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to extreme environmentsHorikawa, Daiki*; Yamaguchi, Ayami*; Sakashita, Tetsuya; Tanaka, Daisuke*; Hamada, Nobuyuki*; Yukuhiro, Fumiko*; Kuwahara, Hirokazu*; Kunieda, Takekazu*; Watanabe, Masahiko*; Nakahara, Yuichi*; et al.
Astrobiology, 12(4), p.283 - 289, 2012/04
Times Cited Count：25 Percentile：69.33(Astronomy & Astrophysics)We examined the hatchability of hydrated and anhydrobiotic eggs of the tardigrade to hatch after ionizing irradiation (helium ions), extremely low and high temperatures, and high vacuum. Anhydrobiotic eggs (50% lethal dose; 1690 Gy) were substantially more radioresistant than hydrated ones (50% lethal dose; 509 Gy). Anhydrobiotic eggs also have a broader temperature resistance compared with hydrated ones. Over 70% of the anhydrobiotic eggs treated at high and low temperatures, but all of the hydrated eggs failed to hatch. After exposure to high vacuum conditions, the hatchability of the anhydrobiotic eggs was comparable to that of untreated control eggs.
; A New model animal for astrobiologyHorikawa, Daiki*; Kunieda, Takekazu*; Abe, Wataru*; Watanabe, Masahiko*; Nakahara, Yuichi*; Yukuhiro, Fumiko*; Sakashita, Tetsuya; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; et al.
Astrobiology, 8(3), p.549 - 556, 2008/06
Times Cited Count：108 Percentile：92.21(Astronomy & Astrophysics)We report the successful rearing of the herbivorous tardigrade, , by supplying the green alga 
as food. The life span was 35 d, deposited eggs required 5.7 d to hatch, and animals began to deposit eggs 9 d after hatching. The reared individuals of this species had an anhydrobiotic capacity throughout their life cycle in egg, juvenile, and adult stages. Furthermore, the reared adults in an anhydrobiotic state were tolerant of temperatures of 90
C and -196C and exposure to 99.8% acetonitrile or irradiation with 4000 Gy 
He ions. Based on their life history traits and tolerance to extreme stresses, 
might be a suitable model for astrobiological studies of multicellular organisms.
-ray on the tardigrade 
Horikawa, Daiki*; Sakashita, Tetsuya; Katagiri, Chihiro*; Watanabe, Masahiko*; Kikawada, Takahiro*; Nakahara, Yuichi*; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; Higashi, Seigo*; et al.
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 116, 2007/02
no abstracts in English
Horikawa, Daiki*; Sakashita, Tetsuya; Katagiri, Chihiro*; Watanabe, Masahiko*; Kikawada, Takahiro*; Nakahara, Yuichi*; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; Higashi, Seigo*; et al.
International Journal of Radiation Biology, 82(12), p.843 - 848, 2006/12
Times Cited Count：144 Percentile：99.16(Biology)no abstracts in English
; A Model for astrobiological studiesHorikawa, Daiki*; Kunieda, Takekazu*; Abe, Wataru*; Koshikawa, Shigeyuki*; Nakahara, Yuichi*; Watanabe, Masahiko*; Iwata, Kenichi*; Sakashita, Tetsuya; Hamada, Nobuyuki*; Higashi, Seigo*; et al.
no journal, ,
We report the first successful rearing of the herbivorous tardigrade, , by supplying a green alga as a food. The reared individuals of this species had an anhydrobiotic capacity throughout their life cycle, from eggs, to juveniles, and to adults. Reared adults, while in an anhydrobiotic state, were tolerant to temperatures -196C and 100C. Furthermore, they were shown to be tolerant to the exposure to 99.8% acetonitrile, 1 GPa of hydrostatic pressure, or 5000 Gy of He ion radiation. We will report the details of these results, along with the description of their life history. Due to the observed tolerance to such extreme environmental conditions, we propose R. varieornatus to be included as a suitable model for astrobiological studies of multicellular organisms.
-rays tolerance in water bearsHorikawa, Daiki*; Watanabe, Masahiko*; Nakahara, Yuichi*; Kikawada, Takahiro*; Okuda, Takashi*; Sakashita, Tetsuya; Funayama, Tomoo; Hamada, Nobuyuki*; Wada, Seiichi*; Kobayashi, Yasuhiko; et al.
no journal, ,
no abstracts in English
Horikawa, Daiki*; Sakashita, Tetsuya; Katagiri, Chihiro*; Watanabe, Masahiko*; Nakahara, Yuichi*; Kikawada, Takahiro*; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; Higashi, Seigo*; et al.
no journal, ,
no abstracts in English
Wadachi, Hiroki*; Kunieda, Takekazu*; Abe, Wataru*; Nakahara, Yuichi*; Watanabe, Masahiko*; Sakashita, Tetsuya; Hamada, Nobuyuki*; Kobayashi, Yasuhiko; Higashi, Seigo*; Okuda, Takashi*
no journal, ,
We collected some kinds of tardigrade to develop multi-cellular model oraganism for extremotolerant. Among four kinds of collected tardigrade, we found that a tardigrade at Sapporo-city feeded 
and could breed. The life-time of in an artificial culture condition is about 35 days and 5.7 days for hatching. During the whole life-time, one animal laids 8 eggs. In addition, it was observed that could enter an ametabolic dry state called anhydrobiosis in all stages of life-time. Furthermore, we observed a high surviving-rate even if exposed in various kinds of extreme environments.
