Search results

Introduction: The meteorite classification processes require a sequence of semi-destructive to destructive analyses to elucidate the internal texture and chemical composition of the sample. Several methods have been proposed for classifying meteorites using a non-destructive approach such as magnetic susceptibility [1] or 3D petrographic analysis [2]. Specimens with unique orientation forms such as cone or shield-shaped, are often prioritized for non-destructive classification due to their significant exhibition value and insight into the aerodynamics of extraterrestrial material during their atmospheric entrance [3,4]. In this study, we present a description employing non-destructive analysis to classify a newly found flattened shield-shaped Antarctic meteorite discovered during the Belgian meteorite reconnaissance expedition 2022-2023 in the Sør Rondane area, East Antarctica [5]. This approach promises to provide detailed internal structural and information on physical properties without compromising the integrity of the sample. Methods: We utilized the X-ray Computed Tomography (XCT) RX Solutions EasyTom150 device at the Institute of Natural Sciences (Brussels, Belgique) to analyze the sample with dimensions of 37.1 mm x 44.0 mm x 52.6 mm (Fig. 1). A copper filter of 0.4 mm was used. The sample was scanned at a voxel size of 58.2 μm using the large focal spot mode at 145 kV, 38 W and 260 μA. We employed the program 3D Slicer [6] to analyze the three-dimensional properties and calculate the physical parameters. Additionally, magnetic susceptibility measurements were conducted on the field using an SM30 instrument. Preliminary results: Various forms of deformation, notably radial extension features, were detected, likely indicative of shock experiences undergone by the sample before entering the Earth’s atmosphere, hence corroborating its extraterrestrial origin (Fig. 1). Preliminary magnetic susceptibility measurement on the field indicated a value typical of L chondrites (log χ ~ 4.7 [5]). The interior XCT slices reveal that the sample comprises a dense metallic phase with few non-metallic inclusions, primarily located on the face opposite to the entry direction (red arrow in Fig. 1b). The total volume measures 22.09 cm3, with a corresponding mass of 151.1 g, indicating a meteorite bulk density of 6.8 g cm-3 comparable to iron meteorites (bulk density between 7 and 8 g cm-3 [7]). This is at odds with the preliminary magnetic susceptibility measurement. Additional non-destructive analyzes will be needed, notably μ-XRF measurements to offer a better comprehension of the origin of the sample. This underlines the difficulty of classifying a sample in a non-destructive manner

In February 1971, a meteorite fell on the roof of a barn belonging to Mr. E. Schmitz in Tintigny, a village in southern Belgium. Upon its recovery, its meteoritic origin was confirmed by the schoolteacher, Mr. A. Rossignon who then looked after the sample. In 2017, for the first time, the meteorite was given to specialists for a detailed examina-tion and classification. We used various analytical techniques to characterize its mineralogy, elemental, and isotopic composition. Based on the obtained data, we classified it as a polymict eucrite, a meteorite originating from 4 Vesta, and named it Tintigny [1]. Tintigny is partly covered by shiny black fusion crust. Its interior mainly exhibits a light grey color and shows a brecciated texture composed of a fine-grained matrix, hosting darker crystals and cm-sized dark grey clasts. Under the microscope, a brecciated sub-ophitic basaltic texture mainly composed of plagioclase/maskelynite and clinopy-roxene is dominant. In addition to the dominant sub-ophitic texture, at least three distinct textures exposed in clasts are observable. At least two generations of shock effects (such as fractures), are present in the sample: those limited to clasts and large crystals, and those that crosscut both the large grains and the matrix. The accessory minerals include troilite, ilmenite, chromite, FeNi metal, and silica. Mineral chemistry calculations of pyroxene end-members show ranges from 8.5 to 60.7 mol% for enstatite, 30.1–70.0 mol% for ferrosilite, and 2.6–38.4 mol% for wollastonite. Based on these values, most pyroxenes in Tintigny are pigeonite and augite [2]. The Fe/Mn ratios of pyroxenes range from 27.1 to 39.3, with the highest ratio observed in pyroxene from the symplectitic clast. Fe/Mn and Fe/Mg ratios in low-Ca pyroxene (Wo<10) are 30.2±4.4 and 0.8±0.3, respectively. These ratios in high-Ca pyroxene (n=8) are 34.3±3.7 for Fe/Mn and 2.6±2.4 for Fe/Mg. The average pyroxene Fe/Mn ratio for all pyroxene is 32.5±4.4 (SD, n=14). Fe/Mg ranges from 0.6 to 8.2, with an average value of 1.8±2.0 (SD, n±14). Considering pyroxene Fe/Mn ranges of 40±11, 62±18, 32±6, and 30±2 for basaltic rocks from the Earth, Moon, Mars, and 4 Vesta (eucrites), respectively, and based on our data, particularly those of low-Ca py-roxene, Tintigny falls in the range of basaltic eucrites [3]. The bulk rock Fe/Mn and Fe/Mg ratios of Tintigny are 33.9 and 3.1, respectively. These values overlap with those measured for howardite-eucrite-diogenite (HED) and martian meteorites [4]. With a Ga/Al ratio of 4.17×10-5, Tintigny falls within the range of those of eucrites. Using the CI-normalized elemental concentration, we can see strong simi-larities between Tintigny and noncumulate eucrites, which is also reflected based on the abundance of TiO2 (0.63) and FeO/MgO ratio (2.66) in Tintigny. The bulk oxygen isotopic composition of Tintigny, as determined by laser fluorination, is also consistent with it being an HED (δ17O=1.72±0.04 ‰; δ18O=3.76±0.08‰; Δ17O=-0.25±0.01 ‰ (n=2, errors 2SD)), with a composition that plots close to the Eucrite Fractionation Line [5]. Based on the Meteoritical Bulletin Database, only 70 HED falls have been reported so far. Including Tintigny, only 39 eucrite falls are known to date, 11 of them occurred in Europe, with Tintigny being the only one from Belgium. In addition to the scientific importance of studying a eucrite fall like Tintigny, we emphasize the significance of the discovery of a historical meteorite fall by drawing attention to national scientific heritage that must be properly un-derstood and safeguarded for generations of scientists, scholars, and amateurs to come. Nowadays, together with four other meteorites from Belgium (Hautes Fagnes LL5, Lesves L6, St. Denis Westrem L6, and Tourinnes-la-Grosse L6), the Tintigny achondrite is exhibited in the meteorite gallery of the Institute of Nat-ural Sciences in Brussels and is open to the public for visits.

Cryptic diversity among deep-sea malacostracans is increasingly unveiled through molecular analyses, helping to reassess biodiversity in abyssal and hadal zones and establish baselines before inevitable mineral exploitation. Cryptic diversity, which is the presence of morphologically similar but genetically distinct lineages within what appears as a single species, is marked by genetic variation, structured populations, and high differentiation among geographically distant populations, often isolated over evolutionary timescales. Although cryptic diversity is prevalent in Lyssianassoidea amphipods, Abyssorchomene distinctus emerges as an exception. Analysing mitochondrial COI and nuclear 28S genes from 373 specimens across three ocean basins, we observed no cryptic diversity in A. distinctus. Instead, our results indicate a single, widely distributed population spanning ~24,000 km across the Southeastern Indian and Northeastern Pacific Oceans. Evidence includes a predominant ancestral haplotype in a star-shaped COI network, a skewed nucleotide mismatch distribution, and deviations from neutrality tests, all suggesting a unique population expansion event. This finding positions A. distinctus as one of only five known deep-sea amphipod species with confirmed wide cross-ocean distribution. To explore if this genetic pattern extends to other Lyssianassoidea amphipods, we are conducting similar analyses on Orchomenella pinguides, a circumpolar Antarctic species with minimal prior genetic characterization. Our preliminary study includes 48 specimens from the Ronne Ice Shelf, examining COI and 28S genes to assess genetic structure, cryptic diversity, and intra-specific variation. We plan to expand our sample size to compare genetic differentiation between populations from the Ronne Ice Shelf and publicly available COI sequences databases from the Australian Antarctic Territory, and Southeastern Filchner area in the Weddell Sea.

The African clawed frog (Xenopus laevis) is an aquatic invasive species of amphibian imported from South Africa for medical research and aquarium pet trade. Released on purpose or by accident, an invasive spread of Xenopus laevis to natural ecosystems was registered on most continents. In the absence of natural predators, their population densities can increase quickly causing damage to local aquatic ecosystems. Using external morphology of adults and tadpoles, osteology from high-resolution microcomputed tomography, vocalization analysis and DNA sequence data, this study assessed the identity of a reproducing Belgian Xenopus population at the current northernmost edge of the distribution of the genus in Europe. Morphological analysis of adult and tadpoles confirms that the Xenopus population from Comines-Warneton belongs to the species Xenopus laevis. Genetic analysis indicates two phylogeographic lineages of South African origin invading France, one originating from northern South Africa and Rooikrantz Dam and the other originating from the southwestern Cape. Given the relative isolation of the Belgian pond, the abundance of Xenopus laevis in the pond, and the presence of tadpoles as well as subadults and large adults, it is certain that X. laevis has been present since several years. Most likely surrounding streams and ponds are also housing them and the area needs to be monitored closely in the future to prevent further spread. Citation: Pauwels, O.S.G., Brecko, J., Baeghe, D., Venderickx, J., Backeljau, T. & Vanderheyden, A. 2024. Morphological, acoustic and genetic identification of a reproducing population of the invasive African clawed frog Xenopus laevis (Anura, Pipidae) recently discovered in Belgium. Abstract 248 in: ICAIS 2024 Abstracts of Presentations. 23rd International Conference on Aquatic Invasive Species, May 12-16, Halifax, Canada.

Brazil occupies almost half of the surface area of South America and covers different climatic zones, which leads to great ecological diversifications, forming distinct biogeographical areas or biomes. This reflects the megadiversity of Brazilian flora and fauna, including the high level of endemism. A literature review in 1994 recorded 260 species in 53 genera of recent non-marine ostracods from the South America (MARTENS & BEHEN, 1994). Of these, 91 species in 32 genera occurred in Brazil according to a 1998 checklist (MARTENS et al., 1998). Here, we present the results of recent inventories of freshwater ostracods from Brazil, including an overview of the geographical distribution of species. The expeditions of the PELD (Long-term Ecological Research Program in the Upper Paraná River Floodplain) and SISBIOTA (National Biodiversity Research System program - carried out in four Brazilian floodplains), increased these numbers to 133 species in 41 genera, including the descriptions of 31 new species in nine new genera (e.g. FERREIRA et al., 2020; ALMEIDA et al., 2023). The highest richness of ostracods has been found in the Atlantic Forest biome, which includes the upper Paraná River floodplain. The Amazon biome, where the Amazon floodplain is located, had the lowest diversity of ostracods but has also received much less attention in recent decades: the upper Paraná River floodplain has almost continuously been monitored since 2004, while only two (2011 and 2012), relatively short, collecting trips have been made in the Amazon floodplain. Thus, these results emphasize the relevance of long-term biodiversity monitoring studies. In addition, our results show that there is still little knowledge about the biodiversity of Brazilian ostracods, given that extensive areas remain unexplored.

Polar ecosystems harbour a unique cold-adapted biodiversity that is threatened by rapid environmental change and increasing anthropogenic impact. In this context, multi-scale data on connectivity and adaptation are essential for supporting exploitation and conservation management of living resources and ecosystems. Notably, marine protected areas are most effective if implemented as a network that considers functional diversity and connectivity within and between species. In the present study, 607 individuals of ten Trematomus species were sequenced using ddRAD sequencing techniques. Thousands of genomic variants were used to investigate inter- and intraspecific patterns of divergence and connectivity across the Southern Ocean shelf. Moreover, genomic SNPs that showed evidence of selection (“outlier loci”) were used to explore potential local adaptation of the populations to different environmental conditions. Population structure analyses of four different species (T. loennbergii, T. eulepidotus, T. scotti and T. newnesi) suggest long- range dispersal across the Weddell Sea and even along the entire West Antarctic coast that might be facilitated by the Weddell Sea Gyre and Antarctic Coastal current. A genetic break at the level of the Filchner Trough was observed in several species. The strong outflow from the Filchner-Ronne ice shelf may separate the trough area from the remaining Weddell Sea habitat. Finally, results suggest that previously undetected cryptic diversity may be present within T. eulepidotus and T. loennbergii. Altogether, the present results contribute to the assessment of diversity, connectivity and adaptation on the Southern Ocean shelf, which is imperative in view of unprecedented global change.

The unique cold-adapted ecosystems of the Southern Ocean are threatened by rapid environmental change and increasing anthropogenic impact. Marine protected areas (MPAs), areas of ocean where human activities are limited or prohibited, have been increasingly promoted as a tool for mitigating ocean threats and conserving biodiversity. National governments and the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is progressing towards establishing a representative network of MPAs in the Southern Ocean. Connectivity is now widely recognized to be a crucial variable for the design and management of MPA networks through the effects that movements of individuals and genes have on population viability, metapopulation persistence, and resilience to disturbance. The understanding of connectivity patterns is required to prioritize the allocation of conservation effort towards, for instance, areas acting as central connection nodes in a network of MPAs. The COPE project aims to advance the understanding of genetic connectivity and adaptation in key benthic and pelagic Antarctic organisms (crustaceans and actinopterygian fishes) using population genomic approaches (ddRAD sequencing). Thousands of genomic variants were used in two model genera, the Charcotia amphipod and the Trematomus fishes, to provide estimates of neutral and adaptive genetic variation and structure at different trophic levels and at a circumpolar scale. The results of the COPE project will contribute to our understanding of the spatial and functional distribution of biological variation in the Southern Ocean, required to develop suitable management and conservation strategies through CCAMLR.

Polar ecosystems harbour a unique cold-adapted biodiversity that is threatened by rapid environmental change and increasing anthropogenic impact. In this context, collecting data on connectivity between populations is essential for supporting conservation management of living resources and ecosystems. Genetic connectivity is the extent to which populations in different parts of a species' geographical range are linked by the exchange of larvae, juveniles or adults (which are the vectors of genetic material). In the Southern Ocean, several Marine Protected Areas (MPAs) – large areas where human activities are restricted or prohibited to promote conservation – are established or under negotiations. Such MPAs are most effective if implemented as a network that considers genetic diversity and connectivity within and between species. In the present study, 607 individuals of ten Trematomus species were sequenced using reduced representation sequencing techniques. Thousands of genomic variants were used to investigate inter- and intraspecific patterns of divergence and connectivity across the Southern Ocean shelf. Population structure analyses of four different species (T. loennbergii, T. eulepidotus, T. scotti and T. newnesi) suggest long- range dispersal across the Weddell Sea and even along the entire West Antarctic coast that might be facilitated by the Weddell Sea Gyre and Antarctic Coastal current. A genetic break at the level of the Filchner Trough was observed in several species. The strong outflow from the Filchner-Ronne ice shelf may separate the trough area from the remaining Weddell Sea habitat. Finally, results suggest that previously undetected cryptic species may be present within both T. eulepidotus and T. loennbergii. Altogether, the present results contribute to the assessment of diversity and connectivity on the Southern Ocean shelf, which is imperative in view of unprecedented global change.

Around 40 million years ago, Antarctica’s geographic isolation led to a dramatic cooling of its marine shelf, causing many lineages to go extinct whilst others adapted and flourished. Among the successful ones is the amphipod family Iphimediidae. Here, we apply advanced phylogenetic, comparative, and morphometric methods to explore the evolutionary processes which generated the exceptional diversity of this clade. To this purpose, three types of data were collected: (1) a novel phylogeny of the family was reconstructed from a multigene molecular dataset, (2) 3D shape data were obtained by applying geometric morphometric methods on micro-CT scans, and (3) stable isotope ratios (δ13C and δ15N) were measured and used as proxy for trophic ecology. First, possible evolutionary correlations between mouthpart shapes and stable isotope ratios were examined. Significant correlations suggest that mouthpart shapes are adapted to the food source. Second, species boundaries were investigated using a combination of DNA-based delimitation methods and detailed morphological/morphometric analyses, revealing that Iphimediidae species diversity is greatly underestimated. Most described species were found to be complexes of multiple, morphologically similar species. Finally, changes in lineage diversification rates were explored alongside the evolution of morphological traits. Late bursts of lineage diversification (appr. 7-3 Mya) combined with a late partitioning of mouthparts’ shape diversity might result from the invasion of novel ecological niches. Plio-Pleistocene glacial cycles, which have been hypothesized to act as a diversity pump, might also have promoted such late diversification events in Antarctic iphimediids. This integrative approach, applied here for the first time in Antarctic invertebrates, enhances our understanding of the evolutionary dynamics shaping Antarctic shelf biodiversity.