Essai sur les chiffres arabes : leur origine, leur forme et leur emploi

par J.-B. Réveillau

Species boundaries and phylogenetic relationships between Atlanto-Mediterranean shallow-water and deep-sea coral associated Hexadella species (Porifera, Ianthellidae)

11 páginas, 5 figuras, 2 tablas.Coral reefs constitute the most diverse ecosystem of the marine realm and an increasing number of studies are focusing on coralspeciesboundaries, distribution, and on processes that control species ranges. However, less attention has been paid to coralassociatedspecies. Deep-sea sponges dominate cold-watercoral ecosystems, but virtually nothing is known about their molecular diversity. Moreover, speciesboundaries based on morphology may sometimes be inadequate, since sponges have few diagnostic characters. In this study, we investigated the molecular diversity within the genus Hexadella (Porifera, Demospongiae, Verongida, Ianthellidae) from the European shallow-water environment to the deep-seacoral ecosystems. Three molecular markers were used: one mitochondrial (COI) and two nuclear gene fragments (28S rDNA and the ATPS intron). Phylogenetic analyses revealed deeply divergent deep-sea clades congruent across the mitochondrial and nuclear markers. One clade contained specimens from the Irish, the Scottish, and the Norwegian margins and the Greenland Sea (Hexadella dedritifera) while another clade contained specimens from the Ionian Sea, the Bay of Biscay, and the Irish margin (H. cf. dedritifera). Moreover, these deeply divergent deep-sea clades showed a wide distribution suggesting a connection between the reefs. The results also point to the existence of a new deep-seaspecies (Hexadella sp.) in the MediterraneanSea and of a cryptic shallow-waterspecies (Hexadella cf. pruvoti) in the Gorringe Bank. In contrast, low genetic differentiation between H. cf. dedritifera and H. pruvoti from the MediterraneanSea was observed. All Hexadella racovitzai specimens from the MediterraneanSea (shallow and deep) to the Atlantic formed a monophyletic group.The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007–2013) under the HERMIONE project, grant agreement No. 226354. J.R. had a Special Research Fund (BOF) from Ghent University. Lab work and visit to the Department of Biology (University of Bergen) was funded by Bergens Forskningsstiftelse.Peer reviewe

Influence of the Mediterranean Outflow Water on benthic ecosystems: answers and questions after a decade of observations

Deep-water Circulation: Processes & Products. International Congress 16-18 june 2010, Baiona, Pontevedra, Spain.-- 2 pagesCold-water coral (CWC) ecosystems are closely tied to oceanography; they necessitate a careful balance of bottom current strength in order to survive. The discovery of the large CWC mounds in the Porcupine Seabight gave insight to the strong association with the dynamics of a very distal Mediterranean Outflow Water (MOW), both in the present-day as in the geological past. Although the MOW is thoroughly mixed north of Iberia, its physical characteristics enable local enhancing through internal tides. Observations of CWC reefs along the Bay of Biscay and the Cantabrian margins confirm this water mass is a real driver of benthic habitats (corals and oysters), controlling both physical (morphological) as oceanographic factors. They also give hints regarding the possiblenucleation and growth patterns of the large CWC mounds as well as their (palaeo)environmental constraints. However, the discovery of «dead» CWC reefs on mounds along the Moroccan margin has left many questions on the influence of intermediate water masses on these ecosystems and calls for a thorough investigation of the local palaeoceanography; are these glacially thriving reefs influenced by MOW or meddies