How do some animals glow? — Speaking of Chemistry

Fireflies, frogs, jellyfish, mushrooms, and
even parrots have mad glowing skills. Humans may rule the natural world, but we
seriously missed the boat when it comes to emitting light from our own bodies. So how do these creatures do it? So the first thing you need to know is that
there are two ways to get your glow on. There’s bioluminescence—what these fireflies
are doing—and fluorescence—which is what’s going on with these parrots. Many people conflate bioluminescence and fluorescence,
but you guessed it, there’s a difference. Let’s start with fluorescence, which also
happens to be this recently-discovered South American tree frog’s party trick. In full sunlight the frog appears yellow,
but in twilight the amphibian’s fluorescence steps up its game, making the creature appear
an eerie lime green. To fluoresce, the frog—and any other fluorescing
creature—just needs two things. A molecule with excitable electrons and the
right wavelength of incoming light. For excitable molecules, the frogs rely on
chemicals called hyloins, which reside in the animal’s skin and glands. Incoming light excites the molecule’s electrons
and as those electrons settle back down, the molecules release some light of their own. Nobody knows yet why the frog fluoresces,
but it’s probably to communicate a message… perhaps it’s a little fluorescent flirtation
for froggy paramours? In any case, scientists were pretty stoked
to find a fluorescent tree frog. Fluorescence is rare in land animal. It’s more often found in sea creatures,
such as turtles and fish. Of course there’s some notable exceptions
of natural fluorescence on land, such as these scorpions and parrots. My favorite example of natural fluorescence
happens to be the blue light emitted by nematode worms as they die. Full disclosure, I’m not a huge fan of worms. I’ve found them terrifying since I was wee. So it doesn’t surprise me that they have
a creepy death ceremony. The worms fluoresce blue thanks to a glycosylated
anthranilic acid pigment that absorbs light and then emits blue wavelengths. The death glow begins in a worm’s gut and
spreads to the whole body as the creature wends its way to the wormy afterlife. The scientists who discovered this macabre
fluorescence are using it to better understand the process of death. And that shines some light onto why scientists
are so into glowing animals in general. Studying these creatures, whether they fluoresce
or bioluminesce, has helped advance biology, medicine, imaging, and sensor technologies. So what about the other variety of animal
glow? So bioluminescence requires oxygen and some
fancy chemical equipment. What’s amazing is that this chemical equipment
is remarkably similar in most organisms that bioluminesce—think fireflies, jellyfish,
bacteria, and even this mushroom from Brazil, whose glowing skills were recently discovered. To emit light through bioluminescence, you
need a molecule called luciferin and you need an enzyme called luciferase. Luciferase takes oxygen and plops it onto
the luciferin. The outcome is a molecule called oxyluciferin
whose electrons are in an excited state. When the electrons in oxyluciferin calm back
down, they release light, which makes the organism glow. To recap, in both fluorescence and biolouminescence,
light is emitted when an excited molecule’s electrons calm down. The major difference between the two is that
with fluorescence, you also need to start with a little bit of light to emit light. With bioluminescence you need oxygen, an enzyme,
and some nifty chemistry to glow. And some creatures have the enviable ability
to do both. Probably the most famous of these glowers
is the jellyfish Aequorea victoria. This sea creature uses bioluminescence to
produce a faint blue light. Some of that light can then be used to excite
a green fluorescent protein—better known as GFP—in the jellyfish. Sound familiar? Research on the molecule garnered Roger Tsien,
Osamu Shimomura, and Martin Chalfie the 2008 Nobel Prize in Chemistry. GFP has become one of science’s most valuable
proteins for exploring biology and biochemistry. It’s also been used to make all kinds of
animals glow green. So maybe there’s still hope for those humans
who want to hack in a bit of glow. Personally I might stick with my glow sticks. What’s your favorite glowing creature? Tell us about it in the comments.


  1. That Plane August 14, 2017 at 4:16 pm


  2. David Phillips August 15, 2017 at 10:14 am

    Excellent presentation!

  3. Manzel Montes December 6, 2017 at 2:02 am

    M favorite is the jellyfish

  4. Bousquet Jeannette March 12, 2018 at 8:07 am

    I really liked this video. We learned a lot about bioluminescence 😮

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