Torulene (3',4'-didehydro-β,γ-carotene) is a carotene (a hydrocarbon carotenoid) which is notable for being synthesized by red

pea aphid ''Acyrthosiphon pisum'', commonly known as the pea aphid (and colloquially known as the green dolphin, pea louse, and clover louse), is a sap-sucking insect in the family Aphididae. It feeds on several species of legumes (plant family Fabaceae) w ...

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Acyrthosiphon pisum ''Acyrthosiphon pisum'', commonly known as the pea aphid (and colloquially known as the green dolphin, pea louse, and clover louse), is a sap-sucking insect in the family Aphididae. It feeds on several species of legumes (plant family Fabaceae) ...

''), imparting the natural red color to the aphids, which aids in their camouflage and escape from predation. The aphids have gained the ability to synthesize torulene by

horizontal gene transfer Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction). H ...

of a number of genes for carotenoid synthesis, apparently from fungi. Plants, fungi, and microorganisms can synthesize carotenoids, but torulene made by pea aphids is the only carotenoid known to be synthesized by an organism in the animal kingdom.

References

{{Carotenoids Carotenoids Plant physiology Cyclohexenes