How many eyes can a scallop have along the edge of its mantle?

A scallop can have up to 200 eyes along the edge of its mantle.

These small eyes are arranged in a row around the shell’s open margin. Each eye contains a cornea, lens, retina, and mirror-like tissue that reflects light toward the retina, allowing the scallop to detect changes in its surroundings.

Scallop eyes do not form images as detailed as human eyes. Instead, they are especially useful for sensing movement, shadows, and approaching predators. This helps a scallop decide when to close its shell or swim away.

Scallops are bivalve molluscs, related to clams, oysters, and mussels. Many bivalves have simple light-sensitive structures, but the large number and relatively complex arrangement of scallop eyes make them particularly notable. Scallops can also swim by rapidly clapping their shells, forcing water through the mantle cavity.