Humans—and many other animals—have only one heart. However, there are three members of the animal kingdom that have multiple hearts, which sometimes happen to be located in strange places.
Cardiovascular health is far more intricate for humans than for most other animals, as we are one of the few living creatures that can experience heart attacks. Admittedly, some birds and primates can also have them, but these multi-hearted organisms below are entirely free of this dangerous deficiency.
While earthworms may not seem all that interesting, inner workings are pretty complex. One of the most notable complexities is the five pairs of structures that carry out the basic functions of a heart within the common earthworm. Some people say that earthworms have five hearts; others argue that they have ten; still others claim that they have no hearts at all.
The earthworm’s heart-like internal organs are called aortic arches, and they perform a task quite similar to what the human heart does—they pump internal oxygen through the worm’s body. These structures are located close to the worm’s mouth, which is perhaps even more startling than its five hearts.
Hagfish are a strange, eel-like marine fish that regularly produce enough slime to fill a gallon-sized jug. This fibrous slime works as a cocoon to protect the hagfish from danger. The hagfish’s entire body is strange, with rudimentary vertebrae and a partial skull counted among the list of oddities.
But the strangest thing about the hagfish is its four hearts. Only one of these serves as the main pump known as the brachial heart, while the other three function as accessory pumps. They are located at various points throughout the hagfish’s body.
Both the octopus and squid have three hearts. Two of these are branchial hearts, which are tasked with pushing blood that requires oxygen through the gills. The other heart, known as the systemic heart, then pumps oxygen-filled blood back through the body.
The squid’s two branchial hearts can be found in the base of its gills, while its systemic heart is sandwiched between the other two.
While not all creatures have hearts (because some don’t have blood or don’t need oxygen pushed through their system), those that do usually don’t need more than one. The three organisms above are unique in many ways, but they definitely set the record for the most hearts!