Effects of l-carnitine enrichment on the population growth, egg ratio and body size of the marine rotifer, Brachionus rotundiformis

Abstract

l-Carnitine enrichment has shown considerable influence on the population growth, reproduction and individual growth of rotifer, Brachionus rotundiformis. Rotifers were enriched with 8 levels of l-carnitine supplements dissolved in Nannochloropsis oculata culture medium in a 3 ml-individual culture trial for 10 days, and 5 levels in Chlorella vulgaris culture medium in one l batch culture trial for 5 days. In the batch culture trial, 42, 38 and 50% increase in population densities ( P < 0.05) were observed in 1, 10 and 100 mg l − 1 treatments, respectively, whereas, the 1000 mg l − 1 treatment had a significant decrease in population density (34–45%, P < 0.05) and markedly higher egg ratio ( P < 0.05). The 1000 mg l − 1 l-carnitine-enriched rotifers obtained significantly smaller body size ( P < 0.01), but those enriched with the other 3 levels of l-carnitine (1, 10, 100 mg l − 1) showed larger body size. In the individual culture trial, an increasing trend was observed in population density after 5 days and 10 days of culture in 0.001–10 mg l − 1 treatments. The results suggest that l-carnitine could be a positive factor to enhance reproduction and population growth on enriched rotifers directly or/and indirectly under the optimum concentration. The lipid metabolism in rotifers may be carnitine-dependent.