Earthworms have five pairs of heart-like organs called "aortic arches." These arches are distributed throughout the body to keep the blood flowing in such a narrow and confined space. This is why some earthworms can grow into a new worm if cut apart — although this can also depend on the species of worm.
More facts about earthworms:
- The Giant South African Earthworm is the largest species of earthworm. It can grow up to 22 feet (about 6 m) long, although a length of 6 feet (2 m) is more usual.
- Earthworms don't have any lungs; rather, they breathe through their skin. Their skin has to be kept moist for them to be able to breathe, which is why they secrete slime all over their bodies, and why earthworms die if they become too dry.
- Earthworms are hermaphroditic, and although they usually reproduce with other worms, some species are capable of self-fertilization.
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