A reflection on reproductive adaptation to ephemeral and deep-sea habitats in symbiotic bivalve’s species

Bivalves are among the dominant fauna occurring at deep-sea cold seeps, hydrothermal vents and organic falls worldwide. This is due to their ability to establish symbioses with sulphur- and/or methane-oxidizing bacteria, or with cellulolytic bacteria which produce or fragment organic compounds, that sustain the carbon supply to their hosts. Full picture of their reproductive cycle from the emission of the gametes, the larval stages (dispersal), the settlement and the reproduction of the adults (maturity and breeding) is still not fully understood in some of these species. We propose here to present some recent findings on reproduction. First, the mytilid species Idas modiolaeformis inhabiting cold seeps from eastern Mediterranean and organic falls, is a hermaphroditic species in which production of male and female gametes likely alternates, and size at first maturity occurs very rapidly after settlement of post-larva with the identification of the germinal cells. Small size of specimens and acquisition of mature gametes at early stages in ontogenic life cycle, exist also in other symbiotic deep-sea bivalves such as in the small vesicomyid Isorropodon bigoti and the thyasirid Thyasira sp. nov. recovered from the cold seeps off Guiness in the Gulf of Guinea. Third, nonetheless dwarfism was highlighted in the whale bone-eating polychaete Osedax spp. but this was recently found in wood-boring bivalve of the genus Xylophaga and from our colonization devices filled with wood substrates (named CHEMECOLI) deployed in Rainbow at 2300 meters for one year on hydrothermal vent chimneys in the Mid-Atlantic Ridge. First post-larvae were observed to be attached to adults and appeared to be after microscopies studies dwarf males filled with mature spermatozoan ready to fertilize mature oocytes from females that they were attached to. Overall, size at first maturity, dwarfism, and alternate sex will be discussed in adaptation to patchy, ephemeral and deep-sea habitats constraints and compared to the knowledge of the reproduction of shallower marine bivalve’s species.

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First Name: 
Sylvie Marylène
Last Name: 
Gaudron
Telephone: 
0033 (0)144273781
Affiliation: 
University of Pierre and Marie Curie (UPMC), UMR7138 CNRS France
First Name: 
Sven
Last Name: 
Laming
Affiliation: 
University of Pierre and Marie Curie (UPMC), UMR7138 CNRS France
First Name: 
Kamil
Last Name: 
Szafranski
Affiliation: 
University of Pierre and Marie Curie (UPMC), UMR7138 CNRS France
First Name: 
Emile
Last Name: 
Demoyencourt
Affiliation: 
University of Pierre and Marie Curie (UPMC), UMR7138 CNRS France
First Name: 
Takuma
Last Name: 
Haga
Affiliation: 
Marine Biodiversity Research Program, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Japan
First Name: 
Sébastien
Last Name: 
Duperron
Affiliation: 
University of Pierre and Marie Curie (UPMC), UMR7138 CNRS France
Choose keywords that are most applicable to your abstract. (Three maximum.): 
Early life history (reproduction, dispersal, settlement, recruitment)
Abstract ID: 
CBE5-101