An octopus has three hearts—and each has a different job. Two send blood to the gills, where it picks up oxygen. The third circulates that oxygen-rich blood through the rest of the body.
## Two hearts for the gills The pair of branchial hearts sits near the gills. Each pumps blood through one gill, helping it collect oxygen from the water. From there, the blood travels onward to the rest of the body.
## One heart for the body The systemic heart pumps oxygenated blood around the octopus. When an octopus swims, this heart can slow or stop beating temporarily, which may help explain why swimming is tiring for these animals. They often choose to crawl instead.
This three-heart arrangement is part of the octopus’s remarkable adaptation to life underwater. For more on octopus biology, explore [Smithsonian Ocean’s overview of octopuses](https://ocean.si.edu/ocean-life/invertebrates/octopuses).
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