Rhabdochona (Rhabdochona) acuminata (Molin, 1860) (Rhabdochonidae) parasitizes the intestine of several species of fish and it has a broad geographical distribution. The present study is the first to report adult specimens of this helminth in Acestrorhynchus britskii Menezes, 1969 and Acestrorhynchus lacustris Lütken, 1875 (Acestrorhynchidae), collected in the Três Marias reservoir, upper São Francisco River, State of Minas Gerais, Brazil. At the same locality, Rhabdochona sp. larvae were found in sympatric populations of forage fishes, Tetragonopterus chalceus Spix & Agassiz, 1829 and Triportheus guentheri (Garman, 1890) which are potential prey to the piscivorous Acestrorhynchids and they are mentioned as possible intermediate or paratenic hosts of this parasite species. The parasite indices of R. acuminata were not influenced by either sex or total length of these piscivorous h...

Prosthenhystera obesa (Diesing, 1850) (Digenea, Callodistomidae), parasitizes the gall bladder of freshwater fish and was first found in Leporinus reinhardti Lütken, 1875 (Characiformes, Anostomidae) and Pimelodus pohli Ribeiro & Lucena, 2006 (Siluriformes, Pimelodidae). These omnivorous fish were collected in the upper São Francisco River, Minas Gerais, Brazil. prevalence (%) and mean abundance of P. obesa were 1.58% and 0.02 ± 0.127 in L. reinhardti, and 3.85% and 0.04 ± 0.196 in P. pohli, respectively. Prosthenhystera obesa has already been reported in a carnivorous characin Salminus franciscanus Lima & Britski, 2007 and in an omnivorous pimelodid Pimelodus maculatus Lacepède, 1803 both in the São Francisco River, but their ecological parameters are here presented for the first time together with the data for L. reinhardti and P. pohli, two new hosts in the Neotropical R...