Freshwater pearl mussel

The freshwater pearl mussel is one of the longest-living invertebrates in existence. The oldest known specimen in Europe was caught in 1993 in Estonia when it was 134 years old. Like all bivalve molluscs, the freshwater pearl mussel has a shell consisting of two parts that are hinged together, which can be closed to protect the animal's soft body within. The shell is large, heavy and elongated, typically yellowish-brown in colour when young and becoming darker with age. Older parts of the shell often appear corroded, an identifying feature of this mussel species. The inner surface of the shell is pearl white, sometimes tinged with attractive iridescent colours. Like all molluscs, the freshwater pearl mussel has a muscular 'foot'; this very large, white foot enables the mussel to move slowly and bury itself within the bottom substrate of its freshwater habitat.