Naked mole rat queens produce a chemical that stops other females from reproducing.Credit: Neil Bromhall/Getty
Naked mole rat (Heterocephalus glaber) queens produce a chemical that prevents other females in their colony from reproducing.
A study published today in Nature suggests that this compound maintains a strict social structure that is dominated by one queen, even when the animal is not present1. The chemical’s odour alters the production of hormones in other females, which stifles their ability to bear young.
The study is a “game changer”, says Melissa Holmes, a behavioural neuroscientist at the University of Toronto, Canada, because it explains “a longstanding mystery”: why only one female in a naked mole rat colony reproduces.
All for one
Known for their hardiness and unusual longevity, naked mole rats are eusocial, which is extremely rare in mammals. In this social structure, the queen is responsible for all reproduction in its colony, while other, infertile individuals rear the offspring and complete laborious tasks such as gathering food.
However, unlike other eusocial animals, such as bees, every female naked mole rat can become a queen. But most are stuck in a “stalled puberty phase”, says Lisa Stowers, a neuroscientist at Scripps Research in San Diego, California. These females’ reproductive organs are underdeveloped, and levels of the hormone prolactin are elevated. But how one female holds on to the throne, and halts reproduction in others, has been a mystery.
To find out, Mohammed Khallaf, a neuroscientist at the Max Delbrück Center for Molecular Medicine in Berlin, and his colleagues swabbed naked mole rats of different social ranks to determine the odour chemicals that they produced. One chemical, called isopropyl myristate (IPM), was found in abundance in queens and was almost entirely absent from other colony members. Production of this compound fluctuates with the queen’s reproductive cycle, peaking during ovulation.
“We were really aiming to just identify the chemical profile of the naked mole rats,” says Khallaf. “I got very excited when we found this compound that’s only produced by the queen.”
Brain imaging showed that exposure to IPM stimulated olfactory neurons — cells responsible for processing information about incoming smells — in non-breeding females, which suggests that these individuals react to the chemical’s scent.
To pinpoint the chemical’s effects, the team removed some non-breeding females from the colony and used a drug to block the ability to smell in others. In both instances, the mole rats’ levels of prolactin dropped, enabling those that were paired with males to mate. The presence of IPM alone — even in the absence of a queen — was enough to block reproduction and maintain the status quo in a colony, further experiments showed.
