Studies on factors biasing the primary sex ratio toward females in the oriental tea tortrix, Homona magnanima(Lepidoptera : Trotricidae)

在日本茨城筑波的东方茶蛾中发现了雌性偏向性比例（鳞翅目：茶蛾科）。全雌株与正常株的平均卵孵化量无显著差异。在全雌株幼虫中观察到超过50%的死亡率，这表明雌株幼虫是由于雄株后期杀死而产生的。雌性偏向的性别比例是母系遗传和维持的，甚至当雌性与正常品系的雄性回交时也是如此，因此暗示细胞质寄生是其原因。这种现象在抗生素存在的情况下持续存在，并且没有线索表明是由引起其他男性死亡现象的病原体感染的。如立克次体、沃尔巴克氏体、螺旋体或原生动物寄生虫。当将全雌菌株的雌成虫卵巢匀浆注射到正常菌株的幼虫体内时，这种杀雄特性会遗传给下一代，因此其病原体也可能是水平传播的。采用蔗糖密度梯度离心法从全雌菌株雌成虫卵巢中纯化出病原。蔗糖密度梯度离心得到一条清晰的条带，其中含有直径为20 nm的球形病毒样颗粒。当用蛋白酶K处理时，感染完全丧失。然而，当用紫外线处理时，传染性并没有丧失。

A female-biased sex ratio was found in the oriental tea tortrix, Homona magnanima (Lepidoptera : Tortricidae), in Tsukuba, Ibaraki, Japan. There was no difference in mean egg hatch between the all-female and normal strains. Greater than 50% mortality was observed in the all-female strain larvae, suggesting that female-only broods are produced as a result of late male-killing. The female-biased sex ratio was maternally inherited and maintained, even when females were backcrossed with males of the normal strain, thus implicating cytoplasmic parasitism as its cause. The phenomenon was persistent in the presence of antibiotics, and was not clue to infection by agents that cause other male-killing phenomena. such as Rickettsia, Wolbachia, Spiroplasma, or protozoan parasites. When a homogenate of ovaries of female adults of the all-female strain was injected in normal strain larvae, this male-killing trait was transmitted to the next generation thus, its causative agent is likely transmitted horizontally as well. The causative agent was purified from ovaries of female adults of the all-female strain using the sucrose density-gradient centrifugation. One clear band was obtained by the sucrose density-gradient centrifugation and contained spherical virus-like particles with a diameter of 20 nm. When the agent was treated with Proteinase K, infectivity was completely lost. However, when the agent was treated with UV, infectivity was not lost.