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And yes. They have a complex circulatory system and can have from two to 15 pairs of hearts. Why so many?
It’s just that they need to distribute the blood throughout the body and some species can reach 3 meters in length (!), like the giant Megascolides australis, found in Australia.
The circulatory system of earthworms has two main blood vessels that run the length of the animal’s body. One of these vessels is the ventral artery, through which the blood passes, carrying oxygen to the organs. The other is the dorsal vessel, which brings blood back. Both are linked to all pairs of hearts, which are shaped like an arch. “They are dilated and contractile sacs, which propel the blood flow through the body”, says zootechnician Afrânio Augusto Guimarães, owner of a company specialized in the creation of earthworms. But if, on the one hand, they have a lot of hearts, on the other, they don’t have lungs! The organ is not needed, as earthworms breathe through their skin. Another anatomical curiosity – the best known – is the fact that they are hermaphrodites; that is, they have reproductive organs of both sexes. However, the earthworm alone does not self-fertilize and needs a partner to reproduce.