pilnu

Pilnu, also known as *Piliostoma*, is a genus of freshwater mollusks belonging to the family Margaritiferidae. These are large, thick-shelled mussels found in rivers and streams. Their shells are typically ovate and dark in color, often brown or black, with a rough outer surface. The interior of the shell, known as the nacre or mother-of-pearl, is usually white or bluish.

The genus Pilnu is characterized by its robust shell structure and the presence of two strong, heavy pseudocardinal teeth and two lateral teeth in each valve. These teeth help to firmly anchor the two halves of the shell together, providing protection against predators and strong currents. The soft body of the mussel is a filter feeder, drawing water through its mantle cavity and extracting small food particles such as algae and organic detritus.

Historically, species within the Pilnu genus have been found in various parts of North America and Asia. However, many populations have experienced significant declines due to habitat degradation, pollution, and the introduction of invasive species. Conservation efforts are underway in some regions to protect the remaining populations of these ecologically important bivalves. Their presence or absence in a waterway can be an indicator of water quality.