Have you ever seen a firefly blinking on a warm summer night? Then, you’ve witnessed bioluminescence, the production and emission of light by a living organism. While a few terrestrial creatures—certain bugs, fungi and even a small snail—produce light, it’s the underwater world that is truly abuzz with bioluminescence.
One of the most ubiquitous examples of marine bioluminescence is the anglerfish, a chill-inducing bony fish that inhabits the deep sea. A bright bulb is attached to a fleshy spiny extension from the female anglerfish’s head. In the dark ocean waters, the light lures unsuspecting prey into a mouth crammed full of sharp teeth.
Bioluminescence is the result of a chemical reaction, and the color of the light produced varies by creature and habitat. Most ocean dwellers emit light in the blue-green spectrum, which happens to be more visible in the deep ocean. But bioluminescence isn’t limited to the deep sea!
Tiny marine plankton, called dinoflagellates, float in large concentrations near the surface of the ocean. Many of these dinoflagellates are bioluminescent. Their light is motion-activated, giving the water a blue-green glow in the presence of a passing ship, wave or swimming animal.
Unlike the anglerfish that uses its light to attract prey, dinoflagellates use light to deter predators—the sudden flash disrupts their feeding. Other marine animals, like jellies and cephalopods, also use light for defense.
Brittle stars and some sea cucumbers can detach bioluminescent body parts, sending predators after the appendages as they escape unseen. Instead of ink that would be rendered useless in the deep ocean’s murky waters, the vampire squid ejects a glowing goo to distract predators as it flees.
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