Changes in gut content and composition of juvenile Artemia after oil enrichment and during starvation

Some predators, such as spiny lobster phyllosoma larvae, tear Artemia to pieces before ingestion. This results in the loss of gut content, which may partly negate the benefits of enrichment with essential fatty acids (EFA). Therefore, the influence of gut content on the lipid composition of juvenile Artemia (5 day old) was examined by starvation alone or starvation with forced gut evacuation using 20-30 um plastic beads. Artemia gut content at 3 h and 6 h after the completion of feeding did not contribute significantly to the total lipid or fatty acid profiles of the Artemia. Artemia subjected to starvation alone (without beads) failed to evacuate their gut over the 6 h starvation period suggesting they require the intake of suitable sized particulate matter to undertake gut evacuation. To assess the uptake of EFA in nauplii (day 2) and juveniles, an enrichment diet containing high levels of arachidonic [AA, 20:4(n-6)] and eicosapentaenoic acid [EPA, 20:5(n-3)] was compared to a basal oat-based diet and a commercial oil emulsion high in docosahexaenoic acid [DHA (22:6(n-3)]. Both AA and EPA were increased in juvenile Artemia within a 24 h enrichment period at a rate proportional to their inclusion in the enrichment, while DHA was incorporated to a lesser degree. For all three EFA, the percentage loss during 6h starvation was small, but was greater for DHA than EPA or AA. Juvenile Artemia, a life stage seldom used in feeding regimes, have the ability to assume the AA and EPA profile of their dietary source. The ability to produce a larger food source with a non-traditional fatty acid profile may be valuable for a number of larval crustacean and fish species