Regulation of polyunsaturated fatty acid (PUFA) synthesis in Artemia salina during development

In the aquaculturally important brine shrimp Artemia salina polyunsaturated fatty acid (PUFA) composition changes as a function of the diet and the developmental stage. Brine shrimp adults on a yeast diet have high level of 20:4 n-3 while those on an algal-live yeast diet have high levels of 18:26 n-6. The compositional analyses also indicate that uptake or synthesis of 18:2 n-6 (linolcic acid) is enhanced only in the presence of algae. Overall this results in the highest 18:2 n-6/18:3 n-3 ratios in the adults on the algal-live yeast diet, specifically in the adult females suggesting a reproductive role for n-6 PUFAs. A change in the 18:2 n-6 level is first observed in 1-2 mm feeding nauplii. Synthesis of 18:2 n-6 is suggested by in vivo and microsomal analyses. A developmental role of 20:4 n-6 is suggested in the juveniles where levels of 20:4 n-6 are high, independent of the type of diet. In addition, development time, weight, length, and lipid content are correlated with the type of diet. While the 20:4 n-6/18:2 n-6 ratios are lowest in the adults on the algal-live yeast diet, 20:4 n-6 levels are highest in brood carrying females on this diet. The animals on this diet develop faster into adults and weigh the most.; Immediately after hatching, brine shrimp nauplii are rich in fatty acids and PUFA synthesis is high. Cytosolic saturated fatty acid and oleic acid synthesis are increased at two and four hours of incubation of 24-48-hour nauplii in vivo. At six hours, levels of 18:0, 18:3,/22:6 n-3 and 20:5 n-3 are highest. 18:2 n-6 is synthesized in vivo.; For the first time, desaturation of {dollar}{bsol}sp{lcub}14{rcub}{dollar}C 18:0 is shown in the crude preparation of Crustacean microsomes. Carbon monoxide, and inhibitor of the mitochondrial electron transport chain and not the microsomal, does not inhibit the microsomal desaturases while potassium cyanide inhibits the brine shrimp mitochondrial and microsomal electron transport chains. Under optimal conditions the synthesis rate of 18:1 n-9 is 2.61 pmol/min mg microsomal protein. In a ten-minute microsomal desaturation assay the components of the n-3 PUFA biosynthetic pathway are synthesized in sequence, first 18:1, 18:2 and 18:3 and finally 18:4 n-3 and 20:5 n-3. PUFAs of the n-6 series are synthesized in this development stage, but less label is recovered in n-6 PUFAs. This confirms the results obtained from the PUFA composition analyses.; Other regulators of lipid and PUFA synthesis may include the Crustacean hormones methyl farnesoate and ecdysone. Initial studies indicate the presence of methyl farnesoate in the brine shrimp cysts. The presence of ecdysone in A. salina has already been established.