Sönke JohnsenLive Science ContributorSönke Johnsen is professor of biology at Duke University. He is the author of "The Optics of Life: A Biologist’s Guide to Light in Nature" and the coauthor of "Visual Ecology." 'An ancient, complex, and very serious game is going on': The weird ways creatures feed in the open ocean Sea angels — a type of swimming slug — that live in the open ocean are carnivorous little creatures that have evolved to feed on sea snails.
