Lipid labeling with32P-orthophosphate and14C-acetate in marine copepods

Freshly collectedCalanus pacificus were maintained in sea water containing 25 μCi/ml ³²P]orthophosphate or 1 μCi/ml ¹⁴C]acetate at 10 C for 24 hr. The animals took up label from the environment and incorporated it into various lipid fractions. After incubation with ¹⁴C]acetate the order of specific activity of the different lipid classes was: phospholipids > free fatty acids > wax esters > triglycerides. Argentation thin layer chromatography of the fatty acid methyl esters showed that ca. 50% of the activity was in saturated fatty acids and 34% in polyunsaturated acids. When the animals were exposed to ³²P]orthophosphate, lysophosphatidyl choline became most heavily labeled, followed by lysophosphatidyl ethanolamine, sphingomyelin, phosphatidyl ethanolamine, and phosphatidyl choline. Comparison of the data obtained with those available for decapods and mammals revealed striking similarities between these phylogenetically distant groups. It is believed that labeling the lipids of marine and freshwater planktonic crustaceans in this way will provide much information about the metabolism of lipids in these organisms.