The Octopus: Three Hearts, Blue Blood, Alien Intelligence?

Added: 2026-05-26

[00:00:00]Why would an animal need three hearts?

[00:00:02]Octopuses evolved one of the strangest circulatory systems in the entire animal kingdom. Two of their hearts pump blood to the gills where oxygen is absorbed from seawater. The third heart then pumps that oxygen-rich blood through the rest of the body. But here's the fascinating part. When an octopus swims, the main heart actually stops beating temporarily. Swimming becomes so exhausting that octopuses often prefer crawling across the ocean floor instead.

[00:00:31]Why is their system so unusual? The answer lies in their blood. Unlike humans, octopus blood uses copper-based hemocyanin instead of iron-based hemoglobin. This makes their blood blue and helps transport oxygen more efficiently in cold, low-oxygen, deep-sea environments. But hemocyanin is less efficient at circulation, so evolution compensated by adding extra hearts. Over millions of years, octopuses evolved an extraordinary body plan optimized for survival in harsh oceans. Three hearts, blue blood, flexible bodies, and massive intelligence, octopuses are so bizarre that some scientists once joked they look almost alien. Yet every part of them is a product of evolution solving survival problems in its own remarkable way.