New tardigrade found in Japanese auto park

In a report from early March 2018, researchers announced the formal identification of a new species of tardigrade, Macrobiotus shonaicus. The discovery was detailed in a scientific paper published on February 28, 2018, in the open-access journal PLOS ONE. This finding officially increased the number of tardigrade species known to exist in Japan from 167 to 168.

The tardigrade, a microscopic invertebrate also known as a water bear, was found in an unexpected location, highlighting the organism’s ubiquity and resilience. Its discovery stemmed from a small sample of moss collected from a decidedly urban environment.

Discovery in an Urban Setting

The specimen that led to the identification of the new species was collected by Kazuharu Arakawa, a researcher at Keio University. According to the report, Arakawa scraped a small sample of moss that was growing on the concrete surface of a parking lot next to his apartment building in Tsuruoka City, Yamagata Prefecture.

This mundane origin underscores how new species can be found in common, human-altered landscapes, not just in remote or pristine ecosystems. Ten individual tardigrades were isolated from this single moss sample. These specimens were then used to establish a laboratory culture, allowing researchers to obtain the larger population needed for comprehensive morphological and genetic analysis.

Identification and Classification

To confirm the animal was an undescribed species, the research team employed an integrative taxonomy approach, combining physical observation with DNA analysis. Under microscopic examination, the tardigrades and their eggs displayed a unique combination of characteristics. Genetic sequencing provided further evidence, placing M. shonaicus within the hufelandi group, a complex of closely related tardigrade species.

The formal scientific paper was titled, “An integrative description of Macrobiotus shonaicus sp. nov. (Tardigrada: Macrobiotidae) from Japan with notes on its phylogenetic position within the hufelandi group.” The specific name shonaicus was chosen to honor the Shōnai region of Japan where the city of Tsuruoka is located.

Distinctive Reproductive Features

A primary distinguishing feature of Macrobiotus shonaicus lies in the morphology of its eggs. The eggs are adorned with flexible, tentacle-like filaments that radiate from the surface. The report at the time noted that these features might assist the egg in attaching to the substrate where it is laid.

While similar filaments are found on the eggs of other species in the same genus, such as M. paulinae from Africa and M. polypiformis from South America, the eggs of M. shonaicus are different. Their distinction comes from the solid surface of the eggshell located between the bases of these filaments. This specific combination of traits was not present in any previously documented tardigrade, serving as a key marker for its classification as a new species.

The Context of Tardigrade Research

Tardigrades have long fascinated scientists since their initial discovery by German zoologist Johann August Ephraim Goeze in 1773. They are extremophiles, meaning they can survive conditions that would be lethal to nearly all other known life forms. They achieve this by entering a state of suspended animation called cryptobiosis, where their metabolic processes almost completely stop.

In this state, they can withstand near-total dehydration, extreme temperatures from over 150°C (300°F) down to near absolute zero, intense radiation, and the vacuum of outer space. The study of these mechanisms has potential applications in fields like cryopreservation and the development of methods to protect biological materials. The discovery of new species like M. shonaicus provides scientists with more subjects to study these unique survival abilities, with the initial specimens being used to start a laboratory culture for ongoing research.

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