For decades, carotenoids have attracted attention for their roles as vitamin-A precursors, antioxidants, and immunostimulants, but we still understand very little about the metabolic processes that accompany these compounds. Animals like birds use carotenoids to color their feathers and bare parts to become sexually attractive. They commonly metabolically derive their body colorants from dietar...

Parasites induce phenotypic modifications in their hosts, which can compromise host fitness. For example, the parasitic fly Philornis downsi, which was recently introduced to the Galápagos Islands, causes severe naris and beak malformation in Darwin’s finches. The fly larvae feed on tissues from the nares of developing finch nestlings, thereby altering the size and shape of the nares and beak. ...