Marine biologists exploring the deep sea off the coast of Monterey Bay have discovered a curious species of invertebrates that lures its prey by flashing brilliant red lights at the ends of its twitching tentacles.

The wormlike members of a marine tribe known as siphonophores are a striking example of evolution having endowed an organism with a feature even its closest relatives don't possess: a set of genes for "bioluminescent" light, which in an immature animal flashes blue but switches to deep red as it matures.

Distantly related to jellyfish and corals, the animals are a newfound species of an obscure genus called Erenna -- whose other luminous members use their light only to defend themselves against larger predators, not to hunt and kill prey on their own, according to Steven D. Haddock of the Monterey Bay Aquarium Research Institute.

"They're pretty amazing animals," Haddock said in an interview. "They may look like simple creatures, but they show an incredible level of detail in their development and their bioluminescence."


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They are the first marine invertebrates known to emit light at the red end of the spectrum, rather than the blue or green.

Haddock and his colleagues discovered three members of the rare and as yet unnamed species swimming a mile to a mile and a half deep. The seagoing researchers spotted the strange organisms through the "eyes" of their remotely operated unmanned submarine, the Tiburon. They were cruising 100 miles out -- at the extreme end of the Monterey Canyon, a major undersea feature of California's coastal geology -- and observing from far above, aboard the research institute's surface vessel, the Western Flyer.

The animals are extremely fragile and can break into fragments at a touch, but Haddock and his colleagues managed to collect one with the suction tool of the Tiburon and keep it alive briefly to study its anatomy.

Their discovery is being reported today in the journal Science.

Like their relatives the corals, the animals are long and slender "colonial" organisms, composed of many individual "zooids" attached to each other that act as if they were one and reproduce by budding.

The three that Haddock and his colleague found were only a few inches long and were swimming with the luminous red branches -- armed with stinging cells -- on the tips of their tentacles, flicking and writhing like blazing hairs of a mythical Medusa.

Two of the three specimens that Haddock's team observed held the half- digested bodies of tiny fish, and it seemed clear to the scientists that the red bioluminescence was the deadly lure that attracted and killed them. Fish are rare at those extreme depths, Haddock explained, but when they do thrive, they dine on tiny phosphorescent crustaceans called copepods -- and the red luminescence of the siphonophores apparently mimics the attractive brightness of the fishes' regular prey. Scientists have long believed that deep-sea animals can't see red light, but these siphonophores are the first exception to that idea, and there may be many others, Haddock believes. Even the fish that the siphonophores attract may be discerning the bright luminescence not just as light but also as the color red, he said.

At the California Academy of Sciences in San Francisco, Gary Williams, a biologist who specializes in corals and their relatives, said he was astonished at the evidence that Haddock's organisms appeared to use red light to attract prey.

It's well known, he said, that even humans can't clearly see red objects in water depths much below 60 feet. For marine organisms to emit red light at depths over a mile poses a fresh mystery about the sensitivity of deep-water animals to varying frequencies of the spectrum.

"It's a fascinating discovery," he said.

Haddock's colleagues include Casey Dunn, an evolutionary biologist at Yale; Philip Pugh of Britain's National Oceanography Center; and Christine Schnitzler of MBARI, the Monterey research institute.