Bioluminescence
Human beings are remarkable creatures. We’re well known for using large-scale cooperation and the transmission of knowledge to improve things over generations.
We also glow in the dark. We are less known for this.
Bioluminescence in humans arises mainly because of our metabolism. Our bodies are filled with cells, where lots of little chemical reactions produce energy. When sugar or fat is broken down in a cell, a lot of energy is released, helping to provide the fuel you need to do the things you do.
Some of the energy, however, is “extra”, and it ends up exciting other molecules inside the cell. This uncomfortable “excited” state can’t last forever, and the molecules “want” to release that extra energy. One way this energy is released is by way of a photon—a tiny packet of light.
I wrote about this idea a bit here:
The amount of light that comes from humans as a part of this process is very, very small—too small for even the best human eyes to detect. But hey, at least we glow in the dark just a little bit!
Sadly, goats are not even a little bioluminescent.
However, their eyes do appear to “glow in the dark” because of their highly reflective nature! I feel like partial credit is due.
Probably the most common example of this phenomenon, and one that you really can see at night, is that of fireflies. While it’s all about metabolism with humans, fireflies use a specialized organ just for the purpose of glowing.
A compound called luciferin (cute, right?) mixes with oxygen and ATP (sometimes called “the energy currency” of the cell), putting the luciferin into an excited state (remember, the molecules “want” to be at their lowest energy state).
The chemical reaction once again leads to a photon being released, and so the firefly’s butt lights up. Fireflies have control over how much oxygen gets there, mainly to attract mates (but also sometimes to scare away predators).
Bioluminescence is one of those phenomena that surely would have captivated our oldest ancestors. It’s a visible manifestation of how cool nature is!
Were you fascinated by fireflies when you were growing up? Are you still fascinated by them? What are some other weird facts about biology you know?
Man, there are a lot of cool mating rituals in the animal kingdom, but it sure is hard to beat "My butt is literally glowing!"
Well played, fireflies. Well played.
Whales have internet. Maybe. There is a theory that humpback whale songs, which travel vast underwater distances, are encoded transferences of emotion, allowing all individuals who hear and recognise a specific song to join together into a singular, emotional and informational experience while separated physically. And that’s basically information networking! (Fact curtesy of the podcast Radio Lab, from where I get 80 percent of my brain at any time).
Thank you for a fun article about bioluminescence - I did not know that I glowed in the dark. Even a little bit.