While it is commonly believed that the more complex an organism, the more complex the arrangement or organization of internal organs, earthworms are different. Though not as complex as humans, an earthworm has five different hearts. The hearts, however, referred to as aortic arches, are not referred to as true hearts, when compared to the structure and properties of those of other organisms.
Strictly speaking, an earthworm has about ten different “hearts”, but only five of those ten perform the function of pumping blood throughout the body of the earthworm.