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Convincing a predator to attack you might seem like a bad idea, but Trinidadian guppies have a whole bag of evolutionary tricks to help them do just that. But why do they do it, and how does it help them survive?

Hosted by: Michael Aranda

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Sources:
https://doi.org/10.1016/j.cub.2020.05.017
https://doi.org/10.1093/cz/zow051
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https://doi.org/10.1016/j.cub.2018.04.078
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Go to Brilliant.org/SciShow to learn how you can level up your STEM skills this year. ♪♪♪. Convincing a predator to attack might seem counterproductive if you don't want to be eaten.

And getting them to attack your head might seem like the absolute worst idea ever. But that's exactly what these little guppies do. They taunt larger fish and get them to attack at their eyes.

And that's actually safer for them! Let me explain. Trinidadian guppies are eaten by bigger fish called cichlids, which are ambush predators.

So when a cichlid is hungry, it hides and waits for a smaller fish to swim within reach. And then—boom! It's like a yummy fish dinner was delivered straight to its door.

But these guppies have figured out how to make the cichlids attack on their terms, allowing them to lure the predators into missing. First, they draw the cichlids' attention using conspicuous coloration: highly noticeable colors that get the hunter looking where the guppy wants it to attack. But here's the thing: If the guppies were always conspicuously colored, they'd know where a cichlid would attack, but not when.

Which is why they can change their color. And specifically, they can change the color of their eyes. Normally, their irises are silver, but they can turn them black.

See, the color comes from cells that have sacs of pigment inside. Melanin, the black pigment that guppies use to change their eye color, is found in a special type of cell known as a melanophore. And when melanin is at the center of the melanophore, light can pass through most of the cell.

But if it's spread out, it creates a layer that absorbs light and makes the cell look black. So when a guppy spots a predator, hormonal and nervous responses signal their melanophores to rearrange. Proteins pull melanin from the center of each cell out across the entire thing.

And the whole eye goes black in about three seconds. Those black eyes are much more noticeable, so when a guppy changes its eye color, it's basically daring the cichlid to aim for its head. Which, I know, seems like the last place you'd want to be bitten.

But if the attack is aimed there instead of its middle—where the cichlid would usually attack— the guppy can bend around its center to dodge the predator. So basically, they use their eyes kind of like a matador cape, luring danger into lunging at the wrong angle, and allowing the guppy to twist away at the last second and escape. And the international team of researchers who wrote about this amazing tactic in a 2020 Current Biology paper found that larger guppies are even better at this, as their center pivot point is even further from their eyes.

So they think this adaptation may have allowed this species to evolve a bigger size overall. So next time you're faced with a stressful situation, consider tackling it like a guppy: head on. And if that's how you tackle everything in your life, you might love a premium subscription to Brilliant.

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And, if you're one of the first 200 people to sign up for an annual premium subscription at that link, you'll get 20% off! Plus, you'll be supporting us here at SciShow, so: thank you! ♪♪♪.