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Despite the commercial importance of Greenland Halibut (Reinhardtius hippoglossoides), important gaps still persist in our knowledge of this species, including its reproductive biology and sex determination mechanism. In this study, we combined single molecule sequencing of long reads (Pacific Sciences) with Chromatin Conformation Capture sequencing (Hi-C) data to provide the first chromosome-level genome reference for this species. The high-quality assembly encompassed more than 598 Megabases (Mb) assigned to 1 594 scaffolds (scaffold N50 = 25 Mb) with 96 % of its total length distributed among 24 chromosomes. The investigation of its syntenic relationships with other economically important flatfish species revealed a high conservation of synteny blocks among members of this phylogenetic clade. Sex determination analysis revealed that flatfishes do not escape the rule applied to other teleost fish and exhibit a high level of plasticity and turnover in sex-determination mechanisms. A whole-genome sequence analysis of 198 individuals allowed us to draw a full picture of the molecular sex determination (SD) system for Greenland Halibut, revealing that this species possesses a very nascent male heterogametic XY system, with a putative major effect of the sox2 gene, also described as the main SD driver in two other flatfishes. Interestingly, our study also suggested for the first time in flatfishes that a putative Y-autosomal fusion could be associated with a reduction of recombination typical of early steps of sex chromosome evolution.

International audience; The Arctic is undergoing widespread warming. In order to understand the impact of climate change on Arctic marine food webs, we studied the at-sea distribution of foraging little auks in contrasting conditions of the Greenland Sea. While the eastern side of the Greenland Sea has experienced recent warming, the western side is still dominated by cold, Arctic water in the East Greenland Current. We hypothesized that foraging little auks would be found in greatest abundance in cold Arctic waters bearing more lipid-rich prey, allowing them to deliver more energy-rich food to their chicks. To test our hypotheses, we made ship-borne bird observations and zooplankton tows, as well as analyses of chick meals at 2 little auk colonies adjacent to 3 distinct water masses in the Greenland Sea. Associated with the coldest water in the East Greenland Current, we found the highest concentrations of large Calanus copepods (C. glacialis and C. hyperboreus), as well as the highest concentrations of foraging little auks, indicating a relationship that is likely to be disrupted by increasing water temperatures. To assess potential future impacts of ocean warming, we used a coupled atmosphere-ocean global climate model (AOGCM) to predict Greenland Sea sea-surface temperatures over the study area at the end of the 21st century. Our results suggest that 4 of 8 little auk breeding colonies in the North Atlantic may be negatively impacted as temperatures exceed the thermal preferenda of large Calanus, which is the preferred prey of little auks during the breeding season

The Atlantic sector of the Arctic is currently undergoing large-scale changes in the distribution of water masses in response to the pronounced positive values of the North Atlantic Oscillation. As a consequence the area surrounding little auk Alle alle colonies on Svalbard has experienced an increase in the inflow of Atlantic water. In this study, the influence of water mass dis- tribution on the foraging ecology of little auks was examined through simultaneous measurements made at colonies in Hornsund Fiord (77° 03' N, 15° 10' E) and at sea. In the colony we measured chick diets, while at sea, we assessed the distribution of foraging little auks and the zooplankton available to them within different water masses. Our results indicate that little auks feed mainly on the large copepod Calanus glacialis. They restrict their foraging activity to Arctic water that contains this cope- pod and avoid Atlantic water that contains a smaller copepod, C. finmarchicus. Little auks breeding on Svalbard may be impacted by climate change because during years when the flow of Atlantic water increases, they may be forced to forage in areas with sub-optimal conditions.

Sponges (phylum Porifera) are benthic filter-feeding animals that play an important role in nutrient cycling and habitat provision in the deep sea. Sponges collected between 2010 and 2014 during annual multispecies trawl surveys conducted by Fisheries and Oceans Canada (DFO) in Baffin Bay, Davis Strait and portions of Hudson Strait were taxonomically examined. In total ~2500 specimens were identified, comprising over 100 sponge taxa. Sponges from the order Poecilosclerida comprised nearly half the identified species. This report summarizes sponges from the family Dendoricellidae (class Demospongiae, subclass Heteroscleromorpha, order Poecilosclerida) and family Tedaniidae (class Demospongiae, subclass Heteroscleromorpha, order Poecilosclerida). A total of six species are described, from genera Dendoricella (Dendoricellidae) and Tedania (Tedaniidae). These species are: Dendoricella flabelliformis, Dendoricella cf. flabelliformis, Dendoricella aff. flabelliformis, Dendoricella sp. 1, Tedania (Tedania) suctoria, and Tedania sp. 1. Descriptions include morphological and spicule descriptions, spicule dimensions, and taxonomic discussion. Les éponges (phylum Porifera) sont des animaux filtreurs benthiques qui jouent un rôle important dans le cycle des éléments nutritifs et la production d’habitats dans les profondeurs de la mer. Les éponges recueillies au cours des relevés plurispécifiques annuels au chalut entre 2010 et 2014 effectués par Pêches et Océans Canada (MPO) dans la baie de Baffin, le détroit de Davis et certaines parties du détroit d'Hudson ont été examinées sur le plan taxonomique. Au total, 2 500 spécimens ont été identifiés, et ceux-ci représentaient plus de 100 taxons d'éponges. Presque la moitié des espèces recensées étaient de l'ordre Poecilosclerida. Le présent rapport fait état des éponges appartenant à la famille Dendoricellidae (classe Demospongiae, sous-classe Heteroscleromorpha, ordre Poecilosclerida) et à la famille Tedaniidae (classe Demospongiae, sous-classe Heteroscleromorpha, ordre Poecilosclerida). En tout, six espèces des genres Dendoricella (Dendoricellidae) et Tedania (Tedaniidae) sont décrites. Il s'agit des suivantes : Dendoricella flabelliformis, Dendoricella cf. flabelliformis, Dendoricella aff. flabelliformis, Dendoricella sp. 1, Tedania (Tedania) suctoria et Tedania sp. 1. Les descriptions portent sur les éléments morphologiques et comprennent des détails descriptifs et dimensionnels sur les spicules ainsi que des observations sur les aspects taxinomiques.

Sponges (phylum Porifera) are benthic filter-feeding animals that play an important role in nutrient cycling and habitat provision in the deep sea. Sponges collected between 2010 and 2014 during annual multispecies trawl surveys conducted by Fisheries and Oceans Canada (DFO) in Baffin Bay, Davis Strait and portions of Hudson Strait were taxonomically examined. In total ~2500 specimens were identified, comprising over 100 sponge taxa. Sponges from the order Poecilosclerida comprised nearly half the identified species. This report summarizes sponges from the family Dendoricellidae (class Demospongiae, subclass Heteroscleromorpha, order Poecilosclerida) and family Tedaniidae (class Demospongiae, subclass Heteroscleromorpha, order Poecilosclerida). A total of six species are described, from genera Dendoricella (Dendoricellidae) and Tedania (Tedaniidae). These species are: Dendoricella flabelliformis, Dendoricella cf. flabelliformis, Dendoricella aff. flabelliformis, Dendoricella sp. 1, Tedania (Tedania) suctoria, and Tedania sp. 1. Descriptions include morphological and spicule descriptions, spicule dimensions, and taxonomic discussion. Les éponges (phylum Porifera) sont des animaux filtreurs benthiques qui jouent un rôle important dans le cycle des éléments nutritifs et la production d’habitats dans les profondeurs de la mer. Les éponges recueillies au cours des relevés plurispécifiques annuels au chalut entre 2010 et 2014 effectués par Pêches et Océans Canada (MPO) dans la baie de Baffin, le détroit de Davis et certaines parties du détroit d'Hudson ont été examinées sur le plan taxonomique. Au total, 2 500 spécimens ont été identifiés, et ceux-ci représentaient plus de 100 taxons d'éponges. Presque la moitié des espèces recensées étaient de l'ordre Poecilosclerida. Le présent rapport fait état des éponges appartenant à la famille Dendoricellidae (classe Demospongiae, sous-classe Heteroscleromorpha, ordre Poecilosclerida) et à la famille Tedaniidae (classe Demospongiae, sous-classe Heteroscleromorpha, ordre Poecilosclerida). En tout, six espèces des genres Dendoricella (Dendoricellidae) et Tedania (Tedaniidae) sont décrites. Il s'agit des suivantes : Dendoricella flabelliformis, Dendoricella cf. flabelliformis, Dendoricella aff. flabelliformis, Dendoricella sp. 1, Tedania (Tedania) suctoria et Tedania sp. 1. Les descriptions portent sur les éléments morphologiques et comprennent des détails descriptifs et dimensionnels sur les spicules ainsi que des observations sur les aspects taxinomiques., ACKNOWLEDGEMENTS. This project was funded by Fisheries and Oceans, Canada's International Governance Strategy (IGS) Research Fund to EK, through the project "Identification and Mapping through Predictive Modelling of Coldwater Coral and Sponge Species in the Sub-Arctic/Eastern Arctic" which ran from April 2014 to March 2017. This report was produced through the project "SponGES - Deep-sea Sponge Grounds Ecosystems of the North Atlantic: an integrated approach towards their preservation and sustainable exploitation" program, under H2020 - the EU Framework Programme for Research and Innovation (Grant Agreement no. 679849). We thank Cam Lirette (BIO) for his help in organizing the data and producing map templates to produce figures from, Emilie Pothier for ArcGIS assistance, and Lindsay Beazley and Dr. Javier Murillo for their review of an earlier draft of this manuscript.