Monogenean parasites of pelagic fish species in Lake Tanganyika: potential tags for host history and population structure.
|Year of publication||2018|
|Type||Appeared in Conference without Proceedings|
|MU Faculty or unit|
|Description||Lake Tanganyika is the deepest of the African Great Lakes and harbours one of the most diverse fish assemblages. While dozens of studies focus on this lake’s cichlids as model organisms, our knowledge about the economically important fish species is still poor. The fishing effort is concentrated mainly in the lake’s pelagic zone with two clupeid (Limnothrissa miodon, Stolothrissa tanganicae) and four latid species (Lates angustifrons, L. mariae, L. microlepis, L. stappersii) as dominant targets. Additionally, cichlid species including members of the tribe Bathybatini can be found as valuable catch on fish markets. As previous research failed to give a clear picture of their lake-wide population structure, we examined the abovementioned host taxa for the presence of monogenean parasites (Platyhelminthes) to explore 1) which parasites infect the dominant fish species in the pelagic zone of Lake Tanganyika, 2) the parasites’ potential as tags to reveal their hosts’ population structure or history and 3) the origin of these freshwater parasites on these clupeid and latid hosts of marine origin. Samples of 14 host species (representatives of Cichlidae, Clupeidae, Latidae) originated from localities throughout Lake Tanganyika including all three subbasins of the lake. Parasite species identification was based on the sclerotised haptoral and genital structures. Intraspecific differences were analysed using morphometrics and geomorphometrics. Molecular characterisation was conducted using a range of nuclear and mitochondrial markers with different rates of molecular evolution. In general, a low parasite host specificity in the lake’s pelagic zone was documented in all examined fish taxa. In total, four monogenean species of three different genera were identified combining morphological and molecular data. While clupeids were infected by typical freshwater monogeneans assigned to a new genus called Kapentagyrus, three of the four latid species were parasitized by a representative of the marine genus Diplectanum. Based on phylogenetic reconstruction, the origin of diplectanids in African freshwaters is probably connected with latids diverging into African and Asian lineages. Parasite population structure inferred from part of the COI gene shows no north-south gradient. However, morphometric variation of Kapentagyrus tanganicanus and shape variation related to geographic origin inferred from geomorphometric analyses of Cichlidogyrus casuarinus, a monogenean infecting bathybatine cichlids, could be a sign of limited host migration. Therefore, the existence of parasite morphotypes related to the geographic origin of the hosts supports the possibility of using monogeneans as tags for population structure. Interestingly, morphological analyses of K. tanganicanus indicated that phenotypic variation also depended on host species. Similarly, our morphometric and geomorphometric analyses on C. casuarinus show some differentiation influenced by host preference. This pattern observed in different monogenean genera is probably caused by phenotypic changes during ontogenetic development because of its independence of genetic population structure. Recent demographic expansion in species infecting clupeid and cichlid hosts was detected and can be linked with paleogeographic events and climate change, respectively.|