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Abstract: Thirteen new species of gastropods are described from the Zairov 1-2 and Biozaire 1-3 cruises to the methane seeps off the Congo River: Patellogastropoda: Paralepetopsis sasakii sp. nov. (Neolepetopsidae); Cocculiniformia: Pyropelta oluae sp. nov. and P. sibuetae sp. nov. (Pyropeltidae); Tentaoculus granulatus sp. nov. (Pseudococculinidae); Neomphalina: Leptogyra costellata sp. nov. (Family uncertain); Vetigastropoda: Puncturella similis sp. nov. (Fissurellidae); Lepetodrilus shannonae sp. nov. (Lepetodrilidae); Caenogastropoda: Provanna reticulata sp. nov. and P. chevalieri sp. nov., Cordesia provannoides gen. et sp. nov. (Provannidae); Phymorhynchus coseli sp. nov. and P. cingulata sp. nov. (Conidae); Heterobranchia: Hyalogyrina rissoella sp. nov. (Hyalogyrinidae). All species except T. granulatus (from a settlement trap) belong to groups known from cold seeps and the entire seep fauna here is new to science. Biogeographical affinity of this gastropod fauna is to the West Atlantic seeps, not to the Mediterranean seeps or Mid-Atlantic vents. Fragments of the autecology of the species are presented. The evolution of the seep gastropod fauna is briefly discussed and a continuous immigration of taxa is supported. The oldest verified occurrences of modern taxa in the seeps date back to Cenomanian (Cretaceous) time, while some taxa seem not to appear until very late Tertiary. [Copyright &y& Elsevier]

Abstract: A giant 800-m-diameter pockmark named REGAB was discovered on the Gabon continental margin actively emitting methane at a water depth of 3200m. The microbial diversity in sediments from four different assemblages of chemosynthetic organisms, Mytilidae, Vesicomyidae, Siboglinidae and a bacterial mat, was investigated using comparative 16S rRNA gene sequence analysis. Aggregates of anaerobic methanotrophic archaea (ANME-2) and bacteria of the Desulfosarcina/Desulfococcus cluster were found in all four chemosynthetic habitats. Fluorescence in situ hybridization targeting the ANME-2/Desulfosarcina/Desulfococcus aggregates showed their presence few centimeters (3–5cm) below the surface of sediment. 16S rRNA gene sequences from all known marine ANME groups were detected in the pockmark sediments, as well as from both known bacterial partners. The archaeal diversity was limited to the ANME cluster for all investigated samples. The bacterial diversity included members of the Proteobacteria, Bacilliales, Cytophaga/Flavobacteria, Verrucomicrobia, JS1 and Actinobacteria clusters. Bacterial 16S rRNA gene sequences related to those of known sulphide-oxidizing symbionts were recovered from tissues of several invertebrates including vesicomyid clams and siboglinid tubeworms of REGAB. [Copyright &y& Elsevier]