Two new species of Curvianchoratus (Monogenoidea, Dactylogyridae) parasitizing Psectrogasteramazonica (Characiformes, Curimatidae) and a new record for Curvianchoratussingularis in the Tocantins River, Maranhão, Brazil

Several studies have demonstrated parasitism by monogenoids in characiform fish in the Neotropics. During studies on the helminth fauna of curimatids from the Tocantins River, specimens of Eigenmann & Eigenmann, 1889 were examined and species of Hanek, Molnar & Fernando, 1974 were found. Species of the genus are characterized mainly by the complex shape of haptoral anchors with a modified dorsal anchor, composed by two subunits, dorsal-median and dorsal. To date, two species of are known to parasitize curimatid fishes: the type species Hanek, Molnar & Fernando, 1974 and (Suriano, 1980). During examination of specimens of collected in the Tocantins River, Embiral, Imperatriz, Maranhão State, Brazil, two new species of were found and are described herein. and are characterized by possessing the male copulatory organ formed by a long cirrus and a claw-shaped accessory piece, connected to the base of the male copulatory organ by a ligament. The new species differs from the two known congeneric species mainly by the morphology of the dorsal-median and dorsal subunits of the dorsal anchor. also differs from other species of the genus by the absence of the ventral bar and by the size and shape of the ventral bar. An amendment to the diagnosis of is provided to accommodate the new species. The present study increases the number of species to four and extends the occurrence of the genus to the Tocantins-Araguaia Basin.