ENRICHMENT OF THE ROTIFER BRACHIONUS-PLICATILIS FED AN ANTARCTIC BACTERIUM CONTAINING POLYUNSATURATED FATTY-ACIDS

The Antarctic bacterium, strain ACAM 456, is known to produce eicosape ntaenoic acid (20:5n - 3, EPA). Following growth in batch culture, sus pensions of this bacterium, at initial concentrations of 10(7), 10(8) and 10(9) cells ml(-1), were used as foods for three respective cultur es of the rotifer Brachionus plicatilis. At 6 and 24 h, rotifers were removed, harvested and extracted for analysis of fatty acid compositio n, which was compared to that of rotifers grown on baker's yeast. Inco rporation of EPA, along with bacterial fatty acid markers (i13:0, i15: 0 and 14:0), was evidenced at all bacterial food concentrations tested , The highest observed incorporation occurred when rotifers were grown in the medium initially containing 10(9) bacteria ml(-1). After 24 h of feeding, the level of EPA reached 9.4% of total fatty acids in the fed rotifers (6.7 ng of EPA rotifer(-1)). ACAM 456, a bacterial strain with the ability to produce EPA, was therefore shown to be a potentia l alternative enrichment food for the rotifer Brachionus plicatilis un der feeding conditions that may be applicable to many Australian maric ulture operations.