Effect of enriched Brachionus plicatilis and Artemia salina nauplii by microalga Tetraselmis chuii (Bütcher) grown on four different culture media on the growth and survival of Sparus aurata larvae
The growth, developmental stages and survival rates of Sparus aurata larvae fed with Brachionus plicatilis and Artemia salina nauplii enriched by microalga Tetraselmis chuii were studied. Two experiments were carried out; the first concerning with culturing the microalga (T. chuii) in four different media, then using these cultures for enrichment of the rotifer (B. plicatilis) and brine shrimp (A. salina) nauplii). The second experiment was considered the application of enriched B. plicatilis and A. salina were used for feeding S. aurata larvae. Mean growth and survival rate of larvae were used for evaluation of the best medium. Erdschriber medium was considered the best algal medium compared with the other media used because the cell density were the highest (24.5 X 106 cell.ml-1) on the 11 day (late logarithmic/early stationary phase of growth), the highest survival and greatest growth rates of S. aurata larvae were noticed. The total fatty acids in T. chuii especially the polyunsaturated fatty acid were represented by content 5.5% [arachidonic acid (ARA)], 4.8% [eicosapentaenoic acid (EPA)] and 5.0% [docosahexaenoic acid (DHA)] to the total fatty acids. The higher production of total fatty acids in B. plicatilis fed on T. chuii grown in Erdschriber medium was due to the accumulation of polysaturated fatty acids (PUFAs) (94.7% of the total lipids). EPA was absent, while DHA (22:6ω3) was enhanced and constituted 657.49 μg.g-1 (91.4% of the total fatty acids). Saturated fatty acids were detected more than unsaturated one (63% of the total fatty acids), in case of A. salina fed on T. chuii grown in Erdschriber medium, especially the short chain fatty acids (C16:0, C18:0 and C21:0). On the other hand PUFAs constituted 22.3% of the total fatty acids, due to the presence of DHA which formed 8.0% of the total fatty acids, while ARA and EPA were absent. The results show that B. plicatilis and newly hatched Artemia enriched with T. chuii grown on was effective for good growth and survival rate of S. aurata larvae.
Key words: Tetraselmis chuii, Erdschriber medium, Brachionus plicatilis, Artemia salina, Sparus aurata larvae, growth rate, survival.