The effects of temperature and dietary fatty acids on the fatty acid composition of harpacticoid copepods, for use as a live food for marine fish larvae

Abstract

Two marine harpacticoid copepod species, Amonardia sp. and Tisbe sp., were isolated from plankton collected near Halifax, Nova Scotia. The effect of two algal diets ( Dunaliella tertiolecta and Isochrysis galbana) on the essential fatty acid (EFA) composition of Amonardia for use as an alternative live food for coldwater marine finfish larvae was evaluated. This copepod was able to synthesize a significant amount of the EFAs, 20:5 n−3 (eicosapentaenoic acid; EPA, 0.5%) and 22:6 n−3 (docosahexaenoic acid; DHA, 13.6%) from shorter chain n−3 polyunsaturated fatty acids (PUFAs), when fed the algae D. tertiolecta. The marine harpacticoids, Amonardia sp. and Tisbe sp., were fed the same algal diet ( I. galbana) and cultured at 20, 15 and 6°C. The temperature effect on n−3 EFA for both species showed the same general pattern. The concentration of n−3 HUFA decreased in the following order: 6°C>20°C>15°C. The EFA values for marine fish larvae of two cultured harpacticoid copepods, Tisbe sp. and Amonardia sp., are compared with that of wild zooplankton and trochophore larvae of the mussel Mytilus edulis