Naked mole rats continue to produce eggs throughout life, scientists have found, raising hopes of reversing the menopause if experts can work out how they are achieving the feat.
The subterranean rodents are known for their exceptional fertility, where the female queen can continue giving birth into old age.
But until now, scientists did not know whether they were simply born with an exceptional number of eggs, or whether they had managed to find a way of continuing to make new eggs throughout their lives - something no other mammal can do.
A new study by US scientists has shown that they do both. Naked mole-rat females are born with exceptionally large numbers of egg cells compared to mice and death rates of these cells are lower than in mice.
At eight days old, a naked mole-rat female has on average 1.5 million egg cells, about 95 times more than mice of the same age.
Even more remarkably, the study found that eggs continue to develop after birth, with egg-bearing cells still dividing into new cells at 10 years old, suggesting that egg production probably continues throughout their 30-year lives.
“This finding is extraordinary,” said senior author Professor Ned Place, of Cornell University College of Veterinary Medicine.
“It challenges the dogma that was established nearly 70 years ago, which stated female mammals are endowed with a finite number of eggs before or shortly after birth, without any additions being made to the ovarian reserve thereafter.”
Most mammals, including human females are born with a finite number of egg cells, which develop while still in the womb. Because this limited supply of egg cells depletes over time fertility declines with age, eventually stopping altogether in the menopause.
Yet if scientists could find out what genetic process is triggering the continued production of eggs even after birth, they may be able to help women to continue to have their own children later in life.
“This is important because if we can figure out how they’re able to do this, we might be able to develop new drug targets or techniques to help human health,” said lead author Dr Miguel Brieño-Enríquez, assistant professor at University of Pittsburgh’s School of Medicine.
“Even though humans are living longer, menopause still happens at the same age. We hope to use what we are learning from the naked mole-rat to protect ovary function later in life and prolong fertility.”
For the research, scientists compared ovaries from naked mole rats and mice across different stages of development.
Naked mole rats live in colonies of several dozen to hundreds of individuals. Like bees or ants, colony members divvy up tasks, including providing defence, digging tunnels, caring for young and collecting food.
Only the single dominant female in a colony can breed, and the queen suppresses reproduction in other females. Unlike bees or ants, a female naked mole-rat is not born a queen but competes with other females to take the position.
The queen can continue to breed into old age, preserving fertility in a way no other mammal can achieve.=
“Naked mole rats are the weirdest mammals,” added Dr Brieño-Enríquez.
“They’re the longest-lived rodent, they almost never get cancer, they don’t feel pain like other mammals, they live in underground colonies, and only the queen can have babies.
“But to me, the most amazing thing is that they never stop having babies — they don’t have a drop in fertility as they age.”
The research was published in the journal Nature Communications.