From National Geographic:
Many deep-sea creatures use blue or green luminescent light to defend themselves, but this relative of the jellyfish has twitching appendages that glow red—apparently to lure fish to their death. Steven Haddock of the Monterey Bay Aquarium Research Institute and his colleagues collected three Erenna specimens off the coast of California during a deep-sea dive in a submersible. The animals, which cannot themselves see, belong to a new species of siphonophores, the group that includes jellyfish and corals. They are the first marine invertebrates known to produce red luminescent light, and they’re all the more surprising because researchers have generally believed that deep-sea animals can’t detect red light.
More here.