Abstract
The individual fatty acids of mytilids and vestimentiferan (Escarpis sp.) from hydrocarbon seeps exhibit light delta super(13)C-values: from -56.9 to -49.0ppt for the mytilids and from -38.6 to -31.6ppt for the vestimentiferan. Unsaturated fatty acids have lighter delta super(13)C than saturated ones. The variations in delta super(13)C are up to 5.1-6.7ppt (mytilids) and 7.0ppt (vestimentiferan) within a single specimen. It is suggested that a kinetic isotopic effect in the biosynthesis of fatty acids and intermolecular isotope fractionation during fatty acid desaturation and elongation are responsible for the observed distribution pattern. Fatty acids are depleted in super(13)C relative to the gills of the mytilids, whereas fatty acids of the vestimentiferan are enriched relative to trophosomes. The difference in delta super(13)C of fatty acids between mytilids and vestimentiferan reflects the differences in substrates (methane vs. CO sub(2)), and the different chemosynthetic processes of the invertebrates.