The term carotene (also carotin, from the Latin carota, "carrot") is used for many related unsaturated hydrocarbon substances having the formula C₄₀H_x, which are synthesized by plants but in general cannot be made by animals (with the sole known exception of some aphids and spider mites which acquired the synthetic genes from fungi). Carotenes are photosynthetic pigments important for photosynthesis. Carotenes contain no oxygen. They absorb ultraviolet, violet, and blue light and emit orange or red light, and (in low concentrations) yellow light.