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Why do earthworms need body segments for efficient burrowing and locomotion?

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Least tern, Sternula antillarum, flying with wings raised and its yellow-tipped black bill pointed forward. — Locomotion These birds largely reside in coastal areas of North America, although some populations live in the continent's interior along large rivers.

Earthworms rely on body segmentation to facilitate efficient locomotion and burrowing through the use of a hydrostatic skeleton. Within the body, the coelom—a fluid-filled cavity—is divided into successive, isolated segments by partitions.12

This compartmentalization is essential for movement because it creates independent, fluid-filled spaces of fixed volume against which the body wall muscles can work. By alternating the contraction of circular muscles (which elongate the segment) and longitudinal muscles (which shorten and widen it), the earthworm can generate controlled, localized deformations of its body shape.3214

During burrowing and crawling, these segments act as anchor points; when a segment shortens and widens, it pushes against the burrow wall or soil, while the elongated segments move forward. Because the coelomic fluid is incompressible, the volume within each segment remains constant, allowing the muscles to function antagonistically to produce the peristaltic waves of contraction that propel the worm forward. This segmental organization allows the earthworm to exert force precisely where needed to penetrate soil or move across surfaces.123