Blue Mussel (also known as Common Mussel)
Phylum: Mollusca, Class: Bivalvia, Order: Mytilida, Family: Mytilidae, Genus: Mytilus, Species: Mytilus edulis · Mytilidae (Mussel family) · Bivalve (two-shelled), whole shell, wedge-shaped
Species
Mytilus edulis
Shell Type
Bivalve (two-shelled), whole shell, wedge-shaped
Family
Mytilidae (Mussel family)
Size
Approximately 0.75 inches (2 cm), which is small/juvenile for this species. Adults typically range from 2 to 4 inches (5 to 10 cm).
Color & Pattern
Dark blue to blackish exterior with subtle growth lines and concentric rings; pearly, iridescent nacre on the interior. The color is natural and relatively unweathered.
Rarity
Very Common
Habitat
Marine and brackish intertidal to shallow subtidal zones, attaching itself firmly to hard substrates such as rocks, pier pilings, and shell beds using strong byssal threads.
Geographic Range
Boreal and temperate waters of the Northern Hemisphere, including the North Atlantic coasts of North America and Europe, extending into parts of the North Pacific.
Description
A small, asymmetrical, wedge-shaped bivalve shell with a pointed umbo at the anterior end and a rounded, expanded posterior margin. The exterior surface is smooth except for fine concentric growth lines, showing a deep blue-black hue characteristic of healthy specimens.
Key Features
Wedge-shaped outline, terminal (front-most) umbo, lack of prominent teeth on the hinge line, and a dark bluish-black exterior paired with an iridescent interior.
Collector Value
Low commercial or monetary value due to their extreme abundance, though they are frequently collected by casual beachcombers and nature enthusiasts.
Condition Notes
Good condition; intact single valve with natural coloration preserved, slight wear along the margin, graded as Good collectibility.
Interesting Facts
Blue mussels use tough protein fibers called byssal threads (often referred to as 'beard') to anchor themselves securely to rocks, withstanding powerful ocean waves. They are also widely cultivated for human consumption.
Ecological Role
Important filter feeders that improve water quality by consuming phytoplankton and suspended particles. They form dense beds that provide crucial microhabitats and shelter for numerous other intertidal species.
Similar Species
Ribbed Mussel (Geukensia demissa), which features distinct vertical ribs along the shell surface, and the Mediterranean Mussel (Mytilus galloprovincialis), which has a slightly wider shell profile.
Beach Finding Tips
Look along rocky shores, jetties, piers, and beaches adjacent to mussel beds at low tide, where dislodged single valves and whole shells frequently wash ashore.