Octopuses are some of the ocean’s most fascinating creatures—and not just because of their eight arms and uncanny intelligence. One of the most unique things about them is that they have not one, not two, but three hearts. This remarkable circulatory setup plays a vital role in how octopuses live and move through their underwater world.
The Role of Each Heart
Octopuses have a complex cardiovascular system consisting of three hearts that work together to keep blood pumping. Two of these hearts are called branchial hearts, and they’re located near the gills. Their job is to pump deoxygenated blood through the gills, where it picks up oxygen. Once the blood is oxygen-rich, it travels to the third heart, known as the systemic heart, which then circulates it to the rest of the body.
Interestingly, the blood of an octopus is also quite different from ours. It’s blue, not red, due to a copper-rich protein called hemocyanin, which helps them transport oxygen more effectively in cold, low-oxygen environments like the deep sea.
Why the Systemic Heart Stops During Swimming
Here’s where things get even more curious. When an octopus swims—especially using jet propulsion, which is their fastest but most energy-intensive form of movement—the systemic heart actually stops beating. This means oxygenated blood stops flowing to the body during this time, putting the octopus under temporary cardiovascular stress.
Because of this, octopuses prefer crawling to swimming. Crawling along the ocean floor uses less energy and doesn’t interfere with their circulation. Swimming is generally reserved for quick escapes or short-distance travel.
Nature’s Trade-Off
This three-heart system shows how evolution has equipped octopuses for their unique lifestyle. It’s a design that supports their solitary, bottom-dwelling behavior while also allowing short bursts of speed when needed. But it also comes with trade-offs: their powerful jetting ability is costly in terms of oxygen delivery.
So, the next time you see an octopus glide or dart across the sea, remember—it’s not just showing off. It’s making a calculated move that temporarily shuts down part of its circulatory system. With three hearts, even a simple swim becomes a marvel of biological engineering.