Four species of Scombridae from the coast of Rio de Janeiro, southwest Atlantic Ocean were found to
be parasitized with species of Didymozoidae (Digenea): Thunnus atlanticus (Lesson) a new host record for
Nephrodidymotrema ahi Yamaguti, 1970, Didymocystis neothunni (Yamaguti, 1970), and Didymozoon longicolle
(Yamaguti, 1970); Thunnus obesus (Lowe) parasitized by Didymozoon longicolle and reported as a new host for
Nephrodidymotrema ahi; Thunnus albacares (Bonaterre) parasitized by Nephrodidymotrema ahi, and Katsuwonus
pelamis (Linnaeus) by Didymozoon longicolle. Measurements, figures, and parameters of infection are presented
