That’s because Orbach is aiming to understand reproduction in animals like dolphins, harbour porpoises and harbour seals. Rather inconveniently for her, these critters aren’t exactly exhibitionists: Much of their time is spent underwater and out at sea. So, she found a way to bring their mating habits to her, by studying their anatomy in the lab. A new paper published in the journal Proceedings of the Royal Society B recounts the latest results of her work.
Orbach was inspired by work done on insects and lizards. Researchers let them mate naturally, then dropped them in liquid nitrogen to flash freeze them and their active genitalia. It’s a technique she described to Newsweek as “really exciting, but totally not feasible for anything larger than a tiny insect.”
Larger as in, say, a 70-pound male harbor porpoise, whose penis (which is retractable and prehensile, by the way) you can see to scale here, in extremely rare footage of an above-surface mating attempt:
Orbach started by reaching out to a network of research and conservation scientists, requesting corpses of recently deceased harbour porpoises, common bottlenose dolphins, short-beaked common dolphins and harbour seals. Each animal’s reproductive tract was cut out, frozen and shipped to Orbach and her colleagues to study.
The team wanted to see how the penises and vaginas fit together. So, Orbach took casts of the vaginas and then the team needed to inflate the penises to mimic how they behave in live animals.
That’s trickier than it may sound, since the animals Orbach studies have, as she describes it, “a very different penis type” from humans and many other mammals. Those penises are encased by sponge-like tissue, which fills with blood to create an erection. Not so in dolphins, porpoises, seals and their relatives. “It’s full of tough elastin tissue, so it’s very resistant to bending,” Orbach says. Colleague Diane Kelly, a biologist at the University of Massachusetts, realized she needed a way to pressurize salt water to pump into the penises. She turned to the gas, nitrogen, that is pressurized to put bubbles in a Guinness or a nitro brew coffee. That gave the salt water enough force to push its way into each penis.
Then, the scientists set about understanding how each species’ anatomy fit together. That included inserting each preserved penis into its matching vagina to scan, plus creating 3-D models of the interactions.
Looking at the pairs, Orbach says she and her colleagues were struck by the tight fit. “We were basically looking at two identical structures,” she says. “This is coevolution at its finest.” The team saw two different types of this phenomenon, in which the penis and vagina change in lockstep with each other.