Lipid content and composition of some midwater crustaceans from the Southern Ocean

The decapods Pasiphaea scotiae (Stebbing), P. rathbunae (Stebbing), Petalidium foliaceum Bate and Acanthephyra pelagica (Risso) and the mysid Gnathophausia gigas (W.-Suhm) have been sampled from the Southern Ocean. Lipid contents were generally very high, 5 to 25% fresh weight in immature and male Pasiphaea scotiae, 7 to 17% in Acanthephyra pelagica and up to 20% in both Gnathophausia gigas and Petalidium foliaceum. Carotenoid pigment contents were also high compared with benthic decapods. In most species the major storage lipid was wax ester, although in Pasiphaea scotiae triacylglycerol was of equal or greater importance. Fatty acid compositions were typical of marine invertebrates from pelagic and shallow-water benthic habitats, although P. scotiae and Acanthephyra pelagica contained substantial levels of 20:1 in the triacylglycerol. Wax ester alcohol compositions were unusual in that both 20:1 and 22:1 were present as a suite of positional isomers. The variation in lipid content and composition with sex and season in both Pasiphaea scotiae and Acanthephyra pelagica indicated that the major factor influencing lipid storage in these organisms was the pattern of food availability, although they would clearly also benefit from the associated increased buoyancy. High-latitude midwater crustaceans contain much more lipid than the same or related species from lower latitudes. This parallels the increasing seasonally of production towards the poles, indicating that this seasonality influences the biology of the underlying mesopelagic community