While advances in live feed manipulation have been made, no artificial feed can fully replace zooplankton, making live feed indispensable for many species in marine hatcheries. Despite lacking essential fatty acids (FA) for marine larvae development, particularly EPA (eicosapentaenoic acid – 20:5(n-3)), DHA (docosahexaenoic acid – 22:6(n-3)) and ARA (arachidonic acid – 20:4 (n-6)), Artemia, is widely favored due to its broad acceptance.
Cysts of three strains – Vinh Chau (VC), Great Salt Lake (GSL), and San Francisco Bay (SFB) – were hatched (2 gL-1) under standardized conditions. After a 24-hour hatching period, the nauplii (approximately 263±14 animals ml-1) were collected and either enriched with INVE Aquaculture’s Selco® emulsion or left unenriched (Control- NE). Following the enrichment, the animal’s gut was cleared using Silicon Dioxide (SD) at a density of 1gL-1 for 2h, rinsed, and stored in clean seawater at either 27ºC (E27) or 16ºC (E16). Samples from each treatment were collected at specific intervals post-hatching (24, 48, 50, 53, 56, 62, and 74h) for Fatty Acid Methyl Ester (FAME) analysis. Data was analyzed by three factors: Artemia strain (GSL, SFB, VC), time after hatching (48h, 50h, 53h, 56h, 62h, 74h), and treatment (NE, E27, and E16). Differences in FA (area %) were compared within strains to evaluate enrichment (NE vs. E27) and temperature effects (E27 vs. E16), and across strains to assess strain influence.
FAME analysis identified 42 fatty acids (FAs) across strains, with only seven showing no significant differences throughout the experiment. The remaining 35 FAs were further analyzed and results showed an inconsistent FA behavior across treatments (Table 1), with significant degradation differences observed within each strain (Table 2). The difference in FA composition across strains, suggests that strains use different FA degradation pathways under identical conditions. Animals from the E27 treatment showed the highest number of significantly different FAs across all strains and those from the E16 the greatest discrepancies emphasizing temperature’s effect on FA composition. Spaghetti plots confirmed linear time progression and strain-specific differences in FA levels. Enrichment affected the FA levels across strains differently, with EPA, increasing significantly in SFB but less so in GSL and VC Artemia. DHA, initially minimal or absent across strains, showed the greatest increase after enrichment. Its degradation afterwards is likely linked to synthesis of EPA as literature suggests a natural conversion of DHA into EPA.