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Marine ecosystems are responsible for virtually all production of omega-3 (ω3) long-chain polyunsaturated fatty acids (PUFA), which are essential nutrients for vertebrates. Current consensus is that marine microbes account for this production, given their possession of key enzymes including methyl-end (or "ωx") desaturases. ωx desaturases have also been described in a small number of invertebrate animals, but their precise distribution has not been systematically explored. This study identifies 121 ωx desaturase sequences from 80 species within the Cnidaria, Rotifera, Mollusca, Annelida, and Arthropoda. Horizontal gene transfer has contributed to this hitherto unknown widespread distribution. Functional characterization of animal ωx desaturases provides evidence that multiple invertebrates have the ability to produce ω3 PUFA de novo and further biosynthesize ω3 long-chain PUFA. This finding represents a fundamental revision in our understanding of ω3 long-chain PUFA production in global food webs, by revealing that numerous widespread and abundant invertebrates have the endogenous capacity to make significant contributions beyond that coming from marine microbes. ; This work received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) funded by the Scottish Funding Council (grant reference HR09011), and their support is gratefully acknowledged. Access to the Institute of Aquaculture laboratories was funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262336 (AQUAEXCEL), Transnational Access Project Number 0095/06/03/13 ; Peer reviewed

Publisher's version (útgefin grein) ; Genomes are dynamic biological units, with processes of gene duplication and loss triggering evolutionary novelty. The mammalian skin provides a remarkable case study on the occurrence of adaptive morphological innovations. Skin sebaceous glands (SGs), for instance, emerged in the ancestor of mammals serving pivotal roles, such as lubrication, waterproofing, immunity, and thermoregulation, through the secretion of sebum, a complex mixture of various neutral lipids such as triacylglycerol, free fatty acids, wax esters, cholesterol, and squalene. Remarkably, SGs are absent in a few mammalian lineages, including the iconic Cetacea. We investigated the evolution of the key molecular components responsible for skin sebum production: Dgat2l6, Awat1, Awat2, Elovl3, Mogat3, and Fabp9. We show that all analyzed genes have been rendered nonfunctional in Cetacea species (toothed and baleen whales). Transcriptomic analysis, including a novel skin transcriptome from blue whale, supports gene inactivation. The conserved mutational pattern found in most analyzed genes, indicates that pseudogenization events took place prior to the diversification of modern Cetacea lineages. Genome and skin transcriptome analysis of the common hippopotamus highlighted the convergent loss of a subset of sebum-producing genes, notably Awat1 and Mogat3. Partial loss profiles were also detected in non-Cetacea aquatic mammals, such as the Florida manatee, and in terrestrial mammals displaying specialized skin phenotypes such as the African elephant, white rhinoceros and pig. Our findings reveal a unique landscape of "gene vestiges" in the Cetacea sebum-producing compartment, with limited gene loss observed in other mammalian lineages: suggestive of specific adaptations or specializations of skin lipids. ; This work was supported by Project No. 031342 cofinanced by COMPETE 2020, Portugal 2020 and the European Union through the ERDF, and by Fundac¸a~o para a Cie^ncia e a Tecnologia through national funds. R.R.F. thanks the Danish National Research Foundation for its support of the Center for Macroecology, Evolution, and Climate (grant DNRF96). We acknowledge the various Cetacea genome consortiums for genome sequencing and assemblies. We also thank Gısli Vikingsson at the Marine and Freshwater Research Institute in Iceland for lending us the Larsen gun and to North Sailing whale watching for the use of their zodiac. ; Peer Reviewed

Using a new fossil-calibrated mitogenome-based approach, we identified macroevolutionary shifts in mitochondrial gene order among the freshwater mussels (Unionoidea). We show that the early Mesozoic divergence of the two Unionoidea clades, Margaritiferidae and Unionidae, was accompanied by a synchronous split in the gene arrangement in the female mitogenome (i.e., gene orders MF1 and UF1). Our results suggest that this macroevolutionary jump was completed within a relatively short time interval (95% HPD 201–226 Ma) that coincided with the Triassic–Jurassic mass extinction. Both gene orders have persisted within these clades for ~200 Ma. The monophyly of the so-called "problematic" Gonideinae taxa was supported by all the inferred phylogenies in this study using, for the first time, the M- and F-type mitogenomes either singly or combined. Within Gonideinae, two additional splits in the gene order (UF1 to UF2, UF2 to UF3) occurred in the Mesozoic and have persisted for ~150 and ~100 Ma, respectively. Finally, the mitogenomic results suggest ancient connections between freshwater basins of East Asia and Europe near the Cretaceous–Paleogene boundary, probably via a continuous paleo-river system or along the Tethys coastal line, which are well supported by at least three independent but almost synchronous divergence events. ; The authors wish to thank the Editor and the three anonymous reviewers for helpful remarks and suggestions that improved the quality of the manuscript. This research was developed under ConBiomics: the missing approach for the Conservation of freshwater Bivalves Project N° NORTE-01-0145-FEDER-030286, cofinanced by COMPETE 2020, Portugal 2020 and the European Union through the ERDF, and by FCT through national funds (UID/Multi/04423/2019). FCT also supported MLL (SFRH/BD/115728/2016). The Russian Ministry of Education and Science (project no. 6.2343.2017/4.6), the Federal Agency for Scientific Organizations (project no. 0409-2015-0143), the Presidium of the Russian Academy of Sciences (scientific program no. 52), and the Russian Foundation for Basic Research, RFBR (project no. 17-45-290066) supported INB. Permits for fieldwork and sampling in Malaysia were issued by the Malaysian Ministry of Higher Education (FRGS/1/2015/WAB13/UNIM//1). ; info:eu-repo/semantics/publishedVersion

The decline of freshwater biodiversity hás reached alarming proportions. The extinction rate of freshwater biodiversity is predicted to be five times faster than ali other groups of species. The Unionidae, being the largest of the freshwater bivalve families, is among the most endangered group in the world. They are important providers of aquatic ecosystem services and are characterized by an unusual pattem of mtDNA inheritance. However, phylogeny, population genetic structure and species-level diversity remains unclear for much of the group. With an experienced and well-qualified team, the present proposal aims to define the most important freshwater mussel taxa and most criticai áreas for conservation, at European and Global leveis, to inform the most relevant policy niakers. This will be achieved by integrating a genomics approach with available distribution data, in order to determine and map global species richness, phylogenetic diversity, and weighted endemism. This complementary approach will not only help conserve this vulnerable group but will offer wider benefits to freshwater ecosystems whose billions of people depend globally. Additionally, as these animals have an extraordinary unusual pattern of mtDNA inheritance, they will be used as model-taxa to study the evolution of mtDNA and life in general. ; This research was developed under Project Nº NORTE-01-0145-FEDER-030286 (ConBiomics: the missing approach for the Conservation of freshwater Bivalves), co-financed by COMPETE 2020, Portugal 2020 and the European Union through the ERDF, and by FCT through national funds. ; info:eu-repo/semantics/publishedVersion