Freshwater Mussel

Margaritifera margaritifera

The freshwater pearl mussel (Margaritifera margaritifera) is a large bivalve reaching up to 15 cm in length, found in clean, fast-flowing rivers and streams across the Northern Hemisphere. Its shell is dark brown to black, elongated and kidney-shaped, often eroded and pitted in older specimens. It is one of the longest-lived animals known, with individuals documented at over 250 years old. These mussels are filter feeders, drawing water through their siphons and extracting algae, bacteria, and organic particles, with each adult filtering up to 50 liters of water per day. This filtration plays a vital role in maintaining water quality. Their reproductive cycle is remarkable: females brood larvae (glochidia) in their gills before releasing them into the water, where they must attach to the gills of juvenile salmon or trout to complete their development. After several months, the young mussels drop off and bury themselves in clean gravel substrate. Once common, the species is now critically endangered across most of its range due to pollution, habitat degradation, and declining host fish populations.