Monogenean parasites of cichlids: model systems for speciation and invasion biology?
|Year of publication||2014|
|MU Faculty or unit|
|Description||The stunning diversity of cichlid fishes (Cichlidae) has greatly enhanced our understanding of speciation and adaptive radiation. In contrast, little is known about the evolution of the parasites that infect cichlid species. The enormous diversity of Lake Tanganyika with its cichlid and non-cichlid fish species flocks and its importance as cradle and reservoir of ancient fish lineages seeding other radiations, has resulted in a significant body of literature in the fields of biodiversity and evolution. The lake also harbours various invertebrate taxa that underwent radiation in situ. Remarkably, until recently virtually no research was carried out into the Tanganyika parasite fauna. Parasitism is the most common lifestyle on Earth in terms of species diversity, and it is established in speciation biology that parasites are prone to radiate. Hence, parasitic organisms seem a high-potential subject for speciation studies in ancient lakes. We explore the diversity and speciation of the “species flock” of monogenean flatworms infecting Tanganyika cichlids. Monogenea was chosen because of the species richness and host-specificity of its representatives. Their simple (one-host) life cycle ensures a tight association with the respective host species. Therefore, these parasites constitute prime “markers” for coevolutionary processes and host taxonomy and evolution. We set off focusing on the endemic cichlid tribe Tropheini. Combining molecular sequence data (various portions of the nuclear ITS rDNA, mitochrondrial cox1) and morphological identification (using hard parts of attachment and copulatory organs), we discovered high host-specificity in monogeneans belonging to Cichlidogyrus (Dactylogyridae) parasitizing tropheines. Phylogenetic congruence between the flatworm and cichlid phylogeny may be caused by concomitant divergence and cospeciation events, while some historical host-switches are also apparent. Furthermore, within-host speciation caused the representatives of this parasite genus to surpass the species richness of its host radiation. Investigating other host lineages in Lake Tanganyika demonstrated that Cichlidogyrus species followed different speciation pathways in different cichlid tribes, e.g. lacking the host-specificity found for tropheine parasites. This expansion to other cichlid tribes underscores the uniqueness of Lake Tanganyika’s cichlid flock from a parasitological point-of-view as well, as demonstrated by the discovery of a putatively new dactylogyrid genus. Apart from the Lake Tanganyika biodiversity hotspot, several primarily riverine cichlids of the Congo Basin are important to fisheries, aquaculture and aquaristics. We recently started exploring their monogenean fauna as well. The aim is to investigate the potential of these parasites as a threat and a tool in introduced alien species research: the risk of introduction of non-native monogeneans into the Congo with (Nile) tilapia introductions, and the potential of monogeneans in stock identification. We will outline the strategy of this research project, combining barcoding and marker optimization with the reconstruction of historical parasite communities. This research is supported by the Czech Science Foundation P505/12/G112 (ECIP), the Austrian Science Fund (FWF), the Research Foundation – Flanders (FWO– Vlaanderen), the King Leopold III Fund for Nature Conservation and Exploration, and the Belgian Federal Sciency Policy (BRAIN-be project BR/132/PI/TILAPIA).|