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A gymnodont fish jaw with remarkable molariform teeth from the early Eocene of Gujarat, India (Teleostei, Tetraodontiformes)
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The lower jaw of a gymnodont fish collected from the lower Eocene Cambay Shale Formation in Gujarat Province, western India, has fused dentaries without a beak and a remarkable series of teeth that are unique among all known fossil and living Tetraodontiformes. The teeth are molariform, with raised spokes radiating inward from the emarginated peripheral edge of the crown. Tooth development is intraosseous, with new teeth developing in spongy bone before they erupt and attach to the dentary by pedicels. Although many of the 110 tooth loci in the fossil have lost their teeth, in life the teeth would have grown to fit tightly together to form a broad and continuous crushing surface. The estimated age of the Cambay Shale vertebrate fauna is ca. 54.5 Ma, making the jaw the second oldest confirmed gymnodont fossil. Preliminary comparisons with extant taxa of gymnodonts with fused dentaries (e.g., Diodon, Chilomycterus, and Mola) show detailed similarities in jaw structure, but further study of the dentition is needed to better understand the evolutionary position of the new fossil. We describe the new gymnodont as yAvitoplectus molaris, gen. et sp. nov., in yAvitoplectidae, fam. nov., and place the family as incertae sedis within Gymnodontes.
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RBINS Staff Publications 2017
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New extralimital record of a narwhal (Monodon monoceros) in Europe
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RBINS Staff Publications 2018
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Mobility and origin of camels in the Roman Empire through serial stable carbon and oxygen isotopes variations in tooth enamel
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Although camels are not indigenous to Europe, they have been found at several sites from several Roman provinces dating from the beginning of the 1st century AD onwards. It must have been beneficial to bring them there. Based on finds of remains from juvenile individuals (e.g. from Tanais), it has been suggested that the Romans might have systematically bred camels within Europe. For this study, we took serial samples of the enamel of four camels from European sites (Innsbruck-Wilten, Mamer-Bertrange, Tongeren, and Trier) dating to the 2nd - 4th century AD. We measured the relative abundances of carbon and oxygen isotopes of the carbonate fraction from the tooth enamel. The continuous record of oxygen and carbon isotopic composition of the intra-tooth enamel serial samples reflects the climate and habitat in which an individual lived during the time of tooth mineralization. We used these data to make a rough evaluation of the areas of origin consistent with the relative abundances of the isotopes from the enamel of the camels and attempt to reconstruct their life history and mobility behavior based on the different ecological characteristics of the habitats represented in the isotopic data. Furthermore, the data can function as an additional proxy for species determination, due to the different habitats of Camelus bactrianus and Camelus dromedarius. This work also yields interesting insights on the similarities in the mobility pattern of the camels from Mamer-Bertrange and Trier. In combination with archaeological evidence, it was possible to tentatively connect them with specific military units, i.e. the detachments of the Legio VIII Augusta.
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RBINS Staff Publications 2020
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Period of public commentary begins on the revised proposal of species-group level names, and on the proposal of genus-group level names of the Candidate Part of List of Available Names (LAN) in the phylum Rotifera
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RBINS Staff Publications 2016
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Placoderm assemblage from the tetrapod-bearing locality of Strud (Belgium, Upper Famennian) provides evidence for a fish nursery
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RBINS Staff Publications 2016
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Reduced host-specificity in a parasite infecting non-littoral Lake Tanganyika cichlids evidenced by intraspecific morphological and genetic diversity
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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
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A distinct island population of threatened freshwater fish: to split or lump?
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Freshwater fishes in the Balkans display high percentages of endemic species, many being limited to restricted distributions. Their management, for example, through identification of priority areas for conservation or through re-introduction, is hampered by a poor understanding of their taxonomic diversity and interrelationships. We evaluate the identity of a sand goby belonging to Knipowitschia, limited to a single wetland on the Greek island of Zakynthos. Its representatives morphologically differ sufficiently from their congeners to qualify as a separate species. However, in view of the similarity in mitochondrial ribosomal DNA sequences, the evolutionary plasticity of said morphological characters, and in the absence of a taxonomic revision of the Ionian Ecoregion’s Knipowitschia gobies, describing it as a new species seems unjustified and premature. Rather, we advocate that its unique habitus and its vulnerability as the island’s only resident freshwater fish necessitate conservation efforts as a kind of ‘‘phenotypically significant unit’’. We also propose sand gobies as flagships for wetlands in the region. This case study suggests a possible approach for fish conservation prioritization in the region, taking a precautionary angle in order to avoid taxonomic inflation, which is an imminent risk given the importance of nominal species and endemics in conservation policy.
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RBINS Staff Publications 2016
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First report of monogenean flatworms from Lake Tana, Ethiopia: gill parasites of the commercially important Clarias gariepinus (Teleostei: Clariidae) and Oreochromis niloticus tana (Teleostei: Cichlidae)
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Background: Lake Tana is the largest lake in Ethiopia and the source of the Blue Nile. The lake harbours unique endemic cyprinid fish species, as well as the commercially important endemic Nile tilapia subspecies Oreochromis niloticus tana and the North African catfish Clarias gariepinus. Its endemicity, especially within the Labeobarbus radiation, its conservation importance and its economic indispensability attract scientific interest to the lake’s ichthyofauna. Fish parasites of Lake Tana, however, are hitherto poorly known, and no formal report exists on its monogenean flatworms. For sustainable aquaculture and fisheries development, it is essential to study monogenean fish parasites in these economically most important fish species. Moreover, it remains to be verified whether this unique ecosystem and its endemicity gave rise to a distinct parasite fauna as well. Results: Nile tilapia and North African catfish hosts were collected from Lake Tana in 2013. Nine species of monogenean parasites of two orders, Gyrodactylidea Bychowsky, 1937 and Dactylogyridea Bychowsky, 1937, were recovered. Gyrodactylus gelnari Přikrylová, Blažek & Vanhove, 2012, Macrogyrodactylus clarii Gussev, 1961, Quadriacanthus aegypticus El-Naggar & Serag, 1986 and two undescribed Quadriacanthus species were recovered from C. gariepinus. Oreochromis niloticus tana hosted Cichlidogyrus cirratus Paperna, 1964, C. halli (Price & Kirk, 1967), C. thurstonae Ergens, 1981 and Scutogyrus longicornis (Paperna & Thurston, 1969). Conclusions: Except for M. clarii, all species represent new records for Ethiopia. This first study on the monogenean fauna of Lake Tana revealed that the lake’s North African catfish, as well as its endemic Nile tilapia subspecies, harbour parasites that are known from these host species elsewhere in Africa.
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RBINS Staff Publications 2016
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Cichlids: a host of opportunities for evolutionary parasitology
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Thanks to high species diversity and a broad range of speciation mechanisms, cichlid fishes represent a textbook model in evolutionary biology. They are also of substantial economic value. Despite this importance, cichlid parasites remain understudied, although some are more diverse than their hosts. They may offer important insights into cichlid evolution and the evolution of host–parasite interactions. We review five major lines of research conducted on cichlid para- sites so far: the study of parasite diversity and speciation; the role of parasites in cichlid diversification; the evolutionary ecology of host specificity; historical biogeography; and biological invasions. We call for more research in these areas and suggest approaches to valorise the potential that cichlid parasites hold for the study of evolutionary parasitology.
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RBINS Staff Publications 2016
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Weak link between dispersal and parasite community differentiation or immunogenetic divergence in two sympatric cichlid fishes
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Geographical isolation, habitat variation and trophic specialization have contributed to a large extent to the astonishing diversity of cichlid fishes in the Great East African lakes. Because parasite communities often vary across space and environments, parasites can accompany and potentially enhance cichlid species diversification. However, host dispersal may reduce opportunities for parasite-driven evolution by homogenizing parasite communities and allele frequencies of immunity genes. To test for the relationships between parasite community variation, host dispersal and parasiteinduced host evolution, we studied two sympatric cichlid species with contrasting dispersal capacities along the shores of southern Lake Tanganyika. Whereas the philopatric Tropheus moorii evolved into several genetically differentiated colour morphs, Simochromis diagramma is phenotypically rather uniform across its distribution range and shows only weak population structure. Populations of both species were infected with divergent parasite communities and harbour differentiated variant pools of an important set of immune genes, the major histocompatibility complex (MHC). The overall extent of geographical variation of parasites and MHC genes was similar between host species. This indicates that immunogenetic divergence among populations of Lake Tanganyika cichlids can occur even in species that are strongly dispersing. However, because this also includes species that are phenotypically uniform, parasite-induced evolution may not represent a key factor underlying species diversification in this system.
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RBINS Staff Publications 2016
