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 implicata
alewife floater

L nasuta Full

Ligumia nasuta
eastern 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 cariosa
yellow lampmussel

P cataracta Full

Pyganodon cataracta
eastern floater

The color and texture of the periostracum may conceal or highlight the pattern and color of the growth lines.