Greenish pigments in pea aphids, Acyrthosiphon pisum, may capture sunlight for use in metabolism, according to new French-Israeli research.
These carotenoids produce different color morphs depending on environmental conditions. When it is cold, the aphids have high pigment levels and are green; they have intermediate levels and are orange in optimal conditions; white individuals appear in large populations with limited resources, and have almost no pigment.
Pea aphids are the only known animal to synthesize carotenoids with all other animals obtaining them via diet for immunity and some other functions.
But plants, some fungi, and some bacteria do make these pigments, and use them in photosynthesis.
The scientists studied the aphids’ energy levels in the form of ATP production. They found green ones make more ATP than white ones, and orange ones make more ATP in the light than in the dark.
“Our data suggests strongly that the environmentally guided synthesis of these compounds in aphids plays a role in absorption of sunlight and in electron transfer to mitochondrial protein complexes,” wrote the researchers in their study.
Furthermore, the pigment molecules lie in a layer down to 40 micrometers below the insect’s cuticle, which is an ideal position for trapping sunlight.
However, aphids get plenty of sugar in their diet and excrete any excess, making the scientists wonder why they would need to harvest sunlight for energy.
One possibility is that the pigment acts like a battery, for example when the insects are seeking a new plant to feed on.
The study was published in Nature’s Scientific Reports on Aug. 16. You can view it here.
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