freshwater mussel

mollusk

Also known as: Unionacea, naiad

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Last updated

June 17, 2026

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Freshwater mussels, also known as naiads, are bivalve mollusks belonging to the family Unionidae. They are found in streams, lakes, and ponds worldwide, with about 1,000 known species. Many freshwater mussels are sensitive to water quality changes due to their nature as filter feeders.

These mussels are crucial to aquatic ecosystems, but many species face significant threats. Habitat degradation from damming and channeling rivers, along with increased nutrient and pesticide runoff from agriculture and urban areas, have severely impacted their populations. Furthermore, introduced species like the zebra mussel can outcompete native mussels, driving them towards extinction. In North America, a large percentage of freshwater mussel species are endangered.12

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mussel
The largest family of freshwater mussels is the Unionidae, with about 750 species, the greatest number of which occur in the United States. Many unionid species also live in Southeast Asian waters. Several North American unionids are threatened by habitat degradation, damming, and the invasion of zebra mussels.
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The largest family of freshwater mussels is the Unionidae, with about 750 species, the greatest number of which occur in the United States. Many unionid species also live in Southeast Asian waters. Several North American unionids are threatened by habitat degradation, damming, and the invasion of zebra mussels.
Read More