Tardigrades are microscopic creatures with a gift for survival. These aquatic invertebrates – aka water bears or moss piglets – can withstand exposure to high levels of radiation, the crushing pressure of the deep sea, and even the vacuum of space.

We’ve also learned that water bears have some pretty wild sex, thanks to recent video footage from scientist James Weiss, videographer for YouTube channel Journey to the Microcosmos and author of “The Hidden Beauty of the Microscopic World.”

Weiss, who is an expert in using microscopes to study microbes in ponds, lakes, rivers and seas, created sealed environments on slides to observe the same water bears for weeks. This is how he captured images of tardigrades mating for up to two hours in a row.

He also recorded a 30-minute Tardigrade Threesome – one of the earliest known recordings of tardigrade group sex.

A trio of water bears

Researchers first published details of tardigrade mating behavior in a 2016 paper, but further observations of water bear sex remain fairly limited.

“There weren’t many people studying tardigrades until very recently, so all of these observations come from two well-known tardigradologists,” Weiss said. (Yes, “tardigradologist” is a real word, he added.)

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“I don’t study tardigrades in a traditional, institutional way, but because I’ve had a long interest in them, I’ve gathered a lot of data and observed unique behaviors,” Weiss said.

One of those unique behaviors? A trio of water bears.

While observing tardigrades on his slides, Weiss first noticed two smaller tardigrades that seemed to be attracted to the belly of a larger tardigrade. This was unusual, as usually Tardigrades don’t show such a focused interest in anything.

But even after 20 minutes, the two smaller tardigrades continued to poke the larger one with their mouths. Weiss, who is no tardigrade expert but has seen enough of them in his studies of microscopic creatures, noticed that the larger tardigrade appeared to be carrying unfertilized eggs.

He said the two smaller tardigrades were males “pulling their shots” in an effort to fertilize the female’s eggs.

As Weiss watched, he said the two males continued to sting the female while she was pooping, which Weiss said could be a way to attract the males.

Weiss added, however, that experts’ limited understanding of tardigrade sex makes it impossible to know exactly why she defecated.

“In water, it’s all about chemical signals, so males have to gather information to find females,” Weiss said.

To test this, Weiss separated some mating pairs by gently poking them with cat hair through the microscope slide and coverslip. In each case, the males reverted to the females within minutes.

“So I think there’s chemical signaling, well, pooping releases a lot of signals into the water,” Weiss said.

After about 30 minutes in total, the trio became a duet when a man left the stage.

The remaining male stayed with the female for an additional hour, and Weiss observed similar mating behavior with other tardigrade pairs on the slide.

Water bear breeding

Males are attracted to females with unfertilized eggs or oocytes.

In his book, Weiss observed that men always seem to pursue. “While the females quietly browsed the seaweed, the males ran around like crazy chickens and jumped on the backs of the females and stayed there for an hour and a half,” he wrote.

Once the males have found a female, they latch onto her with their claws and the mates make a wild rhythmic movement until the male finishes, releasing thousands of sperm which probably fertilize the eggs as they enter a opening in the female’s exoskeleton.

But scientists have not yet discovered exactly how fertilization occurs.

Not all water bears need to have sex to reproduce. Weiss said some species of tardigrades include only females, which reproduce asexually via parthenogenesis.

He also said it’s possible that tardigrades change their method of reproduction when under environmental stress, although experts still have a lot to learn about this theory.

But marine species of water bears, like the species recorded by Weiss, include both males and females, and they reproduce by mating.

Water bear birth

A mother water bear can carry about 20 eggs until the eggs begin to hatch one by one — exploding like popcorn, Weiss said.

“It is easy to distinguish a tardigrade hatchling because it has an empty stomach. Just after a week it is ready to reproduce, so it is safe to say that babies have babies two weeks after hatching “, said Weiss.

Water bears are fairly short-lived, with 8 weeks being the longest lifespan Weiss observed in his research.

Watch the tardigrade trio in the video below, starting around 1:25 p.m.

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This article was originally published by Business Insider.

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