Pinecone fish grow about 8 inches (20 centimeters) long and come by their nickname honestly: Their scales are yellow, crisscrossed with black markings in the shape of the scales of a pinecone.

In the pinecone fish, another strain of the bacterium colonizes a light organ within the animal's jaw and helps illuminate the dark reefs in which it forages at night.

“The first time I remember seeing anything bioluminescent I was in Puerto Rico, about 2006, and we were down there doing coral restoration work, which is amazing in itself,” says divemaster ...