Identification of novel n-4 series polyunsaturated fatty acids in a deep-sea clam, Calyptogena phaseoliformis.
Novel fatty acids originated from the cold-seep clam Calyptogena phaseoliformis, collected from hydrothermal vents in the Japan Trench at a depth of 6354-6367 m, were determined by using gas chromatography-mass spectrometry analysis of the 4,4-dimethyloxazoline derivatives. The major fatty acids present in the C. phaseoliformis lipids belong to the n-4 family non-methylene interrupted polyunsaturated fatty acids (NMI-PUFA): 20:3n-4,7,15, 20:4n-1,4,7,15, and 21:3n-4,7,16, with significant levels of 20:2n-7,15 and 21:2n-7,16 as non-methylene interrupted n-7 dienes. Compared with the lipids of shallow-water clam Mactra chinensis, which contains photosynthetic n-3 PUFA, such as docosahexaenoic acid and icosapentaenoic acid, C. phaseoliformis might have an intrinsic mechanism in vivo so as to maintain the fluidity of the high-melting fatty acids in the membrane lipids by exogenous n-4 family PUFA adaptation as substitutes. Such special kinds of fatty acids are assimilated by the symbiotic chemosynthetic bacteria, which use geothermal energy and minerals from the cold-seep vents. Its unique fatty acid composition corresponding to the novel n-4 family NMI-PUFA markedly differs from those of the reported lipid compositions of other marine animals, which depend on the marine grazing food chain originating from phytoplankton. Thus, the present findings confirm a perfect and closed novel food chain in the cold-seep bivalve and in its symbionts, which is independent from the photosynthetic food chain.
Saito
Hiroaki
H
National Research Institute of Fisheries Science, 2-12-4 Fuku-ura, Kanazawa-ku, Yokohama 236-8648, Japan. hiroakis@affrc.go.jp
D000818:Animals; D049872:Bivalvia / Q000737:chemistry*; D002855:Chromatography, Thin Layer; D005231:Fatty Acids, Unsaturated / Q000032:analysis* / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010080:Oxazoles / Q000032:analysis / Q000737:chemistry
D005231:Fatty Acids, Unsaturated; D010080:Oxazoles; C057549:4,4-dimethyloxazoline