Three new Dactylogyrus species ( Monogenea: Dactylogyridae) and redescription of one other, gill parasites of five Labeo spp. (Cypriniformes: Cyprinidae) from the Sanaga basin (Cameroon, Central Africa)

Three new and one already known species of Dactylogyrus Diesing, 1850 are described from five species of Labeo (Cyprinidae) sampled in the middle section of the Sanaga hydrosystem (Centre Region-Cameroon): Dactylogyrus sanagaensis sp. nov. from Labeo sanagaensis Tshibwabwa, 1997, L. nunensis Pellegrin, 1929, L. camerunensis Trewavas, 1974 and L. annectens Boulenger, 1903; Dactylogyrus nachtigalensis sp. nov. and D. yassensis Musilova, Rehulkova & Gelnar, 2009 from Labeo batesii Boulenger, 1911; and Dactylogyrus djimensis sp. nov. from Labeo camerunensis. Dactylogyrus sanagaensis sp. nov. is close to D. longiphalloides, D. longiphallus, D. leonis, D. marocanus, and D. dembae, however it can be easily distinguished from these species by the size of MCO. Dactylogyrus nachtigalensis sp. nov. is similar to D. dembae and D. sanagaensis sp. nov. but this new species can be mainly differentiated by the length of penis. Dactylogyrus djimensis sp. nov. mostly similar to D. omega can be differentiated from it by the penis diameter. Dactylogyrus yassensis collected from Cameroon doesn't significantly differ morphometrically from the original description, thus extends the distribution of this species to Sanaga basin. Monogenean species collected from Labeo spp. in the middle section of the Sanaga hydrosystem were classified into two morphological groups: the 'pseudanchoratus-like group' and the 'cyclocirrus-like group' newly defined herein. Phylogenetic relationships are suggested among Dactylogyrus species.