Knockin’ Dolphin Boots
RESEARCHERS MAKE A HUGE BREAKTHROUGH IN UNDERSTANDING HOW DOLPHINS DO WHAT THE BIRDS AND THE BEES DO
FEMALE GENITALIA are something of a mystery to scientists, male and female. “It’s much easier to study something external than internal to the body,” says Dara Orbach, who researches anatomy at Dalhousie University, in Halifax, Nova Scotia. For this reason, male reproductive organs have long been the low-hanging fruits of sexual reproduction research, while knowledge about the role of vaginas in successful mating is murky at best. That imbalance has thwarted our understanding of many aspects of copulation. Until now—at least when it comes to dolphins.
Orbach studies reproduction among cetaceans, the group of water-dwelling mammals that comprises dolphins, porpoises and whales. Several years ago, she learned that female dolphins have unusual folds in their vaginas, and she suspected this feature could be a way for females to make fertilization more difficult, thereby controlling which male gets the job done. (That thinking went against the scientific grain—most research has females playing a more passive role.) Orbach theorized that the folds might work like Cinderella’s glass slipper: Only a proper-fitting penis can get sperm to egg. Many species have this approach to mating, known as cryptic female choice, but no one had checked whether dolphins did. That’s in large part because it’s very hard to see dolphin vaginas in action.
But science, like love, finds a way. Orbach and colleagues obtained reproductive tracts excised from dolphins, porpoises and seals that died naturally. (“I get very stinky packages in the mail,” she says.) Her colleague Diane Kelly, a biologist at the University of Massachusetts, Amherst, inflated the penises fully erect with a pressurized pump to examine how they fit inside a female. They then inserted the inflated penises into thawed vaginas and, using computed tomography imaging, peered inside.
The images were striking— Orbach could see how, exactly, the male and female parts fit together. The bottlenose dolphin vagina is like a plaster-cast mold of the bottlenose dolphin penis. The tight fit hints at the ability of the females to control paternity, says Orbach, who presented the work at the recent Experimental Biology 2017 conference. The slightest turn of the female’s body could stop the penis from successfully navigating the vaginal folds and penetrating deep enough for fertilization. “Potentially, she has the ability to control fertilization success,” Orbach says, “without the male’s knowledge.”
Understanding the genitalia of marine mammals could improve our understanding of how diseases of the reproductive tract affect copulation, says Kathleen Colegrove, a veterinary pathologist at the University of Illinois at Urbana-champaign. In addition, she says, the work could inform assisted breeding efforts, such as those focused on cetaceans in captivity. Orbach notes that such detailed insights into genitalia interaction could lead to the creation of a synthetic vagina that helps endangered species reproduce by providing a realistic experience for male dolphins.
But Orbach is less concerned about the practical application than about simply expanding scientific knowledge. Rather than discussing the offbeat subject of her research, it’s this aspect she finds most difficult. “My biggest challenge is to explain why it matters to understand the system for the sake of understanding it.” In other words, people don’t always understand the porpoise.
Orbach is now planning more studies, because in science it’s always OK to have an inflated view of male anatomy.