The presence of one heart is ingrained into our idea of biology thanks to our own bodies as well as the majority of those we see around us.  But did you know there are a handful of animals with multiple hearts?

1. Octopus/Squid


These similar creatures are both cephalopods and have three hearts in total, one systematic to go along with two “gill hearts” that force blood to the gills.

2. Earthworms


While it is not technically a “heart,” the aortic arch of the earthworm performs a similar function and is commonly referred to as one for the sake of simplicity. An earthworm has five arches/hearts that are segmented and pump blood throughout its body. 

3. Hagfish

Wikimedia Commons

Who knew such a nasty creature could have so many hearts? The hagfish has four of them, one main three-chambered systematic heart and three accessory pumps.

BONUS: Humans

Yes, there are seriously humans with more than one heart. This is thanks to the medical development of a “piggyback” heart transplant operation that adds an extra heart as opposed to replacing the original. The latter continues to function, but at a much lower level, while the transplant heart takes over most of the heavy lifting. One person who had the procedure as a baby later had it reversed, and when the second heart was removed, her own was able to take back the reins.