In the diverse world of animal physiology, some creatures have evolved remarkably intricate circulatory systems to meet their unique biological needs. Among these adaptations are animals with multiple hearts, a feature that enhances their ability to circulate blood effectively through their bodies.
4 animals with multiple hearts
Octopus
The octopus is perhaps the most famous multi-heart animals. Octopuses pump their blood around their circulatory system using three hearts instead of one. While a ‘systemic’ heart supplies the animal’s body, two ‘branchial’ hearts supply each of the two gills where the blood is oxygenated. The squid also has three hearts, which work in the same way.
- Squid vs octopus: what's the difference between these multiple-limbed sea creatures?
- Watch this incredible rare video of an octopus changing colour on a Welsh beach
- Why do female octopuses die after reproducing?
Earthworms
OK, this one might be a stretch, as technically earthworms don't have hearts, but they do have 5 aortic arches (pseudohearts). Much like hearts, these pseudohearts help blood circulate around the body – only in their case, it's about squeezing, rather than pumping.
Hagfish
The hagfish is not only famous for being the slimiest animal on earth - producing over 1 litre of slime in under 0.1 seconds - but also for having five hearts. Yes, you read that right, five hearts!
Its complex circulatory system features a three-chambered systemic heart, along with two accessory hearts, one portal heart, and one caudal heart. The systemic heart is responsible for pumping blood through the gills and then distributing it via arteries throughout the rest of the body. The accessory hearts, which are situated on the venous side of the circulation, help return blood to the systemic heart.
And their hearts are so incredible that they can keep on beating for 36 hours without any oxygen.
Cuttlefish
Like its cephalopod cousins (the octopus and the squid), cuttlefish also have three hearts to help them cope with the conditions of deep-sea life. Two of these pump blood to its gills, while the third circulates blood around the body. The blood is blue, thanks to the copper-rich protein it contains, known as hemocyanin, which transports oxygen around the body. Mammal blood is red due to its iron-rich haemaglobin, which does the equivalent job.
Animal with the biggest heart
It's no wonder that the biggest heart belongs to the biggest animal, the blue whale - and its the length of a person. Measuring an impressive 5 feet long, 4 feet wide, and 5 feet tall, it weighs about 181kg.
The animal that can regrow a heart
We have all heard about the lizard that can regrow a tail, or the flatworms' remarkable ability to repair and regenerate. Dice a flatworm any which way and each fragment will in time become a fully functional creature. However have you heard of the animal that can regrow a heart? Yes really...
In 2002 scientists found zebrafish were able to fully regenerate their hearts within 2 months of being damaged. Now that is an envious skill...