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Da Costa F.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Robert R.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Robert R.,French Research Institute for Exploitation of the Sea | Quere C.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | And 2 more authors.
Lipids | Year: 2015

Essential fatty acids (EFA) are important for bivalve larval survival and growth. The purpose of this study was to quantitatively assess for the first time through a mass-balance approach dietary EFA incorporation and synthesis within Crassostrea gigas larvae. A first experiment was carried out using two microalgae, Tisochrysis lutea (T) and Chaetoceros neogracile (Cg), as mono- and bi-specific diets. A second experiment using a similar design was performed to confirm and extend the results obtained in the first. Flow-through larval rearing was used for accurate control of food supply and measurement of ingestion. Non-methylene-interrupted fatty acids were synthetized from precursors supplied in the diet: 16:1n-7 and 18:1n-9, mediated by Δ5 desaturase. Moreover, this Δ5 desaturase presumably allowed larvae to convert 20:3n-6 and 20:4n-3 to 20:4n-6 and 20:5n-3, respectively, when the product EFA were poorly or not supplied in the diet, as when larvae were fed T exclusively. Under our experimental conditions, none of the diets induced 22:6n-3 synthesis; however, 22:6n-3 incorporation into larval tissues occurred selectively under non-limiting dietary supply to maintain optimal levels in the larvae. This combination of flow-through larval rearing and biochemical analysis of FA levels could be applied to additional dietary experiments to precisely define optimal levels of EFA supply. © 2015 AOCS.


Da Costa F.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Petton B.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Mingant C.,Ifremer Laboratoire Des Science Of Lenvironnement Marin Umr 6539 | Bougaran G.,Ifremer Laboratoire Physiologie et Biotechnologies des Algues Nantes Cedex 3 France | And 5 more authors.
Aquaculture Nutrition | Year: 2015

Effects of a remarkably high overall lipid Tisochrysis lutea strain (T+) upon gross biochemical composition, fatty acid (FA), sterol and lipid class composition of Crassostrea gigas larvae were evaluated and compared with a normal strain of Tisochrysis lutea (T) and the diatom Chaetoceros neogracile (Cg). In a first experiment, the influence of different single diets (T, T+ and Cg) and a bispecific diet (TCg) was studied, whereas, effects of monospecific diets (T and T+) and bispecific diets (TCg and T+Cg) were evaluated in a second experiment. The strain T+ was very rich in triglycerides (TAG: 93-95% of total neutral lipids), saturated FA (45%), monounsaturated FA (31-33%) and total fatty acids (4.0-4.7 pg cell-1). Larval oyster survival and growth rate were positively correlated with 18:1n-7 and 20:1n-7, in storage lipids (SL), and negatively related to 14:0, 18:1n-9, 20:1n-9, 20:4n-6 and trans-22-dehydrocholesterol in membrane lipids (ML). Surprisingly, only the essential fatty acid 20:5n-3 in SL was correlated positively with larval survival. Correlations suggest that physiological disruption by overabundance of TAG, FFA and certain fatty acids in larvae fed T+ was largely responsible for the poor performance of these larvae. 'High-lipid' strains of microalgae, without regard to qualitative lipid composition, do not always improve bivalve larval performance. © 2015 John Wiley & Sons Ltd.

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