How Many Hearts Do Octopuses Have? (And Why One Stops When They Swim!)
If an octopus tells you their heart beats for you, make sure to ask them WHICH one! The heart is a crucial organ so is it any surprise that our octopus (eh hem alien) friends would have THREE of them! In this blog post, we are breaking down how these octopus hearts work and answering the burning question of why they need so many in the first place. Spoiler alert: it has to do with their BLUE BLOOD!
🫀 What are the 3 hearts in an octopus for?
🧠 Quick Answer: An octopus has three hearts—two branchial hearts pump blood to the gills, and one systemic heart pumps it to the rest of the body. When an octopus swims, the systemic heart stops.
Like most vertebrates, our solitary heart is ingrained into our biology. It’s an essential part of our circulatory system and we depend on it to pump blood and circulate oxygen around our bodies.
The vast majority of animals only have one heart but naturally, leave it up to the cephalopods to buck this trend and evolve to have MULTIPLE hearts!
So, how many hearts does an octopus have?
Shouldn’t they have just one like us? Okay, maybe they have 2? Nope, octopuses have three hearts. Mind-blowing isn’t it? What kind of sweet love are they offering here?
Well, there is one main heart called the systemic heart, which acts much like our own heart pumping blood throughout the body. In addition, octopuses have two branchial hearts, which pump blood through their gills, all of which are located in their mantle.
The bulbous sac, usually behind the octopus’s eyes, houses all the important organs such as their:
- Gills
- Stomach
- Reproductive organs
- And, their hearts!
🐙 Octopus Fun Fact
The only cephalopod without three hearts is the Nautilus, a famous outlier for most cephalopod standards. Due to their smaller size and chill lifestyle, the Nautilus only use a single heart to keep them going- just like us, humans!
How does it all work?
Unlike most mollusks, octopuses have a closed circulatory system where blood travels within a network of arteries and capillaries inside the body (like us humans!).
The branchial hearts are located near the gills where they receive deoxygenated blood returning from the body and get rid of waste like carbon dioxide. While the blood passes over the gills, it also loads up on oxygen (much like our blood does as it passes by our lungs).
This nicely oxygenated blood gets pumped via the branchial hearts to the main heart (aka systemic heart) which then distributes it throughout the body.
🐙 Octopus Fun Fact
Cephalopods aren’t the only animals with a funky heart configuration! Cockroaches have one heart that is divided into 13 chambers (humans only have four chambers) and earthworms have five pseudo-hearts distributed throughout their bodies.
The hagfish is another sea creature that has multiple hearts! It has 4 hearts:
- One of them serves as the systematic heart, responsible for pumping blood throughout the body.
- The other three operate as auxiliary hearts, which help the circulatory system in pumping blood.
Wondering WHY they need three hearts?
It all has to do with their blood… which is BLUE!
Cephalopods have a copper-containing protein called hemocyanin that binds oxygen so it can be transported within the blood. Hemocyanin floats freely within the blood and is colorless until it picks up an oxygen molecule. Because the hemocyanin protein contains copper it turns blue when oxygenated.
This is different from humans who have an iron-rich protein known as hemoglobin, which makes our blood red!
Having blue blood sounds pretty wild…
But what does this have to do with needing more hearts?
The hemocyanin proteins floating around in octopus blood are complex and large making their blood THICK. When your blood has the consistency of honey, it requires a lot of extra energy and pressure to push it through your body.
The two branchial hearts basically act as additional pumps to take some stress off the main systemic heart. This doesn’t mean the main heart can slack.
In fact, it still works so hard that when an octopus is actively swimming, it will eventually tire out, shut down, leaving only the branchial hearts pumping!
Octopuses usually only swim in short bursts preferring to crawl, float, or straight up chill so they can keep all their hearts pumping. No big cardio workouts for cephalopods!
🐙 Octopus Fun Fact
Did you know there’s a heart condition named after an octopus trap? Tako is Japanese for Octopus. Takotsubo cardiomyopathy or “broken heart syndrome” comes from the name of a pot which Japanese fishermen would use to trap octopus.
The condition occurs when the heart muscle becomes suddenly weakened or stunned by severe emotional or physical stress.
Takotsubo cardiomyopathy is a temporary heart condition that develops in response to an intense emotional or physical experience. It’s also known as stress cardiomyopathy or broken heart syndrome.
— Limmer Education (@LimmerEducation) February 14, 2022
(Happy Valentine’s Day! Stay safe out there.) #EMS #EMT #Paramedic #AEMT pic.twitter.com/OgRmTS1mUQ
Octopus hearts- the more the merrier!
It’s starting to seem like octopuses love extra organs. Four limbs? Nah, let’s double that and have eight! One brain? Mmm, let’s have nine and spread eight of them throughout our arms. One heart? No thanks, lucky number three!
At this point it’s surprising they only have two eyes…wait 👀
Octopus Hearts Frequently Asked Questions
Three! 💙💙💙
Octopuses have two branchial hearts, which pump blood through the gills to pick up oxygen, and one systemic heart, which circulates that oxygenated blood throughout the rest of the body. This unique three-heart system is a hallmark of cephalopod physiology!
Because their blue blood requires extra circulation support.
Octopuses don’t use red, iron-rich blood like we do. Instead, they use hemocyanin—a copper-based oxygen transporter that turns their blood blue. But there’s a trade-off: blue blood doesn’t carry oxygen as efficiently, especially in chilly or low-oxygen waters.
So how do they keep their body oxygenated?
Evolution handed them a trio of hearts:
🫀🫀 Two Branchial hearts: These sit near the gills. Each of these hearts pumps deoxygenated blood directly through a gill to collect oxygen—think of them as the “oxygen pickup crew.”
🫀 One Systemic heart: This one’s the boss. It receives the freshly oxygenated blood from the gills and circulates it through the rest of the body.
This whole system makes sure that even with slow-moving, thick blood, oxygen gets where it needs to go.
Not always!
The systemic heart actually stops beating when the octopus swims. It’s thought to be a way to conserve energy during intense movement. This is one reason octopuses prefer crawling over swimming!
No. 😔 💔💙💔
Each of the three hearts has a specialized role. The systemic heart maintains circulation to the body, while the branchial hearts handle oxygen uptake at the gills. There is no evidence of functional redundancy (they don’t back each other up)—meaning damage to one heart would seriously compromise oxygen transport and survival. Octopus Hearts = vital and non-redundant.
No branchial heart? No oxygen pickup.
No systemic heart? Oxygen can’t travel to the body.
That’s why an octopus can’t survive the loss of a heart…lose one, and the whole circulatory system goes down!
Yes!
Every known octopus species—from deep-sea octopods to tropical reef octopuses—All have the same three-heart setup. It’s a defining feature of their circulatory system.
Just three hearts—not nine.
The “nine hearts” myth likely comes from confusion with the “nine brains” fact (one central + eight satellite or peripheral brains in the arms). While octopuses are neurologically complex, their circulatory system is firmly a three-heart operation!
So many things—where do we start?
Octopuses have three hearts and blue copper-based blood; humans have one heart and red iron-based blood.
The octopus systemic heart temporarily stops when swimming; the human heart never takes breaks.
Octopus hearts pump blood through a closed circulatory system, but their oxygen transport system is less efficient than ours due to hemocyanin.
Blue.
Their blood contains hemocyanin, a copper-based molecule that turns blue when oxygenated—just like how human blood turns red from iron-based hemoglobin.
They keep beating—but slow down.
When an octopus sleeps, its systemic and branchial hearts continue beating, but at a reduced rate, conserving energy. During quiet sleep, the heartbeat is steady and slow. But during active sleep—a phase scientists think may be similar to REM sleep in humans—the octopus’s skin changes color, its arms twitch, and its heartbeat becomes irregular.
This has led researchers to suggest that octopuses may be dreaming. If true, they’d be one of the few invertebrates known to have such vivid sleep cycles. And yes—while all that dreaming is going on, their three hearts are still quietly working behind the scenes.
The blue color comes from hemocyanin in the blood, not the muscle tissue of the heart. The hearts themselves are pinkish or greyish-white—not sapphire gems like you’d hope. 💎
Because jet propulsion puts the squeeze on circulation!
Here’s what’s happening under the octo hood:
When an octopus wants to swim, it draws water into its mantle cavity (inhales)—that’s the big bag lookin’ thing behind its eyes. Then, it forcefully contracts (exhales) its mantle muscles to push that water out through a funnel (called the siphon), rocketing the octopus backward. This is called jet propulsion.
But here’s why one heart stops: that powerful squeeze also compresses the veins returning blood to the systemic heart (the one that pumps oxygenated blood through the body). With reduced venous return, the heart doesn’t have enough incoming blood to pump out—so it temporarily stops beating!
For our visual minded folks, picture an octopus’s mantle cavity like a water balloon being filled through a thin straw. The straw represents the veins bringing blood back to the heart.
Now—squeeze that balloon hard. What happens? The straw collapses. No more water can enter.
That’s what happens when an octopus swims: the mantle contracts to force water out (jet propulsion), but the pressure is so strong it compresses the veins that feed the systemic heart. With no incoming blood, the heart pauses until the pressure eases.
This is why benthic octopuses, like Octopus vulgaris, prefer crawling. Walking doesn’t interfere with circulation, so all three hearts keep working. Swimming is fast but costly—like sprinting while holding your breath!
If you want to educate yourself some more about all sorts of different cephalopods, take a look at our encyclopedia. Or, what we call it, our Octopedia!
Connect with other octopus lovers via the OctoNation Facebook group, OctopusFanClub.com! Make sure to follow us on Facebook and Instagram to keep up to date with the conservation, education, and ongoing research of cephalopods.
More Posts To Read:
- Blue-Lined Octopus Mating Explained: Why Males Inject Venom During Sex
- Octopus Expert Reacts to Viral Octopus Riding a Shark (and More)
- Octopuses Punch Fish That Cheat During Hunts, New Study
- Do Octopus Bite?
- Does Octlantis Exist?
Corinne is a biologist with 10 years of experience in the fields of marine and wildlife biology. She has a Master’s degree in marine science from the University of Auckland and throughout her career has worked on multiple international marine conservation projects as an environmental consultant. She is an avid scuba diver, underwater photographer, and loves to share random facts about sea creatures with anyone who will listen. Based in Japan, Corinne currently works in medical research and scientific freelance writing!
