Imagine a superhero whose power is releasing an odor so strong their enemies stop fighting. For naked mole-rats, such power lies with the queen.
A potent compound allows naked mole-rat queens to control their colonies, researchers report July 15 in Nature. Individuals exposed to the odor will not fight or mate until the queen and her scent are gone.
Naked mole-rats live in cooperative societies where a single female reproduces while others forage and care for offspring. The queen maintains her status by repressing the sexual activity of everyone else. When she dies, high-ranking members become sexually active and will fight viciously to crown a new queen.
After discovering that naked mole-rats recognize other colonies by their smell, neuroscientist Gary Lewin wondered if odors mattered within the colony, too. Using a technique invented for collecting odor samples from outdoor toilets, he and his collaborators isolated a compound unique to queens called isopropyl myristate. While odorless to humans, it activates a naked mole-rat’s olfactory cortex — the region of the brain responsible for smell.
To test the compound’s potency, the team removed the queen and treated the colony daily with isopropyl myristate. “In the entire three months, there was no fighting. Everybody was cool with each other … and there was no sex,” says Lewin, of the Max Delbrück Center in Berlin. But as soon as the researchers stopped treatment, fighting quickly followed. “Within a week we had the first death. And a few weeks later, we saw mating events and a new queen emerged.”
In another experiment, the researchers isolated pairs of nonbreeding males and females and exposed some of them to the compound. After four weeks, five of the six pairs left to their own devices were pregnant. But there were no pregnancies or mating among pairs exposed to isopropyl myristate.
Blood work showed the compound regulates fertility hormones, lowering progesterone and raising prolactin to suppress pregnancy. Without the odor, females become sexually active.
Monitoring queens throughout the estrous cycle revealed that the queen produces isopropyl myristate only when she’s pregnant or preparing for pregnancy. If she stops, the other mole-rats know the queen’s not doing her job, so they kill her, Lewin says.
This level of coordination is extremely rare among mammals, he says. “We think of that as something uniquely human, but it’s actually something that mole-rats have been doing for millions of years before we even appeared on the scene.”
