| Budget Amount *help |
¥16,000,000 (Direct Cost: ¥16,000,000)
Fiscal Year 2003: ¥8,800,000 (Direct Cost: ¥8,800,000)
Fiscal Year 2002: ¥7,200,000 (Direct Cost: ¥7,200,000)
|
|---|
| Research Abstract |
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.
|
