The Louisiana pearlshell, Margaritifera hembeli, is a rare species of bivalve mollusk in the Margaritiferidae family. This freshwater mussel is native to Louisiana in the United States, and was previously present also in Arkansas. It grows to a length of about 10 cm (4 in) and lives on the sand or gravel stream-bed in riffles and fast flowing stretches of small streams. Its life cycle involves a stage where it lives parasitically inside a fish. This mollusk is sensitive to increased sedimentation and cannot tolerate impoundments. Because of its limited range and its population decline, the International Union for Conservation of Nature has rated this mollusk as being "critically endangered".