Extremely Messy Tardigrade Sex Has Been Filmed For The First Time


Robin Andrews

Science & Policy Writer

A 3D rendering of a 1.5mm-long tardigrade. 3Dstock/Shutterstock

Tardigrades are amazing. Sure, they probably don’t steal a sixth of their DNA from other organisms, but they have survived five mass extinctions, can survive in deep space, and are adorably tiny. As it turns out, they also have marathon sex sessions.

Funnily enough, scientists haven’t until now taken a good long look at the sex lives of tardigrades, despite the fact that they have had nearly 250 years to do so. Writing in the Zoological Journal of the Linnean Society, it appears that these horny little superheroes go at it for at least an hour.


The study, headed by researchers at the Senckenberg Museum of Natural History in Germany, is a gloriously surreal read full of bizarre and explicit linguistic flourishes.

“We provide new insights into the mating behaviour of a bisexual tardigrade, Isohypsibius dastychi, revealing a process much more complex than expected,” it begins, highlighting the scientific novelty.

For this particular piece of research, 30 tardigrade couples were chosen to go on a bit of speed dating, all filmed on camera in the name of science. During mating, the females lay their eggs while molting, where they are implanted within the outmost layer of their skin.

The males then quickly make a beeline for the egg-laying females, and put them in a rather uncomfortably sounding headlock. As males and females look exactly alike, the only way males could be distinguished from females by the researchers was via this randy behavior.


The two of them then dance and wriggle around a bit in order to stimulate each other. The female “gently pokes” the male, while “contracting the sucking pharynx.”

Over the course of the next 60 minutes, the males ejaculate their semen via an all-purpose orifice above the anus – the “cloaca” – into the females’ outer skin layers. This means that fertilization occurs outside the body.

Tardigrade sex under a scanning electron microscope. The male is on the right, curled up around the female. In this clip, if you look closely, you can see sperm being ejaculated towards the female. ScienceAlert via YouTube

The researchers explain that the males “have a large testis filled with spermatozoa,” and that during the jiggling, “semen was ejaculated several times.” Blimey.


The researchers are clearly quite pleased with their findings. Pointing out that this is the first time the act itself has been filmed on a microscopic camera, they are barely able to contain their scientific revelry.

“In the present study, this behaviour was not only observed in more than 30 couples, but in six cases we were even able to see the spermatozoa being ejaculated,” they write. The team also note that “unfortunately, we are not able to give a detailed description of the spermatozoa.”

Well, there’s always next time on 50 Shades of Tardigrade.


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