Characteristics of fatty acid composition of the deep-sea vent crab, Shinkaia crosnieri Baba and Williams.

The neutral and polar lipids of the Galatheidae vent crab, Shinkaia crosnieri, with its eggs were studied to assess its lipid physiology and trophic relationship at hydrothermal vents. The vent crab obtained many of its lipids from Bathymodiolus mussels and chemosynthetic microorganisms which live on a mat of long, silky setae on the crab body as exosymbionts. In all lipid classes, the major monounsaturated fatty acids were 16:1n-7 and 18:1n-7, which originate from bacteria. The major polyunsaturated fatty acids (PUFA) in the triacylglycerols were 16:2n-4, 18:2n-4, 18:2n-7, 18:3n-4,7,10, and 16:2n-3, while those of the crab polar lipids were 16:2n-4, 18:2n-4, 18:3n-4,7,10, 20:4n-6 (arachidonic acid), 20:5n-3 (icosapentaenoic acid), and 22:6n-3 (docosahexaenoic acid) in the phosphatidylethanolamine, and 16:2n-4, 18:2n-4, and 18:3n-4,7,10, with noticeable levels of 20:4n-6, 20:5n-3, and 22:6n-3 in the phosphatidylcholine. In the crab and its eggs, TAG and phospholipid PUFA consisted primarily of n-4 family (n-4 and n-7) methylene-interrupted PUFA with n-3 and n-6 PUFA. The unique fatty acid composition mix of n-3, n-4, and n-6 PUFA in S. crosnieri lipids suggests the vent crab utilizing chemosynthetic bacteria, which produce both unusual n-4 and normal n-3 and n-6 PUFA. Such unique fatty acid composition differs from that reported for other common marine animals, which depend on organic matter derived from phytoplankton lipids.