Contrasting Host-Parasite Population Structure: Morphology and Mitogenomics of a Parasitic Flatworm on Pelagic Deepwater Cichlid Fishes from Lake Tanganyika

Little phylogeographic structure is presumed for highly mobile species in pelagic zones. Lake Tanganyika a unique ecosystem with speciose and largely endemic fauna famous its remarkable evolutionary history. In bathybatine cichlid fishes, the pattern of lake-wide population differentiation differs among species. We assessed congruence between cichlids their parasitic flatworm Cichlidogyrus casuarinus to test magnifying glass hypothesis. Additionally, we evaluated use PoolSeq approach study intraspecific variation dactylogyrid monogeneans. The C. ex Hemibates stenosoma was based on portion cox1 gene combined morphological characterisation. mitogenomic 80 parasite samples from one spatially constrained metapopulation using shotgun NGS. While no clear geographic genetic detected parasites, both host-related phenotypic apparent. incongruence north-south gradient observed H. may be explained by broad host range this including eupelagic that form panmictic populations across lake. addition, present first mitogenome propose methodological framework studying