Animals With Multiple Hearts
OCTOPUS If you’ve ever wondered which animal has 3 hearts, it’s the octopus. Octopuses or octopi (both are technically correct) are one of the most well-known animals with multiple hearts. There are hundreds of species of octopus, but all have three hearts: one heart to pump their blood throughout their circulatory system, and two to pump blood through their gills.
SQUID Much like their cousins the octopi, squids come in hundreds of species with widely varying sizes, but all have three hearts. These hearts serve the same functions as the hearts of the octopus: one pumps blood throughout the body, and two pump blood over the gills.
EARTHWORMS Earthworms are one of the most common animals with multiple hearts. These decomposers can be found pretty much everywhere, as long as there’s dirt for them to live in. Earthworms have five hearts, although they’re very primitive organs.
HAGFISH While they’re most famous for their ability to produce enormous amounts of slime, hagfish also have four hearts. One heart functions as the main circulatory organ, while the other three supplement it’s pumping power. Hagfish live in oxygen-poor water, so their hearts can pump for up to 36 hours with no oxygen.
CUTTLEFISH The cuttlefish is a close relative of two other animals with multiple hearts: the octopus and the squid. Not quite the same as its cousin, the cuttlefish has just three hearts: one heart pumping blood throughout the body and two hearts pumping blood over the gills.
COCKROACHES Cockroaches, everybody’s least-favorite bug. Their ability to survive in harsh conditions and with severe injuries is well-known, and one of the reasons they’re so hard to kill is that they have 13 hearts. Experts now say that it’s just one heart, with 13 chambers, but in many ways this is just semantics. The chambers are lined up in sequence, each one pumping blood to the next one in line.
HORSES Yes, the horse! Possibly the most surprising animal on this list, few people would of a horse as an animal with multiple hearts. At the bottom of each foot is a specialized organ commonly called a frog. While not a true heart, the frog acts as a blood reservoir. Each time the foot is placed on the ground, the blood in the frog is pump out of the frog and into the horses’ arteries. So, while some may not consider them hearts, frogs do pump blood around the horse’s circulatory system, which means they perform the function of a heart.
HUMANS While humans are not born with two hearts like the other animals on this list, believe it or not, some humans can have two hearts. Sometimes, when a heart transplant is needed, the original heart is not removed completely because it’s still partially functional. The new heart is grafted onto the old one, thus giving the patient two hearts. So this one may not really count, but there are people out there walking around with 2 hearts.