Students With Magnifying Glass
Before taking samples, students carefully examined the environment. Thomas Evaldsen
In a small Danish cemetery, a researcher hovers over a fallen tree covered by a rich green mat. She collects samples of lichen and moss and places them into two separate coffee filters. Meanwhile, her colleague holds a wet test strip in the air to measure the habitat’s ammonia level, and another researcher checks GPS readings and records the location on a map of Denmark. These researchers are hoping to gather microscopic creatures in the largest experiment of its kind—and they’re only 10 years old.
Guided by their teachers, nearly 30,000 Danish schoolchildren, ages 7 to 16, helped scientists from the Natural History Museum of Denmark catalog tiny, water-dwelling animals known as tardigrades, or water bears, and their microhabitats. Their contributions, published in October 2024 in Frontiers in Zoology, nearly quadrupled the number of known tardigrade species in Denmark and offered new insights into the biodiversity of these extraordinary animals.
Though inconspicuous—the largest reach only about one millimeter in length—tardigrades are incredibly resilient. They can survive everything from freezing to extremely high temperatures, as well as most kinds of radiation and the vacuum of outer space. Although they are water animals, tardigrades can endure dry spells thanks to special proteins that protect their cells until water is available again.
“The more species you know and more environments in which they are present you know,” says Roberto Guidetti, a zoologist at the University of Modena and Reggio Emilia in Italy who wasn’t involved in the study and has a tardigrade species dedicated to him, “the better you can understand their ecology, their evolution and also the mechanisms that led to the development of these extraordinary capabilities.”
Tardigrade
A tardigrade, or water bear Connect Images / Gregory S. Paulson via Getty Images
These remarkable qualities make tardigrades a fascinating subject of study for biotechnologists who have harnessed their dehydration abilities to develop dry vaccines, which might save lives in regions with limited refrigeration. In the future, tardigrade survival mechanisms and a better understanding of their genetics and habitats could also help us slow down aging processes, inform space exploration or aid in assessing environmental health, particularly in response to human-induced changes.
But humans are generally unaware of the rich microscopic world beneath our feet, in part because until relatively recently, scientists had few tools to accurately catalog such tiny species. However, DNA analysis methods developed over the last decade now allow researchers to distinguish between similar but distinct species, and to identify new species and study their geographical distributions. These techniques have helped scientists map tardigrade biodiversity, revealing connections between species and their habitats.
This large study was made possible by Mass Experiment, a citizen science project led by Astra, the Danish National Center for Science Education, involving hundreds of schools across Denmark. Armed with precise instructions, children collected 8,000 samples of mosses and lichens from local parks, forests and other spots. They were especially encouraged to collect samples from cemeteries, which host a variety of life yet are largely understudied habitats.
Gathering numerous samples from a range of locations is key to studying tardigrade biodiversity. To have a reasonable chance of finding even a single member of a rarer tardigrade species, researchers needed to collect and analyze thousands of samples. This made the citizen science approach a great tool for the scientists.
“It would simply take me weeks, if not months, to get to all these islands and islets,” says Piotr Gąsiorek, a tardigradologist at the Jagiellonian University in Poland and the study’s lead author.
Students With Lichen
Tardigrades often live in lichens. Jakob Vind
Once the samples reached the Natural History Museum of Denmark, Gąsiorek discarded low-quality samples and those likely containing what he calls “rat tardigrades”—commonplace species he was confident would appear in other samples. This left the researchers with almost 700 high-quality samples ready for further analysis.
In the samples, they identified 55 tardigrade species, 14 of which were species known in Denmark previously. At least nine species had not been described before. Gąsiorek is particularly proud of discovering male representatives of multiple species, which aren’t common since many known land tardigrades are females that reproduce asexually.
At least one of the newly discovered species—which turned out to be surprisingly widespread—will be described in detail, with a full genome. This won’t be the first full tardigrade genome to be sequenced, but it will be among the first with both male and female individuals.
Guidetti is more impressed by the citizen science approach and the speed of sample analysis than by the number of species found. He points out that tardigrade biodiversity is so understudied that “it’s not so hard to find new species,” but he adds that the citizen science approach was “very innovative.” He also notes that a lot remains to be discovered given that Gąsiorek’s research focused solely on mosses and lichens, leaving out many tardigrade-friendly environments such as freshwater sediments or the sea.
Gąsiorek points out that their goal wasn’t merely to document all tardigrade fauna, but to study tardigrade habitat preferences. They now have samples connecting tardigrade species with the moss and lichen species where they were found. This will help researchers determine which species of mosses and lichens are tardigrades’ favorites, which in turn will help them understand which mosses and lichens co-evolved with which tardigrades.
The Danish schoolchildren were proud of their contributions to science. Mass Experiment’s coordinator, Lene Christensen, estimates that over 60 percent of participating students are now more interested in science than they were before the study began, in part because “they were out in nature doing the real stuff,” Christensen says, comparing Mass Experiment to cooking soup rather than studying the recipe.
This approach to studying tardigrade biodiversity extends beyond Denmark. Guidetti’s team is working with schools all over Italy on a similar experiment, with the added bonus that children will be able to name any newly discovered species. He hopes to instill a love and appreciation for these minuscule animals in young scientists.
“We lost for retirement a lot of specialists,” he says. “But the new generation is coming.”
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Filed Under: Animals, Environment, Nature, Weird Animals