Fatty Acids of Abyssal Echinodermata, the Sea Star Eremicaster vicinus and the Sea Urchin Kamptosoma abyssale: A New Polyunsaturated Fatty Acid Detected, 22:6(n-2).

Fatty acids (FA) of two species of abyssal Echinodermata-the sea star (Asteroidea) Eremicaster vicinus and the sea urchin (Echinoidea) Kamptosoma abyssale-from the Kuril-Kamchatka Trench, collected at depths of 5210 and 6183 m, were analyzed. Lipids of these deposit-feeding animals showed similar FA compositions: 20.05-16.08% saturated, 42.20-39.50% monoenoic, and 37.75-44.42% polyunsaturated FA, respectively. The contents of odd- and branched-chain FA were 17.35% and 8.80%, respectively. A significant part of FA was represented by uncommon FA such as 21:4(n-7), 22:4(n-8), 22:5(n-5), and 23:4(n-9), earlier discovered in deep-sea foraminifera. Also, the newly found acid, related to the ω2 family, Δ5,8,11,14,17,20-22:6(n-2), amounted 1.60% and 0.33% of total FA, respectively, for the two species. Such unusual FA composition of these abyssal species can be explained by the transfer and modification of FA from consumed foraminifera, which in turn, feed on bacteria.