| unique evolution of vitamin a as an external pigment in tropical starlings. | pigments are largely responsible for the appearance of organisms. most biological pigments derive from the metabolism of shikimic acid (melanins), mevalonic acid (carotenoids) or levulinic acid (porphyrins), which thus generate the observed diversity of external phenotypes. starlings are generally dark birds despite iridescence in feathers, but 10% of species have evolved plumage pigmentation comprising bright colors that are known to be produced only by carotenoids. however, using micro-raman s ... | 2019 | 31097603 |