Lipid biosynthesis in adult Acyrthosiphon pisum: Effect of age and symbiont population

The incorporation of [1‐14C]acetate into total lipids in 1‐day‐old adult pea aphids is 3.3‐fold higher than in 20‐, 22‐, and 24‐day old adults. The polar lipid fraction was the main lipid class synthesized at any age and contained primarily eighteen carbon fatty acids. While the relative mass of 18:0, 18:1 and 18:2 decreased in older aphids, the relative amount of label incorporated into these fatty acids remained constant. Myristic acid was the main fatty acid of the triacylglycerol fraction, and the relative amount of radioactivity incorporated into this fatty acid decreased in older aphids. Twenty‐day‐old aphids had 60% fewer mycetocytes than did 1‐day‐old insects. We conclude that symbionts within the mycetocytes do not appear to be involved in the synthesis of linoleic acid, while their role in the synthesis of myristic acid is less clear.