STABLE-CARBON-ISOTOPE COMPOSITION OF FATTY-ACIDS IN HYDROTHERMAL VENTMUSSELS CONTAINING METHANOTROPHIC AND THIOTROPHIC BACTERIAL ENDOSYMBIONTS

Fatty acid biomarker analysis coupled with gas chromatography-isotope ratio mass spectrometry was used to confirm the presence of methanotro phic and thiotrophic bacterial endosymbionts in the tissues of a hydro thermal vent mussel (Bathymodiolus sp.), collected from the Menez Gwen vent field on the mid-Atlantic ridge, Monounsaturated (n-8) fatty aci ds, which are diagnostic of methanotrophic bacteria, were detected in all three types of tissues examined (gill, posterior adductor, and man tle), although levels were highest in gill tissues where the bacteria were found, Stable-carbon-isotope compositions (delta-C-13 per mille r elative to that of Peedee belemnite) of fatty acids for all three tiss ues ranged from -24.9 to -34.9%., which encompasses the range predicte d for both thiotroph- and methanotroph-based nutrition. The data sugge st that these thio-and methanotrophic bacterial endosymbionts are equa lly important in the nutrition of the vent mussel at this particular r ent site.