Four new species of Cichlidogyrus (Platyhelminthes, Monogenea, Dactylogyridae) from Lake Victoria haplochromine cichlid fishes, with the redescription of C. bifurcatus and C. longipenis

African cichlids are model systems for evolutionary studies and for host-parasite interactions, because of their adaptive radiations and because they harbour many species of monogenean parasites with high host-specificity. Here, we sampled five locations in southern Lake Victoria, the youngest of the African Great Lakes. We surveyed gill-infecting monogeneans from 18 cichlid species belonging to the Lake Victoria radiation superflock and two cichlid species representing two older and distantly related lineages. We found one species of Gyrodactylus (Gyrodactylidae, Monogenea), Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, and seven species of Cichlidogyrus (Dactylogyridae, Monogenea). Four species are herein described: Cichlidogyrus pseudodossoui n. sp., C. nyanza n. sp., C. furu n. sp., C. vetusmolendarius n. sp.. Another species is reported but not formally described (because of few specimens and morphological similarity with C. furu n. sp.). Two other species are redescribed: Cichlidogyrus bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Our results confirm that the monogenean fauna of Victorian littoral cichlids displays lower species richness and lower host-specificity than that of Lake Tanganyika littoral cichlids. In C. furu n. sp., hooks V are clearly longer than the other hooks, highlighting the need to re-evaluate the current classification system of haptoral configurations that considers hook pairs III-VII as rather uniform. Some morphological features of C. bifurcatus, C. longipenis and C. nyanza n. sp. suggest that these are closely related to other congeners that infect haplochromines. We also found morphological indications that representatives of Cichlidogyrus colonised Lake Victoria haplochromines or their ancestors at least twice, which is in line with the Lake Victoria superflock being colonized by two cichlid tribes (Haplochromini and Oreochromini).