Unionida

Unionida is an order of freshwater bivalve mollusks, including river mussels and their relatives. Many species have complex life cycles in which larvae develop as parasites on fish.

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Bivalvia: Bivalvia is a class of mollusks whose bodies are enclosed by two hinged shells. Unionida is one order within this class of two-shelled mollusks.
Fish host: A fish host is a fish that supports the development or survival of a parasite. Unionid larvae often must attach to suitable fish before they can develop into juveniles.
Freshwater mussel conservation: Freshwater mussel conservation protects mussel species, their habitats, and the ecological processes they depend on. Many unionid species are threatened, making their protection a major conservation effort.
Margaritiferidae: Margaritiferidae is a family of freshwater mussels that includes the freshwater pearl mussels. This unionid family contains long-lived species associated with clean, well-oxygenated rivers.
Freshwater mussel decline: Freshwater mussel decline is the reduction or loss of mussel populations and species in rivers and lakes. Unionida includes many species affected by habitat loss, pollution, dams, and invasive species.
Mollusca: Mollusca is a large animal phylum that includes snails, clams, octopuses, and their relatives. This phylum provides the broader evolutionary context for Unionida.
Mussel infestation of fish: Mussel infestation of fish is the temporary attachment of parasitic mussel larvae to a fish’s gills or fins. This is the stage at which many unionids use fish to disperse and transform.
Freshwater mussel propagation: Freshwater mussel propagation is the captive breeding and rearing of mussels for research or population recovery. Propagation programs raise unionid juveniles when wild recruitment is inadequate.
Unionidae: Unionidae is a large family of freshwater mussels found across much of the world. It is the principal and most species-rich family within Unionida.
Cryptic species complex: A cryptic species complex is a group of distinct species that appear very similar and are difficult to distinguish. Hidden diversity can complicate unionid identification and estimates of conservation risk.