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Endocranial morphology of Palaeocene Plesiadapis tricuspidens and evolution of the early primate brain
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Expansion of the brain is a key feature of primate evolution. The fossil record, although incomplete, allows a partial reconstruction of changes in primate brain size and morphology through time. Palaeogene plesiadapoids, closest relatives of Euprimates (or crown-group primates), are crucial for understanding early evolution of the primate brain. However, brain morphology of this group remains poorly documented, and major questions remain regarding the initial phase of euprimate brain evolution. Micro-CT investigation of the endocranial morphology of Plesiadapis tricuspidens from the Late Palaeocene of Europe—the most complete plesiadapoid cranium known—shows that plesiadapoids retained a very small and simple brain. Plesiadapis has midbrain exposure, and minimal encephalization and neocorticalization, making it comparable with that of stem rodents and lagomorphs. However, Plesiadapis shares a domed neocortex and downwardly shifted olfactory-bulb axis with Euprimates. If accepted phylogenetic relationships are correct, then this implies that the euprimate brain underwent drastic reorganization during the Palaeocene, and some changes in brain structure preceded brain size increase and neocortex expansion during evolution of the primate brain.
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RBINS Staff Publications
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Endogenous toxins and the coupling of gregariousness to conspicuousness in Argidae and Pergidae sawflies
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RBINS Staff Publications 2018
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Endosymbiont dominated bacterial communities in a dwarf spider
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The microbial community of spiders is little known, with previous studies focussing primarily on the medical importance of spiders as vectors of pathogenic bacteria and on the screening of known cytoplasmic endosymbiont bacteria. These screening studies have been performed by means of specific primers that only amplify a selective set of endosymbionts, hampering the detection of unreported species in spiders. In order to have a more complete overview of the bacterial species that can be present in spiders, we applied a combination of a cloning assay, DGGE profiling and high-throughput sequencing on multiple individuals of the dwarf spider Oedothorax gibbosus. This revealed a co-infection of at least three known (Wolbachia, Rickettsia and Cardinium) and the detection of a previously unreported endosymbiont bacterium (Rhabdochlamydia) in spiders. 16S rRNA gene sequences of Rhabdochlamydia matched closely with those of Candidatus R. porcellionis, which is currently only reported as a pathogen from a woodlouse and with Candidatus R. crassificans reported from a cockroach. Remarkably, this bacterium appears to present in very high proportions in one of the two populations only, with all investigated females being infected. We also recovered Acinetobacter in high abundance in one individual. In total, more than 99% of approximately 4.5M high-throughput sequencing reads were restricted to these five bacterial species. In contrast to previously reported screening studies of terrestrial arthropods, our results suggest that the bacterial communities in this spider species are dominated by, or even restricted to endosymbiont bacteria. Given the high prevalence of endosymbiont species in spiders, this bacterial community pattern could be widespread in the Araneae order.
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RBINS Staff Publications
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Endosymbiont induced sex-ratio distortion in the dwarf spider Oedothorax retusus.
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RBINS Staff Publications
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Enhanced surveillance of monkeypox in Bas-Uélé, Democratic Republic of Congo: the limitations of symptom-based case definitions
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RBINS Staff Publications 2022
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Enkele onbekende Nederlandse schelpenverzamelingen uit de 19e eeuw
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RBINS Staff Publications 2019
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Enkele opmerkelijke personen - Quelques personnes remarquables
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RBINS Staff Publications 2022
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Ensemble analysis and forecast of ecosystem indicators in the North Atlantic using ocean colour observations and prior statistics from a stochastic NEMO–PISCES simulator
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RBINS Staff Publications 2023
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Environment and subsistence in north-western Europe during the Younger Dryas: An isotopic study of the human of Rhünda (Germany)
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RBINS Staff Publications 2016
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Environmental and climatic reconstruction of MIS 3 in northwestern Europe using the small-mammal assemblage from Caverne Marie-Jeanne (Hastière-Lavaux, Belgium)
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Marine Isotope Stage 3 (MIS 3, ca. 60–30 ka) is characterized by dynamic alternations of forest expansion with semi-arid area expansion in accordance with the warming and cooling, respectively, of the sea-surface temperatures in Northern Europe. It was in this context of rapid fluctuations that the terrestrial sequence of Caverne Marie-Jeanne (Hastière-Lavaux, Belgium) in northwestern Europe was formed. The habitat weighting method and the bioclimaticmodel, as well as the Simpson diversity index, are applied to the small-mammal assemblage of CaverneMarie-Jeanne in order to reconstruct the environmental and climatic fluctuations that are reflected in the MIS 3 sequence of the cave. Revision of the small-mammal fossil material deposited in the collections of the Royal Belgian Institute of Natural Sciences (RBINS, Brussels, Belgium) shows that the lower layers (6 to 4) of the cave, pertaining to MIS 3 (ca. 50–40 ka), underwent cold, dry environmental and climatic conditions for these layers. This is indicated by temperatures lower than at present and precipitation slightly higher than at present, together with an environment dominated by openwoodland formations and open dry meadows. Our results are consistent with the available chronological, large-mammal, herpetofaunal and mollusc datasets for this lower part of the sequence. They are also consistentwith regional loess studies in Belgium andwith previouswork performed on small mammals from MIS 3 in Belgium and elsewhere in Europe.
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RBINS Staff Publications 2017
