Objective: This study reports the presence of a copepod, affecting adults of the torrent catfish in a tributary of the San Juan River in the southern part of South America.
Materials and methods:The fish (48.1-54.1 mm standard length) were collected in Los Bretes, San Juan province, Argentina. They were anesthetized, fixed in formalin, preserved in ethanol and deposited in the Ichthyological Collection of the FACEN.Results: Three torrent catfish (Trichomycterus corduvensis) examined were infested with nine copepod parasites (Lernaea cyprinacea), which were attached to the gill, urogenital opening, and base pectoral fin.Conclusion: According to our results, this is the first record of parasitism of Lernaea on the torrent catfish (T. corduvensis) and a new locality from the Andean Mountains of Argentina.