Eggs of the digenean trematode Stephanostomum tenue, are ingested by the introduced Eastern Mud Snail Ilyanassa obsoleta, and hatch into redia larvae, which develop into cercaria, a swimming infective form. Cercaria emerge into the water and are ingested by a small fish, such as Menidia sp (silversides, smelts), the second intermediate host. These small fishes are eaten by a wide range of larger fishes, including true basses (Moronidae, e.g. Striped Bass (Morone saxatilis), sculpins (Cottidae), Midshipmen (Batrachoididae), puffers (Tetradonidae). The Eastern Mudsnail, and presumably, its parasites, were introduced to the West Coast in the 19th century with transplants of Eastern Oysters (Crassostrea virginica). This parasite infects marine fishes, including striped bass and steelhead trout, but adverse impacts are not known.