The monogenean fauna of cichlids from the Congo River

The cichlid assemblages inhabiting African rivers and small standing waters have not received the same scientific attention as their Great Lakes’ counterparts, who surpass them in morphological diversity and species richness, and are well-known models in evolutionary biology. However, several primarily riverine cichlids of the Congo Basin are important to fisheries, aquaculture and aquaristics. This contribution focuses on a hidden element of biodiversity associated with these cichlids: a very diverse group of parasites, namely monogenean flatworms. Their simple lifecycle and high host-specificity render them an interesting source of information for the study of the ecology and evolution of their hosts. We aim to present an overview of current work on monogenean flatworms in the Congo Basin, highlighting areas of cross-fertilisation between ichthyology and parasitology, as well as some potential applications. Our results draw from morphological and genetic analyses of host fish and flatworm parasites. Three main research lines will be addressed: 1) The monogenean fauna of cichlids from the Congo, and its relationship with adjacent river basins, underlining the use of monogeneans as biogeographical markers. 2) The influence of cichlid ecology and evolution on monogenean speciation. Here, we focus on one of the sources of the Congo, namely Lake Tanganyika. Its cichlid diversity provides an ideal test case for the use of monogeneans as models in adaptive radiation research. 3) Parasites as a threat and a tool in introduced alien species research: the risk of introduction of non-native monogeneans into the Congo with tilapia introductions, and the potential of monogeneans in stock identification. These examples underscore the added value of including parasitological studies into biodiversity research.