Most animals can synthesize A scorbic Acid from glucuronic acid, but fish and crustaceans lack the enzyme gluconolactone oxidase necessary for the last step in this biosynthesis (Chatterjee, 1973; Dabrowski, 1990). Therefore, they depend on constant supplies of acceptable amounts of vitamin C through the feed. Currently, fish larvae in aquaculture rely primarily on commercial live feed enrichments to supply the required amount of Vitamin C. Due to the high amount of vitamin C found in Chlorella vulgaris, we looked at the potential replacement of commercial enrichment diets during the first 21 days post-hatching with Chlorella vulgaris.
Materials and Methods
This trial tested the use of Chlorella vulgaris on pikeperch ( Sander lucioperca) larvae during first feeding. The trial included three live feed enrichment treatments and one control, fed to the larvae for the first 21 days post-hatching. The first treatment exposed the live feed to the “Selco Spresso” enrichment diet by INVE, while in the second treatment, Ascorbic acid was used on the live feed. The third treatment used Chlorella vulgaris as the live feed enrichment, and the control treatment used Nannochloropsis occulata. After 21 days post-hatching, a representative sample of larvae (100 per treatment) from the four treatments was challenged for 180 minutes in high salinity (15ppt) to test resilience and cortisol levels. Growth, survival, and bladder inflation data were also collected.
Significant differences were found between treatments regarding stress resilience to the salinity challenge and cortisol levels compared to the control treatment and between enrichments. Significant differences were also found in larvae Vitamin C concentration after 21 dph. No differences were found in the growth or survival (average 65%), although chlorella treatment had the highest survival (72%).
The results suggest that using Chlorella Vulgaris in live feed during the pikeperch larval stage, positively enhances stress resilience and could potentially replace the use of more expensive commercial enrichment diets.
Chatterjee, I. B. (1973). Evolution and the biosynthesis of ascorbic acid. Science, 182(4118), 1271-1272.
Dabrowski, K. (1990). Absorption of ascorbic acid and ascorbic sulfate and ascorbate metabolism in common carp (Cyprinus carpio L.). Journal of Comparative Physiology B, 160, 549-561.