Freshwater bivalve

Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs live in the sea, but in addition, a number of different families live in fresh water (and in some cases, also in brackish water). These families belong to two different evolutionary lineages (freshwater mussels and freshwater clams), and the two groups are not closely related. Freshwater bivalves have a simple morphology that varies among taxa, and are distributed around most regions of the world. Species in the two groups vary greatly in size. Some pea clams (Pisidium species) have an adult size of only 3 mm. In contrast, one of the largest species of freshwater bivalves is the swan mussel, in the family Unionidae; it can grow to a length of 20 cm, and usually lives in lakes or slow rivers. Freshwater pearl mussels are economically important as a source of freshwater pearls and mother of pearl. While some species are short-lived, others can be quite long-lived, with some species registering longevity in the hundreds of years. Freshwater bivalves live in many types of habitat, ranging from small ditches and ponds to lakes, canals, rivers, and swamps. The ecology of freshwater bivalves varies among species with regards to differences in reproduction and predation. In spite of their variety of ecosystems, freshwater bivalves are some of the most endangered species on the planet. In North America, many freshwater mussel species have gone extinct, and of those remaining, 65 percent are rated as endangered, threatened or vulnerable. Droughts, forest clearing, farming, some uses of dams for water management, and changes in water temperature can all pose threats. Restoration efforts focus on rebuilding lost mussel populations in the wild and using those mussels to improve and protect water quality and restore broader ecosystems.