[Introduction] Two classes of molluscs occur in Palaearctic freshwater habitats: Gastropoda and Bivalvia. Molluscs are present in most Palaearctic freshwater habitats. Frequently terrestrial snails fall into aquatic habitats, and care should be taken not to confuse them with aquatic taxa. Many taxa are protected by local and regional conservation and/or fishing laws, and several invasive species have been reported in Palaearctic waters. Freshwater mollusc identification is primarily based on shell morphology. However, shell shape can be modified substantially by water currents, available minerals, and predatory pressures (summarized in Rogers & Wethington, 2007). Consequently, we recommend that identifications be based on a series of specimens when possible.

[Limitations] Freshwater mollusc identification is primarily based on shell morphology. However, shell shape can be modified substantially by water currents, available minerals, and predatory pressures (summarized in Rogers & Wethington, 2007). Consequently, we recommend that identifications be based on a series of specimens when possible.

[Material preparation and preservation] Empty shells should be gently cleaned using ethyl alcohol and water. Shells can be air dried. Whole animals and soft-tissue samples should be preserved according to the recommendations described below for each class.