It is a beautiful thing when social media allows us to come together and shine a light on the issues that really matter in the world! And this hasn’t been demonstrated more than with the hashtag #JunkOff, where scientists have been tweeting photos of the male genitalia of their research species. The tweets have included a wide variety of species from cheetahs to spiders. Not only do the viral tweets shine light on the humorous side of biological research, but also on the significance of genitalia in our understanding of evolution.
One of the most astounding aspects of this online movement is the mind-boggling diversity of male genitalia in the animal kingdom!
Pythons, for example, have a two-headed member forming a Y-shaped hemipenis. However, when copulating the males only use one half of the organ, usually alternating from one to the other for each copulation.
Another penis that we have mentioned before is that of the echidna! As well as being a mammal that lays eggs (weird) the males have four heads on their penises! It is actually impossible for all four heads to fit in the female reproductive tract during sex so only two will enlarge and ejaculate at a time. This feature had puzzled scientists for a long time until they observed strong male-competition for females. Having more heads ejaculating increases the amount of sperm a male can use for insemination, and therefore a higher reproductive success. Crazy!
It’s not just reptiles and mammals with crazy pee-pees! The black widow spider males actually have a corkscrew-shaped member (also know as embolis). These emboli actually detach into the females reproductive tract during copulation. We all know the trick of leaving an article of clothing at your lady-friend’s place to come back for again later, but this is some next level creepy!
All of this lends a hand to our understanding of evolution! Male genitalia are front and center in sexual selection and are therefore found to evolve six times faster than other physical traits. It has been documented that very closely related species exhibit drastically different male genitalia. Before genetic barcoding was used to distinguish species from one another, differences in male genitalia were a major clue in identifying new species!
So who won the #JunkOff? We all won!