How Many Hearts Does an Octopus Have? 25 Facts

Hearts and blood: facts 1–5

• 1. An octopus has three hearts: two branchial hearts for the gills and one systemic heart for the body.
• 2. It has two gills, each served by a branchial heart.
• 3. Oxygenated octopus blood appears blue because it contains copper-based hemocyanin.
• 4. Humans use iron-containing hemoglobin instead; blue octopus blood is not caused by ink.
• 5. The systemic heart stops beating during swimming, making sustained jet-propelled swimming demanding.

Arms, senses and camouflage: facts 6–15

• 6. Octopuses have eight arms; they are not the same arrangement as a squid’s eight arms and two longer tentacles.
• 7. Suckers can grip objects and sense chemicals on surfaces, sometimes described as tasting by touch.
• 8. Many neurons are outside the central brain, particularly in the arms, allowing substantial local processing.
• 9. The popular phrase “nine brains” oversimplifies that distributed nervous system.
• 10. A hard beak lies at the mouth where the arms meet and helps break food apart.
• 11. The soft body can squeeze through narrow gaps, although the beak limits the smallest opening.
• 12. Chromatophores are pigment-containing skin structures involved in changing colour.
• 13. Some octopuses can also change skin texture, creating bumps that help match a rough background.
• 14. Their eyes have a camera-like arrangement, a striking case of similarity with vertebrate eyes despite separate evolutionary histories.
• 15. Many species eject ink as a defence, but not every octopus species has an ink sac.

Behaviour and life history: facts 16–25

• 16. Octopuses are predators, and many feed on crustaceans and other small marine animals.
• 17. Jet propulsion expels water through a siphon; crawling is another important way to move.
• 18. Some octopuses have opened jars or solved tasks in controlled settings.
• 19. Veined octopuses have been observed carrying coconut shells for shelter, an example of tool use.
• 20. An octopus can regenerate a lost arm; regrowth takes time and is not invulnerability.
• 21. Males transfer sperm using a modified arm called a hectocotylus.
• 22. In many species females guard eggs, stop feeding and die after the reproductive period.
• 23. Lifespan varies, but many octopuses live only about one or two years.
• 24. Giant Pacific octopuses are among the largest species and can live longer than that short typical span.
• 25. Dumbo octopuses have ear-like fins and live in deep water; those “ears” are not mammalian hearing organs.

Are octopuses dangerous to touch?

Three hearts does not mean three separate personalities