Jellyfish and other marine animals could be using their fluorescent proteins to attract prey.
Proteins such as green fluorescent protein (GFP) are invaluable tools for biologists in the lab, but their role in nature has not been clear. Steven Haddock at Monterey Bay Aquarium Research Institute in Moss Landing, California, and Casey Dunn at Brown University in Providence, Rhode Island, placed the flower hat jellyfish (Olindias formosus, pictured in blue light) in a tank along with its rockfish prey and separated the two with a transparent wall. When they exposed O. formosus to blue light (the light of its underwater habitat), the tips of its tentacles fluoresced green and the rockfish attacked the barrier more often than under yellow or white light or when the jellyfish was replaced with a non-fluorescent decoy.
Herbivorous prey may be seeing the fluorescence as an indicator of chlorophyll, which also fluoresces.
Biol. Open http://doi.org/6qd (2015)