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Tardigrade Mating Finally Caught on Camera, Is Suitably Weird


Tardigrade Phineas Jones/Flickr
Tardigrade Phineas Jones/Flickr

There are a lot of celebrity sex tapes out there, but the one that has a lot of scientists excited these days is the one that finally catches the tardigrade, the toughest animal in the world, in the act. Unsurprisingly, tardigrade sex is a bit unconventional, and, according to a new study in the Zoological Journal, it involves an awful lot of foreplay.

Tardigrades, all the rage on the internet and sometimes called water bears or moss piglets, rarely do anything the standard way. For instance, they live everywhere, from the highest mountains to the deepest oceans, and it's unbelievably difficult to kill one of these microscopic creatures. You can dry them out, starve, freeze, burn, irradiate, poison them, or stick them down in the deepest, most pressurized ocean trench. You can expose them to the vacuum of space!

Subjected to any of these trials, a tardigrade will transform into a desiccated little husk, but when it's over, you just add a little water to that corpse, and it will plump back up and be on its way, munching on algae like usual. When brought back to Earth after spending 10 days blasted by space radiation, a tardigrade will happily revive and lay a clutch of viable eggs.

Since discovering them in 1773, we've learned amazing things about these indestructible creatures, but their mating behavior has remained a mystery. Of course, there are around 1,200 species of the phylum Tardigrada out there, and not all of them mate in the same way — some are bisexual, some are hermaphroditic, while others reproduce asexually. But new video footage captured by a team of researchers at the Senckenberg Museum of Natural History in Görlitz, Germany provides some insight into how the deed is done in one bisexual species of tardigrade called Isohypsibius dastychi. And though it might not look like much to the untrained eye, the researchers assure us that things gets weird. If you're up for some microscopic copulation, you can check it out for yourself right here: 

The animals mate right after the female has molted, something that happens several times each year. The researchers paired off 30 male-female couples (assessing the sex of a tardigrade is no easy task in itself!) and filmed them doing their thing. They found that after the female's outer skin detaches, she lays eggs inside it. If, for whatever reason, no male happens to waddle by after she lays her eggs, no biggie, she just reabsorbs them back into her body. But if there is a male around, he sort of wraps his body around her head, and the two engage in an hour-long mutual stimulation marathon in which he might ejaculate several times into the space between her old skin and her new skin, fertilizing her eggs in the process.

Witnessing this unusual sex spectacle has raised almost as many questions with researchers as it's answered. For instance: How does the male his semen to the right place if he's essentially injecting it under her skin? And why so much foreplay for such a tiny beast?

But with all the surprising dimensions to the water bear, did anybody think tardigrade sex was going to be unremarkable?