We've read how plants communicate with each other by chemicals, and we've read about parasites that change the behavior of other animals, but this takes the cake. Tomato plants have shown the ability to protect themselves from caterpillars by inducing them to eat each other instead! University of Wisconsin in Madison treated tomato plants with methyl jasmonate (MeJA), a chemical known to communicate a pest warning between plants. The tomatoes then geared up for an attack by changing their own chemistry.
The researchers then allowed caterpillars of a common pest, the small mottled willow moth (Spodoptera exigua), to attack the crop. Eight days later, they observed that plants more strongly cued with MeJA had lost less biomass compared with control plants or with ones that had received a weaker induction. This showed that the reaction was somehow effective at protecting the plants.
Next, the team wanted to test whether the plants’ response was triggering cannibalistic behaviour in the caterpillars. So they cued tomato plants with MeJA and then fed leaves from cued plants and non-cued control plants to single caterpillars in containers that also contained a set number of dead caterpillars. Two days later, the team observed that caterpillars fed with leaves from the treated plants had turned onto the dead larvae earlier, and had eaten more of them, than those fed with leaves from control plants.
The scientists noted that caterpillars will eventually eat their dead comrades, but inducing them to turn to cannibalism earlier is a good way for a plant to protect itself. Read more about this research at Nature. -via reddit
(Image credit: PLoS Biol)