Identification of an early male-killing agent in the oriental tea tortrix, Homona magnanima

Arthropods are frequently infected with inherited symbionts, which sometimes confer fitness benefits on female hosts or manipulate host reproduction. Early male killing, in which infected males die during embryogenesis, is induced by some bacteria, such as Wolbachia and Spiroplasma. A female-biased sex ratio has been found in Homona magnanima, collected from a tea plantation in Japan. Here, we examined the male-killing trait in H. magnanima and identified the agent that induces early male killing. The sex ratio distortion (SR) strain produced only females and no males, and its egg hatch rate was significantly lower than that of the normal (N) strain. The N strain was infected with only Wolbachia, whereas the SR strain was infected with both Wolbachia and Spiroplasma. Antibiotic treatment with 0.10% tetracycline restored the 1:1 sex ratio in the SR strain. Females treated with 0.05% tetracycline were positive for Spiroplasma but not for Wolbachia and showed a female-biased sex ratio, whe...