood to the rest of the body. Their blood is blue because it contains hemocyanin, a copper-based molecule that carries oxygen more efficiently in cold, low-oxygen environments.[3]
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Octopus skin can sense light
Octopus skin contains the same light-sensitive proteins found in their eyes. This allows their skin to respond directly to changes in light, helping them camouflage even without relying entirely on vision.[3]
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Octopuses are soft-bodied mollusks
Although octopuses are mollusks like clams and snails, they lost their shells through evolution. Because they have no bones, even large octopuses can squeeze through openings no larger than a coin.[3]
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Octopus Survival and Defense
Octopuses can change color and texture instantly
Octopuses can change their appearance in less than 30 milliseconds by expanding pigment sacs in their skin called chromatophores. They can also alter their skin texture, forming bumps and ridges to mimic rocks, coral, or seaweed.[3]
![Octopus squirting ink]()
Cephalopod ink contains metals, enzymes, and melanin
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Octopus ink is both camouflage and a weapon
Octopus ink clouds help confuse predators, but the ink also contains compounds that can irritate and disorient attackers. If an octopus fails to escape its own ink cloud, it can even be harmful to the octopus itself.[3]
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Octopuses can regrow lost arms
If an octopus loses an arm to a predator, it can regenerate the limb completely, with no loss of function. Unlike lizards that regrow simpler tails, octopus arms return fully functional.[3]
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Size, Species, and Lifespan
Octopuses are found in all oceans
Octopuses are found in all oceans at every depth. There are no known freshwater octopus species.[3]
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The largest and smallest octopus species
The largest octopus in the world is the Pacific octopus, Enteroctopus defleini. It weighs up to 33 lbs (15kg) and has an arm span of up to 14 ft (4.3 m). It also has three hearts and nine brains. The smallest octopus species is Octopus wolfi, which is about 1 inch (2.5 cm) and weighs less than 0.035 oz (1 g).[3]
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Octopuses lifespans are surprisingly short
Despite their intelligence, most octopuses live very short lives. Smaller species may live only six months to a year, while even the longest-living octopuses rarely survive beyond three or four years.[3]
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Reproduction and Life Cycle
Octopuses lay eggs and die shortly afterward
Octopuses are oviparous, meaning they lay eggs. After mating, males decline rapidly, and females devote themselves entirely to guarding their eggs. Once the eggs hatch, the female dies shortly afterward.[3]
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Male octopuses use a specialized mating arm
Male octopuses transfer sperm using a specialized arm called a hectocotylus. Some males have been observed keeping this arm tucked close to their body, possibly to protect it from damage.[3]
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Strange and Lesser-Known Octopus Fact
Octopuses have beaks, not teeth
An octopus’s mouth is located beneath its arms and contains a sharp, parrot-like beak used to break through shells and tear food apart.[3]
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Some octopuses can move on land
Some octopuses can walk—and even run—on land. According to one veterinarian, chasing an octopus on land is like "chasing a cat."[3]
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Baby octopuses are incredibly small
When an octopus hatches, it can be as small as a flea, yet it is fully independent from birth.[3]
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Famous and unusual Octopuses
Blue-ringed octopuses are beautiful but deadly
Blue-ringed octopuses produce venom powerful enough to be fatal to humans. Despite their small size, they are considered among the most dangerous marine animals in the world.[3]
![Opistoteuthis Adorabilis Fact]()
The Opistoteuthis adorabilis is oh so adorable
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A tiny octopus charmed scientists
A tiny octopus that was discovered in the 1990s is so cute that researchers are considering naming it Opistoteuthis adorabilis.[1]
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All octopuses produce venom used to subdue prey
Octopus venom contains enzymes that help immobilize and partially digest prey, making it easier for the octopus to feed. With the exception of the blue-ringed octopus, this venom is not dangerous to humans.[3]
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Octopus blood isn't as efficient as human blood
Because the octopus's oxygen-carrying pigment (hemocyanin) isn't as efficient as hemoglobin, the octopus has evolved two accessory hearts.[3]
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The plural of octopus is "octopuses"
The plural of octopus is not octopi because the word is Greek "octopous," not Latin. The Greek plural would be octopodes, but scientists refer to them as octopuses.[3]
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Octopuses are believed to be the smartest invertebrate on the planet.
They also have the largest brain of any other invertebrate.[2]
![Octopus Intelligence Fact]()
Octopuses are the most intelligent invertebrates on earth
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Octopuses have been known to rip the stinging tentacles from a Portuguese Man-O-War and use them as weapons.[3]
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An octopus's appendages are called arms
They are not called tentacles.[3]
![Octopus Arms]()
An octopus has hundreds of suckers running down each arm; each one acts similar to a nose and a tongue
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Octopuses can not only change color . . .
They can also change texture.[3]
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Octopuses do not have bones.
This means that even large octopuses can fit through openings the size of a coin.[3]