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A less traditional method of encouraging reproduction?

Image: Jesse Orrico

Pheromones are small chemical signalling molecules produced and released by organisms that affect the physiology of others in that species.

A paper by Aprison & Ruvinsky in 2016 published in Current Biology explores the effects of these male-produced ‘scents’ on female reproductive behaviour in the simple, model organism Caenorhabditid elegans (nematodes/roundworms).

This so-called ‘lab workhorse’ is known for expanding knowledge and understanding of fundamental biological processes that can then be targeted to improve human health.

The role of male-produced pheromones in manipulating the timing of females’ sexual maturation to prime them for reproduction has been well established in mice.

Aprison & Ruvinsky proposed that the same basic mechanism of controlling the rate of sexual maturation is true for C. elegans. They consequently suggest that it may be a generally common and shared feature of animals, including humans.

The hypothesised system involves just two distinct pheromones produced by the male. The male does not need to be present to make the female increase her reproductive effort – the lingering smell of minute amounts of the two pheromones is enough to make the female alter her physiological balance in favour of reproduction. Even sterile females (those with no eggs) are affected so.

The first male-specific pheromone is an ascaroside, a small fatty molecule with a variety of functions, that delays reproductive senescence (the point at which cells are alive but no longer able to divide) by slowing the ageing of the mature female roundworm’s reproductive system.

The second unidentified pheromone accelerates the development of the last larval stage, which is functionally similar to inducing early onset puberty in juvenile human females.

In short, a male-produced ascaroside and a currently unknown second signal delay reproductive senescence and promote sexual maturation in potential female mates.

Unfortunately, these pheromones also accelerate female ageing in general, thus shortening the female’s overall lifespan. It is thought that this disruption to normal body maintenance is unintentional, and detrimental consequences are purely incidental.

Males act to maximise female readiness for reproduction, not to harm them; whether or not pheromones are harmful to fitness under natural conditions is unclear.

These findings could be key in providing potential drug targets to treat a number of human health issues. Disrupting them could delay early onset puberty and slow mature ageing in females.

Conversely, using them could prolong female fertility. These therapeutic promises are supported by a study published in Biological Psychiatry that highlights the possible relationship between female reproductive lifespan and ageing by suggesting that women who enter the menopause earlier age quicker.

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