Lipid class and fatty acid composition of copepods (Calanus finmarchicus, C. glacialis, Pseudocalanus sp., Tisbe furcata andn Nitokra lacustris) fed various combinations of autotrophic and heterotrophic protists

摘要

Tisbe furcata, Nitokra lacustris, Calanus finmarchicus and Calanus glacialis were reared for several months in the laboratory prior to feeding selected diets. Copepods were fed Isochrysis galbana, Tetraselmis sp., Dunaliella tertiolecta, Thalassiosira pseudonana, Rhodomonas sp., Rhodomonas lens and Oxyrrhis marina individually or in combination. Oxyrrhis marina itself was fed up to four of the algae species. The lipid class and fatty acid composition of the copepods was determined and compared with each other, the diets and with wild C. finmarchicus, C. glacialis and Pseudocalanus sp. Cultured O. marina, T. furcata and N. lacustris had greater proportions of essential 22:6ω3 or 20:5ω3 acids than in their diets suggesting nutritional enrichment through synthesis or preferential retention. Lower proportions of 18:3ω3 than in their diets fed individually or in combination suggests desaturation and elongation of 18:3ω3. Stable isotope analysis of the heterotroph samples and their dietary sources revealed similar values for 18:3ω3 in each dietary pair and different ones for 22:6ω3 and 20:5ω3 supporting derivation from precursors rather than trophic magnification. Principal components analysis of copepods and their diets showed cultured Calanus spp. to have the most similar fatty acid composition to their diet indicating little modification or sequestration of polyunsaturated fatty acids.