How do clams burrow into sand or mud?

Clams burrow into sand or mud using a specialized, muscular foot and a rhythmic process known as the contract-anchor-extend mode of locomotion.12

The burrowing cycle typically follows these steps:

• Extension: The clam extends its bladelike foot anteriorly from between its shell valves by contracting transverse muscles and pumping blood into the foot.12
• Anchoring: Once extended, the tip of the foot dilates to create an anchor within the sediment.12
• Retraction: The pedal retractor muscles contract, pulling the shell downward toward the anchored foot. This process is often aided by the clam closing its shell valves sharply, which forces water out of the mantle cavity to fluidize the surrounding sediment, making it easier to penetrate.12
• Repetition: The clam repeats this sequence, often alternating the pull between the left and right sides, which causes the shell to wobble and sink deeper into the substrate.2

This efficient mechanism allows clams to protect themselves from predators while remaining connected to the surface through their siphons for feeding and respiration.32