Cystobranchus is a monotypic genus of annelids belonging to the family Piscicolidae.[1] The species of this genus are found in Europe and Northern America. The World Register of Marine Species accepts one species within Cystobranchus.[2] Cystobranchus is also known as a leech, and it is a freshwater leech, usually found in revisers, streams, lakes, and ponds across North America. They often attach themselves on the external part of freshwater fish and feed on their blood. In doing so, a possible process of infestation could occur causing the fish to be more suspectable to stressors and diseases. E. M., Light, J. E., & Williams, J. I. (2005). Redescription of Cystobranchus virginicus Hoffman, 1964, and Cystobranchus salmositicus (Meyer, 1946) (Hirudinida: Piscicolidae) from Freshwater Fishes in North America. Comparative Parasitology, 72(2), 157–165. https://doi.org/10.1654/4161/
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