noun, plural: carotenoids
(botany) Any of the pigment molecules, typically yellow, red, and orange, that interact with chlorophylls inside chloroplasts when they absorb light primarily for photosynthesis and protection from photodamage, and are also found in chromoplasts where they are produced and stored
(zoology) A yellow, red, and orange pigment found in the tissues of certain animals
Photosynthetic autotrophs have pigments that absorb light energy to synthesize complex organic material from inorganic sources. There are three basic types of photosynthetic pigments: (1) chlorophylls, (2) carotenoids, and (3) phycobilins. Chlorophyll is the major light-absorbing pigment within the chloroplast of photoautotrophs, such as higher plants. There are photoautotrophs that have additional pigments to aid in light absorption. Their pigments act as an accessory, thus the name accessory pigments, in a way that they do not transfer light energy directly to the photosynthetic pathway but to the primary pigment, chlorophyll. Examples of accessory pigments are carotenoids and phycobilins.
Carotenoids are accessory pigments that are typically yellow, red and orange. They are insoluble in water in contrast to phycobilins that are water-soluble. They occur in chloroplasts where they aid in the light absorption for photosynthesis. They are also found in chromoplasts. There are various carotenoids and they are grouped into xanthophylls and carotenes.
Carotenoids that are produced by animals were observed in aphids and spider mites. These animals are believed to have acquired the genes and ability from fungi.1
1 Altincicek, B., Kovacs, J. L., & Gerardo, N. M. (2011). “Horizontally transferred fungal carotenoid genes in the two-spotted spider mite Tetranychus urticae”. Biology Letters 8 (2): 253–257.