Aphids, those sap-sucking foes of gardeners, come in a variety of colours. We usually think of them as green, but pea aphids sometimes wear a fetching red ensemble. That may not strike you as anything special; after all, lots of animals are red. But the aphid’s colour is unique in a couple of extraordinary ways.
The colour comes from pigments called carotenoids. Animals use them for all sorts of purposes; they act as antioxidants, and they contribute to red, orange and yellow colours. But the pea aphid is one of only a few known species (all aphids) that manufacture their own carotenoids; everyone else gets theirs from their food. But it’s the source of the pea aphid’s ability that’s truly remarkable – it stole the skill from fungi. By integrating fungal genes into its own genomes, it gained a superpower that almost all other animals lack.
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