See how this school of tiny fish uses bacteria to glow in the dark

August 14, 2019 — While scuba diving at night along a coral reef in the Solomon Islands, marine biologist and National Geographic Explorer David Gruber witnessed what he describes as "the closest [he's] had to an Avatar moment. Thousands of flashlight fish swam before him, forming shapes, and illuminating the dark ocean waters. What he saw could be the largest school of glowing fish ever seen and captured on camera. Casting a vibrant blue glow as they swim, flashlight fish owe their bioluminescence to the bacteria that grow in an organ underneath their eyes. It's a symbiotic relationship that allows the bacteria to obtain extra oxygen needed to survive, and the fish benefit from the glowing light emitted from the organ, which they can ""blink"" on and off using special skin folds. In a recent study published in PLOS ONE, it was observed that flashlight fish use the glowing light to coordinate their schooling and avoid predators. Read more about how flashlight fish glow and school at night.