SHELL MICROSTRUCTURES IN LOPINGIAN BRACHIOPODS: IMPLICATIONS FOR FABRIC EVOLUTION AND CALCIFICATION

The study of the shell microstructure of brachiopods is fundamental to understand their evolutionary history and their biomineralization process. Here, species of forty Lopingian brachiopods genera, representative of twenty-seven different families, are investigated using the Scanning Electron Microscope. The investigated specimens come from different paleogeographic localities in the Palaeotethys/Neotethys oceans. The studied brachiopods show a large variability of the shell fabric, which is mainly related to the organization of its structural units: laminae, fibers and columns, possibly crossed by pseudopunctae or punctae. For the Strophomenata, the laminar fabric of Productida is crossed by pseudopunctae with taleolae and the laminae are often organized in packages, with the blades oriented about perpendicular to each other; this feature is less evident in the laminar Orthotetida, which bear pseudopunctae without taleoae. For the Rhynchonellata, fibrous fabrics are either impuctate in the Spiriferida, most Athyridida and Rhynchonellida, or with punctae, as observed in the Orthida, Terebratulida and in the Neoretziidae (Athyridida). The fibers show a range of sizes and shapes also in the same specimens and the transition to the columnar layer is different than in Strophomenata.The arrangement of the structural units revealed that the disposition of the organic membranes, on which biomineralization took place, was highly variable among the taxa. On the other hand, two distinctive features are analogous among distantly related groups, i.e. the Strophomenata and the Rhynchonellata: the presence of a columnar tertiary layer underlying the secondary fabric and the alternations between fibers/laminae of the secondary layer and columns of the tertiary layer. This suggests that there are common factors controlling the development and evolution of the shell fabric in all rhynchonelliformean brachiopods that can be linked to their taxonomical position, to their environmental requirements and to constraints imposed by their low-energy life-style. This should be taken into account to understand how these calcifying organisms responded and will respond to environmental and climate change in past and future times

FOREWORD. PROCEEDINGS OF THE 8TH INTERNATIONAL BRACHIOPOD CONGRESS BRACHIOPODS IN A CHANGING PLANET: FROM THE PAST TO THE FUTURE, MILANO, 10-14 SEPTEMBER 2018

The 8th International Brachiopod Congress took place in the prestigious venue of the Univer¬sity of Milano, Italy, in September 2018, after the previous edition held in Nanjing, China, in 2015. 150 participants from universities and re¬search institutes from all over the world attended the meeting, from Argentina, Armenia, Austria, Belgium, Canada, China, Czech Republic, Den¬mark, France, Germany, Hungary, Iran, Israel, It¬aly, Japan, New Zealand, Poland, Russia, Slovakia, Spain, Sweden, United Kingdom, and United States of America. Besides oral and poster scientific sessions, pico-presentations of young researchers, and two prestigious plenary lectures, the Congress was preceded and followed by three field trips (Spain, United Kingdom and Sicily), and by two mid-con¬gress day excursions at Castell’Arquato and Grigna Mountains. During the congress, all the topics and the re¬cent advances in the study of brachiopods, marine invertebrates that have dominated the Palaeozoic seas and had an important role in the Phaneorozo¬ic benthic communities, have been touched: from systematics and evolution to biostratigraphy, pala¬eoecology, palaeobiogeography, mass extinctions, and the biology of recent taxa. One of the novelties of this edition was a session dedicated to brachio¬pod shells as biomineral archives of fundamental importance to understand the evolution of marine calcifiers during climate and environmental changes in recent and deep time. So, also biomineralization and geochemistry were among the topics of the event. The high scientific level, activity and wide and interdisciplinary interests of the brachiopod re¬searchers’ community are testified by the numerous contributions received for the Proceedings of the 8th International Brachiopod Congress, 16 of which are published open access in issue 125/3 of Rivista Italiana di Paleontologia e Stratigrafia

Assessing ocean acidification and carbon cycle perturbations during the end-Permian extinction using boron isotopes

The Permian-Triassic mass extinction represents the most severe environmental crisis in Earth’s history, which dictated the course for evolution of life until today. Volcanism from Siberian traps played a significant role involving a substantial input of relatively light carbon into the atmosphere leading to a combination of global warming by ~6°C, sporadic anoxia or euxinia, and ocean acidification. However, its detailed manifestation and environmental impact is yet to be fully understood. This lack of knowledge also extends to a better quantification of emitted and sequestered carbon budgets (cf. Gutjahr et al., 2017)

Mapping of recent brachiopod microstructure: a tool for environmental studies

Shells of brachiopods are excellent archives for environmental reconstructions in the recent and distant past as their microstructure and geochemistry respond to climate and environmental forcings. We studied the morphology and size of the basic structural unit, the secondary layer fibre, of the shells of several extant brachiopod taxa to derive a model correlating microstructural patterns to environmental conditions. Twenty-one adult specimens of six recent brachiopod species adapted to different environmental conditions, from Antarctica, to New Zealand, to the Mediterranean Sea, were chosen for microstructural analysis using SEM, TEM and EBSD. We conclude that: 1) there is no significant difference in the shape and size of the fibres between ventral and dorsal valves, 2) there is an ontogenetic trend in the shape and size of the fibres, as they become larger, wider, and flatter with increasing age. This indicates that the fibrous layer produced in the later stages of growth, which is recommended by the literature to be the best material for geochemical analyses, has a different morphostructure and probably a lower organic content than that produced earlier in life.  In two species of the same genus living in seawater with different temperature and carbonate saturation state, a relationship emerged between the microstructure and environmental conditions. Fibres of the polar L. uva tend to be smaller, rounder and less convex than those of the temperate L. neozelanica, suggesting a relationship between microstructural size, shell organic matter content, ambient seawater temperature and calcite saturation state

Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations

The Permian/Triassic boundary approximately 251.9 million years ago marked the most severe environmental crisis identified in the geological record, which dictated the onwards course for the evolution of life. Magmatism from Siberian Traps is thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Here we present a new boron-isotope-derived seawater pH record from fossil brachiopod shells deposited on the Tethys shelf that demonstrates a substantial decline in seawater pH coeval with the onset of the mass extinction in the latest Permian. Combined with carbon isotope data, our results are integrated in a geochemical model that resolves the carbon cycle dynamics as well as the ocean redox conditions and nitrogen isotope turnover. We find that the initial ocean acidification was intimately linked to a large pulse of carbon degassing from the Siberian sill intrusions. We unravel the consequences of the greenhouse effect on the marine environment, and show how elevated sea surface temperatures, export production and nutrient input driven by increased rates of chemical weathering gave rise to widespread deoxygenation and sporadic sulfide poisoning of the oceans in the earliest Triassic. Our findings enable us to assemble a consistent biogeochemical reconstruction of the mechanisms that resulted in the largest Phanerozoic mass extinction

Human DDX3 protein is a valuable target to develop broad spectrum antiviral agents

Targeting a host factor essential for the replication of different viruses but not for the cells offers a higher genetic barrier to the development of resistance, may simplify therapy regimens for coinfections, and facilitates management of emerging viral diseases. DEADbox polypeptide 3 (DDX3) is a human host factor required for the replication of several DNA and RNA viruses, including some of the most challenging human pathogens currently circulating, such as HIV-1, Hepatitis C virus, Dengue virus, and West Nile virus. Herein, we showed for the first time, to our knowledge, that the inhibition of DDX3 by a small molecule could be successfully exploited for the development of a broad spectrum antiviral agent. In addition to the multiple antiviral activities, hit compound 16d retained full activity against drug-resistant HIV-1 strains in the absence of cellular toxicity. Pharmacokinetics and toxicity studies in rats confirmed a good safety profile and bioavailability of 16d. Thus, DDX3 is here validated as a valuable therapeutic target

Foreword 125-3 - Proceedings of the 8th International Brachiopod Congress

The 8 th International Brachiopod Congress took place in the prestigious venue of the University of Milano, Italy, in September 2018, after the previous edition held in Nanjing, China, in 2015. 150 participants from universities and research institutes from all over the world attended the meeting, from Argentina, Armenia, Austria, Belgium, Canada, China, Czech Republic, Denmark, France, Germany, Hungary, Iran, Israel, Italy, Japan, New Zealand, Poland, Russia, Slovakia, Spain, Sweden, United Kingdom, and United States of America

Strontium isotope stratigraphic insights on the end-Permian mass extinction and the Permian-Triassic boundary in the Dolomites (Italy)

The Dolomites (Southern Alps, Italy) is a most significant region to investigate the evolution of shallow-marine ecosystems during the end-Permian mass extinction (EPME). Shallow-marine ecosystems are complex places from an oceanographic viewpoint and combine high biological productivity and ecological diversity. Therefore, establishing the timing and correlation of globally recognisable events in this region are fundamental to interpreting the biological crisis that followed. We took advantage of the Strontium Isotope Stratigraphy (SIS) concept to correlate our stratigraphic succession, ranging from the upper Bellerophon (Bulla Member, upper Changhsingian) to the lower Werfen (Tesero Member, upper Changhsingian - lower Induan) Formations of the Dolomites, to the Meishan (Zhejiang Province, China), the Global Stratotype Section and Point (GSSP) for the Permian–Triassic boundary. We integrated new and previously published 87Sr/86Sr data from well preserved brachiopods and show that the topmost part of the Bellerophon Formation (the Bulla Member) correlates with beds 24 e-f of the GSSP section, while the Tesero Member, where the Permian-Triassic boundary is located, is characterised by more radiogenic Sr isotope ratios than expected. Differences in Sr isotope ratios may be due to small-scale variations in local paleoenvironmental and paleogeographic conditions/settings. Continental weathering of sedimentary or igneous rocks, distance from terrestrial environment and nearby occurrence of radiogenic rocks might also produce locally variable Sr isotope signatures especially in shallow water environments complicating the application of SIS principles

The paradox of the end Permian global oceanic anoxia

Geochemical results argue against global anoxia as a or the cause for the end Permian mass extinction. Instead, they suggest that the water column was oxic and sometimes the sediment pore water was suboxic, which is the norm. Anoxia, if present, may reflect local conditions developed in deep water settings, but that have to be supported by concrete and direct evidence