Manipulation of the fatty acid composition of phosphatidylcholine and phosphatidylethanolamine in rotifersBrachionusNevada andBrachionusCayman

Abstract

Rotifer cultures of Brachionus Nevada and Cayman were grown semi-continuously, fed live Rhodmonas baltica algae, and cultures were diluted daily (20% day−1). The enrichment diets Marol E (triacylglycerol-rich) and PL (cod roe emulsion, phospholipid-rich) were added to both cultures (Nevada 40 ng ind−1 day−1 and Cayman 25 ng ind−1 day−1, respectively). After 4 days of enrichment (dilution rate: 20% day−1), Cayman rotifers–fed Marol E had comparable (P > 0.05) quantitative amounts of DHA (docosahexaenoic acid, 22:6n-3) to natural harvested copepods, which were analysed for comparison, and the Cayman strain had generally more efficient incorporation of HUFAs (highly unsaturated fatty acids) than the Nevada strain. However, the percentage DHA of the total fatty acids in copepods were much higher than in enriched rotifers (P < 0.05). The PC-DHA (DHA in phosphatidylcholine) and PE-DHA (DHA in phosphatidylethanolamine) levels of copepods were up to 50%, which was highly unlikely for rotifers to reach. The increase of DHA in total phospholipids of rotifers was mainly due to an increase of DHA in PC, whereas the PE-DHA was only weakly affected by dietary lipids. The per cent PC-DHA levels in rotifers were positively related to the total dietary DHA levels (P < 0.0001), independent of the PC-DHA content in the diets.