Guppy habitats in northern Trinidad
Examples of guppy habitat in Northern Trinidad. The stream on the left, Aqui River, receives more light and therefore has higher carotenoid availability than the small tributary of the Paria River, on the right. Guppies obtain carotenoids from algae, which grows on submerged rocks. The submerged rocks in the stream on the left are shades of red, green and brown, because they are covered with a thin film of algae. In contrast, the rocks in the stream on the right are bare.
(Credit: Greg Grether/UCLA ecology and evolutionary biology)