Proving it could be more help than pest, the cockroach could hold the answer to increased fertility problems in women who put off having children, scientists announced today.
Earlier research by biologists at the University of Manchester found that when female dusky roaches were prevented from mating, they lost fertility in later life. The roaches also became less choosy about who they mated with once they were finally let loose with the males.
Suggestions that a woman's reproductive history can affect her ability to have children in the future have been puzzling scientists for years. A number of researchers have claimed that if a woman gives birth before the age of 25, it can delay her natural menopause.
The Manchester University biologists have now turned to the mating behaviour of the dusky roach, the Nauphoeta cinera, to try to find the reasons behind this.
Dr Patricia Moore, from the university's faculty of life sciences, said: "This cockroach is unusual in that it gives birth to live young, rather than laying eggs, even nurturing them in their first few hours of life.
"The females also experience reproductive cycles and show age-related decline in fertility and so provide an excellent opportunity to examine the mechanisms by which females lose reproductive potential as they delay breeding."
Dr Moore's latest research, published in the science journal Evolution and Development, suggests a natural biochemical reaction is to blame for the decline in the cockroaches' fertility.
The insects which live for about a year - reaching sexual maturity at six days old - so the biologists decided to investigate what happened if they delayed mating by two weeks.
Dr Moore said: "As we expected, the eggs that would have been fertilised had the female been allowed to mate were discarded through a natural, controlled process of cell death, called apoptosis.
"But we also observed that apoptosis began to occur in the cells of eggs that wouldn't yet have been used - eggs-in-waiting if you like."
Dr Moore believes that there are complicated evolutionary arguments behind why perfectly healthy eggs should begin to die.
She said: "We suggest that reduced fertility brought about by delayed reproduction occurs because evolution has not been able to adapt to what is an artificial situation - the cockroach is unable to refine getting rid of eggs that are no longer needed.
"In humans, of course, this artificial situation is created by cultural influences that see women not giving birth until long after reaching sexual maturity.
"Although it's hard to compare the experiences of the female cockroach to humans, the biological mechanisms are similar and so an inappropriate apoptosis response to the 'mistiming' of reproduction may explain the evolution of the loss of fertility with age."
