Comparison of the growth and fatty acid compositions of Rotifer Brachionus calyciflorus fed with two freshwater microalgae Chlorella sp. and Scenedesmus obliquus

The rotifer Brachionus calyciflorus is a promising candidate for feeding freshwater fish larvae with its suitable size and the high reproductive rate in cultural media. In this research, effects of two microalgae, Scenedesmus obliquus and Chlorella sp. on growth rate and fatty acid composition of B. calyciflorus was investigated. We used EPA medium together with two freshwater microalgae at the same density to culture the rotifer. Primary density of rotifers in 11 balloons was 30ind.ml-1. Results showed that the rotifers fed with Chlorella sp. had significantly higher growth rate than those fed with S. obliquus. Maximum density of rotifers fed with Chlorella sp. and S. obliquus reached 478 and 328ind. Ml ^(-1) after 7 days, respectively. Mean daily growth rate was 0.61 and 0.42 for rotifers fed with Chlorella sp. and S. obliquus, respectively. Rotifers fed with Chlorella sp. and S. obliquus had high amount of linoleic acid (16.24 and 18.47%, respectively) and linolneic acid (15.14 and 16.59%, respectively). The amount of highly unsaturated fatty acid (HUFA) in the rotifers fed with Chlorella sp. was 7.7% which was much higher than those fed with S. obliquus (4.246%). Results show that B. calyciflorus fed with Chlorella sp. had higher growth and nutritional quality than those fed with S. obliquus. We suggest that Chlorella sp. be used in mass culture of the rotifer

Isolation and semi-intensive culture of freshwater rotifer Brachinus calyciflorus of Anzali Lagoon

Brachionus calyciflorus is a freshwater rotifer that is used as a live food for intensive production of freshwater fish larvae. In this research, the possibility of isolating, purifying and semi-intensive production of freshwater rotifer was investigated in laboratory condition. Sampling was done at Anzali Lagoon in autumn 2005 and the species was identified and isolated using invert microscope. For culture of the rotifer, EPA medium was used together with freshwater chlorella sp. at 1×10^6 cells/ml density. Rotifers were produced as batch culture. Primary density of rotifers in 11 balloons was considered to be 30ind/ml. Results showed that the maximum density of rotifer reached 453°43ind/ml in the seventh day and mean growth rate per day was 0.50. The average of the lorica length and width was 204 and 167 microns and the average of the egg length and width was 121 and 95 microns, respectively. This experiment indicated that freshwater rotifer attains suitable growth parameters in laboratory condition in a relatively short time. Also, we successfully determined the protocol for semi-intensive artificial production of the species