Karyological and taxonomic studies of Dugesia japonica from the Southwest Islands of Japan-II |
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Authors: | Sachiko Tamura Iwashiro Oki Masaharu Kawakatsu |
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Institution: | (1) Ôsaka Prefectural Institute of Public Health, Nakamichi-1-chôme 3-69, Higashinari-ku, 537 Ôsaka, Japan;(2) Ôsaka Environmental Project Authority, MFC 7F, Uchihon-machi 1-2-15, Chû'ô-ku, 540 Ôsaka, Japan;(3) Biological Laboratory, Fuji Women's College, Kita-16, Nishi-2, Kita-ku, 001 Sapporo (Hokkaidô), Japan |
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Abstract: | The karyotypes of Dugesia japonica from the southern part of the Southwest Islands of Japan (the Nansei Shotô) include diploidy, triploidy, mixoploidy, and mixoaneuploidy. Animals having karyotypes based on n = 8 were found on Okinawa Island, Ishigaki Island, Iriomote Island, and Yonaguni Island, while animals having karyotypes based on n = 7 were found on Okinawa Island, Miyako Island, and Ishigaki Island. Toward the northern end of this island chain, at Tanegashima Island, Yakushima Island, and Amami-Ôshima Island, karyotypes based on n = 8 occurred; and on one of these, Tanegashima Island, n = 7 also occurred. Our data provide further support of the karyotypical distinction between the two subspecies of D. japonica: D. j. japonica has karyotypes based on n = 8 and D. j. ryukyuensis has karyotypes based on n = 7. Taking into consideration the geological history of the Southwest Islands and the ties of their faunas to those of adjacent areas, we can explain the current geographical distribution of the two subspecies in these islands as the result of two separate invasions by D. japonica, one in the Miocene and one after the early Quaternary. |
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Keywords: | Turbellaria Tricladida Dugesia karyology taxonomy Japan |
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