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These deep-ocean starfish can see—and glow—in the dark

Hundreds of meters under the sea, the only light is the eerie glow of bioluminescent creatures like vampire squid, anglerfish, comb jellies, and starfish. Now, researchers have discovered that many of these deep-sea starfish have fully developed eyes, which they may use to hunt down glowing prey—and mates. Most shallow-water starfish have compound eyes at the tip of each arm, which produce simple images of large stationary objects like coral. To find out whether starfish in the deep ocean also retain functional eyes, researchers examined 13 species living at a range of depths off the coast of Greenland. They found that all but one had eyes, including three kinds of starfish which lived in water below 320 meters, deep enough to receive almost no light from the surface, the researchers report today in the Proceedings of the Royal Society B. Among these was Novodinia americana, whose eyes contained enough ommatidia—the individual units that make up a compound eye—to produce an image of a few hundred pixels: practically high definition for a starfish. N. americana could also emit light from across the entire surface of its body. The researchers speculate that this combination of bioluminescence and well-developed eyes allows the starfish to communicate visually with potential mates—a complex behavior never before observed in the creatures.