MEPS 142:175-184 (1996)  -  doi:10.3354/meps142175

Fatty acid characteristics in two symbiotic gastropods from a deep hydrothermal vent of the West Pacific

Pranal V, Fiala-Médioni A, Guezennec J

Two deep-sea gastropods, Ifremeria nautilei and Alviniconcha hessleri, collected on a hydrothermal site of the North Fiji Basin (Southwestern Pacific) were analysed for polar and neutral lipids using gas-liquid chromatography/mass spectrometry. A high level of monounsaturated fatty acids (MUFAs) and a low level of omega3 series polyunsaturated fatty acids (PUFAs) indicated that nutrition of both gastropods was related to a food web based mainly on bacterial supply. From differences in MUFA distribution between the 2 gastropods, it appeared that most of the energy requirements of A. hessleri were supplied by sulfur-oxidizing endobacteria whereas I. nautilei probably had a mixotrophic diet based on endogenous as well as exogenous bacteria. Given the relatively high level of linoleic acid, which represented from 2 to 8% of the phospholipid fatty acids, hydrothermal gastropods did not appear to be depleted in omega6 PUFAs. It was hypothesized that they obtain linoleic acid from a pathway different to that in heterotrophic marine molluscs. In contrast to omega6 PUFAs, both hydrothermal gastropods appeared to be depleted in omega3 PUFAs, indicating the limited importance of photosynthesis-based food supplies. Some non-methylene-interrupted dienes, particularly 20:2omega9,15 which represented from 9 to 18% of the phospholipid fatty acids, may be synthesized by deep-sea symbiotic molluscs in order to restore the depleted omega3 PUFAs considered as essential for animals. Gills of both gastropods had high levels of neutral lipids, mainly MUFAs that may have originated from degradation of endobacterial phospholipids.

Hydrothermal vents · Gastropods · Chemosynthetic bacteria · Biomarkers · Fatty acids · Phospholipids · Neutral lipids

Full text in pdf format