Effect of dietary arachidonic acid levels on growth and survival of gilthead sea bream (Sparus aurata L.) larvae

In order to determine the effect of different levels of arachidonic acid (A A) in microdiets on growth and survival of gilthead seabream larvae, two ex periments were carried out. In the first experiment, 17-day old larvae were fed microdiets for 14 days. In this trial, we tested four diets with a sim ilar docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio and AA in the range of 0.1%-1.8% dry weight (d.w.) and a fifth diet with 1.0% d.w. o f AA and a different DHA/EPA ratio. In the second experiment, 16-day old la rvae were fed for 21 days on two microdiets with levels of 0.1% and 1.0% d. w. AA. All diets in the two experiments had the same total n - 3 HUFA level . Growth was measured by total length and dry body weight of larvae. Larval lipids were extracted and fatty acid compositions of total neutral lipid ( NL) and total polar lipid (PL) fractions were determined by gas chromatogra phy. In the first experiment, the diet containing 1.8% d.w. of AA showed th e best survival (P < 0.05) but did not improve growth rate. In the second e xperiment, an increase in the AA dietary level from 0.1% to 1.0% d.w. signi ficantly improved (P < 0.05) larval growth. EPA accumulation in the PLs of the larvae was negatively affected by the inclusion of dietary AA. When wor king with a fixed dietary n - 3 HUFA level (2.2% d.w.), the effect of dieta ry AA on larval growth was masked by that of the dietary DHA/EPA ratio. How ever, when DHA/EPA ratio in diet was unchanged (similar to 1.8), it was pos sible to improve larval growth by supplementing the diet with 1.0 d.w. of A A. The negative effect produced by the increment of dietary PLA on the EPA incorporation into the larval PLs may be related to a competition interacti on. (C) 1999 Elsevier Science B.V. All rights reserved.