Highly fluorescent photoreceptor pigments in blue-green, red, and some other algae. They contain a linear tetrapyrrole prosthetic group for light harvesting. They also contain bile pigments and an apoprotein. This family of pigments includes the blue phycocyanins, the red phycoerythrins, and the pale blue allocyanins. These pigments may form phycobilisome, attached to the photosynthetic membrane. Phytochromes are also related pigments.  light-harvesting protein,  phytochrome; Wu SH et al 1997 J Biol Chem 272:25700.