Mammal penises, including those of cetaceans, are pretty easy to find, while vaginas are more difficult to examine; historically, accounts of animal reproduction have emphasized the features of penises and theories of sperm competition, but a burgeoning scientific emphasis on whale vaginas is revealing structures and strategies that are amazing and wonderful.
Scientific American visits Dr Sarah Mesnick from NOAA's Southwest Fisheries Science Center and Scripps UCSD, learning how she is plumbing (!) the depths of whale vaginas using Victorian anatomical drawings andautopsies of beached whales and bycatch. She's looking forward to examining a baleen whale's reproductive tract, which is big enough to walk through.
Mesnick is finding that, unlike most mammals, whales and dolphins have remarkably complex and convoluted vaginas. Normally, a mammalian vagina is a simple tube or cavity, with the cervix at the far end. But this is not so in some whales and dolphins, where a series of flaps, folds, blind alleys and funnels presents a dizzying maze for sperm to negotiate. "It's a gauntlet. Our very first one, when we opened it up, there were so many structures in there we could not figure out how a sperm would be able to swim from one end to the other," Mesnick says.
They found that some species have multiple funnels. Others have flaps or multiple folds. These structures were first described as a "pseudocervix" because they superficially looked like the true cervix. Not every species looks this complicated; other species have far less ornamentation.
The diversity is one of the reasons these structures are so hard to map: there are no consistent reference points to know where you are once you are exploring them – each vagina looks different. As Mesnick notes, "We're getting to the point now that if we open a tract up we can tell you the species, just by looking at the structures in the vagina." Now I'm thinking vagina-based species identification books.
Getting to Know Whale Vaginas in 7 Steps [Marah Hardt/Scientific American]