Meeting Abstract
Monarch butterfly larvae, Danaus plexippus, have a diet entirely composed of milkweed, (Asclepias) while the adults use nectar from a variety of sources. While the nectar eaten by the adults contains minimal lipids, the milkweed has a variety of lipids, and their constituent fatty acids help provide their nutritional needs. Asclepias tuberosa was selected to identify the fatty acids that the monarchs are ingesting. Milkweed leaves were sliced into small segments, dried, and then weighed. We hand collected monarch caterpillars and butterflies, and turned each into a slurry with a tissue tearor. Lipids from all samples were extracted via a mixture of chloroform, methanol, and water in a 4:2:1 ratio and then converted to fatty acid methyl esters (FAMEs) to be analyzed by gas chromatography. The most common fatty acid present in the milkweed was linolenic acid, or 18:3 (about 60% of all fatty acids). The caterpillars showed the most common to be palmitic acid, or 16:0, followed by 18:3. The adults showed oleic acid, or 18:1, as the most common fatty acid. This suggests that monarchs acquire the major starting lipid, 18:3, and turn it into different fatty acids for storage and utilization. Interestingly, different stages of the monarch’s life have a different fatty acid profile, suggesting they utilize different lipids during different life stages. One unexpected result was that some monarchs showed as high as 50% 18:3 while other samples showed 0%.
