Evidence for a specific red light photoreceptor in aphids

Aphid species are supposed to have three spectral types of photoreceptors (blue, green, and UV). The light intensity is known to regulate the polymorphism of aphids, the photoreceptors being involved in the transmission of the light signal. For example, in Sitobion avenae clones more alatae are produced at low light intensities. Moreover, S. avenae clones synthesize carotenoids at high light intensity resulting in different colours; these carotenoids play a role in protecting their bacterial endosymbionts. We investigated specific responses in aphids triggered by the light of different wavelengths. Our experiments provide evidence that S. avenae has a photoreceptor for red light, which is complementarily needed besides the blue photoreceptor to synthesize carotenoids.