How small is an earthworms heart?

An earthworm's heart is quite small, typically measuring just a few millimeters in length. Earthworms have five pairs of aortic arches, often referred to as "hearts," which are responsible for pumping blood throughout their bodies. These structures are not true hearts like those found in vertebrates but serve a similar function in maintaining circulation within the worm's segmented body. Overall, their heart system is adapted to their simple and efficient circulatory needs.