Stars SparkStars Spark
A new discovery every day

Did you know?

One useful fact with a clear picture, plus a small idea to explore and think about.

A friendly octopus in a coral reef showing its hearts🐙 Ocean secrets

From the fact archive Saturday, 12 September 2026

An octopus has three hearts!

Two hearts pump blood to the gills, while the third sends blood around the rest of the body.

Octopus blood is blue because its oxygen-carrying protein contains copper instead of the iron found in ours.

Trusted source: Smithsonian Ocean