The octopus is one of nature’s strangest masterpieces.
Three hearts. Eight arms. And a nervous system that’s... basically everywhere.
🩵 Here’s the Setup:
Two branchial hearts: These pump blood to the gills to get oxygen.
One systemic heart: This pumps the oxygenated blood to the rest of the body.
And here’s the twist:
In many octopuses, the systemic heart’s output is strongly reduced or may stop during sustained swimming. Jet swimming is energetically costly, so they often crawl when they can; the response varies with species and activity.
🩸 Also Weird? Their Blood Is Blue.
Unlike humans (iron-based, red blood), octopuses use copper-based hemocyanin, which turns blue when oxygenated.
Hemocyanin carries oxygen in their blood; it can function across a range of temperatures, though it is not simply “perfect” for low-oxygen water.
So yes — three hearts and blue blood. They’re basically sea royalty.
🧠 And While We’re Here...
Their nervous system is distributed: a central brain coordinates with large nerve centers in the arms. “Nine brains” is a playful shorthand, not nine separate brains.
They can camouflage instantly.
Some species can even use tools.
So the next time you’re impressed by a multitasker, remember the octopus —
part alien, part genius, and equipped with a circulation system unlike ours. Smithsonian Ocean on cephalopod hearts and blood