How many hearts does an octopus have?
An octopus has three hearts. Two pump blood through the gills to pick up oxygen, and the third pumps that oxygen-rich blood to the rest of the body.
The two smaller hearts are called branchial hearts. Each one sits near a gill and pushes blood through it. The larger systemic heart then sends the oxygenated blood to the organs and arms. This system helps the octopus move enough oxygen around its body in cold, low-oxygen water.
Octopus blood is blue, not red. It uses a copper-based protein called hemocyanin to carry oxygen, while human blood uses iron-based hemoglobin. Hemocyanin works well in cold water but carries less oxygen, which is another reason the octopus needs extra pumping power.
Why octopuses prefer crawling
When an octopus swims, its main systemic heart actually stops beating. That makes swimming tiring, so octopuses usually crawl along the seafloor instead. Octopuses also have about 500 million neurons, two-thirds of them in their eight arms, which can taste and feel what they touch.
Did You Know?
Octopuses are closely related to squid and cuttlefish, which also have three hearts and blue blood. Most octopuses live only one to two years, and many species die soon after breeding.