- 39 ISOLATION AND SELECTION OF TETRASELMIS STRAINS FOR FEEDING. - GEO-DUCK LARVAE AT VANDON, QUANG NINH. - Three Tetraselmis strains were successfully isolated from the shrimp farming at Vandon, Quangninh. - Among them, Tetraselmis strain T1 showed best growth. - Fatty acid profile of Tetraselmis strain T1 consisted of C 16 and C 18. - -linolenic acid and linoleic acid accounted for 34.2% of total fatty acids, half of total unsaturated fatty acids. - The result suggested the high quality of as food for aquatic animals like geo-duck. - On the way to apply Tetraselmis strain T1 in feeding geo-duck, outline for its biomass production was structured.. - Geo-duck is a bivalve species, which inhabits commonly in Quang Ninh and is served as a specialty with high nutrition [3]. - However, geo-duck resource is decreasing seriously. - 40 way to find suitable food for sustainable development and conservation of this resource we carried out the research “Isolation and selection of Tetraselmis strains for feeding Geo-Duck larvae at Vandon, Quangninh”.. - Isolation and classification of Tetraselmis strains. - Tetraselmis strains were isolated based on their morphological properties using micropipettes [5,9]. - Cell density was determined with a Neubauer haemocytometer in three replicates. - In order to survey the influence of temperature on photosynthetic system of Tetraselmis strains, florescence indexes were measured using Plant Efficiency Analyser (PEA), Hansatech Intruments Ltd., Englanh, from which Fv/Fm ratio was calculated [1,2].. - Fatty acids were identified by comparing retention times with those of a calibration standard solution.. - Isolation of Tetraselmis strains. - Tetraselmis strains were isolated from the seawater at the shrimp farming in Vandon, Quangninh and signified as T1, T2, T3. - Cell density was determined every 2 days until 6 days of cultivation. - Cell density (x104/ml). - The growth of three Tetraselmis strains T1, T2, T3 3.2. - Taxanomic properties of Tetraselmis T1 species. - Observation on the morphology of Tetraselmis T1 species (Fig. - Morphology of Tetraselmis strain T1 3.3. - Tetraselmis strains are photoautotrophic microorganisms. - In this study, f/2, ESM and ASW medium were used for Tetraselmis strain T1.. - Cell density of Tetraselmis. - Cell density (10 4 / ml) f/2. - 12.5 44. - 12.5 37.5. - 12.5 22. - The growth of Tetraselmis T1 on different media. - Data showed the population density of Tetraselmis T1 increase steadily on f/2 medium and reach the maximum (122x10 4 cells/ml) on the eighth day of culture. - It is suggested that f/2 is the most suitable for culturing Tetraselmis strain T1 and can be applied for biomass production in aquaculture.. - The effect of temperature on photosystem II of Tetraselmis T1. - The data suggested low heat-tolerance ability of Tetraselmis T1. - Analysis of fatty acid components of Tetraselmis T1. - Fatty acids are mostly located in the cell membrane, which is much enough to apply to taxonomic characterization.. - Furthermore, most animals cannot synthesize essential fatty acids (linoleic and linolenic acid) thus have to depend on the diet [4,6]. - Fatty acid components of Tetraselmis strain T1 were analysed.. - The fatty acid profile of Tetraselmis strain T1 (Table 2) consisted of huge range of fatty acids from 12C to 23C with C 16 and C 18 being most abundant. - The unsaturated fatty acids accounted for 68.5%, among which C 18 polyunsaturated fatty acids (PUFA) were the major.. - linoleic acid are essential fatty acids that can be converted into long-chain PUFA in algae, which many marine animals showed limited ability [8]. - This result suggested high quality of Tetraselmis T1, which can be applied in aquatic food webs such as for feeding geo-duck.. - Percentage composition of fatty acids in Tetraselmis strain T1. - Fatty acids Quantities. - Biomass collecting of Tetraselmis strain T1. - In order to collect biomass from Tetraselmis strain T1 for feeding geoduck larvae 8 day age, Tetraselmis strain T1 was cultured in f/2 medium, grown at room temperature and illuminated under neon light (Philips daylight tubes) 4000 - 5000 Lux as the following scheme with illustrated pictures.. - Microalgae volume was used depending on geo-duck larvae density in the container. - At Van Don, Quang Ninh, we have been fed geoduck larvae with 120 – 180 liters microalage with cell density 12.2-12.5 10 5 cells/ml for one tank about 2.510 5 – 16.610 5 geo duck larvae/m 3 per day. - Stock culture Cell density 2.25-3.310 5. - cells/ml. - 2-6 litre flask After 5-7 days, cell density. - 5,610 5 cells/ml. - 30–60 litre plastic bag Cell density 8.8- 12.2 10 5. - 160 litre tank After 4-6 days, cell density. - 12.2 – 12.5 10 5 cells/ml 10 litre container After 2-3 days, cell density. - 8.5-1110 5 cells/ml. - Three Tetraselmis strains were successfully isolated from the shrimp farming at Vandon, Quangninh and annotated as T1, T2, T3. - Among them, Tetraselmis strain T1 showed best growth and well cultured in f/2 medium.. - Fatty acid composition of Tetraselmis strain T1 was typical of most green algae with high content of C 16 and C 18 acids. - Approximately 68.5% of total fatty acids were unsaturated, among which -linolenic acid and linoleic acid were major components. - The data suggested the signification of using Tetraselmis strain T1 in feeding geo- duck as high quality food. - The outline of biomass production of Tetraselmis strain T1 for aquaculture of geo-duck larvae in Van Don, Quang Ninh was established.. - Producing techniques of Geo-Duck. - Fatty acids composition of 10 microalgal species Songklanakarin J. - The high content of polyunsaturated fatty acids in Nannochloropsis limnetica (Eustigmatophyceae) and its implication for food web interactions, freshwater aquaculture and biotechnology. - Biomass production, total protein, chlorophylis, lipids and fatty acids of freshwater green and blue-green algae under different nitrogen regimes. - Fatty acids from Microalgae of the genus Pavlova