This blue our mind and left us green with envy—fluorescing animals at the Aquarium!
Fluorescence is what you get when short-wavelengths of light—like UV and blue light—excite electrons in substances, causing them to radiate back longer wavelengths of light—like greens, yellows and reds. (This is not to be confused with bioluminescence, where chemical reactions inside animal bodies are producing their own light.)
Fluorescence in animals is widespread, and may serve different purposes. For some animals, fluorescence is merely a fun physics phenomenon without an intended purpose—shark skin, shrimp shells and human fingernails all fluoresce without much apparent benefit.
But for others—like anemones, jellies and even mantis shrimp—fluorescence may be a way to lure prey toward a dastardly demise, with brightly illuminated stinging tentacles and ensnaring traps standing out against what appears to us to be but a banal background.
Blue lights and yellow filters to highlight fluorescent wavelengths are excellent tools to track the reproduction and development of certain critters. Our Jelly Team previously used fluorescence to complete the life cycle of the flower hat jelly!
Special thanks to brilliant Aquarist Christy for sharing the tube anemone photos and gifs in this thread from their rounds at the Aquarium! And if you’d like more on the subject, check out this talk with Monterey Bay Aquarium Research Institute’s Dr. Steve Haddock all about animal light: