10 Surprising Facts About Octopuses

Verfasst von Sentient Beings Alliance

Octopuses are among the most fascinating animals on Earth. They seem both familiar and completely alien at the same time: intelligent, curious, and adaptable — yet biologically so unusual that some scientists describe them as “alien-like.”

Here are ten scientifically documented facts that show why octopuses continue to surprise even researchers.

Crab and Octopus

1. Octopuses Have Three Hearts

Yes, really.

  • Two hearts pump blood through the gills

  • A third supplies the rest of the body with oxygen

Even more astonishing: When an octopus swims, its central heart temporarily stops beating. This is why many octopuses prefer crawling along the seafloor rather than swimming continuously. (Smithsonian Magazine)

2. Their Blood Is Blue

Humans transport oxygen using iron-containing hemoglobin. Octopuses, on the other hand, use hemocyanin, a copper-containing protein.

This makes their blood appear blue.

There is an advantage to this: Hemocyanin works particularly well in cold, oxygen-poor water — ideal for life in the deep sea. (Smithsonian Magazine)

3. Two-Thirds of Their Neurons Are Located in Their Arms

An octopus’s nervous system works very differently from ours.

Around two-thirds of its neurons are located not in the brain, but in the arms. This allows the arms to:

  • respond independently

  • investigate objects

  • coordinate movements

Researchers therefore sometimes refer to this as a form of “decentralized intelligence.” (Smithsonian Magazine)

4. They Can Taste With Their Arms

An octopus’s suckers are not only used for gripping.

They contain chemical receptors that allow the animals to “taste” their surroundings. An octopus can therefore simultaneously

  • feel

  • grip

  • and taste

… with the same arm. (Ocean Action Hub)

5. They Can Squeeze Through Tiny Openings

Octopuses have no bones. The only hard part of their body is their beak.

This means that if the beak can fit through an opening, the rest of the body can usually fit through as well.

This allows octopuses to:

  • escape from aquariums

  • squeeze through extremely narrow gaps

  • move in an almost “liquid” way

This ability has made them famous escape artists. (Ocean Action Hub)

6. Octopuses Use Tools

For a long time, tool use was considered something primarily associated with primates or birds.

But octopuses have been observed:

  • carrying coconut shells

  • later using them as shelter

  • deliberately manipulating objects

This is considered evidence of complex problem-solving behavior. (Smithsonian Magazine)

7. They Don’t Just Change Color - They Also Change Their Skin Texture

Octopus camouflage goes far beyond color.

They can:

  • change their patterns

  • alter the texture of their skin

  • and imitate rocks, coral, or sand with remarkable precision

This is made possible by specialized skin cells called chromatophores. Some species can change their appearance within fractions of a second. (BBC Earth)

8. Octopuses May Sleep in a Way Similar to Dreaming

In 2023, researchers published evidence in Nature of REM-like sleep phases in octopuses.

During these phases:

  • the animals rapidly change their skin patterns

  • move their eyes and arms

  • show increased neural activity

This does not automatically mean that octopuses “dream” in the same way humans do. But their sleep phases are clearly more complex than previously assumed. (Nature)

9. Octopuses Are Remarkably Intelligent

In experiments, octopuses have been able to:

  • open screw-top jars

  • solve mazes

  • remember solutions

  • distinguish between individual humans

They also show curiosity and individual behavioral differences.

For invertebrates, this is remarkable — and one of the reasons scientists are closely studying their capacity for sentience. (Smithsonian Magazine)

10. Octopus Mothers Sacrifice Themselves for Their Offspring

After laying their eggs, many females guard them for weeks or months.

They:

  • constantly clean the eggs

  • supply them with oxygen

  • defend them against threats

During this time, many females stop eating entirely and die shortly after the young hatch. (PBS)

Conclusion

Octopuses are not “simple sea creatures.”

They possess:

  • complex nervous systems

  • remarkable problem-solving abilities

  • extraordinary adaptations

  • and behaviors that continue to surprise even experienced scientists

Perhaps that is why they fascinate us so much: They show that intelligence and complex behavior can emerge in ways that are completely different from those found in humans.

And that is precisely what makes the question of how we treat these animals so relevant.

Sentient Beings Alliance