Unusual methylene-interrupted polyunsaturated fatty acids of abyssal and hadal invertebrates

The purpose of this study was to identify specific profiles of unusual methylene-interrupted polyunsaturated fatty acids (PUFAs) in megabenthic invertebrates inhabiting the Kuril-Kamchatka Trench, adjacent areas of the Pacific Ocean and the Sea of Okhotsk at the depths between 3206 and 9581 m. The analyzed taxa contained twelve of unusual methylene-interrupted PUFAs. The fatty acid (FA) 21:4n-7 was commonly found in many megabenthic invertebrates. A high level of long-chain FA 26:7n-3 was detected in abyssal ophiurioides. Some unusual n-7 FAs (possibly, derived from bacterial precursors) were found in the thyasirid bivalve Axinulus sp., which did not host chemotrophic symbionts, but could use pedal feeding. The sea urchin Kamptosoma sp. and the starfish Eremicaster sp. contained n-8 and n-5 PUFAs, typical of the Foraminifera living in the Kuril-Kamchatka Trench. The dominant species of holothurians at the bottom of the Kuril-Kamchatka Trench contained 21:4n-6 and 23:2n-6. An unusual (uncommon) very long-chain FA 32:5n-3 was found in the glass sponge Hyalonema sp. This data can be used to select model taxa for screening biologically active substances. Considering the low biomass levels of deep-sea invertebrates, the development of their cell cultures will be needed for further progress in this field.