Supplementation of EPA and DHA emulsions to a Dunaliella tertiolecta diet: effect on growth and lipid composition of scallop larvae, Argopecten purpuratus (Lamarck, 1819)

N. Nevejan, I. Saez, G. Gajardo, P. Sorgeloos-2002

Aquaculture, 217(1-4): 613-632
Abstract:

Hatchery-reared Argopecten purpuratus larvae were fed a Dunaliella tertiolecta-diet (DUN-diet) supplemented with 0%, 20% or 40% of a highly unsaturated fatty acid (HUFA) lipid emulsion (ICES Reference Emulsions), rich in docosahexaenoic acid (22:6n-3, DHA) and eicosapentaenoic acid (20:5n-3, EPA). A standard diet (ST-diet), consisting of a mixture of Isochrysis galbana (T-iso) and Chaetoceros neogracile was used as a positive control. The supplementation of 20% and 40% HUFA-emulsion to the DUN-diet led to a significantly better daily growth rate (136–177% as compared to DUN-diet) and a higher percentage of eyed-pediveliger larvae in comparison with the non-supplemented DUN-diet. Practically no eyed-larvae were present when fed with D. tertiolecta only, whereas 17% of the larvae developed an eyespot when fed a 20% HUFA-supplement. An increase of the lipid supplement from 20% to 40% further improved the larval performance, although the difference was not significant and less than compared with the changes between the non-supplemented DUN-diet and the DUN+20%-diet. The poor performance of larvae that received D. tertiolecta only was attributed to the depletion of the lipid reserves in the triglyceride fraction and possibly to the very low levels of saturated fatty acids 14:0 and 16:0, rather than to the low levels of EPA and DHA (in absolute terms). Limited biosynthesis of DHA from EPA as a precursor molecule is proposed. Despite similar relative and absolute fatty acid levels of DHA and EPA in larvae that received the ST-diet and the DUN+40%HUFA-diet, the former performed significantly better. Other factors such as the arachidonic acid (20:4n-6) content and the n-3/n-6 ratio are suggested to play a determining role.

(Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Rozier 44, 9000, Ghent, Belgium, e-mail of P. Sorgeloos: patrick.sorgeloos@rug.ac.be)

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