Adductor muscles (bivalve)

The adductor muscles are the main muscular system in bivalve mollusks (e.g. in clams, scallops, mussels, oysters, etc.).

Adductor muscles leave noticeable scars or marks on the interior of the shell's valves.

Those marks (known as adductor muscle scars) are often used by scientists who are in the process of identifying empty shells to determine their correct taxonomic placement.

Most bivalve species have two adductor muscles, which are located on the anterior and posterior sides of the body.

The resiliency of the ligament is what causes the valves of the bivalve mollusk to open when the adductor muscles relax.

Marine blue mussel , Mytilus edulis , showing some of the inner anatomy, including the white posterior adductor muscle which is visible in the upper image, and has been cut in the lower image to allow the valves to open fully.
One shrimp and large adductor muscles from seven individuals of the giant scallop which are about to be cooked