Excess water is eliminated from the mussel via the kidneys. Initially, the hemolymph is ultrafiltered through the pericardial gland cells located on the pericardial wall (Giamberini and Pihan 1996) into the cavity of the pericardium.
Large blood proteins, lipids, and carbohydrates cannot pass through the pericardial filter (McMahon 1991). From the pericardial cavity, the fluid passes into the kidneys via the renopericardial openings in the pericardial wall and the renopericardial canals. Organic waste accumulates by active transport across the kidney walls where it is combined with the filtrate. This excretory fluid is released through nephridopores in the epibranchial cavities and carried out of the mussel via the exhalant siphon.