New species and records of Anacanthorus (Monogenoidea: Dactylogyridae) from the gills of Brycon amazonicus (Characiformes: Bryconidae) in the Peruvian Amazon.

Five species belonging to Anacanthorus Mizelle & Price, 1965 were found parasitizing the gills of Brycon amazonicus (Agassiz) collected in the Peruvian Amazon: A. spiralocirrus Kritsky, Thatcher & Kayton, 1979, A. femoris n. sp., A. kukamensis n. sp., A. rarus n. sp. and A. sabaloi n. sp. Anacanthorus femoris n. sp. presents a membranous accessory piece with flared tip, hooks with proximal bulbous base containing 1 translucent region; A. kukamensis n. sp. presents an accessory piece with two branches, one with can-opener-shaped termination and the other with denticles in the lateral margin and at both ends of the distal portion, hooks with expanded proximal bulbous base with central and elliptical translucent region; A. rarus n. sp. presents a MCO as a long sclerotized tube, slightly sinuous, with folds in its middle region, with proximal region with circular opening and distal region with rough termination. The accessory piece is small and curved, hooks with expanded proximal bulbous base with central, elliptical translucent region, elongate shank, truncate thumb, slightly curved shaft and inconspicuous point; in A. sabaloi n. sp. the MCO is a long sclerotized reflexive tube, with membranous appearance from its middle part towards the end, with distal and proximal end with an inwardly directed fold, the accessory piece is a membranous sheath that envelops the MCO just before the reflection zone. The four new species found in this study are the second records of species of Anacanthorus described from a fish host from the Peruvian Amazon.