Over time, earthworms have developed several structural, physiological and behavioral adaptations through evolution. These beneficial features have allowed them to become better suited to their environment.
Structural adaptations encompass the physical features that help earthworms to survive. An earthworm has no legs or antennae, the absence of which allows them to move through their underground burrows easily. Another bodily feature that facilitates the earthworm's movement is its setae, bristly hairs that are all over the earthworm's body. The setae provide traction, allowing earthworms to move through the soil more easily. The earthworm's muscular structure includes latitudinal muscles as well as circular muscles that surround each body segment, giving the earthworm the needed strength to push through the soil. When feeding, the earthworm pushes its pharynx out of its mouth and uses it to grip its food and then pull it back into its mouth.
Physiological adaptations are those that relate to the earthworm's metabolism and how it regulates bodily functions. Some earthworms are able to secrete a mucus that helps them to move through the soil. If soil temperatures become too dry or hot for earthworms, they are able to coil themselves into a tight ball and excrete a protective mucus to reduce water loss, simultaneously slowing their metabolic rate.
Behavioral adaptations include behaviors learned by earthworms over time in order to increase their chances of survival. When earthworms feel vibrations they move closer to the surface, in case the vibrations are caused by an underground predator, such as a mole, searching for food. Earthworms are sensitive to light and usually are found above ground at night only. Earthworms lose moisture through their skin. As a result, they are only found above the surface when the ground is wet.