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Parasitic wasps use their venom to turn unsuspecting insects into incubators for their young, but it's unclear how such a diverse, widespread group of insects evolved specialized poison to hijack their hosts. A new study of wasps' venom-producing genes found they primarily code for something else, and that the insects lead a genetic double-life.
"Making venom is sort of their night job," John Werren, a biologist at University of Rochester and author on the study, tells Axios.
Why it matters: Across the spectrum of life, genes can quickly evolve entirely new functions. Venomous animals serve as good models because they're constantly evolving new venoms to out-compete their prey's immunity. New traits might evolve by co-opting existing genes more often than previously thought; the study shows that evolution occurs in more ways than we imagine, says Mrinalini, a venom biologist at the National University of Singapore and a study author,: "It gives us a new perspective on how we understand survival, disease, development, reproduction, and every other aspect of life."
What they did:
By comparing the venom genes of four closely-related wasps that used fairly different hosts, the study authors were able to figure out which genes involved in toxin-production evolved most recently. Even the two most closely-related wasps had very different genes active in their venom glands, indicating that their venom evolves quickly. Most venomous animals appear to evolve new genes when an extra copy of an existing gene is accidentally created. That spare copy accumulates mutations, until it becomes capable of producing toxin. But when they looked at those genes, half of them didn't have a different copy with a different job floating around.
What they found:
Instead of rapidly-mutating venom-specific genes, the genes that were used most often active in the wasps' venom glands were also used in other places in the insect's body. The genes had been taken on a second job. "This wasn't an evolution of a gene, it was an evolution of when and where they were expressed, or how they were turned on and off," says Werren.