Vertebral microstructure marks the emergence of pelagic ichthyosaurs soon after the End Permian Mass Extinction

Ichthyosaurs were the first fully marine tetrapods, and evolved a streamlined body, flippers, live birth, and endothermy-like physiology. However, the transition to these adaptations and how it relates to divergence into ocean environments is ambiguous. Here, we use vertebral bone microstructure to document the first ontogenetic series of two Early Triassic taxa that include the oldest ichthyosaur foetal fossils. One series is from Grippia, an early ichthyopterygian with a small body, and limbs with some plesiomorphic features. The other is a large, contemporaneous ichthyosaur, Cymbospondylus. Together, they phylogenetically bracket the ichthyopterygian-ichthyosaurian transition. Grippia has a unique microstructure with a distinctive compacted outer layer, whereas Cymbospondylus vertebrae are cancellous throughout, indicating a different ecology and swimming style. The dissimilar distribution of woven-parallel complex in the histology between the two taxa indicates that growth progressed at different speeds. We also document birth lines in ichthyosaurs for the first time. Pelagic, tail-propelled, rapid-growing ichthyosaurs were thus present less than five million years after the End Permian mass extinction, alongside more anguilliform ichthyopterygians. These data capture the ecological and evolutionary transition from reptiles with eel-like swimming to whale-like ichthyosaurs, implying a paradigm shift in ecology and physiology that paved the way for ichthyosaur radiation

Element mobility during regional hydrothermal sodium and magnesium alteration: implications for ore formation in the Bergslagen ore district, Sweden

Ore-distal hydrothermal alteration zones are commonly suggested as a source of metals to ore-forming fluids. The Bergslagen ore district, Sweden exhibits extensive ore-proximal and ore-distal alterations and has been used as a typical locality for establishing the hydrothermal leaching model for volcanogenic massive sulphide (VMS) deposits. The ore-distal alteration in the region has been reported as depleted in ore-forming metals but robust mass change evaluations are lacking. Defining least-altered reference compositions is a major hurdle in Bergslagen due to compositional variation in the stratigraphy, extensive alteration, and high-grade metamorphic overprint. This study presents mass balance calculations for Na- and Mg-altered rocks in the Hällefors area using a set of systematically defined least-altered samples. Results show systematic mobility of light rare earth elements (LREE, here La-Eu; e.g., 80% of the Ce is mobilised during alteration which equates to 60 µg/g Ce), but no mobility of base metals. Precursor rock compositions have conspicuously low base metal concentrations (median: Zn 10 µg/g, Pb 2.5 µg/g; n = 13) compared to other volcanic centres in Bergslagen. Major base metal deposits occur in areas where least-altered volcanic rocks have higher base metal concentrations (e.g., Garpenberg; median: Zn 31.50 µg/g; Pb 11.75 µg/g; n = 10). The REE contents in least-altered rocks are relatively elevated in areas that host REE mineralisation such as the Riddarhyttan area. The results indicate that regional differences in metal fertility of the volcanic host succession may be a primary control on the metal enrichments, including REEs, occurring in the ore deposits throughout Bergslagen

Origins and diversity of Greenland’s Qimmit revealed with genomes of ancient and modern sled dogs

The Qimmeq (Greenland sled dog) has worked continuously with the Inuit in Greenland for more than 800 years. However, they now face drastic population declines caused by climate change, urbanization, and competition from snowmobiles. This study sequenced 92 modern and ancient genomes to investigate how centuries of isolation shaped the regional Qimmeq populations and the impact of European contact. We found distinct regional populations and evidence for two migrations of dogs into Greenland with the Inuit from Canada. Furthermore, we found that there is minimal European ancestry in present day Qimmit and limited recent inbreeding despite low heterozygosity. These insights are critical for conservation efforts aimed at preserving the Qimmit amid environmental changes and cultural transitions

Combining Individual‐Based Radio‐Tracking With Whole‐Genome Sequencing Data Reveals Candidate for Genetic Basis of Partial Migration in a Songbird

 Partial migration is a phenomenon where migratory and resident individuals of the same species co-exist within a population, and has been linked to both intrinsic (e.g., genetic) as well as environmental factors. Here we investigated the genomic architecture of partial migration in the common blackbird, a songbird that comprises resident populations in the southern distribution range, partial migratory populations in central Europe, and exclusively migratory populations in northern and eastern Europe. We generated whole-genome sequencing data for 60 individuals, each of which was phenotyped for migratory behavior using radio-telemetry tracking. These individuals were sampled across the species' distribution range, including resident populations (Spain and France), obligate migrants (Russia), and a partial migratory population with equal numbers of migratory and resident individuals in Germany. We estimated genetic differentiation (FST) of single-nucleotide variants (SNVs) in 2.5 kb windows between all possible population and migratory phenotype combinations, and focused our characterization on birds from the partial migratory population in Germany. Despite overall low differentiation within the partial migratory German population, we identified several outlier regions with elevated differentiation on four distinct chromosomes. The region with the highest relative and absolute differentiation was located on chromosome 9, overlapping PER2, which has previously been shown to be involved in the control of the circadian rhythm across vertebrates. While this region showed high levels of differentiation, no fixed variant could be identified, supporting the notion that a complex phenotype such as migratory behavior is likely controlled by a large number of genetic loci

A new species of Anthocotyle (Polyopisthocotyla: Discocotylidae) from the gills of the European hake Merluccius merluccius (Teleostei, Merlucciidae) with a revision of the composition of the genus

This study revisits the taxonomy of Anthocotyle merluccii, originally described from the European hake Merluccius merluccius in the northeast Atlantic, addressing discrepancies in clamp morphology across populations. The original description from Belgium noted near-equal anterior clamp sizes, contrasting with populations from Plymouth (Atlantic) and the Mediterranean, which show marked size differences, questioning their conspecificity. We describe A. radkeaminorum n. sp. from M. merluccius in the western Mediterranean (off Algeria), distinguished from A. merluccii (Belgium) by differing anterior clamp size, genital atrium spine number, and overall anterior clamp dimensions. Populations from Plymouth, previously attributed to A. merluccii, are herein assigned to A. aff. merluccii based on differences in morphometrical traits pending further investigations. Additionally, A. radkeaminorum n. sp. differs from A. americanus in body and clamp size, atrial spine count, and hosts. Based on analysis of morphological and molecular data, we refute the synonymy of A. merluccii and A. americanus, and we reinstate the latter as a valid species. The distinction between A. merluccii and A. americanus was further supported by divergence in cox1 gene sequences analyzed from GenBank (10–11%). Finally, inconsistencies in terminal lappet hook morphology are discussed, cautioning against its use in species delineation. This work highlights the need for continued research to resolve species relationships within this genus.Systematics and integrative taxonomy of Monogenea parasitizing fishes of Swede

An unexpected gills roommate from museum collections: description of a new species of Microcotyle Van Beneden & Hesse, 1863 (Mazocraeidea: Microcotylidae) from the ballan wrasse Labrus bergylta Ascanius (Teleostei, Labridae) off Sweden with novel data for Microcotyle donovani Van Beneden & Hesse, 1863

Natural history museums serve as vital repositories of biodiversity, offering extensive parasitological datasets crucial for taxonomical and ecological studies, supporting the work of taxonomists for conservation efforts, and natural system integrity. The Swedish Museum of Natural History (Stockholm, Sweden) houses a significant collection of parasitic Platyhelminthes, including unstudied material collected by Theodor Odhner. Herein, we provide novel morphometrical and anatomical data for Microcotyle donovani Van Beneden & Hesse, 1863, type species of Microcotyle Van Beneden & Hesse, 1863 from the type-host Labrus bergylta off Sweden, Northeast Atlantic, and we describe M. odhnaturiks n. sp. from the gills of L. bergylta off Sweden, both found in T. Odhner’s collection. Microcotyle odhnaturiks n. sp. differed from Microcotyle spp. from Atlantic waters and labrid hosts by morphometrical (number and size of clamps, number of rows of testes) and anatomical characters (extension of the caeca, organization of the germarium). An anatomical comparison, particularly of the ovarian region, indicates significant differences between M. odhnaturiks n. sp., M. donovani, and other Microcotyle species, confirming the presence of two distinct Microcotyle species on L. bergylta. Microcotyle odhnaturiks n. sp. was differentiated from M. donovani by having a complex, inverted question mark–shaped germarium, caeca not confluent posteriorly, and by lacking conical expansions on rims of buccal suckers, among other features. The discovery raises the number of Microcotyle species parasitizing labrid fishes to four and marks the first Microcotyle species reported from Sweden and Scandinavian waters. We also discuss hosts and distribution of Microcotyle spp. in Atlantic waters.Systematics and integrative taxonomy of Monogenea parasitizing fishes of Swede

Properties of inflowing Pacific and Atlantic water govern total and methylated mercury profiles in the Arctic Ocean

High methylmercury (MeHg) concentrations in Arctic marine biota have been linked to high MeHg uptake driven by shallow MeHg peaks at water depths of 100–300 m in the Arctic Ocean. To understand how the biogeochemical characteristics of each basin affects the distribution of total Hg (THg) and MeHg across the Arctic Ocean, the spatial patterns of THg and MeHg were investigated using data from new transects in the Beaufort Sea (BS) and previously published Arctic Ocean expeditions covering the Canada Basin and Makarov Basin in the Pacific sector, and Amundsen Basin and Nansen Basin in the Atlantic sector. In the BS, the THg concentration in the polar mixed water increased with salinity (r = 0.87, p < 0.01), which was linked to THg transport from the Chukchi Shelf. Transport of Hg from the Chukchi Shelf also drove elevated THg concentrations in the polar mixed water and halocline water in the Canada Basin and Makarov Basin compared to other Arctic basins. The MeHg concentration in the BS was positively correlated with the biological index in the Pacific summer water (r = 0.86, p < 0.01), demonstrating that intrusion of warm and nutrient-rich Pacific water promotes MeHg production in the BS. In line with this result, chlorophyll-a showed a comparable cross-basin trend to that of MeHg, with the highest values in the Nansen Basin. In the halocline water, MeHg concentrations were highest in the Canada Basin likely due to the largest availability of Hg(II). On the contrary, MeHg concentration was highest in the Nansen Basin in the Atlantic water layer, which could be related to the higher seawater temperature and enhanced biological production. The results of this study underscore the critical role of Pacific and Atlantic inflows in modulating the profiles of THg and MeHg in the Arctic Ocean