Mussels are filter feeders, taking in water via one opening in the shell (the inhalant aperture) and expelling waste via another opening (the exhalant aperture). These apertures, along with the foot, aid in breathing, feeding and reproduction. They are the only parts of the body that emerge from the shell but can be withdrawn very quickly to prevent predation (6). Mussels respire via gills that absorb oxygen from the water; they are fairly inefficient at absorbing oxygen but make up for this set back by having large gills and a high volume of water passing over the gills (6). This particular mussel is an omnivore, feeding on planktonic organisms such as algae and microscopic freshwater animals (6).
During reproduction, male Cumberland bean pearly mussels release sperm into the water column, where the flow of the river transports the sperm to the female. The female collects the sperm by extruding a tentacle-like organ called the siphon. The sperm then enters the marsupium, which is a specially adapted water tube near the gills that stores eggs to be fertilized and houses the developing larvae. This is an important adaptation as if larvae were released straight away they would be washed downstream and end up at an unsuitable habitat (6). Measuring just 0.2 millimetres (7), the larvae of mussels, also known as glochidia, are parasites of fish; the Cumberland bean pearly mussel distributes its larvae on to the river bed in spidery mucous strands where they attach on to the gills or fins of a host fish (2). Here the larvae complete development into juvenile mussels, before dropping off the fish to the streambed (2).