An international team of biologists from Poland and Japan has discovered and described a new species of tardigrade. Details of the micro-animal’s discovery are published in the journal PLoS ONE.
Macrobiotus shonaicus. Scale bars in μm. Image credit: Stec et al, doi: 10.1371/journal.pone.0192210.
First discovered in 1773 by the German zoologist Johann August Ephraim Goeze, tardigrades are water-dwelling, eight-legged, segmented micro-animals.
These creatures can live for up to 60 years, and grow to a maximum size of 0.5 mm, best seen under a microscope.
They are able to survive for up to 30 years without food or water, for a few minutes at temperatures as low as minus 272 degrees Celsius (minus 457 degrees Fahrenheit) or as high as 150 degrees Celsius (302 degrees Fahrenheit), and minus 20 degrees Celsius (minus 4 degrees Fahrenheit) for decades. They also withstand pressures from virtually 0 atm in space up to 1,200 atm at the bottom of the Marianas Trench.
Dr. David Sloan of Oxford University and colleagues recently found that tardigrades will survive all astrophysical calamities, such as large asteroid impacts, supernovae and gamma ray bursts, since these events will never be strong enough to boil off the world’s oceans.
Tardigrades have barrel-shaped bodies with four pairs of stubby legs. The body consists of a head, three body segments with a pair of legs each, and a caudal segment with a fourth pair of legs.
Also known as water bears or moss piglets, they are commonly found in mosses, lichens, leaf litter and soil.
About 1,200 known species form the phylum Tardigrada, a part of the superphylum Ecdysozoa.
Named Macrobiotus shonaicus, the new tardigrade species was found by Keio University researcher Kazuharu Arakawa and Jagiellonian University’s Daniel Stec and Łukasz Michalczyk in Otsuka-machi, Tsuruoka-City, Japan.
“We collected a sample of moss from a car park in Japan and examined it for tardigrades, extracting 10 individuals from the sample, which were used to start a laboratory culture to obtain more individuals required for the range of analyses,” the scientists explained.
“We then used phase contrast light microscopy and scanning electron microscopy as well as analyzed the DNA for four molecular markers to characterize the new species and determine where it fit in the phylogenetic tree.”
To distinguish between different tardigrade species, the team paid special attention to their eggs.
“Macrobiotus shonaicus has a solid egg surface, placing it in the persimilis subgroup within the hufelandi complex,” the authors said.
“The eggs also have flexible filaments attached, resembling those of two other recently described species, Macrobiotus paulinae from Africa and Macrobiotus polypiformis from South America.”
“We revisit the large and long-standing Macrobiotus hufelandi group of tardigrades, originally described by Schultze in 1834 and where Macrobiotus shonaicus also belongs, and suggest that the group contains two clades with different egg morphology,” Dr. Arakawa said.
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D. Stec et al. 2018. An integrative description of Macrobiotus shonaicus sp. nov. (Tardigrada: Macrobiotidae) from Japan with notes on its phylogenetic position within the hufelandi group. PLoS ONE 13 (2): e0192210; doi: 10.1371/journal.pone.0192210
