Researchers found male roundworms secreted signaling molecules that actually shortened the lifespan of females.
The team believes this "male-induced demise" could serve the purpose of killing of their male offspring's food competition, or it could be to reduce the mating options for other males, a Stanford University Medical Center news release reported.
The team looked at Caenorhabditis elegans roundworms. In this species there are males and hermaphrodites (those with both male and female reproductive organs). The hermaphrodites can self-reproduce, but are more successful if they mate with a male.
"We've found that males induce the expression of a large number of genes involved in sensation and signaling in hermaphrodites," Anne Brunet, PhD, associate professor of genetics, said. "This raises the possibility that the male-induced demise is not just due to the physical stress of copulation but instead involves some degree of active signaling. Indeed, we found that just placing hermaphrodites on plates where males had previously been present was sufficient to induce the premature demise of hermaphrodites."
Researchers are skeptical as to if this phenomenon exists in the mammal world, because females are usually necessary in raising and caring for the young.
"In worms, once the male has mated and eggs are produced, the hermaphrodite mother can be discarded," Brunet said. "The C. elegans mother is not needed to care for the baby worms. Why should it be allowed to stay around and eat? Also, if she dies, no other male can get to her and thus introduce his genes into the gene pool."
The team found hermaphrodites' lifespans were 20 percent shorter when there was an active presence of young males. They ruled out exhaustion from mating as the cause because even sterile hermaphrodites experienced a shorter life.
"Even long-lived and stress-resistant hermaphrodites were highly susceptible to the premature demise induced by males," Brunet said.
The team chalked the phenomenon up to pheromones.
"Males that are deficient in pheromone production no longer induce a strong premature demise of hermaphrodites," Brunet said, "and hermaphrodites that cannot sense pheromones are resistant to male-induced demise."
"Male-induced demise" has been observed in flies as well.
"The observation that this male-induced demise is present in several species of worms and has also been shown in flies suggests that it could have some adaptive benefits," Brunet said. "It will be interesting, of course, to determine whether males also affect the lifespan of females in other species, particularly mammals."
