Book 6, Question 34
Why Does an Octopus Have Three Hearts?
An octopus has three hearts because two pump blood past the gills for oxygen and the third sends it to the rest of the body.
An octopus is a mollusk, not a fish, and it has three hearts. Two hearts serve the gills, and a third heart serves the rest of the body. That is one reason it is one of the most amazing animals in the sea!
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Quick answers
What color is octopus blood?
An octopus has blue blood.
Sources: NOAA Ocean Service, Science News Explores, Smithsonian Magazine, Smithsonian Magazine
From the book
Page from A Million Whys Book 6
More fun facts
- Two of an octopus's hearts pump blood past the gills to pick up oxygen.
- The third heart sends that oxygen-rich blood to the rest of the body.
- An octopus has blue blood.
- Two-thirds of an octopus's nerve cells are in its arms, not its head.
- Sea stars have no heart at all. They move seawater through their bodies instead.
- A fossil once called the earliest known octopus turned out not to be an octopus after all.
Sources: NOAA Ocean Service, Science News Explores, Smithsonian Magazine, Smithsonian Magazine
Questions kids ask
What color is octopus blood?
Blue.