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Freshwater Molluscs
Freshwater molluscs are members of the Phylum Mollusca, this includes animals like clams, mussels, and snails. These molluscs live in freshwater habitats. These habitats include systems like lotic (flowing water) such as rivers, streams, canals, springs, and cave streams (stygobite species) and lentic (still water) such as lakes, ponds (including temporary or vernal ponds), and ditches.

The two major classes of molluscs have representatives in freshwater: the gastropods (snails) and the bivalves (freshwater mussels and clams.) Other classes within the Phylum Mollusca include cephalopods, scaphopods, polyplacophorans, etc. The members of these classes are all marine and never made the transition to a freshwater habitat.

A few species of freshwater molluscs are among the most notorious invasive species. In contrast, numerous others have become threatened or have become extinct in the face of anthropogenic change.

Bivalves
Any freshwater body water is suitable for bivalves to live in. Rivers, lakes, and streams are the most common places to find them. They are unable to freely swim so they stay in the sediment and can attach themselves or move slightly using their foot. They bury themselves in the sediment in the bed or in undercuts along the sides of the body of water. In North America they are most diverse in the Mississippi and Ohio River drainages.

Gastropods
Gastropods can live completely in water, completely on land, or a combination of the two. Some snails are equipped with the ability to breathe underwater via an operculum and some do not. They are able to move around on the bottom and along the sides of the body of water. They live in the sediment or in vegetation, this is wear they graze for food or hide from predators. They typically stay in the same area throughout their entire life.

https://molluskconservation.org/Snails_NaturalHistory.html

Bivalves
Bivalves have unique and complex life cycle. The male releases a sperm ball which will then be taken up by numerous females. The fertilized eggs will then start to develop in the female's gill slits. Once the egg develops into a larva it is called a Glochidium. The female will then expel the glochidia to attach to the gills of a host fish. The glochidia will then develop into juveniles and fall off the host fish to settle into the sediment and grow into adults.

Gastropods
Gastropods have a simple life cycle when compared to the bivalves, although unlike the bivalve most freshwater gastropods are hermaphroditic. This means that most individuals have both male and female reproductive organs. Gastropods reproduce sexually, the male will insert a sperm ball into the oviduct of the female. The female will then lay fertilized, gelatinous eggs by the water's edge. The eggs then hatch and that snails come out very similar to the adult form. They are born with their shell and it grows as they grow.

Conservation Status
There are 298 species of freshwater mussels and 700 species of freshwater snails in North America. Many species within the classes Bivalvia and Gastropoda are endangered or at risk. Around 70% of North America's freshwater bivalve species are endangered or extinct. Out of the 298 species of freshwater mussels 29 are extinct and 83 are endangered. Of the 700 species of freshwater snails 67 are extinct and 278 are endangered. Freshwater mollsucs are being threatened by numerous anthropogenic factors. Some of these factors include habitat loss, habitat degradation, commercial use, sedimentation, and hydrologic changes.