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Brine shrimp, Artemia sp., nauplii are used throughout the world for the culture of larval aquatic organisms, especially fish and crustaceans. Recent studies have shown that the nutritional quality of Artemia can vary greatly from batch to batch and that Artemia fall basically into two categories: those that can only support survival, growth, and reproduction of freshwater organisms, and those that can also support survival, growth, and reproduction of saltwater organisms. The difference arises because marine organisms require certain essential fatty acids that freshwater organisms do not.
ASTM Standard E 1203 describes procedures for evaluation and use of Artemia nauplii as food for toxicity test organisms [Practice for Using Brine Shrimp Nauplii as Food for Test Animals in Aquatic Toxicology Tests (E 1203)]. One suggested procedure is the determination of the fatty acid composition of the Artemia. However, different laboratories around the world use different analytical methods for determination of lipid content and fatty acid composition and different ways of expressing the results. Until recently, most investigators reported the amount of each fatty acid as a percentage of the total amount of all fatty acids (the area percent method). Now, reports of absolute amounts of each fatty acid (mg fatty acid/g tissue) are increasingly seen. The results are sometimes expressed on a wet-weight basis, sometimes on a dry-weight basis.
An international interlaboratory exercise was conducted to investigate the variability associated with the preparation and analysis of samples and the reporting of fatty acid composition data for two samples of Artemia supplied to the laboratories by the Artemia Reference Center (ARC). Results reported to the ARC indicated that intralaboratory variability in determinations of total lipid content and fatty acid composition by the area-percent method was generally low, with a coefficient of variation (CV) around 5 to 7% on average. Intralaboratory variability in determination of fatty acid composition by the mg/g method was higher, with CVs greater than 10% in several cases. Interlaboratory variability was generally much greater, with CVs of > 20% for total lipid content, 8 to 27% for composition of individual fatty acids determined by the area-percent method, and 12 to 49% for composition of individual fatty acids determined by the mg/g method. Thus, the precision of the data from any given laboratory is generally adequate, but the accuracy may not be. Nevertheless, in this case, data from each of the laboratories would support the decision to use these particular Artemia only for freshwater organisms.
brine shrimp, Artemia, fatty acids, interlaboratory exercise
Research associate, Artemia Reference Center, State University of Ghent, Ghent,
Research assistant professor, Department of Zoology, University of Rhode Island, Kingston, RI
Senior scientist, Belgian National Science Foundation, Artemia Reference Center, State University of Ghent, Ghent