Hermaphrodite Female Roundworms Shrivel Up and Die After Sex

For some female roundworms, mating is the final act in life. But new research from Princeton University reveals why these worms die after mating: Male's sperm and seminal fluid trigger pathways that cause the females to dehydrate, prematurely age and die.

Colleen Murphy, an associate professor of molecular biology at Princeton, said that the female worms' lifespan in cut by about a third upon copulation, but that their death fits into a general framework of sperm competition that has been observed throughout nature.

While previous research has documented shortened lifespans in female roundworms after mating, this study is the first that documents body shrinkage and links their death directly to sex.

"The fact that sex essentially kills the mothers after they have produced the males' progeny has never been reported before and is shocking to most people who hear this story for the first time, including researchers who study these worms," Murphy said.

Murphy and her colleagues found that the biological pathways that lead to the death of the worms are also the ones responsible for slowing down aging in the worms during times of low nutrition.

"The males are taking these pathways and running them in reverse, causing the acceleration of aging and death," Murphy said.

"That these pathways can be hijacked and run in reverse in a simple organism might suggest that that could also happen in more complex organisms," said Murphy. "So the work can help us understand male-female interactions and how they influence female longevity and reproduction."

Interestingly, female species of this particular roundworm, Caenorhabditis elegans, are hermaphrodites - they carry both eggs and sperm within them. They do not actually need male worms to reproduce. But the male worms need the females to mate with if they are to pass on their genes.

"The hermaphrodites try to avoid the males - they will try to sprint away from them. The males have to hunt them down to get them to mate," Murphy said.

The researchers suspect that death is brought upon the females as a way for the males to ensure they do not mate with another male, which would disrupt the male's need to pass on its genetic code. Similar characteristics are seen in a number of other species, including some spider species where the male will secure the spread of his genes by sacrificing himself to the female to ensure she does not mate with another.

Murphy and graduate student Cheng Shi, lead author on the paper, published the research in the journal Science.