How Many Hearts Does an Octopus Have? (And Other Fun Facts)

The fact that an octopus has three hearts is just one of the many things that makes this unusual sea creature so fascinating.

For as far as science has come, there is still so much we don’t know about the mysterious octopus.

While they don’t live very long, they do leave their mark. Enter the octopus’s garden to find out more about the life of this fascinating and intelligent sea creature.

1. Yes, the Octopus Has 3 Hearts

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Octopuses are invertebrates with soft bodies — so, they don’t have bones. Most live in the deeper parts of the ocean, where temperatures are below freezing, and there is less oxygen. As a result, octopuses have evolved to have multiple hearts.

How many hearts does an octopus have, exactly? They have a total of three hearts that pump oxygenated blood into every part of them. Two hearts move blood to the gills, and the third (and largest) moves and circulates it to the rest of the body.

They also have eight limbs, two eyes and nine brains. (We’ll get to that a little later).

2. They Give It All Up for Parenthood

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Mating isn’t a romantic dance for octopuses — it’s actually fatal for all parties.

When it’s time to mate, multiple males offer their spermatophores to a female by either inserting it into the tubular funnel she normally uses to breathe or literally handing it over, arm to arm. The males then wander away to die.

A female lays about 40,000 eggs, which she obsessively guards for the duration of her life to the point that she stops eating. When the eggs hatch, her body breaks down, bit by bit, until she dies.

Only about 1 percent of the eggs survive into adulthood.

3. Octopuses Are All Venomous — But Not Dangerous (to Humans Anyway)

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An octopus catches its prey by breaking into that animal’s shell (if it has one) and injecting it with venomous saliva, which paralyzes it.

All octopuses have this ability, but don’t worry about coming across one — most are not dangerous to humans.

4. The Tiny Blue-Ringed Octopus Packs a Deadly Punch

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We did say “most” octopuses are harmless, but not all. The blue-ringed octopus is, in fact, deadly.

Even though it’s only 5 to 8 inches in size, the blue-ringed octopus can kill an adult human with just one bite. You won’t even know you’ve been bitten because its bite is said to be painless.

5. A Variety of Sizes

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Octopuses vary in size. The smallest, Octopus wolfi, measures just 2.5-centimeters long and weighs less than 1 gram.

On the opposite end of the spectrum is the giant Pacific octopus, which grows to 16-feet long and weighs about 110 pounds, although one came in at a whopping 30 feet and 600 pounds.

6. More Brains Than One

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Remember those nine brains from earlier?

Each brain (aside from the main one that controls the body), controls an arm. This allows each arm to work independently. Cool, right?

7. The Common Octopus

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The octopus we’re likely more familiar with than any other is the common octopus (Octopus vulgaris), which measures 12- to 36-inches long and weighs between 6.6 and 22 pounds).

The common octopus lives in most waters around the globe, from Japan to the Mediterranean Sea and the Atlantic Ocean.

8. Lost an Arm? No Problem!

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Octopuses arms take a beating. They are vulnerable to damage and often rip off.

Not that this stops the octopus — they regrow the lost arm and the brain that goes with it in about 100 days.

9. An Animal of Many Colors

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Octopuses can easily camouflage themselves by changing color in the blink of an eye.

This is due to chromatophores, which are the cells behind their transformation. Each one has a sac filled with pigment. As the muscles around it tense, the sacs stretch, and more color is visible.

10. Breathing Skills

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Octopuses breathe very much like fish do — by extracting water through their gills.

And, like fish, if they are out of water for too long, they cannot breathe. They survive only for a short time.

11. True Blue Bloods

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Octopuses have evolved to have copper-based blood. The copper base is known as hemocyanin, which makes the animal’s blood blue.

Hemocyanin is more efficient at moving oxygen in the deep ocean, where temperatures are frigid and oxygen is lacking.

12. An Octopuses Garden

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While some species show social skills, generally, octopuses are not very social. They live alone in rock dens that they build by moving rocks and shells.

These palatial, underwater “cribs” can sometimes even have their own door.

13. The Octopus Has Keen Eyesight

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Octopuses have strong eyesight. In fact, it is better than humans. They also respond to light sources due to their photoreceptors, or sensory cells.

This clear vision allows them to escape predators as well as catch prey easier than many ocean animals.

14. Deep-Sea Defenses

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An octopus sprays ink, which comes from sacs in its gills. This is a defense mechanism used to escape predators.

Species of octopuses that live in the deeper ocean do not produce ink. However, they hide or move at rapid speeds through jet propulsion. This allows them to change direction quickly in the face of an oncoming threat.

15. They Don’t Live Very Long

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Most octopus species mature quickly because their lives are so very short. They live between one to five years.

The larger the octopus is, the longer its lifespan typically is.

16. Not All Octopuses Are Long-Armed

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The Dumbo octopus may be one of the cutest animals in the sea, but it doesn’t have long arms like a normal octopus. Its arms are short and have webbing between them. (Note their cartoon elephant ears!)

There are 13 species of Dumbos. They are quite rare and not often seen because they live almost 10,000 feet below sea level.

17. Octopuses Are Old Souls

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Long before dinosaurs roamed the Earth, the octopus called this place home.

To give you an idea of how old they really are, an octopus fossil, stored at the Field Museum in Chicago, Illinois, belongs to the Pohlsepia species that lived nearly 300 million years ago during the Carboniferous period.

18. They’re Smarter Than You (and Aristotle) May Think

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Believe it or not, the highly intelligent Greek philosopher Aristotle got octopuses all wrong. He said, “The octopus is a stupid creature, for it will approach a man’s hand if it be lowered in the water; but it is neat and thrifty in its habits: That is, it lays up stores in its nest, and after eating up all that is eatable, it ejects the shells and sheaths of crabs and shell-fish and the skeletons of little fishes.”

The truth is, they are whip-smart — they can navigate mazes, solve puzzles and problems and have a great memory. They also can have distinct personalities.

19. They Are a Dangerous Delicacy

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In East Asia, Spain, Greece and many other countries, octopus is a delicacy. It’s mostly consumed in Korea and Japan, but it is also catching on in North America (by way of octopus sushi).

However, eating octopus can kill you. In Korea and Japan, many people eat the animal while it’s still moving, which can cause a choking hazard.

20. They Can Be an Inspiration

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The Netflix documentary “My Octopus Teacher” followed a filmmaker’s unusual friendship with an octopus in the ocean around South Africa. This award-winning film shed light on an octopus’ day-to-day life and behavior, which we discovered had highs and lows, much like our own.

Filmmaker Craig Foster said of the octopus he befriended, “A lot of people say that an octopus is like an alien. But the strange thing is, as you get closer to them, you realize you’re very similar in a lot of ways. You’re stepping into this completely different world, such an incredible feeling, and you feel as though you’re on the brink of something extraordinary.”

21. They Occasionally Prognosticate

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Sometimes, octopuses are used in prop bets, particularly around the Super Bowl and World Cup.

One such famous prognosticator was Paul the Octopus, who came to fame after his accurate predictions in the 2010 World Cup. That year, he was presented with food in boxes displaying the different team flags, and whichever he ate first would be the winner.

Paul correctly predicted all seven of Germany’s World Cup matches that year!

22. They Feel Physical and Even Emotional Pain

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A study has recently found that not only do octopuses feel pain physically, but they also hurt emotionally. They process pain similarly to the way humans do.

Most invertebrates reflectively react to outside stimuli, but the octopus demonstrates negative behavioral changes that do not leave them when they encounter something that hurts.

They avoid places and where they feel pain or otherwise suffer distress.

23. They Can Build ‘Cities’

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While octopuses are generally unsocial, the Gloomy octopus (yes, that’s its name) was found to be living a different reality. Scientists recently witnessed 15 Gloomys living together and communicating in an octopus “city.”

This was the second time an octopus metropolis was found. The first, cleverly dubbed “Octopolis,” was witnessed in 2009.

24. The Future of the Octopus

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While most octopuses aren’t endangered — in fact, some populations are said to be booming – they are under threat, as they are hunted regularly by humans for food.

They are also subject to rising water temperatures due to climate change, which is changing their behavior and development.

25. The Real Kraken

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The mythical Kraken is a giant sea monster in Scandinavian folklore that was said to terrorize sailors off the coasts of Norway and Greenland.

The sea creature is said to be based on an octopus, giant squid or a mix of both. It has been part of monster tales ever since and made its most recent appearance in 2006 in “Pirates of the Caribbean: Dead Man’s Chest.”