Animals
Do octopuses really have three hearts?
The short answer
Yes. An octopus has three hearts: two branchial hearts that push blood through the gills, and one systemic heart that sends it around the body. The systemic heart stops beating when the octopus swims, which is part of why they would rather walk.
The plumbing works like this. Two branchial hearts sit beside the gills and handle oxygenation. The third, larger systemic heart takes that freshly oxygenated blood and distributes it to the rest of the animal. Three pumps, one octopus.
The systemic heart stops during swimming. That makes swimming exhausting in a way crawling is not, and it goes a long way toward explaining why an animal perfectly capable of jetting through open water spends most of its time picking its way along the seafloor on its arms.
The blood itself is the other oddity. Octopuses use copper-based haemocyanin rather than iron-based haemoglobin, which moves oxygen efficiently in cold, low-oxygen water — and turns their blood blue.
Source
- How many hearts does an octopus have?NOAA National Ocean Service