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树上发现了性别比例偏向女性的大卷蛾(Homona MagAnima)。全雌品系与正常品系的平均卵孵化无明显差异。在全雌品系幼虫中观察到的死亡率超过50%，这表明只有雌性品系的幼虫是后期雄性杀戮的结果。即使当雌性与正常品系的雄性回交时，雌性偏向的性别比例也是母系遗传并保持的，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，并不是由导致其他男性死亡现象的病原体感染的线索。如立克次体、沃尔巴克氏菌、螺旋体或原生动物寄生虫。当将全雌品系雌成虫卵巢匀浆注入正常品系幼虫时，这种雄性致死特性被传递给下一代，因此其病原体可能也是水平传播的。用蔗糖密度梯度离心法从该全雌株雌成虫卵巢中提纯了病原物。蔗糖密度梯度离心法得到一条清晰的条带，含有直径为20 nm的球形病毒样颗粒。当该试剂用蛋白酶K处理时，感染性完全丧失。然而，当该试剂被紫外线处理时，感染性并未丧失。

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.