Two new species of Anacanthorus (Monogenoidea, Dactylogyridae) parasitizing serrasalmid fish in Brazil.

During studies on fish parasites, two new species of Anacanthorus were found parasitizing serrasalmid fishes, Anacanthorus simpliciphallus sp. n. from the hybrid Piaractus mesopotamicus x Piaractus brachypomus and Anacanthorus brandtii sp. n. from Serrasalmus brandtii. Anacanthorus simpliciphallus sp. n. resembles Anacanthorus reginae in the morphology of the male copulatory organ (MCO) and accessory piece but differs from A. reginae in terms of the smaller size of the accessory piece, which corresponds approximately half the size of the MCO and by the presence of a conspicuous metraterm, with a membranous terminal region. Anacanthorus brandtii sp. n. differs from Anacanthorus scapanus by the expansion of the accessory piece, from Anacanthorus jegui by the ratio MCO (male copulatory organ) /AP (accessory piece) and by the expansion of hook shank, from Anacanthorus sciponophallus and A. reginae by the ratio MCO/AP. Anacanthorus brandtii sp. n. can be distinguished from A. reginae and A. simpliciphallus sp.n. by the size of hooks which is similar in A. reginae and A. simpliciphallus sp. n. and dissimilar in A. brandtii sp. n. The two new species also differ from each other by the expansion of shank.