Pelagic cichlids and their monogenean fauna in Lake Tanganyika: reduced host specificity and support for the classification of host tribes.
|Year of publication||2017|
|MU Faculty or unit|
|Description||Lake Tanganyika (LT) is a well-known study area localized in the African Rift Valley famous for its huge species richness and has attracted scientist for decades. The most diverse vertebrate family in LT are cichlids with more than 200 species currently placed in 14 different tribes. Surprisingly, the knowledge about parasites in LT is still incomplete and fragmentary and mainly limited to littoral habitats. As was already suggested in previous studies performed in marine systems, parasite species richness decreases in deepwater conditions, but do helminth parasites follow the same pattern in one of the most diverse freshwater ecosystems? Cichlids were already recognised as a remarkable target group in the field of evolutionary biology but what is the role of parasitic flatworms in this story? Does the monogenean morphology follow phylogenetic relationships of their cichlid hosts? Our samples originated from different parts of the lake and represent 11 host species from five cichlid tribes (Bathybatini, Benthochromini, Limnochromini, Tropheini, Trematocarini). Obtained sequence data cover four gene regions with different rates of molecular evolution; more than 180 specimens were used in a morphometric approach, selected sclerotized structures were digitalized looking for shape variation. The results genetically confirmed the previous suggestions about a monogenean species called Cichlidogyrus casuarinus being a generalist infecting six bathybatine hosts. While (geo)morphometrics showed an influence of host species and geographic origin on the morphology of C. casuarinus, the reduction of Cichlidogyrus host specifity among Bathybatini is evident in the genetic part of this study. Moreover, the list of parasites occurring in this lake’s depths was enriched by new Cichlidogyrus species collected from Trematocara unimaculatum and Benthochromis horii, C. brunnensis and C. attenboroughi, respectively. Comparative morphological analysis showed a discrepancy between host and parasite phylogeny of Gnathochromis and its monogenean fauna but supported the recent transfer of Trematocara into a separated tribe. Our morphological results do not suggest a strict monogenean-cichlid co-speciation in LT. Many interesting questions regarding parasite evolution remain to be answered.|