The present study describes lesions caused by Kudoa sp. in the esophageal tissue of mapará catfishes(Hypophthalmus marginatus) collected from Cametá, Tocantins River in the northern Brazil. Fifty refriger-ated H. marginatus specimens were dissected and tissue samples were for embedded in paraffin andstained with hematoxylin-eosi, Masson’s trichrome and Giemsa. Pseudocysts of whitish color w…