Uptake and metabolism of a particulate form of ascorbic acid by Artemia nauplii and juveniles

Abstract

A study was conducted to establish whether a particulate form of ascorbic acid (AA), ascorbyl-2-phosphate (A2P), could be used to enrich Artemia. In the first experiment, we examined the efficiency of A2P conversion to and maintenance of AA by juvenile Artemia (1.5 mm, 5-day-old) held at 9000 L−1 and 28 °C for 24 h. Maximal uptake and assimilation was >10 000 μg AA g−1 dry weight (dw) (representing >1%Artemia dw) at enrichment rates of ≥1.2 g A2P L−1. In the second experiment, a similar biomass of instar II/III nauplii (1 mm, 2-day-old) and juvenile (2.5 mm, 8-day-old) Artemia were enriched for 6 or 24 h at 28 °C before starvation for 6 or 24 h at 18 or 28 °C. At 0 h and after 6 and 24 h enrichment, AA levels were 485, 3468 and 11 080 μg g−1 dw in nauplii and 122, 4286 and 12 470 μg g−1 dw in juveniles. When Artemia nauplii or juveniles were enriched for 6 h and starved for 6 h at 18 or 28 °C, there was no significant reduction in AA. Continuation of starvation to 24 h at 18 and 28 °C reduced the level of AA to 3367 and 2482 μg g−1 dw in nauplii and 3068 and 2286 μg g−1 dw in juveniles. After 24 h enrichment, 6 h of starvation at 18 and 28 °C reduced AA to 8847 and 7899 μg g−1 dw in nauplii and to 9053 and 8199 μg g−1 dw in juveniles. Continuation of starvation to 24 h at 18 and 28 °C further reduced AA levels in nauplii to 6977 and 4078 μg g−1 dw and to 7583 and 5114 μg g−1 dw in juveniles. This study demonstrated that A2P could be assimilated as AA in the body tissue of different-sized Artemia in a dose-dependant manner and AA was depleted during starvation depending on time and temperature.