Any of several bivalves living in rivers and lakes. As filter feeders, freshwater clams concentrate suspended particles — including bacteria, viruses, algal toxins and heavy metals — from their surroundings, so their safety as food depends heavily on the cleanliness of the harvesting waters. Regulatory control typically requires harvesting from classified waters, depuration in clean water, and thorough cooking before consumption. They are eaten in various cuisines, valued for their sweet flesh, but raw consumption carries a significant food-poisoning risk, especially from polluted waters.