Orientador: Vanessa Doro Abdallah Kozlowiski / Resumo: Global biodiversity has been very discussed and some authors have argued of the species of parasites as a fundamental part of this. Thus the aim of the study was to obtain a better understanding of the monogeneans biodiversity of four fish species: Cyphocharax modestus (Fernández-Yépez, 1948), Moenkhausia intermedia (Eigenmann, 1908), Serrasalmus maculatus (Kner, 1858) and Roeboides descalvadensis (Fowler, 1932) from Batalha River, São Paulo State, Brazil. During the period from November 2014 to December 2014, four collections were carried out and with 120 fish caught (30 of each species). Nine species of dactylogirids were found: Curvianchorathus singularis, Dactylogyridae gen. sp., Calpidothecium sp., Palombitrema triangulum, Jainus hexops, Jainus amazonesis, Rhinoxenus piranhus, Anacanthorus sciponophallus and Notozothecium minor. In relation to the species C. modestus, 33% of the specimens were parasitized by monogenetics, being the species: C. sigularis (Prevalence - P = 23.33%, mean intensity - I = 4.14±0.5 and mean abundance - A = 0.97±0.4), P. triangulum (P = 17%, I = 4±0.4, A = 0.67±0.3), Dactylogyridae gen. sp. (P = 3%, I = 1, A = 0.03±0.5) and Calpidothecium sp. (P = 3%, I = 2, A = 0.07±0.4). S. maculatus presented a total prevalence of parasitism by monogenetic species of 87%. The species were: A. sciponophallus (P = 73.33%, I = 22±4.47, A = 16.13±4.0), R. piranhus (P = 70%, I = 5.81±0.94, A = 4.07±0.9) and N. minor (P = 30%, I = 7±1.58, A = 2.1±1.02). M. intermed... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre