Abstract
The faunal diversity of Lake Tanganyika, with its fish species flocks and its importance as a cradle and reservoir of ancient fish lineages seeding other radiations, has generated a consider-able scientific interest in the fields of evolution and biodiversity. The Tropheini, an endemic Tanganyikan cichlid tribe, fills a peculiar phylogenetic position, being closely related to the haplochromine radiations of Lakes Malawi and Victoria. Sev-eral problems remain regarding their genus-level classification. For example, the monotypic genus Interochromis is phyloge-netically nested within Petrochromis; its only representative, I.loocki, has often been reclassified. As monogenean flatworms are useful markers for fish phylogeny and taxonomy, the mono-genean fauna of Interochromis loocki was examined and com-pared to that of other tropheine cichlids. Three new monoge-nean species belonging to Cichlidogyrus are described from Interochromis loocki: Cichlidogyrus buescheri Pariselle and Vanhove, sp. nov., Cichlidogyrus schreyenbrichardorum Pari-selle and Vanhove, sp. nov. and Cichlidogyrus vealli Pariselle and Vanhove,sp. nov. Their haptoral anchors remind more of congeners infecting species of Petrochromis than of all Cichli-dogyrus spp. hitherto described from other tropheine cichlids. Attachment organ morphology has been proven to mirror the phylogenetic affinities of Cichlidogyrus lineages. Therefore the monogenean parasite fauna of I. loocki reflects this host’s posi-tion within Petrochromis. Moreover, I. loocki differs in habitat choice from Petrochromis spp. This study hence confirms that host range and host-specificity in Cichlidogyrus spp.parasitiz-ing tropheines is determined by the host’s phylogenetic position, rather than by a shared ecological niche.