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
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
The environmental and climatic conditions of the Late Pleistocene of Southern Belgium are here determined for the final part of Marine Isotope Stage 3 (MIS 3) and for MIS 2 on the basis of a study of rodent assemblages. This paper provides a synthesis of several sets of environmental and climatic data from Late Pleistocene sites, all of which are located in southern Belgium. One has previously been published (Caverne Marie-Jeanne), and seven are unpublished (Cavernes de Goyet, Trou des Nutons, Trou du Frontal, Trou de Chaleux, Grotte la Chefalize, Trou du Chˆene, and Trou du Sureau). The habitat weighting and quantified ecology methods are applied to rodent material housed in the Royal Belgian Institute of Natural Sciences (RBINS, Brussels), and previous radiocarbon dates are updated, in order to reconstruct past environments. Among all the sites under analysis, the quantified ecology method shows that Trou de Chaleux corresponds to the coldest temperatures and lowest precipitation. Trou de Chaleux, with a chronology between ca. 15,964–14,014 cal yr B.P., could probably be placed in Greenland Stadial 2 (GS2) or Heinrich Event 1 (HE1). It has a rodent assemblage associated with a predominance of open dry and rocky formations, the most abundant species being the collared lemming and the narrow-headed vole. These data are found to coincide with previous studies carried out on the large-mammal, herpetofaunal, and avifaunal associations of the site, as well as on small-mammal associations from other sites in southern Belgium with similar chronology, such as Grotte Walou. Taken together, this indicates that these latest Pleistocene intervals in southern Belgium were characterized by harsh climatic and environmental conditions. In contrast, the other assemblages under study yielded much more heterogeneous results, frequently inconsistent with an attribution to the Pleistocene. This is likely to be a result of their admixture with Holocene material due to recent intrusions.
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RBINS Staff Publications 2023
