Elegant and diaphanous, the jellyfish Pelagia noctiluca is pretty, but packs a punch. These jellies (also called “purple-striped jelly” or “mauve stinger”) produce bright bioluminescent light (noctiluca means “night light”) and feed by catching smaller plankton animals, or zooplankton,
on tentacles laden with stinging cells. Common in coastal waters of
most oceans, they can cause problems for humans—swarms of thousands of Pelagia plagued Mediterranean beaches in summer 2008, causing painful stings to swimmers.
(Photo by Laurence Madin, Woods Hole Oceanographic Institution)