Sahara Ken, Takemura Yoko
Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
J Exp Zool A Comp Exp Biol. 2003 Jun 1;297(2):196-200. doi: 10.1002/jez.a.10250.
The silkworm, Bombyx mori, has a dimorphic sperm system. The eupyrene sperm is the sperm to fertilize eggs and the apyrene sperm plays a crucial role for assisting fertilization. Heat-treated (33 degrees C for 96h) Daizo (DH) males, one of the strains in the silkworm, produce only eupyrene sperm, while in triploid males only apyrene sperm are functional. Though both types of males are found to be sterile, double copulation of the two males with a single female greatly increases fertility. Here we examined the fertilizing ability of eupyrene and apyrene sperm by means of an artificial insemination technique previously established in B. mori. Neither the eupyrene sperm collected from DH males, nor the apyrene sperm from triploid males have the ability to fertilize eggs. Artificial insemination with the mixture of eupyrene and apyrene sperm leveled up the frequency of fertilized eggs to more than 80%. When cryopreserved DH sperm (eupyrene sperm) were subjected to the same experiment, more than 95% fertilized eggs were obtained. These results confirmed that apyrene sperm play an important and indispensable role in fertilization in B. mori. Separate collection of functional eupyrene sperm and functional apyrene sperm and success of fertilization by means of the artificial insemination technique are applicable for further studies to elucidate the function of apyrene sperm.
家蚕（Bombyx mori）具有二态精子系统。真核精子是使卵子受精的精子，而无核精子在协助受精过程中起着关键作用。热处理（33摄氏度，96小时）的大造（DH）雄蚕，家蚕的一个品系，只产生真核精子，而三倍体雄蚕中只有无核精子起作用。尽管这两种类型的雄蚕都不育，但让这两种雄蚕与一只雌蚕进行双重交配可大大提高受精率。在此，我们通过先前在家蚕中建立的人工授精技术，研究了真核精子和无核精子的受精能力。从DH雄蚕收集的真核精子和三倍体雄蚕的无核精子都没有使卵子受精的能力。用真核精子和无核精子的混合物进行人工授精，使受精卵的频率提高到80%以上。当对冷冻保存的DH精子（真核精子）进行相同实验时，获得了超过95%的受精卵。这些结果证实，无核精子在家蚕受精过程中起着重要且不可或缺的作用。通过人工授精技术分别收集功能性真核精子和功能性无核精子并实现受精，适用于进一步研究以阐明无核精子的功能。
