Growth Lines main content.

Growth Lines

Note: In temperate latitudes such as the metro region growth lines are laid down annually. Complete growth lines may thus be counted to approximate mussel age.

A implicata Full
Anodonta implicataalewife floater
Dorsal view of two open mussel shells.
Ligumia nasutaeastern pondmussel
Growth lines vary among species, appearing as concentric circles of ridges or contrasting bands of color that mark the stages of growth.
L cariosa Full
Lampsilis cariosayellow lampmussel
Concentric growth lines in an alewife floater (Anodonta Implicata)
Pyganodon cataractaeastern floater
The color and texture of the periostracum may conceal or highlight the pattern and color of the growth lines.