Exceptional wax ester storage mode of the calanoid copepod Boeckella poopoensis: implications in lipogenic pathways

KOPPRIO, G. A.; KATTNER, G.; GRAEVE, M.; FREIJE, R. H.; LARA, R. J.

AQUATIC BIOLOGY

INTER-RESEARCH

Lugar: Oldendorf/Luhe; Año: 2012 vol. 15 p. 275 - 281

1864-7790

ABSTRACT: The lipid biochemistry of zooplankton was investigated in Lake Chasico, a pampeansalt lake in Argentina. The lipid biomass of the zooplankton community was dominated by thecalanoid copepod Boeckella poopoensis. The major storage lipids during winter were wax estersand triacylglycerols, which reached up to 59 and 37% of the total lipids, respectively. A strikingfeature of the zooplankton fatty acid composition was the extraordinarily high level of 18:4(n-3)and 20:4(n-3) fatty acids, the highest ever reported for the latter in zooplankton. During winter,20:4(n-3) accounted on average for 20% of the total fatty acids in the wax ester fraction and 7% inthe triacylglycerols. The close relationship (r = 0.83, p < 0.001) between the 2 fatty acids impliesthe biosynthesis of 20:4(n-3) in B. poopoensis by chain elongation of 18:4(n-3), a dietary precursorand flagellate marker. The accumulation of 20:4(n-3) may be also partially related to B. poopoensisgrazing on heterotrophic protozoa or non-flagellated chlorophytes, although this fatty acid wasalmost absent in the seston fraction. In summer, wax esters were slightly lower (45%), compensatedby higher phospholipid levels. The 16:0 fatty alcohol moiety was predominant in the waxesters of all samples, corroborating the opportunistic feeding behavior of B. poopoensis. The highamounts of wax esters in zooplankton are typical of marine species, suggesting that the wax esterbiosynthesis of B. poopoensis and the extraordinary fatty acid composition are adaptations to theunstable environmental conditions of salt lakes.