bobtail

In the darkness of the deep ocean, some animals create their own light. Among these is the Hawaiian bobtail squid Euprymna scolopes, which forms a partnership with the luminous bacterium Vibrio fischeri. The squid houses colonies of these bacteria in special light organs, and it can control the brightness and direction of their illuminations. But these organs do much more than produce light - they detect it too. Deyan Tong from the University of Wisconsin has discovered that the organs generate nervous signals when they sense light and they're loaded with proteins responsible for detecting…
The Japanese pinecone fish searches for food with living headlights. This ÂÂhand-sized fish harbours colonies of light-producing bacteria in two organs on its lower jaw. The beams from these organs shine forward, and when night falls and the fish goes searching for food, its jaw-lamps light the way. Elsewhere in the Pacific Ocean, the Hawaiian bobtail squid also uses luminous bacteria, but theirs act as a cloaking device. They produce a dim glow that matches the strength of moonlight from above, hiding the squid's silhouette from hungry fish below. It's a mutual relationship; the squid gets…