Octopuses are equipped with two branchial hearts and one systemic heart and each serves an important purpose. Like humans, octopuses have a closed circulatory system, meaning that closed vessels or tubes transport blood throughout their body.

The two branchial hearts pump blood through the octopus’s gills, where the carbon dioxide is released and oxygen gets absorbed. This process is similar to when the right side of our hearts pass blood through our lungs!

After the blood passes through the octopus’s gills, it enters the systemic heart—the largest of the octopus’s three hearts. The systemic heart circulates the newly oxygenated blood throughout the rest of the octopus’s body and other organs, similar to the main function of the left side of a human’s heart.

The octopus’s systemic heart stops beating when this cephalopod swims, which quickly tires the octopus. This explains why octopuses are more often seen crawling along the ocean floor rather than swimming.

Despite having similar circulatory systems, the color of blood differs between octopuses and humans. Octopus blood contains a copper-rich protein—causing its distinct blue color!

Just in time for Valentine’s Day, show some love with our downloadable Aquarium-themed cards featuring some of our favorite aquatic friends!