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Mussel

Mussels are bivalve mollusks found in both marine and freshwater habitats.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

Mussels are bivalve mollusks found in both marine and freshwater habitats. The name is used for several related groups, especially marine mussels in the family Mytilidae and freshwater mussels in the family Unionidae. Many species attach to surfaces with byssal threads and feed by filtering particles from the water.

Classification

Mussels are bivalve mollusks, meaning they have two hinged shell valves. The term applies to multiple lineages rather than one tightly defined group, including marine Mytilidae and freshwater Unionidae. Mussels are not closely related to other mollusks such as slugs or cone snails.

Habitat and distribution

Mussels live in marine, brackish, and freshwater environments. Marine species are often found in intertidal and shallow coastal zones, while freshwater mussels occur in rivers, lakes, and streams.

Anatomy and feeding

Most mussels have elongated, laterally compressed shells and soft bodies adapted for life in water. They feed by filtering suspended particles, including plankton, from the surrounding water.

Ecology and human use

Mussel beds create habitat for other organisms and can help filter water. Many species are harvested or farmed as food, and some freshwater species are valued for pearls and mother-of-pearl. Mussels are important in Canadian marine and freshwater ecosystems, including Atlantic and Pacific coasts and inland waters. Freshwater mussels in Canada are also of conservation interest because many species are sensitive to habitat change and water quality.

Key facts

  • The term mussel is a common name, not a single precise taxonomic group.
  • Marine mussels belong mainly to the family Mytilidae.
  • Freshwater mussels are a separate group, commonly placed in Unionidae and related families.
  • Many marine mussels attach to rocks or other hard surfaces using byssal threads.
  • Mussels are filter feeders that strain plankton and other particles from water.
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Canadian context

Mussels are important in Canadian marine and freshwater ecosystems, including Atlantic and Pacific coasts and inland waters. Freshwater mussels in Canada are also of conservation interest because many species are sensitive to habitat change and water quality.

Frequently asked questions

Are mussels a single species or group?
They are a common name for several groups of bivalve mollusks, not one single species.
What is the difference between marine and freshwater mussels?
Marine mussels and freshwater mussels belong to different lineages and often differ in habitat, anatomy, and ecology.
How do mussels attach to surfaces?
Many marine mussels anchor themselves with strong byssal threads secreted by the animal.
What do mussels eat?
Mussels are filter feeders that remove plankton and other small particles from water.
Are mussels eaten by humans?
Yes. Mussels are widely harvested and eaten, and some species are farmed commercially.

References

  1. Encyclopaedia Britannica — https://www.britannica.com/animal/mussel
    Supports: Mussels are bivalve mollusks in marine and freshwater families; general classification.
  2. The Canadian Encyclopedia — https://thecanadianencyclopedia.ca/en/article/mussel
    Supports: Canadian context; marine and freshwater mussels and their use as food.
  3. Encyclopedia.com — https://www.encyclopedia.com/plants-and-animals/animals/zoology-invertebrates/mussel
    Supports: Marine and freshwater mussel descriptions, byssal threads, pearls.
  4. The Wildlife Trusts — https://www.wildlifetrusts.org/wildlife-explorer/marine/bivalves/mussel
    Supports: Habitat, filter feeding, byssus threads, marine mussel ecology.