GLOW IN THE DARK
The Japanese Pinecone Fish supposedly glows: it’s not only the body that makes it luminescent, but also the bacteria!
According to a 2008 article written by Kathryn Snavely for The Gale Encyclopedia of Science, there are two phosphorescent organs on the lower jaw of the Japanese Pinecone Fish that attracts the bacteria, which maintain a symbiotic relationship with their host.
The bioluminescence varies from a yellow tint to a bluish-green color, depending on how much light manages to reach the fish, according to a 2014 article about the pinecone fish in the RW Sentosa Blog.
It still isn’t known exactly what those organs are for but there are several guesses: improving vision, finding prey, or communicating with other marine life.