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Lots of animals can change the color of their skin, but there's nothing quite like the chameleon sand tilefish, which can change its appearance in an instant and flash the colors of the rainbow.

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Plenty of animals can change the color of their skin maybe to attract mates or take on the appearance of their surroundings. But there’s nothing quite like the chameleon sand tilefish, which can change its appearance in an instant… and flash the colors of the rainbow.

There’s no question that there’s something special about this fish, but researchers have actually figured out just how it pulls this off and it’s truly not like any other animal. The tilefish lives mostly in the Indo-Pacific, off the coasts of places like Japan and the Philippines… although these days, it’s also pretty popular in aquariums. If you’ve ever seen one, it might look iridescent blue at first, but in the blink of an eye it can switch to something like bright red or yellow which is why it’s also sometimes known as the flashing tilefish.

And in a 2017 study published in the journal. Pigment Cell & Melanoma Research, one researcher tried to track down exactly how they do this. For starters, they figured out that tilefish scales get their color from groups of cells called iridophores.

Unlike, say, a red pigment, which only ever reflects red light, iridophores can change what color they reflect. That’s because they’re made of adjustable reflective cells called platelets. Platelets lie in stacks inside the iridophore, but their spacing and position change in response to chemical signals from the body.

And that change in configuration alters what color the iridophore reflects. Now, lots of iridescent animals get their colors from iridophores, and some of them also change colors, so this isn’t all that unusual. But what’s weird about tilefish is the fact that those colors change fast, sometimes in just half a second.

The researchers figured out that the tilefish’s advantage has to do with the placement of its platelets. In most iridescent animals, they’re spread out throughout the iridophore, but in the tilefish, they just line the iridophore’s edges. That seems to make it easier for those platelets to rearrange themselves, quickly changing the color they reflect.

Like many other color-changing animals, this rearranging is triggered by the organic chemical norepinephrine, which is what the brain uses to transmit messages around the body. So, just like you can squeeze a muscle on command, researchers think tilefish can control their color changes with their minds! But… researchers still aren’t sure why they do this.

I mean, despite being named after the chameleon, camouflage doesn’t seem like too likely an explanation for a flashing fish. But there are lots of other reasons why different animals change colors. Like, when they’re not trying to hide, chameleons also change colors when they fight… or when they’re trying to attract mates.

Then there are animals that change color in response to threats like guppies, whose eyes go black in the face of predators. Any of these could have something to do with why tilefish flash. But for now, all we know is that, whatever the reason, these fish know how to put on a colorful show.

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