Enrichment of live foods with arachidonic acid enhanced stress resistance, digestive enzyme activity, and total antioxidant capacity in yellowfin seabream (Acanthopagrus latus) larvae

Arachidonic acid (AA) is an essential fatty acid that has vital influences on early development in marine fish larvae. In this regard, a 30-day research was run to examine the effects of live food enrichment with graded levels of AA on some physiological responses of Acanthopagrus latus larvae. Four experimental emulsions containing four levels of AA were used to enrich live foods (rotifer and Artemia ), including very low (6%, N), low (12%, L), medium (24%, M), and high (37.8%, H) AA levels. Newly hatched larvae were distributed into twelve 250-L cylindrical tanks with initial density 15,000 larvae in each tank supplied with seawater (23 ± 1 °C; 40.0 ± 1.0 g L −1 ). Nannochloropsis oculata was used in a green water system and live foods were offered to larvae two times daily. Larvae in the H group had lower total length (7.24 ± 0.6 mm) than those in other treatments. The highest survival rate after air exposure and osmotic stress challenges was in the H group. The level of n-6 polyunsaturated fatty acids, mainly AA, was enhanced in the larval whole body with increasing AA level in the emulsion. The highest and lowest alkaline phosphatase activities were in the H and N groups, respectively. The aminopeptidase N and leucine-alanine peptidase activities in the N group were lower than those in the other treatments. The trypsin activity gradually increased with the increment of AA in the emulsions. The highest and lowest chymotrypsin, amylase, and pepsin activities were in H and N groups, respectively. The highest and lowest phospholipase A 2 activity was in the M and N groups, respectively. The activity of catalase in the whole body of the M group was greater than that in the rest of the treatments. The highest and lowest superoxide dismutase activities were in M and N groups, respectively. The activity of glutathione reductase in the L and M groups was higher than that in the rest. Total antioxidant capacity in the whole body of larvae in the N group was lower than that in the other treatments and the H group showed the highest value. The whole body malondialdehyde level in the L group was lower than that in N and H groups and M showed intermediate value. Based on the findings of the present study, moderate levels of AA suggested for the enrichment of live foods in A. latus by considering n-3 long-chain polyunsaturated fatty acid content in the enrichment solution.