Ordovician Bryozoa of Estonia

sessile colonial, filter-feeding animals, many of which possess hard carbonate skeletons of different morphology. The bryozoan faunas of the Ordovician of Estonia were studied early by famous naturalists such as Karl Eduard von Eichwald and WÅadisÅaw Dybowski. Later, in the 20th century, many palaeontologists, among them Ray Bassler, Hendrik Bekker, and Ralf Männil, devoted extensive studies to the Ordovician bryozoans of Estonia. Soviet and Russian specialists contributed to the knowledge about this important group of fossils with numerous publications. The Ordovician deposits bearing abundant and well-preserved bryozoans are well exposed and often easily accessible. Therefore, the Estonian bryozoan faunas are much better studied than the contemporary assemblages of Sweden or Norway. Few representatives of this phylum appeared in the sediments of the Lower Ordovician, but then the group experienced a rapid diversification. The current evaluation of the data (published and based on the results of our own research) on the distribution of bryozoans in the Ordovician (TremadocâHirnantian) deposits of Estonia revealed 194 species of 90 genera. The most diverse bryozoan group is trepostomes, with 77 species of 36 genera. The Sandbian and the Katian show the highest species richness of bryozoans, with 92 and 112 species, respectively. During the Hirnantian, bryozoans in Estonia experienced an immense diversity drop, with only a few species passing through the Silurian. This pattern mirrors the global development of bryozoan faunas during the Ordovician. Ordovician bryozoans of Estonia have been found in diverse environmental settings. The best-known deposit containing excellently preserved bryozoans is kukersite. This oil shale was formed in shallow subtidal shelf conditions, and contains more than 60 bryozoan species. Another famous bryozoan locality is the reefs of the Vasalemma Formation (Katian), exposed in the Vasalemma quarry. The bryozoans found in the Ordovician deposits of Estonia reveal a great variety of growth forms adapted to different biotopes of the sea bottom. The sizes of bryozoans vary immensely within the same assemblages. Some massive trepostomes such as Diplotrypa petropolitana attained heights of up to 20 cm, whereas species such as the cyclostome Kukersella borealis developed colonies less than 0.5 mm in diameter

Scale dependent diversity of bryozoan assemblages in the reefs of the Late Ordovician Vasalemma Formation, Estonia

The fieldwork for BK and AP was partly funded by the Academy of Finland project ‘Ecological Engineering as a Biodiversity Driver in Deep Time’ (Decision No. 309422). Deutsche Forschungsgemeinschaft (DFG) is appreciated for financial support of AE (project ER 278/10.1). The work is a contribution to the IGCP program 735 ‘Rocks and the Rise of Ordovician Life’.The reefs of the Vasalemma Formation, late Sandbian, Late Ordovician, of northern Estonia contain an exceptional rich and abundant bryozoan fauna. They are an example of contemporaneous bryozoan-rich reefs known from around the world, representing the peak diversification interval of this group during the Ordovician. The global Ordovician bryozoan diversification was associated with a decrease in provinciality, a pattern known from other skeletal marine metazoans of this period. The diversification is associated with climatic cooling and increasing atmospheric and sea water oxygenation. However, the mechanisms that led to the bryozoan diversification are poorly known. Here we estimate the bryozoan richness (α and γ diversity) and turnover (β diversity) at the level of samples, reefs, and formations in the Vasalemma Formation and in contemporaneous reef limestone occurrences of the Baltoscandian region. The resulting richness and turnover values differ among the three observational levels and hence are scale dependent. A consistent pattern with lowest between-reef turnover and relatively high between-sample turnover could be detected, reflecting high small-scale (within reef) heterogeneities in lithology and original bryozoan habitat. This is consistent with published work, in which evidence has been presented for small-scale substrate heterogeneity as the most important diversification driver of the Ordovician brachiopod diversification in the Baltoscandian region. The fact that reefs and their local substrate are strongly organism moderated environments sheds light on the potentially important ecosystem engineering role of organisms, such as bryozoans, for the Ordovician diversification.Publisher PDFPeer reviewe

The reengineering of reef habitats during the Great Ordovician Biodiversification Event

Bryozoans, stromatoporoid sponges, and tabulate corals, all colonial metazoans with lamellar, encrusting growth forms, developed and simultaneously diversified during the Great Ordovician Biodiversification Event (GOBE). After revisiting some classic Lower, Middle, and Upper Ordovician reef localities in Laurentia (Franklin Mountains, west Texas, Mingan Islands in eastern Canada, and Champlain Valley in northeastern United States) and Baltica (northern Estonia) and reviewing the literature, we demonstrate that during the Ordovician a newly emerging consortium of sheet-like bryozoans, stromatoporoid sponges, and tabulate corals locally bound together by microbes, automicrite, and cement and solidly rooted in sediment became the dominant reef-builders globally. The diversification of these sheet-like metazoans (SLM), however, clearly lagged behind the first appearance of their respective skeletal ancestors. Their habitat expansion can be exemplified as a case of simultaneous ecological fitting and ecosystem engineering when the independently evolved shared traits were simultaneously co-opted and became advantageous under globally different environmental conditions. This interaction led to the evolutionary diversification of colonial metazoans during the GOBE and to the expansion of novel reef habitats in previously soft-surface settings; a transformation that forever changed marine reefal ecosystems.Peer reviewe

Rare intercroissance tétracoralliaire-bryozoaire dans l'Ordovicien supérieur d'Estonie

Two relatively large specimens of the rugosan Lambelasma sp. are fully intergrown with the bryozoan Stigmatella massalis colony. The intergrown specimen occurs in the Oandu Regional Stage (lower Katian) of Estonia and constitutes the earliest record of bryozoan-rugosan intergrowth from Baltica. Most likely this symbiotic association was accidental. Rugosans presumably benefitted from the bryozoan, which served as an anchor to stabilize them in hydrodynamically active waters. The lack of malformations and no decrease in the size of bryozoan zooids near the rugosans indicate a lack of negative effect of the rugosans on the bryozoan. Bryozoan-rugosan symbiosis is only known from the Ordovician of Baltica and Laurentia.Deux spécimens relativement grands du tétracoralliaire Lambelasma sp. montrent une intercroissance étroite avec une colonie du bryozoaire Stigmatella massalis. Le matériel a été récolté dans l'Étage Régional Oandu (Katien inférieur) d'Estonie et constitue la plus ancienne mention de intercroissance tétracoralliaire-bryozoaire dans l'Ordovicien de Baltica. Très vraisemblablement cette symbiose est accidentelle. Le tétracoralliaire tire probablement bénéfice du bryozoaire dont il se sert comme point d'ancrage pour se stabiliser dans un milieu marin agité. L'absence de malformations et de diminution de la taille des zoécies du bryozoaire au contact du tétracoralliaire indiquent que ce dernier ne perturbe pas le développement du bryozoaire. La symbiose tétracoralliaire-bryozoaire n'est connue que dans l'Ordovicien de Baltica et de Laurentia

Transient permeabilization of living cells: combining shear flow and acoustofluidic trapping for the facilitated uptake of molecules

Here, we present a novel approach for the transient permeabilization of cells. We combined laminar shear flow in a microchannel with chaotic advection employing surface acoustic waves. First, as a fundamental result on the one hand, and as a kind of reference measurement for the more complex acoustofluidic approach on the other hand, we studied the permeabilization of cells in pure shear flow in a microchannel with Y-geometry. As a proof of principle, we used fluorescent dyes as model drugs and investigated their internalization into HeLa cells. We found that drug uptake scaled non-linearly with flow rate and thus shear stress. For calcein, we obtained a maximal enhancement factor of about 12 at an optimum flow rate of Q = 500 µL/h in the geometry used here compared to static incubation. This result is discussed in the light of structural phase transitions of lipid membranes accompanied by non-linear effects, as the plasma membrane is the main barrier to overcome. Second, we demonstrated the enhanced permeabilization of acoustically trapped cells in surface acoustic wave induced vortices in a microchannel, with an enhancement factor of about 18 compared to quasi-static incubation. Moreover, we optimized the trapping conditions regarding flow rate, the power level of the surface acoustic wave, and trapping time. Finally, we showed that our method is not limited to small molecules but can also be applied to compounds with higher molecular weight

High thermoelectric performance in metallic NiAu alloys

Thermoelectric (TE) materials seamlessly convert thermal into electrical energy and vice versa, making them promising for applications such as power generation or cooling. Although historically the TE effect was first discovered in metals, state-of-the-art research mainly focuses on doped semiconductors with large figure of merit, $zT$, that determines the conversion efficiency of TE devices. While metallic alloys have superior functional properties, such as high ductility and mechanical strength, they have mostly been discarded from investigation in the past due to their small Seebeck effect. Here, we realize unprecedented TE performance in metals by tuning the energy-dependent electronic scattering. Based on our theoretical predictions, we identify binary NiAu alloys as promising candidate materials and experimentally discover colossal power factors up to 34 mWm$^{-1}$K$^{-2}$ (on average 30 mWm$^{-1}$K$^{-2}$ from 300 to 1100 K), which is more than twice larger than in any known bulk material above room temperature. This system reaches a $zT$ up to 0.5, setting a new world record value for metals. NiAu alloys are not only orders of magnitude more conductive than heavily doped semiconductors, but also have large Seebeck coefficients originating from an inherently different physical mechanism: within the Au s band conduction electrons are highly mobile while holes are scattered into more localized Ni d states, yielding a strongly energy-dependent carrier mobility. Our work challenges the common belief that good metals are bad thermoelectrics and presents an auspicious paradigm for achieving high TE performance in metallic alloys through engineering electron-hole selective s-d scattering

Diversity and spatial turnover of bryozoan assemblages in the reefs of the Vasalemma Formation (Late Ordovician), Estonia

The reefs of the Vasalemma Formation, late Sandbian, Late Ordovician, of northern Estonia contain an exceptionally rich and abundant bryozoan fauna. They are an example of contemporaneous bryozoan-rich reefs known from around the world, representing the peak diversification interval of this group during the Ordovician. The diversification is associated with global climatic cooling and increasing atmospheric and sea water oxygenation. However, the mechanisms that led to the bryozoan diversification are poorly known. Here we estimate the bryozoan richness (α and γ diversity) and turnover (β diversity) at the level of samples, reefs, and formations in the Vasalemma Formation. The resulting richness and turnover values differ among the three observational levels and hence are scale dependent. A pattern with lowest between-reef turnover and relatively high between-sample turnover could be detected, reflecting high small-scale (within reef) heterogeneities in lithology and original bryozoan habitat. This is consistent with the hypothesis that small-scale substrate heterogeneity was the most important diversification driver in the Vasalemma Formation

Middle Devonian brachiopod-hosted sclerobiont assemblage from the northern shelf of Gondwana (Mader Basin, Morocco): Diversity, colonization patterns and relation to coeval palaeocommunities

Middle Devonian (Eifelian/Givetian transition) brachiopod-hosted sclerobiont assemblage from Gondwana (Morocco, eastern Anti-Atlas, Mader Basin) has been studied for the first time. The analysis of hundreds of brachiopod shells revealed at least 26 sclerobiont taxa, making the studied palaeoecommunity one of the most diverse Middle Devonian sclerobiont assemblage reported to date. The palaeocommunity is dominated by encrusting organisms, in particular bryozoans, foraminifers, ascodictyids and microconchids, whereas bioeroders are represented by Clionolithes and Oichnus ichnospecies. As supported by microfacies, fossil preservation and the presence of encrusting Rothpletzella algae, the sclerobionts developed in a calm, euphotic, offshore marine environment situated below normal wave base. Prevalence of articulated shells without signs of either extensive mineral staining, or taphonomic alteration resulting from hydrodynamic processes, as well as preservation of some delicate encrusters (Vinella, Rothpletzella), indicate that the palaeocommunity did not undergo extensive time-averaging. The hosts were colonized syn vivo, as evidenced by the epibiont growth near the commissure margin, the presence of shell malformations and even embedded auloporid corals and cornulitid tubeworms. Competition for space among sclerobionts was apparently limited, as suggested by the very low number of overgrowth interactions, indicating that the shelly substrate available for colonization was abundant. The presence of the same dominant groups of sclerobionts on different host taxa indicates a lack of species-selectivity by these colonizing sclerobionts. It also suggests that the sclerobiont species pool in the environment was generally similar throughout the deposition of the sampled rock interval. As testified by the host brachiopod and bryozoan species, the sclerobiont assemblage from this locality of northern Gondwana had strong affinities with those from the southern margin of Laurussia, most likely reflecting strong connectivity between these regions provided by the South Equatorial – North Gondwana current system during the late Eifelian Kaˇc´ak transgressive episode

Wt1 transcription factor impairs cardiomyocyte specification and drives a phenotypic switch from myocardium to epicardium.

During development, the heart grows by addition of progenitor cells to the poles of the primordial heart tube. In the zebrafish, Wilms tumor 1 transcription factor a (wt1a) and b (wt1b) genes are expressed in the pericardium, at the venous pole of the heart. From this pericardial layer, the proepicardium emerges. Proepicardial cells are subsequently transferred to the myocardial surface and form the epicardium, covering the myocardium. We found that while wt1a and wt1b expression is maintained in proepicardial cells, it is downregulated in pericardial cells that contributes cardiomyocytes to the developing heart. Sustained wt1b expression in cardiomyocytes reduced chromatin accessibility of specific genomic loci. Strikingly, a subset of wt1a- and wt1b-expressing cardiomyocytes changed their cell-adhesion properties, delaminated from the myocardium and upregulated epicardial gene expression. Thus, wt1a and wt1b act as a break for cardiomyocyte differentiation, and ectopic wt1a and wt1b expression in cardiomyocytes can lead to their transdifferentiation into epicardial-like cells.NM has been funded by SNF grant 320030E-164245 and ERC Consolidator grant 2018 819717. The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia e Innovación (MCIN) and the Pro CNIC Foundation and is a Severo Ochoa Center of Excellence (SEV-2015-0505). Benoît Zuber is supported by SNF grant 179520 and ERA-NET NEURON grant 185536. M.O. was supported by SNF grant PCEFP3_186993.S

Mycobacterium tuberculosis lineage 4 comprises globally distributed and geographically restricted sublineages

Generalist and specialist species differ in the breadth of their ecological niches. Little is known about the niche width of obligate human pathogens. Here we analyzed a global collection of Mycobacterium tuberculosis lineage 4 clinical isolates, the most geographically widespread cause of human tuberculosis. We show that lineage 4 comprises globally distributed and geographically restricted sublineages, suggesting a distinction between generalists and specialists. Population genomic analyses showed that, whereas the majority of human T cell epitopes were conserved in all sublineages, the proportion of variable epitopes was higher in generalists. Our data further support a European origin for the most common generalist sublineage. Hence, the global success of lineage 4 reflects distinct strategies adopted by different sublineages and the influence of human migration.We thank S. Lecher, S. Li and J. Zallet for technical support. Calculations were performed at the sciCORE scientific computing core facility at the University of Basel. This work was supported by the Swiss National Science Foundation (grants 310030_166687 (S.G.) and 320030_153442 (M.E.) and Swiss HIV Cohort Study grant 740 to L.F.), the European Research Council (309540-EVODRTB to S.G.), TB-PAN-NET (FP7-223681 to S.N.), PathoNgenTrace projects (FP7-278864-2 to S.N.), SystemsX.ch (S.G.), the German Center for Infection Research (DZIF; S.N.), the Novartis Foundation (S.G.), the Natural Science Foundation of China (91631301 to Q.G.), and the National Institute of Allergy and Infectious Diseases (5U01-AI069924-05) of the US National Institutes of Health (M.E.)