Blue Mussel (also known as Common Mussel or Edible Blue Mussel)
Phylum: Mollusca, Class: Bivalvia, Order: Mytilida, Family: Mytilidae, Genus: Mytilus, Species: M. edulis · Mytilidae (Mussel family) · Bivalve, whole shell valve, elongated or wedge-shaped fan shape
Species
Mytilus edulis
Shell Type
Bivalve, whole shell valve, elongated or wedge-shaped fan shape
Family
Mytilidae (Mussel family)
Size
Approximately 2 inches, which is within the typical range for this species. Adults generally range from 1.5 to 4 inches in length.
Color & Pattern
Predominantly deep blue-violet to dark purple and black on the exterior surface, showing some concentric growth lines and slight weathering with patches of lighter grey-blue. The umbo (beak) area at the pointed end shows a clean white calcium layer where the outer periostracum has worn away.
Rarity
Very Common
Habitat
Found attached to hard substrates, rocks, pier pilings, and ropes in intertidal and shallow subtidal marine environments. They form dense beds in coastal waters and estuaries, tolerating varying salinities.
Geographic Range
Cold and temperate waters of the Northern Hemisphere, widely distributed along the coasts of the North Atlantic, including North America and Europe, as well as parts of the North Pacific.
Description
An asymmetrical, wedge-shaped bivalve shell featuring a pointed anterior umbo and a rounded posterior margin. The exterior surface displays fine concentric growth lines and exhibits a classic deep blue and purplish coloration characteristic of the species. The texture is relatively smooth except for prominent growth interruptions, and the inner nacreous layer provides a pearly sheen where exposed.
Key Features
Elongated wedge shape, terminal umbo located directly at the pointed tip of the shell, lack of heavy ribs or teeth on the hinge margin, and a distinct deep blue-black exterior color paired with a pearly interior.
Collector Value
Low monetary value due to extreme abundance worldwide, but remains a staple educational specimen and a classic representative of intertidal bivalves for beginner collections.
Condition Notes
Single valve in good condition with minor natural wear near the umbo and margins. The outer dark layer is partially abraded at the tip exposing the white inner shell layer, but the structural integrity is fully intact. Grade: Good.
Interesting Facts
Blue mussels anchor themselves to surfaces using exceptionally strong protein strands known as byssus threads, or 'beard', which can adhere to almost any substrate including rock, metal, and wood. They are also widely cultivated for aquaculture and human consumption.
Ecological Role
Blue mussels act as vital filter feeders, improving water clarity by consuming phytoplankton and organic particulates. They form complex reef-like habitats that provide shelter for numerous small invertebrates, serving as a key food source for crabs, starfish, sea birds, and fish.
Similar Species
California Mussel (Mytilus californianus), which features prominent radial ribs, and the Mediterranean Mussel (Mytilus galloprovincialis), which is often broader and darker; separation requires examining geographic origin and fine morphological ribbing details.
Beach Finding Tips
Look along rocky shores, jetties, piers, and sandy beaches near rocky outcroppings following storm events or high tides, where dislodged mussels and loose valves wash ashore in large numbers.