Which animal has three hearts?
Quick answer
The octopus has three hearts: two branchial hearts pump blood through the gills, and one systemic heart pumps it to the rest of the body. Squid and cuttlefish, its close relatives, also have three hearts. Octopuses also have blue blood.
What each heart does
| Heart | Job |
|---|---|
| Branchial heart 1 | Pumps blood through one gill to collect oxygen |
| Branchial heart 2 | Pumps blood through the other gill |
| Systemic heart | Pumps oxygen-rich blood to the organs and arms |
Interestingly, the systemic heart stops beating while an octopus swims, which may be one reason octopuses prefer crawling: swimming tires them out quickly.
Why three hearts?
Octopus blood is not very efficient at carrying oxygen. The extra hearts push blood through the gills with enough pressure to get oxygen around a very active body.
Why their blood is blue
Our blood uses hemoglobin, which contains iron and looks red. Octopus blood uses hemocyanin, which contains copper and turns blue when it carries oxygen. Hemocyanin works well in cold, low-oxygen water.
More amazing octopus facts
- Brains in their arms: About two-thirds of an octopus’s neurons are in its eight arms, which can taste and touch independently.
- Masters of disguise: They can change color and skin texture in a fraction of a second.
- Escape artists: With no bones, an octopus can squeeze through any gap bigger than its beak.
- Ink: They squirt dark ink to confuse predators.
- Short lives: Most species live only 1–2 years.
Other animals with unusual hearts
| Animal | Hearts |
|---|---|
| Earthworm | Five pairs of “aortic arches” that work like hearts |
| Hagfish | Four hearts (one main, three accessory) |
| Cockroach | A long tube-like heart with 13 chambers |
The human heart has four chambers in a single heart; see how many chambers the human heart has. For ocean life more broadly, read why the ocean is important.
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