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Type: Article
Published: 2020-04-23
Page range: 56–70
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Distribution of Macrobiotus shonaicus Stec, Arakawa & Michalczyk, 2018 (Tardigrada: Eutardigrada: Macrobiotidae) in Japan

School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University
Institute for Advanced Biosciences, Keio University, Japan Faculty of Environment and Information Studies, Keio University, Japan Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan
Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama, Kanagawa, Japan
Tardigrada DNA barcoding geographic distribution karyotype mating tardigrade


To date, only seven species of Macrobiotidae (Parachela; Eutardigrada; Tardigrada) have been reported from Japan, including the recently described Macrobiotus shonaicus Stec et al., 2018 from the Shonai region of Japan. This species has flexible filaments on the egg processes and is known to proliferate only through sexual reproduction. Here, we report a multifaceted analysis of nine populations of M. shonaicus found on four Japanese islands. DNA sequencing of the cytochrome oxidase subunit I (COI) and internal transcribed spacer 2 (ITS-2) of the nine populations revealed 8 and 11 haplotypes, respectively. The extensive morphometric analysis showed considerably greater variability in the morphology of eggs than of animals. In addition to the morphological and molecular data, we confirmed the karyotype and found that all populations had a chromosome number of n = 6. Moreover, we observed and filmed mating behaviour between all studied populations of M. shonaicus. Our results clearly indicated that M. shonaicus is widely distributed throughout Japan.



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