XÁC ĐỊNH LOẠI VÀ MẬT ĐỘ TẢO PHÙ HỢP CHO SỰ PHÁT TRIỂN CỦA ẤU TRÙNG GIUN NHIỀU TƠ (Dendronereis chipolini) GIAI ĐOẠN SỐNG NỔI

The study was conducted to determine the appropriate species and density of alga for the larvae of the polychaete Dendronereis chipolini at the planktonic stage. After hatching, the larvae were fed with 3 different algal species corresponding to 3 treatments including (i) Chaetoceros sp., (ii) Chlorella sp. and (iii) Nannocholoropsis oculata. After 6 days of experiment, the metamorphosis index in the 3 treatments was similar and equal to 3. However, highest growth in length (0.245 ± 0.001mm) and survival rate (37.6 ± 1.48%) of the larvae were obtained in the Chlorella sp. treatment which was statistically significant (P <0.05). Chlorella sp. was used in the successive experiments to determine the most suitable density for the polychaete larvae. The experiment was designed with 4 treatments including 500 cells/ml, 1,000 cells/ml, 1,500 cells/ml and 2,000 cells/ml with 5 replicates. Highest length (0.247 ± 0.008mm) and survival rate (44.4 ± 2.97%) of the larvae were recorded in treatment of 500 cells/ml which was also significantly different (P <0.05). The results showed that the best growth and survival rate of the polychaete Dendronereis chipolini larvae at the planktonic stage can be obtained when they are fed with Chlorella sp. at a density of 500 cells/ml.