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Earth is full of glowing organisms. Some glow in the light of the sun, while others produce their own light in the darkest parts of the planet. This episode, we look at the incredible phenomena of Bioluminescence and Biofluorescence.
In the news
A new species of painted turtle from the Gray Fossil Site
Early herbivorous dinosaurs developed distinct plant-eating styles
Insights into the evolution of human (and Neanderthal) brains
This fossil katydid has the oldest known insect ears
Life, Illuminated
Glowing organisms, generally speaking, come in two varieties:
Bioluminescent organisms produce their own light, typically with chemicals called luciferins which emit light upon being oxidized.
Biofluorescent organisms absorb certain wavelengths of light and re-emit them as different wavelengths, thus giving off a glow. This absorption-and-emission often occurs in certain proteins, minerals, or other molecules.
Top right: A biofluorescent scorpion. Image by Jonbeebe, CC BY-SA 3.0
Bottom left: Bioluminescent mushrooms. Image by Anonymous, CC BY-SA 3.0
Bottom right: Biofluorescent coral. Image by Tiia Monto, CC BY-SA 3.0
Bioluminescence and biofluorescence are astonishingly common. Bacteria, algae, fungi, plants, and many groups of animals include members that luminesce, fluoresce, or both. The effect comes in a wide variety of colors and intensities and can perform many different functions from communication to camouflage.
Image by Casa Rosada, CC BY 2.5 AR
Image by Masaki Miya et al., CC BY 2.0
Image by Ian Alexander, CC BY-SA 4.0
Image by NOAA Ocean Explorer, CC BY-SA 2.0
There are so many fascinating examples of glowing life. Here are some of our favorites that we mentioned in this episode:
Sea snail turns its entire shell into a glowing lamp
Humboldt squids use bioluminescent backlighting to make their colors pop
Dana octopus squids use glowing arms to distract prey
Fluorescent viper tails might attract prey
Glow on Sharks: State of the Art on Bioluminescence Research (technical)
The evolutionary history of bioluminescence and biofluorescence can be tough to study. These traits don’t fossilize very well – although there are fossil fireflies that tell us these animals have been glowing for over 100 million years – so instead researchers turn to genetics data, which indicates that glowing has evolved many times in many different groups.
This is Cretophengodes azari, a Cretaceous glowing beetle related to fireflies.
Top: Topside and underside views of a fossil in amber. Scale bar is 2mm. The small arrowhead points to the glowing organ in the abdomen.
Bottom: Artistic reconstruction of this insect in life.
Images from Li et al. 2021
Image by Mike, CC BY-SA 2.0
So Much to Learn!
Bioluminescence | National Geographic Society
The Ecology of Bioluminescence (technical, open access)
The Ecology and Evolution of Fluorescence (technical, open access)
A brief review of bioluminescent systems (technical, open access)
Why Is (Almost) All Bioluminescence in the Ocean?
Bioluminescent beetles in Cretaceous amber
Reconstructing the light of ancient fireflies
Can biofluorescence help us identify life on other planets? Maybe!
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COMMON DESCENT 
This was such an awesome episode! The viper rattle tidbit was incredible.
An example of biofluorescence that wasn’t brought up (that I think is cool) are some species of crab spiders using it to lure prey. When viewed normally, they look like they’re camouflaged, sitting on flowers in wait for an insect to stop by. But when viewed in UV, they’re actually very conspicuous, but it attracts prey to the flower they’re on!
Sort of related, but I think hawks also take advantage of UV fluorescence by tracking small mammal urine that fluoresces!
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