It might look like this tiny fish is casting its very own Patronus, but what you’re actually witnessing is just as intriguing.
It shows a cardinal fish spitting out an ostracod, an ocean-living animal which uses bioluminescence as a form of self-defence.
When the ostracod is swallowed, it starts to emit a burst of bright light to draw attention to its predator.
“The cardinal fish also has predators and if they can see it they’ll come and eat it,” explains physicist and broadcaster Helen Czerski in a BBC Earth video. “So the ostracod puts out an intense burst of light, the fish spits it out and both go their separate ways.”
The light is generated during a chemical reaction involving luciferin and luciferease. In the depths of the ocean, it’s the only light around.