Biology
Why do octopuses need three hearts?
Quick fact
Two hearts pump blood to the gills, while another pumps blood around the body.
Why this is interesting
An octopus has three hearts, blue blood, and a nervous system unlike almost any other animal on Earth.
Read the full explanation
Understanding Why do octopuses need three hearts?
Octopus blood is blue because it uses a copper-based molecule called hemocyanin instead of the iron-based haemoglobin used by humans.
A deeper explanation
Hemocyanin works especially well in cold environments where oxygen levels are low, helping octopuses survive deep ocean conditions.