An Octopus Has Three Hearts

An octopus does not rely on a single heart. The Natural History Museum in London explains that an octopus’s three hearts have slightly different roles. One heart circulates blood around the body, while the other two pump it past the gills, where it picks up oxygen. The blood itself is unusual as well. The museum notes that octopus blood is blue, because the protein that carries oxygen, haemocyanin, contains copper. Human blood uses haemoglobin, which contains iron. According to the museum, the copper-based protein is more efficient at transporting oxygen in cold and low-oxygen conditions, which makes it well suited to life in the ocean. Three hearts and blue blood are both part of how the animal moves oxygen around its body.