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 A2
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
