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Heat-shock-induced tetraploid and diploid/tetraploid mosaic in pond loach, Misgurnus anguillicaudatus |
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| Authors: | Takafumi Fujimoto Suzu Sakao Kouzou Oshima Etsuro Yamaha Katsutoshi Arai |
| Institution: | 1. Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty and Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, 041-8611, Japan 2. Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, 041-8611, Japan 3. Nanae Fresh-Water Laboratory, Field Science Center for Northern Biosphere, Hokkaido University, 2-9-1 Sakura, Nanae, Kameda, Hokkaido, 041-1105, Japan |
| Abstract: | Tetraploid fish, which are considered as key resources of diploid gametes for further breeding and ploidy manipulation, can be artificially induced by inhibition of the mitotic cell division with hydrostatic pressure or temperature treatments. Although many attempts have been made to induce artificial tetraploid strains, successful establishment of viable and fertile tetraploid strains are rare. In pond loach, Misgurnus anguillicaudatus, natural tetraploid individuals are distributed in wild populations and diploid gametes from the tetraploid fish have been used for the induction of polyploid individuals, but artificially induced tetraploid strains have not been established yet. In the present study, we optimised starting timing of the heat-shock treatment (41 °C for 2 min) to inhibit a mitotic cell division in fertilised eggs of the normal diploid pond loach between 21 and 51 min after insemination at 20 °C. After the treatment, we observed external appearance of hatching larvae and flow cytometrically determined ploidy status of the resultant larvae. Although tetraploid and diploid/tetraploid mosaic larvae were obtained, the optimum timings for induction of tetraploidy varied amongst crosses. Various kinds of ploidy such as haploidy, diploidy, triploidy, pentaploidy, hexaploidy, aneuploidy and mosaic were detected in non-optimum heat-shock timings for tetraploidisation. Survivors, a tetraploid and a diploid/tetraploid mosaic male, matured at the age of 1-year-old, but they produced functional haploid spermatozoa. |
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