There are many wonders of the ocean, including a superpower that only some fish have! It is
called biofluorescence and is when a fish can absorb light and release it, causing the fish itself
to glow. Not only are the fish getting superpowers, but deep below in the sea at a place called
the mesopelagic zone (often called the twilight zone), which is 200 to 1,000 meters deep.

However, don’t get this mixed up with bioluminescence, which is where a fish can produce light
inside themselves so they can glow in the dark.

Scientists have found out that biofluorescence dates back 112 million years. To find this, the
scientists made a map of the 459 biofluorescent fish species. This allowed them to see which
lineages exhibited biofluorescence and where it was most common, particularly noting its
prevalence in coral reef environments. By studying the evolutionary relationships, they are able
to determine when biofluorescence likely emerged and came to be. One reason was that it
came from eels and spread to others while evolving independently in various lineages. They
also looked into fossils on when the animals that had these traits existed. By analyzing the rate
at which new biofluorescent species emerge, they can tell the age of the trait. Because of this,
they were able to find out that there was a sharp increase in glowing animals after the dinosaurs
went extinct.

Scientists have also figured out that these animals have many different colors when they glow.
Most of the time in controlled experiments, the scientists use specialized tools such as blue
excitation lights and emission filters to shine on the animal and stimulate biofluorescence. Then
they capture the light, model it and finally take a look and analyze the color. Sometimes, to
make the light more intense, the scientists do the experiment underwater. However, not all
experiments of this kind are controlled; some are accidental. For example, some researchers
studying coral saw a glowing green eel.

I also have some experience myself. While in Spain, I went to a pond for rowing and canoeing.
Surprisingly, the man who was leading us led us to a secret location. There, we saw biofluorescent algae that glowed bright blue. It is because luciferin and luciferase react and glow. This is a great way to express biofluorescence.

Biofluorescence is a very diverse and cool ability to have as a mammal or fish. In the future,
biofluorescence will spread and show the world in a glowing state.