Octopus Hearts and Blue Blood Explained

Octopuses have three hearts and blue blood. Two hearts pump blood to the gills

while the third pumps it to the rest of the body. Their blood is blue because it contains

copper-based hemocyanin instead of iron-based hemoglobin like humans. This makes them

perfectly adapted to cold ocean environments where oxygen levels are low. When an octopus

swims, the heart that delivers blood to the body actually stops beating, which is why they

prefer crawling.