Arachidonic acid requirements in larval summer flounder, Paralichthys dentatus

The arachidonic acid (20: 4n-6, AA) requirements of larval summer flounder were determined for the rotifer- and Artemia-feeding stages. Experimental emulsions contained adequate n-3 highly unsaturated fatty acid (HUFA) ratios and emulsion levels of AA were set at 0, 3, 6, 9, and 12% (AA0, AA3, AA6, AA9, and AA12). Examination of fatty acid levels in live feeds and larval tissues confirmed the physiological incorporation of fatty acids relative to dietary levels. In the first experiment, survival, growth, and salinity tolerance (2-h in 70parts per thousand) were measured at 18 days after hatch ( dah) after feeding the larvae the various levels of AA. Larvae fed AA6-enriched rotifers were better able to survive the salinity tolerance test. AA enrichment up to 12% had no effect on growth and survival. In the second experiment, larvae were fed AA0- or AA6-enriched rotifers until 23 dah, followed by unenriched 24- and 48-h Artemia nauplii until 32 dah. These larvae then were subdivided and fed AA-enriched Artemia from 33-45 dah. At the end of this experiment, larvae fed AA6-enriched rotifers had higher survival, increased growth, and survived better in the salinity tolerance test (2-h in 80parts per thousand). The enrichment of Artemia did not have any effect on these variables. Thus, the provision of AA6-enriched rotifers ( 10 mg AA g(-1) DW) early in larval development may serve to enhance larval stress tolerance at the rotifer stage while also increasing larval survival, growth, and stress tolerance later in the Artemia stage.