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!
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:
- Reproductive organs
- And, their hearts!
🐙 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.
🐙 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 crazy…
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!
🐙 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 👀
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:
- A Dreaming Octopus? Let’s Look At Cephalopod Sleep Cycles!
- Does An Octopus Have Arms Or Tentacles?
- The Fantastic Phore: Cephalopods Color-Changing Abilities!
- Here’s Everything You Need To Know About Octopus Arms
- 7 Jaw-Dropping Caribbean Reef Octopus Facts
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!