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Effects of microalgal diet on growth, survival and fatty acid composition of larvae rock oyster Striostrea prismatica (Gray, 1825)

Abstract:

The biochemical nature and composition of fatty acids (FA's) in microalgae influence the nutritional quality and efficiency of this food source in bivalve larviculture. This research analyses the effect FA's content of Chaetoceros gracilis and Tisochrysis lutea on the FA's composition, growth and survival of Striostrea prismatica larvae. We analysed the FA's profiles of the microalgae, and the tissue of the larvae during a S. prismatica larviculture at day 1 (“D” larvae), day 8 (umbonate larvae) and day 22 (pediveliger) post fertilization (PF). Larvae growth and survival were evaluated during two phases: phase I from day 1 to day 8 PF and phase II from day 9 to day 22 PF. In phase I, we recorded a daily growth rate of 4.76 μm.day−1, while in phase II we recorded increases of 13.24 μm.day−1. In phase I, survival was 36.6%, and decreased further to 9.3% at the end of phase II. The sharp decrease in survival and low growth during phase I could possibly be explained by a specific nutritional deficiency of the microalgae diet (absence of FA's 15:0, 20:4n-3, 20:4n-6 and 22:5n- 3), especially if we consider the starting FA's profile of the “D” larvae. The larvae showed a high nutritional requirement for palmitic, stearic and oleic FA's and long-chain PUFA's, especially 20:5n-3 and 22:6n-3. The absence of these FA's in the diet and their presence in the larval profile suggest that S. prismatica could have the ability to synthesize these FA's; however, more research is needed to corroborate this hypothesis.