A preliminary investigation of the lipids of abyssal holothurians from the north-east Atlantic Ocean

The dominant lipids of seven species of abyssal holothulians (Oneirophanta mutabilis, Pseudostichopus villosus, Psychropoles longicauda, Deima validium, Parariza prouhoi, Amperima rosea and Molpadia blakei) have been examined in detail. Fatty acid compositions are qualitatively similar to those of shallow-water holothurians, but relatively higher amounts of unsaturated compounds in the deep sea animals are ascribed to an adaptation of the latter to maintain membrane fluidity at high pressure and low temperature. The sterol distributions of abyssal holothurians are complex, with mixtures of C-26-C-30 sterols being present in all of the animals. These are most likely to be dietary in origin; the holothurians substitute Delta(5) with Delta(7) unsaturation, via Delta(5,7) or Delta(0) intermediates. 14 alpha-methylcholest-9(11)-enol, which is a common product of de novo biosynthesis in shallow-water holothurians is absent in all of the deep-water species. Furthermore, cholest-7-enol, the dominant product of de novo biosynthesis in shallow water animals, is a relatively minor component in all of the species, except A. rosea. This holothurian is also the only one that appears to assimilate 4 alpha-methylsterols directly and contains high amounts of steryl sulphates. There are significant interspecies differences in the free sterol distributions which may reflect their different feeding strategies or niches.