Species of Prochilodus Agassiz 1829 are among the most abundant fishes of South America basins and has good potential for pisciculture. During a study of the helminth parasites of Prochilodus lineatus (Valenciennes, 1837) (Characiformes) from Mogi Guaçu River, Brazil, a new species of Tereancistrum was collected. Tereancistrum pirassununguensis n. sp. can be distinguished from the other Tereancistrium species mainly by having a reduced accessory anchor sclerite with a little groove at the end; MCO as a sclerotized coiled tube forming two counterclockwise rings; an accessory piece as an inverted C, rod-like, not articulated at the base of the MCO; curved ventral bar; hooks similar with erect thumb and slightly curved shaft and point, slightly expanded shank proximally. This is the first record of a species of Tereancistrum in the southeastern of Brazil.

Two new species of Pavanelliella (Dactylogyridae) were described and some details about the morphology of Pavanelliella pavanellii Kritsky & Boeger, 1998 were added based on specimens collected from pimelodid fishes from Mogi Guaçu River, Brazil. Pavanelliella takemotoi sp. n., collected from nasal cavities of Pimelodus maculatus Lacepède, 1803 differs from its congeners by having a male copulatory organ (MCO) with 2–5 rings, vaginal canal sinuous without loops in distal portion of vaginal canal and anteriorly directed vagina containing five irregular rings around the vestibule. Pavanelliella laertei sp. n. collected from P. heraldoi Azpelicueta, 2001 is separated from the other species of the genus by lacking a vaginal vestibule and by distal end shape of accessory piece, which resemble flames or is bifurcated with one flank hooked in P. laertei sp. n. The specimens of P. pavane...