Echidnas have a unique 4-headed penis but only use half at a time
The little-known antipodean monotreme's genitalia reveal their secrets to researchers
Using CT scans and 3D models, Australian researchers have been able to learn more about the inner workings of the short-beaked echidna's unique genitalia.
Echidnas are part of the group of mammals known as monotremes, which include the better-known platypus. Monotremes are known for their bizarre adaptations, such as being the only egg-laying mammals, and lactation through their sweat glands instead of nipples.
One of those strange features includes the echidna's four-headed penis, first described in 2007. But when reproductive biologist Jane Fenelon learned that echidnas would only get erections in two heads at a time, she sought to find out why.
"I really wanted to look into how they're actually doing this because we've never seen this in a mammal before. It was very unusual," Fenelon, a researcher from the University of Melbourne, told Quirks & Quarks host Bob McDonald.
While working with Currumbin Wildlife Sanctuary, Fenelon was able to study the anatomy of echidnas that had been killed in road accidents. Using microscopy techniques and CT scans, she was able to create a 3D model of the internal structure of the appendage.
She and her team found that the erectile tissue and the blood supply in the penis is split, so that it can direct blood flow to alternating sides. And while only two of the heads can become erect at one time, the animals could switch sides on command, up to 10 times in a row.
"We think it's because of this unique system they have in the structure, that they just have to change the blood flow. So while one side is recovering, they can just switch the blood flow to the other side and keep going," she said.
Fenelon says that the only other animal she found with an appendage like this is a species of turtle with a five-headed penis. She adds that this confirms a common theory about how penises evolved. "The current theory is that every animal in the animal kingdom that has a penis evolved from a single type. And this provides some more evidence that they did actually have a similar origin because it does look very similar to the turtles," she said.
The study was published in the journal Sexual Development. You can listen to Fenelon's full conversation with Bob McDonald at the link above.
Produced and written by Amanda Buckiewicz