It’s tough being a female in a naked mole-rat colony; they live a long life of servitude, maintaining the tunnels of their underground world and caring for the queen’s offspring. Within the colony, a single ruling female is responsible for all breeding while the rest are rendered to a life of infertility. Scientists have long wondered how the naked mole-rat queen maintains this status quo, and now they may finally have an answer.
In a study published in Nature, a team of researchers suggests that naked mole-rat queens emit a chemical that prevents other females in their colony from reproducing. The compound’s odor induces infertility in the colony’s females, ensuring that the queen is the only one capable of producing offspring so that she may continue to rule over her kingdom uncontested.
A queen’s rule
Naked mole-rats are unique eusocial mammals, living in underground colonies that follow a strict division of labor and are ruled by a single breeding queen. This type of behavior is seen in bee and ant colonies but is extremely rare for mammals.
Unlike bees, however, any female in the naked mole-rat colony can rise to become a queen. When the naked mole-rat queen dies, other females fight for her position until a new one is crowned. Until now, it was unclear how the queen hoards all the power while other members of the colony are unable to reproduce.
Scientists previously suggested that the queen maintained her rule by being larger and more physically assertive than her subordinates. Still, that doesn’t explain how the reproductive organs of other females remain underdeveloped with elevated levels of the hormone prolactin (the main function of which is to stimulate milk production in mammals).
Follow the smell
The researchers behind the new study set out to find the queen naked mole-rat’s deceptive secret to long-term power. The team swabbed naked mole-rats of different social rankings to see what kind of odor chemicals they produce.
They found that queen naked mole-rats produce an abundance of a chemical compound called isopropyl myristate. This specific chemical was almost entirely absent from other members of the colony.
“We were really aiming to just identify the chemical profile of the naked mole rats,” Mohammed Khallaf, a neuroscientist at the Max Delbrück Center for Molecular Medicine in Berlin and co-author of the new study, told Nature. “I got very excited when we found this compound that’s only produced by the queen.”
The production levels of this chemical compound fluctuate with the queen’s reproductive cycle, peaking during ovulation and declining during pregnancy and lactation.
To find out how the chemical compound affected the non-breeding naked mole-rats, the team removed some females from the colony and used a drug to stop their ability to smell. In those cases, their levels of prolactin dropped, and they were able to mate with their male counterparts.
Even in the absence of the queen herself, the scent of the chemical compound was enough to suppress reproduction in the naked mole-rats. The scientists behind the new study are still not sure how the queen’s scent is able to affect the fertility of other females but not her own.
A strange outcome from the recent experiment is that when scientists stopped spraying the chemical compound, violence ensued within the colony until a new queen rose to power. “The idea that a single scent can maintain peace and prevent violence may sound like science fiction,” Khallaf said in a statement. “In the world of naked mole-rats, it is reality.”