Mussel

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Mussel

Mussels are edible shellfish from several families of bivalve molluscs. Most live in saltwater on rocks or other hard surfaces, attached by strong byssal threads (the “beard”). Freshwater mussels exist too, living in lakes, rivers, and streams.

Mussel anatomy
Each mussel has two hinged shells. The shells are made of three layers: a protective outer periostracum, a chalky middle prismatic layer, and an inner iridescent nacre (mother-of-pearl). The shell is held closed by internal muscles, and a large muscular foot helps the animal move or anchor itself. Byssal threads attach the mussel to its substrate, keeping it in place in strong currents.

Life and feeding
Mussels are filter feeders. They take in water through an incurrent siphon, use cilia on their gills to capture plankton, and pass food to the mouth with labial palps. Waste exits through the excurrent siphon. Marine mussels often cluster together on rocks to resist waves and reduce water loss at low tide.

Reproduction
Marine mussels (outside the body) release sperm into the water; fertilization occurs externally, producing free-swimming larvae that drift for weeks to months before settling as young mussels. Freshwater mussels reproduce sexually too, but their larvae (glochidia) temporarily parasitize fish hosts before maturing.

Predators
Humans, starfish, seabirds, and predatory snails eat marine mussels. Freshwater mussels are eaten by muskrats, otters, raccoons, ducks, and other animals.

Distribution and habitat
Marine mussels are common in temperate intertidal zones worldwide and also in tropical areas, though not as abundantly. They occupy exposed shores, salt marshes, quiet bays, and even some deep-sea habitats near vents. Freshwater mussels inhabit permanent lakes, rivers, and canals globally, preferring clean, cool water and minerals for shell-building.

Aquaculture
Mussels are farmed globally. China historically accounted for a large share of production, with Europe (especially Spain) a long-time leader in cultivation, and North America developing mussel farming in recent decades. Grow-out often uses hatchery-produced seed. Methods include bouchot (pole) culture, on-bottom culture, raft culture, and longline culture. Most mussels are harvested after about 12–15 months, then cleaned before sale.

Mussel-inspired materials and environmental uses
The byssal threads that mussels use to attach to surfaces have inspired glue-like substances and coatings for medical and industrial use. Mussel-derived proteins have spurred research into strong bioadhesives and self-assembling materials. Mussels are also used as bioindicators to monitor water quality and nutrient cycling in aquatic systems.

Conservation
Freshwater mussels are among the most threatened groups of animals in many regions, with many species endangered or of concern. Threats include damming, sediment buildup, habitat alteration, and invasive species such as zebra mussels. Conservation efforts focus on protecting habitats and monitoring populations.

Mussels as food
Common edible mussels include blue mussels (Mytilus edulis), Mytilus galloprovincialis, Mytilus trossulus, and the New Zealand green-lipped mussel (Perna canaliculus). Freshwater mussels are edible in some cultures but are less commonly consumed today. Mussels are prepared in many ways—steamed, boiled, baked, fried, or added to soups, stews, and sauces. They should be checked to ensure they are alive before cooking; live mussels close their shells when disturbed. Be mindful of possible toxins from harmful algal blooms in some coastal areas.

Nutrition
A 3-ounce serving of raw blue mussels provides about 70 calories, roughly 10 grams of protein, and small amounts of fat and carbohydrates. They are an excellent source of selenium and vitamin B12, and a good source of zinc and folate.