In an effort to decipher their Morse code-like blinking pattern, Jens Hellinger of Ruhr-University Bochum in Germany, the principal author of the study, and his team analyzed a school of flashlight fish placed in a big tank with fake coral reef under various lab conditions.

What Is A Flashlight Fish?

Flashlight fish (Anomalops katoptron) is also known as the two-fin flashlight fish, splitfin flashlight fish, or lantern fish. It produces light through symbiotic bioluminescent bacteria that live in the tiny light organs under its eyes.

A nocturnal animal, the flashlight fish hides during daytime and goes out to hunt for food at night along steep drop-offs near caves on moonless nights. Flashlight fish are naturally found in tropical aquatic environments in the Indo-Pacific region, such as the Banda Sea near Indonesia.

Presence Of Prey Affects Blinking Pattern and Light Produced

Amazingly, this unique ocean-dweller also has the power to turn its body light on and off like a light bulb or a flashlight simply by blinking. The flashlight fish blinks frequently, as much as 90 blinks per minute.

In their research article published online in the peer-reviewed, open-access journal PLOS One, Hellinger and his team noted that flashlight fish uses its bioluminescence to hunt for and feed on planktonic prey.

"The splitfin flashlight fish Anomalops katoptron use bioluminescent light to detect planktonic prey during the night and adjust the blink frequency in a context dependent manner. The loss of luminescence and subsequent light organ degeneration demonstrates the close symbiotic relation between the fish and its luminescent bacterial symbionts," he explained.

Bioluminescent Animals Under The Sea

Bioluminescence is common in most marine organisms such as bacteria, algae, jellyfish, worms, crustaceans, fish, and sharks. Marine biologists estimate that between 80 and 90 percent of deep-sea creatures are bioluminescent.

This natural phenomenon is made possible through natural chemical processes in the animal's body, which involve the mixture of luciferin (a molecule that produces light when exposed to oxygen) and luciferase (which speeds up the reaction).

Research suggests that bioluminescence has many uses: to seduce potential mate, to hunt and lure prey toward their mouth, or to startle predators.

The most popular bioluminescent creatures are the plant-like dinoflagellates whose blooms trigger the so-called red tides. Although a mere speck in size, they effectively thwart off predators by flashing an electric blue light whenever they sense danger.

Other known bioluminescent sea animals that set the deepest, darkest parts of the ocean aglow are the clusterwink snail, the jellyfish atolla, the colonial jelly, the abraliopsis squid, the vampire squid, and the sea worm tomopteris.

Know more why deep sea creatures glow by watching this video:

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