title: Essential Fatty Acid Assimilation and Synthesis in Larvae of the Bivalve Crassostrea gigas.
abstract: 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.
authors.affiliation: Ifremer/Laboratoire des sciences de l'Environnement Marin (UMR 6539, LEMAR), 29280, Plouzané, France.
authors.forename: Fiz
authors.initials: F
authors.lastname: da Costa
authors.forename: René
authors.initials: R
authors.lastname: Robert
authors.forename: Claudie
authors.initials: C
authors.lastname: Quéré
authors.forename: Gary H
authors.initials: GH
authors.lastname: Wikfors
authors.forename: Philippe
authors.initials: P
authors.lastname: Soudant
mesh_terms: D000818:Animals; D049896:Crassostrea / Q000254:growth & development* / Q000378:metabolism; D019587:Dietary Supplements; D005228:Fatty Acids, Essential / Q000378:metabolism*; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D058086:Microalgae / Q000378:metabolism*
chemical_list: D005228:Fatty Acids, Essential