Kazuharu Arakawa, a molecular biologist at Japan's Keio University, is in the habit of scooping up samples of moss to look for tardigrades—the chubby, strangely adorable microscopic creatures that dwell in moss, lichen and soil. As Stephanie Pappas reports for Live Science, Arakawa recently scraped a bit of moss from the parking lot of his apartment in Tsuruoka City and made an exciting discovery: an entirely new species of tardigrade.
The chunky critter has been dubbed Macrobiotus shonaicus because it was found in the Shōnai region of Japan, and it is the 168th species of tardigrade discovered in the country. More than 1,100 species of tardigrades—also known as “waterbears” and “moss piglets”—have been described around the world. The aquatic invertebrates are as resilient as they are ubiquitous. They can withstand being heated to 300 degrees Fahrenheit, frozen to just a few degrees above absolute zero (-459.7 degrees Fahrenheit), and being pelted with large quantities of radiation. Tardigrades can even survive exposure to outer space.
Like other tardigrades, M. shonaicus has a chunky body, eight legs and a round mouth. But when Arakawa and other researchers analyzed the critter’s genome, they found that its DNA sequence did not match that of any other known tardigrade. Describing their results in the journal PLOS One, the team, which was led by tardigrade expert Łukasz Michalczyk of Jagiellonian University in Poland, writes that M. shonaicus is “unambiguously” a distinct species.
The newly discovered tardigrade boasts a number of other unique features. While most Macrobiotidae are carnivorous (they munch on rotifers, a type of microscopic animal), M. shonaicus subsists on algae. According to George Dvorksy of Gizmodo, M. shonaicus has a distinctive fold on the internal surface of its leg. And the specimens discovered by Arakawa were able to reproduce in a lab—an unusual feature among tardigrades.
“M. shonaicus has two sexes, where other tardigrades that are culturable in labs have been mostly parthenogenetic (females reproduce by themselves without male population)," Arakawa explains to Peter Dockrill of Science Alert. “So it is an ideal model to study the sexual reproduction machinery and behaviors of tardigrades.”
M. shonaicus’s eggs have a solid surface, indicating that the little waterbear belongs to a sub-group of tardigrades known as hufelandi. No other hufelandi species has been reported in Japan, according to the study authors. M. shonaicus’s eggs are also crowned with an unusual ring of stringy, flexible filaments, similar to the eggs of two recently described species from South America.
Scientists are fascinated by tardigrades’ remarkable ability to survive extremely harsh conditions, which may have implications for medical research. But not even experts can resist the waterbears’ funny faces and blubbery bodies.
"As they lumber around under the microscope,” Arakawa tells Dockrill, “clinging on to moss leaves and (apparently) looking about with their tiny eyespots, it is easy to become involved in the drama of their lives."