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Meet the Fish That Has Flashlights for Eyes

When you need a midnight snack, a fridge light can always help you distinguish the pub cheese from the hummus. The flashlight fish doesn't have that luxury.


When you're in the mood for a late-night snack, you can rely on that little light bulb in the fridge to help you distinguish the pub cheese from the hummus.

In the ocean, the flashlight fish doesn't have the same luxury.

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Instead, it uses light organs beneath its eyes, which switch on and off as it blinks, like flashlights. These bean-shaped organs get their illuminating power from the bioluminescent bacteria that live inside them.

Symbiotic relationships can be like a deal with some sick nature demon: Sure, you can have night vision, if you're cool with bacteria sacks under your eyeballs.

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Flashlight fish, more formally known as Anomalops katoptron, turn their lights on and off in what Phys.org describes as "Morse code-like blinking patterns."

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Until recently, scientists weren't sure what the patterns meant: What made these reef fish decide when and for how long to flash their bacteria-assisted headlights?

Maybe they just liked that sci-fi cult look?

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On February 8, a group of German researchers gave a piece of the answer in in the journal PLoS ONE.

In their study, they found that, like our fridge lights, A. katoptron's glowing organs seem to be specifically for illuminating food, which in this case means plankton.

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The researchers determined this by putting the flashlight fish in dark tanks, with or without plankton. When alone without a potential meal, the fish blinked frequently, leaving their lights on and off for about equal amounts of time.

But once plankton came into the picture, they left their lights on longer and blinked five times less frequently, suggesting they might have been hard at work looking for prey.

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So the next time anyone tries to judge you for eating late at night, just know that you're in good company.

If you haven't evolved bacteria sacks under your eyes yet, you're doing just fine.

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