Use of marine yeasts as an available diet for mass cultures of Moina macrocopa.

摘要

A 4-week feeding trial was conducted to test the use of marine yeasts purified from seawater and sediments as a dietary source in cultivating a cladoceran, Moina macrocopa, a potential alternative live food for fish larvae. Optimal growth conditions of two yeast strains were obtained for NaCl concentration, pH and temperature. Moina macrocopa was cultivated using different diets: marine yeasts (Debaryomyces hansenii Yeast-14 and Candida austromarina Yeast-16) and a commercial diet (Erythrobacter sp. S pi -I). The essential amino acids of both the yeast strains were nearly as great as those in M. microcopa. Further, the yeast-fed M. macrocopa had essential amino acid profiles similar to the documented values for rotifers and Artemia enriched in microalgae and commercial diets. Erythrobacter sp. S pi -I lacked n-3 polyunsaturated fatty acids, 20:5n-3 and 22:6n-3, which were also low but detected in both yeasts. An increase in the 20:5n-3 [eicosapentaenoic acid (EPA)] and 22:6n-3 [docosahexaenoic acid (DHA)] levels, compared with the levels in yeast strains themselves, was more pronounced in the 22:6n-3 level of Moina fed the C. austromarina, resulting in a high DHA:EPA ratio. When the Moina diets were switched, their delta 13C values shifted gradually towards the values of the switched diets. Diet switch from Erythrobacter sp. S pi -I to C. austromarina Yeast-16 resulted in a more rapid turnover of Moina tissue carbon than that in the inverse case. When fed a mixed diet, the delta 13C values of Moina tissue approached the value of marine yeasts immediately. These temporal changes in the delta 13C values of Moina tissue indicate the preferential ingestion of marine yeasts and a selective assimilation of the carbon originated from marine yeasts. These findings suggest that marine yeasts, particularly C. austromarina Yeast-16, are highly available to mass cultures of M. macrocopa, providing better nutritional and dietary values than the commercial diet (Erythrobacter sp. S pi -I)..