Females sometimes mate more than once in quick succession, filling their reproductive tract with rival sperm that must compete for access to unfertilized eggs. Two groups now show details of what life must be like for those sperm, with one offering unprecedented movies of this sperm competition. On page 1506, Susanne P.A. den Boer of the university of Copenhagen demonstrates that such rivalries in some ants and bees have led to the evolution of seminal fluids containing toxins that impede rival sperm and to female fluids that counter these toxins. Another team, reporting online in Science, followed red- or green-glowing sperm as they jockeyed their way through the reproductive tracts of fruit flies. Both papers drive home the point that "the competition between males continues in a very fierce way," inside the female, says Tommaso Pizzari, an evolutionary biologist at the Unviersity of Oxford in the United Kingdom.Hmm. It seems a bit more interesting than just the usual narrative of male sperm fighting among themselves. First, there's the matter of reproductive tracts possessing "sperm storage organs" (hell, why not just call them "sperm banks"?)-- which I can't say I'd ever heard of before. Second, the sperm fight among themselves in order to secure a place in the female's "sperm-storage organ" (which doesn't really fit the (largely discredited) courtship narrative of insemination). The third interesting thing is that the queen secretes a fluid that preserves the sperm that make it into the sperm-storage organ from the toxins meant to kill off rival sperm:
Den Boer, University of Copenhagen colleague Jacobus Boomsma, and Boris Baer, now at the University of Perth in Australia, find sperm in some bees and ants do more than physically displace rivals. ...For the multiple mating species studied, two leafcutter ants and the honey bee, seminal fluid form a given male enhanced the survival time of its own sperm in a lab dish but damaged unrelated sperm and even sperm from a brother. Adding spermathecal fluid that an queens make within their reproductive tract countered these effects, say Boomsma....
....Once the sperm reach their destination for long-term storage, the female apparently wants to keep all the sperm healthy and has evolved ways to counter the seminal fluid. This study "beautifully reveals just how nuanced reproduction can be," says Pitnick.
I seem to be hearing Mae West's voice speaking... What's that, Mae? Did I just hear you say " It's not the men in your life that matters, it's the life in your men?"