Effect of lipid supplementation, using oil extracted from Nannochloropsis salina on growth indices and expression of gene associated lipid metabolism in clownfish, Amphiprion ocellaris

This study was performed to evaluate the optimum dietary lipid requirement during the juvenile stage of clownfish, Amphiprion ocellaris. Fifteen days old A. ocellaris (initial body weight of 19.4 +/- 0.057 mg) were fed with different proportions of lipid-enriched diets (5, 10, 15, and 20%) using the oil extracted from microalga Nannochloropsis salina as a major lipid source. End of the experiment, growth was calculated and the results show that juveniles fed with 15% of dietary lipid content have significantly enhanced the growth. Maximum protein efficiency ratio was found in 15% of dietary lipid fed groups, whereas lower protein efficiency and poor growth were observed in 20% of lipid diet fed group. Peroxisome proliferatoractivated receptor beta (PPAR-beta) gene plays an important role in the lipid metabolism. When compared to other experimental groups, higher upregulation (4.12 +/- 0.05 fold) was recorded for PPAR-beta gene in the juveniles fed with 15% of the dietary lipid, whereas downregulation was observed in 20% of the lipid-enriched diet, even at a higher feed intake (881.2 +/- 0.28 mg). Fatty acid analysis of the tissue samples of A. ocellaris showed the significance of eicosapentaenoic acid 20:5 (n-3) in the growth indices. Results suggested that 15% of the lipid-enriched diet is found to be optimal and the PPAR-beta gene could be used as a good indicator for determining the optimum dietary lipid utilization and growth indices in A. ocellaris.