| Project/Area Number |
13556009
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
蚕糸・昆虫利用学
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
KEN Sahara Hokkaido Univ., Grad. School of Agr., Assistant Prof., 大学院・農学研究科, 助手 (30241368)
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| Co-Investigator(Kenkyū-buntansha) |
BANNO Yutaka Kyushu Univ. Grad. School of Agr., Assoc. Prof., 大学院・農学研究科, 助教授 (50192711)
SAITO Yutaka Hokkaido Univ., Grad. School of Agr., Prof., 大学院・農学研究科, 教授 (20142698)
BANDO Hisanori Hokkaido Univ., Grad. School of Agr., Prof., 大学院・農学研究科, 教授 (20189731)
TAKEMURA Yoko Inst. Silkworm Genet. Breed., Research Scientist, 蚕業技術研究所, 研究員
YAMASHIKI Naoko Rakuno-Gakuen Univ., Biology Lab., Assoc. Prof., 環境システム学部, 助教授 (40112578)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Bombyx mori / eypyrne sperm / apyrene spem / cryopreservation / artificial insemination / dimorphic sperm / maintenance of bioresorce / double copulation |
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| Research Abstract |
Lepidopteran insects have dimorphic sperm system, fertilizing eupyrene sperm and anucleate apyrene sperm. We found that polyploid male of Bombyx mori have only functional eupyrene. On the other hand the apyrene sperm is produced alone by heat-shock treatment to pupae of Daizo strain in the silkworm. Thus we successfully separated the eupyrene sperm from the apyrene sperm. Double copulation and artificial insemination experiments with mixing of the separated sperm proved that the apyrene sperm is inevitable for successful fertilization by the eupyrene sperm. These results are first experimental proof of the function of apyrene sperm concerning the fertilization. This experimental system enables us to observe the behavior of individual sperm populations in female reproductive organs. The eupyrene sperm cannot proceed to spermatheca without mixing with the apyrene sperm, resulting no fertilization success.
Artificial insemination to females with cryopreserved eupyrene sperm resulted normal fertility if intact apyrene sperm was supplied. On the other hand cryopreserved apyrene sperm sometimes lost their ability after freeze-and-thaw treatment. Decrease in fertility of cryopreserved sperm seems to be mainly caused by sever damage of apyrene sperm. This greatly varies among silkworm strains. Utilization of resistant strains against freeze-and-thaw for producing polyploid males may be one of the ways to increase the stability of apyrene sperm function. We improved the fertility of cryopreseved sperm stock by applying the apyrene sperm which was kept in liquid nitrogen. The combination system of artificial insemination technique, cryopreservation of sperm and application of separated apyrene sperm constructed in this study is basis to develop the new method to maintain the genetic resources of the silkworm.
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