FactSentinel

Octopuses possess a remarkable circulatory system that includes three distinct hearts and copper-based blood that appears blue. Two of these hearts, called branchial hearts, are dedicated to pumping blood through the gills where it picks up oxygen. The third heart, known as the systemic heart, then circulates this oxygenated blood throughout the rest of the body. This unusual arrangement is an adaptation to the octopus's active lifestyle and high metabolic demands. Interestingly, the systemic heart stops beating when the octopus swims, which is why these creatures prefer to crawl rather than swim for extended periods, as swimming exhausts them quickly.

The blue coloration of octopus blood results from hemocyanin, a copper-containing protein that transports oxygen throughout their bodies. This differs fundamentally from human blood, which uses iron-based hemoglobin and appears red. Hemocyanin is more efficient than hemoglobin at transporting oxygen in cold, low-oxygen environments, making it particularly well-suited for ocean-dwelling creatures. When oxygenated, hemocyanin gives the blood a distinctive blue tint, though it appears nearly colorless when deoxygenated.

These anatomical features are well-documented in marine biology and have been confirmed through extensive scientific research on cephalopods. All octopus species share these characteristics, along with their close relatives like squid and cuttlefish. This unique cardiovascular system represents one of many fascinating adaptations that have allowed octopuses to thrive in diverse marine environments worldwide.