In 2010, scientists at the University of Arizona showed that aphids can produce their own carotene. No other animals are known to produce this important antioxidant and must therefore obtain it from their diets. Aphids apparently acquired this ability to produce carotenoids from a fungal gene that was incorporated into their own genome at some point in evolutionary history. Because aphids were shown to produce large amounts of carotenoids, researchers Valmalette et al., wanted to know if the carotenoids served any other important function(s) in the animals. They observed that pea aphids raised in cold conditions appeared green whereas those raised in warm conditions appeared more red in color leading them to suspect that the carotene may play some role in metabolism. In a recent paper, the researchers presented data showing aphid carotenoid genes are similar to those found in cyanobacteria and chloroplasts, which harvest light to produce energy. Moreover, they discovered that the aphid carotenoids were able to capture light and use it to produce cellular energy (ATP), much like a plant uses photosynthesis to produce ATP.
Valmalette et al., 2012 Scientific Reports doi: 10.1038/srep00579