Comparison of the fatty acid composition of the freshwater fish larvae Tilapia zillii, the rotifer Brachionus calyciflorus, and the microalgae Scenedesmus abundans, Monoraphidium minitum and Chlorella vulgaris in the algae-rotifer-fish larvae food ch

摘要

The lipid and fatty acid composition of species in a food chain in which freshwater T. zillii larva was fed on the freshwater rotifer, Brachionus calyciflorus, which in turn was fed on the microalgae, Scenedesmus abundans, Monoraphidium minitum andChlorella vulgaris, were examined. C. vulgaris had significantly higher lipid content than the other microalgae and this was also reflected in the lipid content of B. calyciflorus fed each of the microalgae separately. Five fatty acids dominated in all the microalgae, namely 18:3n-3, 18:2n-6, 18:0, 18:1 and 16:0 though there were significant differences both in quantitative distribution of these acids and the total fatty acid content. Contents of 18:3n-3, 18:2n-6 and 16:0 and that of total fatty acid ofC. vulgaris were considerably higher than the corresponding values in the other two microalgae. However, these strong differences were not reflected in B. calyciflorus samples fed on these microalgae separately though the one fed on C. vulgaris had slightly higher total fatty acid content than the other 2 rotifer samples. One can consider that the freshwater rotifer B. calyciflorus is capable of creating its own characteristic fatty acid content up to a sufficient level even when cultured with a fattyacid deficient algae probably by consuming excessive amounts of this algae compared with other algae of relatively high fatty acid content. The proximate and fatty acid analysis results of the T. zillii larvae fed the 3 B. calyciflorus samples obtained by culturing with 3 different microalgae were very similar. This was an expected result because the 3 B. calyciflorus samples did not differ much from each other. The low 18:2n-6 (1.66-3.53 mg/g DM) and 18:3n-3 (1.14-1.22 mg/g DM) content and the relatively high 22:6n-3 (10.72-14.38 mg/g DM) content of the T. zillii larvae samples indicated that they were capable of elongating and desaturating both linoleic and linolenic acids of the B. calyciflorus samples.