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What are the functions of a leech's two suckers?

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annelid *The structure of polychaetes.* (Left) Free-moving polychaetes. (A) *Neanthes,* (B) *Nereis.* (Right) Tube-dwelling (sedentary) polychaetes. (C) *Amphitrite,* (D) *Sabella.*

Leeches use their two suckers—one located at the anterior end and one at the posterior end—primarily to facilitate a method of movement known as bottom creeping.123

This process, often described as a contract-anchor-extend method, functions as follows:

Anchoring: The leech uses its posterior sucker to anchor itself to a surface.2
Extension: Once anchored, the leech stretches its body forward.2
Attachment: The anterior sucker, which contains the mouth, attaches to the surface.12
Contraction: The leech then releases the posterior sucker and contracts its body toward the anterior end to complete the movement.2

In addition to this locomotor function, the anterior sucker serves as the site of the mouth, which the leech uses to feed on its host.1