Dictionary of Ichthyology  

parasitism = the manner of life in which an organism lives for some period of time, to its own benefit, in or on another organism (the host) to the host's detriment, e.g. Ichthyomyzon on Esox masquiniongy; Vandellia in the gill cavity of Platystoma.

Ichthyomyzon unicuspis and scars on Esox masquinongy, Ontario, Ottawa River offshore from L'Orignal Bay, October 1997, courtesy of Claude B. Renaud.

Canadian Museum of Nature