Ever found yourself in a hazardous relationship in which your spouse makes your hair go white? Well, if the answer's yes then you're not alone. A new study provides new evidence that key aspects of the social environment of some animals significantly influence life span after researchers found that sexually frustrated fruit flies and "haunted" hermaphrodite nematodes died earlier than expected.
Environmental cues play pivotal rules in an organisms' development and health. It's not only about the space and objects around an animal that influence it however, interactions with other members of the species also have an effect on longevity. For instance, female fruit flies face a dramatic cut in life expectancy after mating since the male fruit fly's seminal fluid contains toxins. Now, a group of researchers led by Scott Pletcher, a geneticist at the University of Michigan, Ann Arbor, found that sexually frustrated fruit flies live a shorter life.
An unshared love
Pletcher and colleagues played a most cruel prank on male fruit flies. The researchers genetically modified some male fruit flies to expel female pheromones that typically invite male for mating. To normal flies' surprise they found they couldn't mate with these strange "females". This sexual frustration caused the males flies to lose fat, become stressed, and decrease in life span by 10%.
After dwelling deeper into the physiological processes sparked by the psychological sexual frustration, the researchers found that some neurons that signal the production of a certain protein which enable the flies to respond to rewards or mating were destroyed. So, basically living in a delusional world was too much for the fruit life as it never got to have a piece (reward) of what it was expecting (anticipation). Similar results were measured after female flies were modified to release male pheromones; this trickery caused female flies to also live shorter lives.
Elsewhere, Anne Brunet, a geneticist at Stanford University in Palo Alto, California, found that nematodes significantly lived less just after sensing the presence of the opposite sex. Now, for this particular nematode species, sex may not be the word to describe them since 99% of all specimens are hermaphrodites (lay eggs and produce sperm at the same time), while only 1% are males.
Simply smelling the opposite sex kills the roundworm
The researchers placed the tiny male roundworms in culture dishes for up to 2 days and then ejected them. In the same dishes, they introduced hermaphrodite worms. Even though the males were gone, the hermaphrodites could still sense them fact which significantly affected their life span. Like in fruit flies, the worms differentiate between sexes using pheromones and in this case, the males' scent persisted in the dishes causing the hermaphrodites to experience premature aging—the worms slow down or become paralyzed, and their muscles and internal organs begin to degenerate. Genetically modified hermaphrodites engineered not to smell pheromones anymore had a normal life span - as in much higher than if they could sense male worms.
“We’ve known for a long time that mating can be harmful,” says Patrick Phillips, an evolutionary geneticist at the University of Oregon in Eugene. But these papers show that “you can have the effects without direct physical contact.”
What about mammals? The researchers say mammals are far more complicated, however I've read before of some studies that suggest castration increases lifespan in males. A very interesting Korean study examined the genealogy records and lifespan of 81 Korean eunuchs to find that their average lifespan is ~14-19 years longer than that of non-castrated men of similar class. Now, the data range is rather narrow but the life expectancy compared to the control general population is so great that it can only make you wonder. Want to live more? Well... you know what to do now.