A significant part of the collection of mid- and Late Cretaceous (Cenomanian, Campanian and Maastrichtian) gastropods, bivalves and worms described and/or illustrated by de Ryckholt in his seminal work Mélanges paléontologiques between 1854 and 1862, has recently been retraced in the historical collections at Liège University. Of the original collection, more than 206 specimens, including 196 nominal types (lectotypes and genotypes), all considered lost, are now available. The genotypes of the gastropod genera Tudicula de Ryckholt, 1862a and Prosopostoma de Ryckholt, 1862a are photographically illustrated for the first time. Prosopostoma bucculans, from the Cenomanian Bernissart Formation (formerly ‘Tourtia de Tournai’), is here chosen as the type species of the genus Prosopostoma, a possible stromboid. We also reassess the stratigraphic age of the type localities under the revised stratigraphic framework of Belgium and a detailed account on the research history of this material, in order to provide a thorough scientific background for future study of this formidable collection.
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RBINS Staff Publications
Lake Tanganyika is well-known for its high species-richness and rapid radiation processes. Its assemblage of cichlid fishes recently gained momentum as a framework to study parasite ecology and evolution. It offers a rare chance to investigate the influence of a deepwater lifestyle in a freshwater fish-parasite system. Our study represents the first investigation of parasite intraspecific genetic structure related to host specificity in the lake. It focused on the monogenean flatworm Cichlidogyrus casuarinus infecting deepwater cichlids belonging to Bathybates and Hemibates. Morphological examination of C. casuarinus had previously suggested a broad host range, while the lake’s other Cichlidogyrus species are usually host specific. However, ongoing speciation or cryptic diversity could not be excluded. To distinguish between these hypotheses, we analysed intraspecific diversity of C. casuarinus. Monogeneans from nearly all representatives of the host genera were examined using morphometrics, geomorphometrics and genetics. We confirmed the low host-specificity of C. casuarinus based on morphology and nuclear DNA. Yet, intraspecific variation of sclerotized structures was observed. Nevertheless, the highly variable mitochondrial DNA indicated recent population expansion, but no ongoing parasite speciation, confirming, for the first time in freshwater, reduced parasite host specificity in the deepwater realm, probably an adaptation to low host availability.
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RBINS Staff Publications 2016
