%0 Journal Article %J Marine Biology %D 2015 %T Epsilonproteobacteria as gill epibionts of the hydrothermal vent gastropod Cyathermia naticoides (North East-Pacific Rise) %A Magali Zbinden %A Marqué, Lise %A Sylvie M Gaudron %A Juliette Ravaux %A Nelly Léger %A Sébastien Duperron %X

Mollusks, and particularly gastropods, are one of the major taxonomic groups at vents. In these ecosystems, devoid of light, chemoautotrophic bacteria are at the base of the food web and symbiotic association between metazoa and these bacteria is numerous. Nevertheless, apart few “large-size” well-known species, the “small-size” gastropods (shell <5 mm), although very abundant, remain poorly studied regarding symbioses. We investigated here Cyathermia naticoides (Warén and Bouchet in Zool Scr 18(1), 1989), a small coiled gastropod found in abundance on the East Pacific Rise among Riftia pachyptila tubes, and usually inferred to graze on tubeworm bacterial cover, and/or filter feeding. Among mollusks, symbioses are well known in large species and almost exclusively rely on sulfide or methane-oxidizing proteobacterial endosymbionts, occurring within the host tissues in gill epithelial bacteriocytes. Combining several approaches (molecular biology, microscopy, stable isotopes analyses), we described here an unusual symbiosis, where autotrophic filamentous Epsilonproteobacteria are located extracellularly, at the base of host gill filaments. Numerous endocytotic lysosome-like structures were observed in the gill epithelium of the animal suggesting bacteria may contribute to its nutrition through intracellular digestion by gill cells. Additional food source by non-symbiotic proteobacteria grazed on R. pachyptila tubes could complete the diet. The possible role of temperature in the selection of Epsilon- vs Gammaproteobacterial partners is discussed.

%B Marine Biology %V 162 %P 435-448 %8 11 Déc 2014 %G eng %U http://link.springer.com/article/10.1007/s00227-014-2591-7# %N 2 %0 Journal Article %J Marine Ecology %D 2015 %T How are microbial and detrital sources partitioned among and within gastropods species at East Pacific Rise hydrothermal vents? %A Sylvie M Gaudron %A Marqué, Lise %A Eric Thiébaut %A Riera, Pascal %A Duperron, Sébastien %A Magali Zbinden %K Chemosynthetic %K gastropods %K mixing model %K Stable isotopes %K trophic niche %K vents %X Abstract For the last few decades, trophic ecology has usually been investigated by using stable isotopes. However, the isotopic signatures of potential food sources in hydrothermal vent ecosystems are often unknown and so their relative contribution to the consumers’ diet, as well as resource partitioning, are then difficult to estimate. Here, we used a recent Bayesian mixing model (stable isotope analysis in R, SIAR) based on δ13C and δ15N to estimate the contribution of multiple food sources to the diet of eight vent gastropods that can reach high densities at hydrothermal vents (Lepetodrilus elevatus, Lepetodrilus pustulosus, Lepetodrilus ovalis, Eulepetopsis vitrea, Cyathermia naticoides, Peltospira delicata, Peltospira operculata and Rhynchopelta concentrica). These species, known as primary consumers (mostly bacterivores and detritivores), were sampled on the South-East Pacific Rise at 17°25′ S and the North-East Pacific Rise at 9°50′ N and 12°50′ N. Several potential food sources were sampled according to the gastropod habitat on the chimney wall, or mussel beds (proxies of Gammaproteobacteria form I RubisCO, Gammaproteobacteria form II RubisCO and Epsilonproteobacteria, biofilms of siboglinid and alvinellid tubes, biofilms of mussel shells and particulate organic matter). Some of these microbial and detrital sources were confirmed as present in the gut content of some small specimens by transmission electron microscopy. Distinct stable isotopic signatures of the potential food sources allowed calculation of their relative contributions to primary consumers’ diets. This revealed that gastropod species living on siboglinid or bathymodiolin habitats are usually generalists, feeding on various pools of microbial or detrital origins. For a particular habitat, sympatric gastropod species partition the food sources, thus avoiding being in competition. Only for the alvinellid habitat Peltospira spp. appeared to be more specialists as the choice of food sources is more reduced. %B Marine Ecology %V 36 %P 18-34 %G eng %U https://onlinelibrary.wiley.com/doi/abs/10.1111/maec.12260 %R 10.1111/maec.12260