Long chain polyunsaturated fatty acid synthesis in a marine vertebrate: Ontogenetic and nutritional regulation of a fatty acyl desaturase with Delta4 activity

Solea senegalensis is an unusual marine teleost as it has very low dietary requirement for long-chain polyunsaturated fatty acids (LC-PUFA) during early development. Aquaculture is rapidly becoming the main source of health-beneficial fish products for human consumption. This, associated with limited supply of LC-PUFA-rich ingredients for fish feeds, render S. senegalensis a highly interesting species in which to study the LC-PUFA biosynthesis pathway. We have cloned and functionally characterized fatty acyl desaturase and elongase cDNAs corresponding to D4fad (with some D5 activity for the n-3 series) and elovl5 with the potential to catalyze docosahexaenoic acid (DHA) biosynthesis from eicosapentaenoic acid (EPA). Changes in expression of both transcripts were determined during embryonic and early larval development, and transcriptional regulation in response to higher or lower dietary n-3 LC-PUFA was assessed during larval and post-larval stages. There was a marked pattern of regulation during early ontogenesis, with both transcripts showing peak expression coinciding with the start of exogenous feeding. Although elovl5 transcripts were present in fertilized eggs, D4fad only appeared at hatching. However, eggs have high proportions of DHA (~ 20%) and high DHA/EPA ratio (~ 11) to meet the high demands for early embryonic development. The fatty acid profile of larvae after the start of exogenous feeding closely reflected dietary composition. Nonetheless, D4fad was significantly up-regulated in response to LC-PUFA-poor diets, which may suggest biological relevance of this pathway in reducing LC-PUFA dietary requirements in this species, compared to other marine teleosts. These results indicate that sole is capable of synthesizing DHA from EPA through a Sprecher-independent pathway

Macrofaunal ecology of sedimented hydrothermal vents in the Bransfield Strait, Antarctica

Sediment-hosted hydrothermal vents, where hot, mineral-rich water flows through sediment, are poorly understood globally, both in their distribution and the ecology of individual vent fields. We explored macrofaunal community ecology at a sediment-hosted hydrothermal vent in the Southern Ocean. This is the first such study of these ecosystems outside of the Pacific and the furthest south (62˚S) of any vent system studied. Sedimentary fauna were sampled at four sites in the Bransfield Strait (Southern Ocean), with the aim of contrasting community structure between vent and non-vent sites. Geochemical data were used to create and test a novel proxy index to quantify the degree of hydrothermal influence and its influence on deep-sea biota. Macrofaunal communities were clearly distinct between vent and non-vent sites, and diversity, richness and density declined towards maximum hydrothermal activity. This variation is in contrast to observations from similar systems in the Pacific and demonstrates the influence of factors other than chemosynthetic primary productivity in structuring infauna at deep-sea vent communities. Vent endemic fauna had limited abundance and were represented by a single siboglinid species at hydrothermally active areas, meaning that that the majority of local biota were those also found in other areas. Several taxa occupied all sampling stations but there were large differences in their relative abundances, suggesting communities were structured by niche variation rather than dispersal ability

Paleocene methane seep and wood-fall marine environments from Spitsbergen, Svalbard

A recently discovered Paleocene seep locality from Fossildalen on Spitsbergen, Svalbard, is described. This is one of a very few seep communities of the latest Cretaceous–earliest Palaeogene age, and the best preserved Paleocene seep community known so far. The seep carbonates and associated fossils have been first identified in museum collections, and subsequently sampled in the field. The carbonates are exclusively ex-situ and come from the offshore siltstones of the Basilika Formation. Isotopically light composition (δ13C values approaching -50‰ V-PDB), and characteristic petrographic textures of the carbonates combined with the isotopically light archaeal lipid are consistent with the formation at fossil hydrocarbon seep. The invertebrate fauna associated with the carbonates is of moderate diversity (16 species) and has a shallow water affinity. It contains a species of the thyasirid genus Conchocele, common in other seeps of that age. The finding sheds new light onto the history of seepage on Svalbard, and onto the evolution and ecology of seep faunas during the latest Cretaceous–earliest Palaeogene time interval

Ecology and Biogeography of Free-Living Nematodes Associated with Chemosynthetic Environments in the Deep Sea: A Review

Background: Here, insight is provided into the present knowledge on free-living nematodes associated with chemosynthetic environments in the deep sea. It was investigated if the same trends of high standing stock, low diversity, and the dominance of a specialized fauna, as observed for macro-invertebrates, are also present in the nematodes in both vents and seeps. Methodology: This review is based on existing literature, in combination with integrated analysis of datasets, obtained through the Census of Marine Life program on Biogeography of Deep-Water Chemosynthetic Ecosystems (ChEss). Findings: Nematodes are often thriving in the sulphidic sediments of deep cold seeps, with standing stock values ocassionaly exceeding largely the numbers at background sites. Vents seem not characterized by elevated densities. Both chemosynthetic driven ecosystems are showing low nematode diversity, and high dominance of single species. Genera richness seems inversely correlated to vent and seep fluid emissions, associated with distinct habitat types. Deep-sea cold seeps and hydrothermal vents are, however, highly dissimilar in terms of community composition and dominant taxa. There is no unique affinity of particular nematode taxa with seeps or vents. Conclusions: It seems that shallow water relatives, rather than typical deep-sea taxa, have successfully colonized the reduced sediments of seeps at large water depth. For vents, the taxonomic similarity with adjacent regular sediments is much higher, supporting rather the importance of local adaptation, than that of long distance distribution. Likely the ephemeral nature of vents, its long distance offshore and the absence of pelagic transport mechanisms, have prevented so far the establishment of a successful and typical vent nematode fauna. Some future perspectives in meiofauna research are provided in order to get a more integrated picture of vent and seep biological processes, including all components of the marine ecosystem

La variation du genre en vieil-anglais : le cas des emprunts

Kharlamenko Oxana. La variation du genre en vieil-anglais : le cas des emprunts. In: Bulletin des anglicistes médiévistes, N°86, Hiver 2015. pp. 1-36

Grammatical gender variation in Old English inanimate nouns

L’existence de noms vieil-anglais au genre variable a été signalée encore à la fin du 19e siècle. Alors que le nombre de noms assignés à plusieurs genres dans les dictionnaires du vieil-anglais est très élevé, il n’existe presque aucune étude approfondie du phénomène. La présente thèse tente de répondre à des questions de ce que l'on désigne comme les noms au genre variable, comment ces noms se distinguent d’autres types de fluctuation dans les documents en vieil-anglais et de ce qui se trouve à l’origine de la variation en genre.Après avoir défini la notion de l’accord et son expression dans les marqueurs, on propose une étude détaillée de toutes les occurrences de trente-six emprunts faits au latin et au vieux-norrois d’une part, et de soixante-dix-huit noms indigènes d’autre part, tous assignés à plusieurs genres dans les dictionnaires. Constatant des évolutions parfois importantes dans l’emploi des marqueurs en discours, on cherche à déterminer s’ils interviennent dans la décision des lexicographes ou s’ils reflètent une variabilité interne aux noms étudiés. La variation se présente ainsi sous deux angles et s’explique à travers deux notions, celle du désaccord, où tout lien entre le nom-contrôleur et les cibles d’accord est rompu, et celle de la variabilité, qui soutient le lien d’accord sur le plan cognitif et permet la transition d’un genre à l’autre selon le choix de l’énonciateur.The existence of nouns of variable genre in Old English was brought to the linguistic community’s attention at the end of the 19th century. Despite the rather high number of nouns assigned to several genders in dictionaries dealing with Old English, to date there has been no substantial study of the phenomenon. This thesis is a usage-based study that explores the notion of nouns of variable gender by distinguishing them from other types of gender-variation in Old English texts. It also explores in detail the factors behind various grammatical gender assignments.It departs from the notion of agreement and its expression in gender-sensitive markers. A corpus of a hundred and fourteen nouns assigned to several genders in the dictionaries – seventy-eight native and thirty-six borrowed from Latin and Old Norse – are analysed in context in order to identify the various factors that influence the lexicographers’ decision-making. Some important developments in the usage of the formerly gender-sensitive markers in the discourse might have influenced the latter to a certain degree. Or, they might be a reflection of variability as an internal feature of the nouns analysed. This study deals with the notion of variation as a cover-term for disagreement, which reflects the discontinuity of the link between a controller and its agreement targets, and, on the other hand, for variability, maintaining the agreement on the cognitive level and allowing the transition from one gender to the other depending on the choice of the speaker