Humans aren't the only species that struggle with sexually transmitted infections. Fruit flies get them, too—for example, a fungus called Metarhizium robertsii (shown above on fly) causes a low-level infection that causes females to have fewer babies. Recent studies have shown that when a female hears a male's courtship song, she starts expressing a gene known as Turandot M. Unlike the title character in the Puccini opera Turandot, these genes are not man-hating princesses who see to it that their suitors get executed. Instead, they're involved in immunity and stress response. A new study, published in the Proceedings of the Royal Society B, shows that TotM helps females beat infections caused by a sexually transmitted fungus. The authors say this shows how the flies have evolved to protect themselves from risky sex—not by buying condoms, but by changing what genes they express.

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