All the more reason to have sex

[Tridimity]

Abstinence causes lifespan issues in Drosophila

Sexual frustration impairs the health of fruit flies and causes premature death, according to new research.

Scientists found that male flies who were stimulated to mate but prevented from doing so, had their lives cut short by up to 40%. Those allowed to copulate not only lived longer but suffered less stress.

The research is published in the journal Cell Science.

In the experiment, the flies were put in close proximity to genetically modified males who had been altered to release female sex pheromones. These hormones are used by flies to judge whether a potential mate is nearby, so when males secreted this sexually charged scent, it instantly aroused other males.But crucially, they were not able to mate.

The flies that were tantalised but denied any action showed more stress, a decrease in their fat-stores and had their lives cut short dramatically.

"We immediately observed that they looked quite sick very soon in the presence of these effeminised males," explained Dr Scott Pletcher at the University of Michigan, US, co-author of the research.

The common fruit fly has a very short life of about 60 days. This makes them an ideal organism to study aging as the genes that regulate a fly's lifespan have been found to closely parallel those in humans.

The team were interested in the neurons involved in aging. A brain chemical called neuropeptide F (NPF) - which has previously been linked to reward - was found to be instrumental.

When flies were exposed to an excess of female pheromones but had no opportunity to mate, their NPF levels increased.

Mating would usually regulate the neuropeptide to normal levels but when it stayed high, it caused the detrimental physiological consequences.

Costly act

The mere act of reproduction normally reduces a fly's life by about 10-15%, but the amount that their life was cut short in this study was unexpected.

"In that context mating can be quite beneficial, which is contrary to dogma. It suggests that the brain is somehow balancing this information about the environment through sensory input," Dr Pletcher told BBC News.

"Evolutionarily we hypothesise the animals are making a bet to determine that mating will happen soon.

"Those that correctly predict may be in a better position, they either produce more sperm or devote more energy to reproduction in expectation, and this may have some consequences [if they do not mate]," Dr Pletcher added.

Female power

Timothy Weil, lecturer at the University of Cambridge zoology department who was not involved with the study, said the work suggested that less successful males could lose out in the race to pass on their genes.

"Sex and food are the biggest drivers of animal behaviour and the female fly here seems to have the power. It could be a way for females to select for the best mates as the males who are not mating as much have negative health effects," he said.

"The work suggests that acting upon these physiological changes is important for the health of the animal," Dr Weil added.

In a separate study on roundworms, also published in Science, a team found that the presence of male pheromones reduced a female's lifespan.

Dr Pletcher said this parallel finding was encouraging because worms and flies have similar pathways, "which have so far been held up in mice and likely in primates too".

http://www.bbc.co.uk/news/science-environment-25120980

 

Edited November 28, 2013 by Tridimity

[Ringer]

I wonder if you would see the same effect in a species that is able to masturbate.

[Tridimity]

I wonder if you would see the same effect in a species that is able to masturbate.

 

Possibly - I guess it is a balance between the effects on lifespan of abstinence versus the effects on lifespan of sexual intercourse (e.g. STIs and STDs). Even if you are in a long-term monogamous relationship, there is no guarantee that your partner is not harbouring an STI, and even if you performed a Western blot on their blood sample and saw with your own eyes a negative result, many infections have a time window before they will become apparent by testing. Just my paranoia But in this context, masturbation would be a safer mode of relieving sexual tension than intercourse.

[GiantEvil]

Perhaps when the male is primed to mate they don't eat? Don't get un-primed, don't eat?

Edited December 1, 2013 by GiantEvil

[Tridimity]

Perhaps when the male is primed to mate they don't eat? Don't get un-primed, don't eat?

 

Perhaps. I should probably read the original research article in full rather than the news feature on its own Maybe they essentially re-allocate to reproductive functions (production of gametes, the physical process of copulation, attraction of the female) energy that would otherwise have been safeguarded for survival functions (anabolism, repair, innate immunity).

 

In Drosophila melanogaster, as in many other animals, courtship is a series of stereotypical behaviors carried out by a male responding to multimodal signals. Because different experimental conditions can engage distinct sensory modalities that affect male behavior, courtship experiments need to be carefully designed. There are several ways to manipulate sensory inputs to the test male. This protocol describes methods for designing and conducting experiments that measure the various parameters of courtship behavior...After or during wing vibration, the male extends his proboscis and licks the female’s genitalia (licking).

Drosophila are gross

 

http://cshprotocols.cshlp.org/content/2007/10/pdb.prot4847.full

 

Edited December 1, 2013 by Tridimity

[Ringer]

We should also keep in mind that the reproductive aspects of Drosophila are far removed from ours. There are mammals that can die from abstinence, but our reproductive system differs enough that I doubt that results of abstinence in Drosophila would give much insight into human abstinence.

[GiantEvil]

Apparently when a male Drosophila is exposed to certain female Drosophila pheromones it triggers an increase in a certain neuropeptide. If the male manages to mate then the neuropeptide levels return to normal. If the male doesn't get to mate then the levels stay high, in which case the male is observed to go sickly.

Sounds kind of like stress in humans, physiologically useful in the short term, long term stress responses tend to be physiologically harmful.

 

Who would have thought that sexual selection and mating ritual could be so complex in Drosophila, and would include oral genital stimulation.

 

Here's another article about Drosophila, sex, and alchoholism; http://www.bbc.co.uk/news/science-environment-17357560

Once again neuropeptide F is implicated as a behavorial mechanism.

 

It seems reasonable to me to suppose that given other equal circumstances, humans who experience more satisfying sex lives probably do live a little longer than otherwise.