Search results

Echinoderms are marine water invertebrates that are represented by more than 7000 extant species, grouped in five classes and showing diverse morphologies (starfish, sea lilies, feather stars, sea urchins, sea cucumbers, brittle and basket stars). In an effort to further study their diversity, DNA barcodes (DNA fragments of the 5’ end of the cytochrome c oxidase subunit I gene, COI) have been used to complement morphological examination in identifying evolutionary lineages. Although divergent clusters of COI sequences were reported to generally match morphological species delineations, they also revealed some discrepancies, suggesting overlooked species, ecophenotypic variation or multiple COI lineages within one species. Here, we sequenced COI fragments of 312 shallow-water echinoderms of the East Coast of South Africa (KwaZulu-Natal Province) and compared morphological identifications with species delimitations obtained with four methods that are exclusively based on COI sequences. We identified a total of 103 morphospecies including 18 that did not exactly match described species. We also report 46 COI sequences that showed large divergences (>5% p-distances) with those available to date and publish the first COI sequences for 30 species. Our analyses also identified discordances between morphological identifications and COI-based species delimitations for a considerable proportion of the morphospecies studied here (49/103). For most of them, further investigation is necessary to keep a sound connection between taxonomy and the growing importance of DNA-based research.

During colonial times, Nile tilapia Oreochromis niloticus (Linnaeus, 1758) was introduced into non-native parts of the Congo Basin (Democratic Republic of the Congo, DRC) for the first time. Currently, it is the most farmed cichlid in the DRC, and is present throughout the Congo Basin. Although Nile tilapia has been reported as an invasive species, documentation of historical introductions into this basin and its consequences are scant. Here, we study the genetic consequences of these introductions by genotyping 213 Nile tilapia from native and introduced regions, focusing on the Congo Basin. Additionally, 48 specimensfrom 16 other tilapia species were included to test for hybridization. Using RAD sequencing (27,611 single nucleotide polymorphisms), we discovered genetic admixture with other tilapia species in several morphologically identified Nile tilapia from the Congo Basin, reflecting their ability to interbreed and the potential threat they pose to the genetic integrity of native tilapias. Nile tilapia populations from the Upper Congo and those from the Middle-Lower Congo are strongly differentiated. The former show genetic similarity to Nile tilapia from the White Nile, while specimens from the Benue Basin and Lake Kariba are similar to Nile tilapia from the Middle-Lower Congo, suggesting independent introductions using different sources. We conclude that the presence of Nile tilapia in the Congo Basin results from independent introductions, reflecting the dynamic aquaculture history, and that their introduction probably leads to genetic interactions with native tilapias, which could lower their fitness. We therefore urge avoiding further introductions of Nile tilapia in non-native regions and to use native tilapias in future aquaculture efforts.

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.

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