Animal IQ

Tomato Plants Can Make Attacking Caterpillars Turn To Cannibalism

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If you're a frequent Curiosity reader, you already know that the plant kingdom is full of BAMFs. Some plants can see, they can hear, and they can come back to life. And if recent research is any indication, if they catch you trying to attack them, you'll be in a world of pain. (If you're a caterpillar, anyway.)

I'd Love To Have You For Dinner

Scientists already knew that when plants are being eaten, they have ways of making themselves unappetizing. Tomato plants do this by producing methyl jasmonate, a stress chemical that's bad for them, but toxic to pests. For a 2017 study published in Nature Ecology & Evolution, researchers from the University of Wisconsin, Madison sprayed different amounts of methyl jasmonate on tomato plants, then unleashed a bunch of caterpillars and sat back to watch the show.

Compared to control plants that weren't sprayed, tomato plants with the highest dose of the chemical had five times as much of themselves left intact. Why? Because instead of eating the plant, the chemical made the caterpillars eat each other. Caterpillars are known to cannibalize in the wild, but that's usually when they don't have enough to eat. When faced with a toxic feast, these caterpillars turned on their brethren — and on the highest dosed plants, caterpillars ate twice as many other caterpillars on the control plants. (The control caterpillars still engaged in some light cannibalism because, well, caterpillars are freakin' vicious).

Chemical structure of methyl jasmonate.

More Morbid Study Is Needed

Of course, this study used a lot more methyl jasmonate than a tomato plant could reliably produce, especially in the moment a caterpillar begins chowing down. But methyl jasmonate also acts as a chemical signal to other plants, which could help them prepare for an oncoming attack. Still, more study needs to be done. "Follow-up experiments are in the works to address the question of how this dynamic plays out when the herbivores can move between multiple plants," says author and ecologist John Orrock. "Now that we've shown that it can happen, we need to figure out how often it does happen."

Bugs Develop A Taste For Each Other When Plants Taste Bad

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