Scientists in Japan have discovered a virus that is able to selectively kill male insects, resulting in generations of all-female offspring. This groundbreaking finding, published in The Proceedings of the National Academies of Sciences, provides strong evidence that there are multiple viruses that have evolved to target and eliminate male insects. This knowledge may prove valuable in controlling populations of pest insects and disease vectors like mosquitoes in the future.
Daisuke Kageyama, one of the authors of the study and a researcher at the National Agriculture and Food Research Organization in Japan, believes that there are likely many more cases like this waiting to be discovered in the near future. The virus was first identified when Misato Terao, a research technician at Minami Kyushu University, stumbled upon caterpillars damaging plants in the campus greenhouse. Fascinated by these intruders, she handed them over to Yoshinori Shintani, an insect physiologist at the university, who later found out that all the caterpillars had developed into female moths.
With curiosity piqued, Dr. Shintani decided to breed these female moths with male tobacco moths. Surprisingly, all of their offspring were females as well and this pattern continued for 13 generations. It became apparent to Dr. Shintani and his colleague, Dr. Kageyama, that they had stumbled upon a “male-killer” phenomenon.
While scientists have long been aware that microbes can influence the reproduction of insects, usually through bacteria, this discovery showed genetic evidence of a previously unknown male-killing virus. However, antibiotics were found to be ineffective in neutralizing the male-killing effect, indicating that bacteria were not responsible. Dr. Shintani and his team confirmed the inheritability of the virus by injecting it into uninfected pupae and moths, which resulted in a significantly higher number of female offspring in subsequent generations.
Additional experiments revealed that the male-killing effect was temperature-sensitive, with the virus becoming less potent and eventually neutralized at higher temperatures. This suggests that the balmy climate in the caterpillar’s native range acts as a natural suppressor of the male-killing effect. The discovery of this virus has important implications for pest control and could potentially help in controlling other related agricultural pests like the tobacco cutworm.
Experts believe that this finding indicates that viral male-killers are more common than previously thought. The knowledge gained from studying these male-killers could eventually lead to the development of a “female-killer” that could be used to combat invasive pests and disease-carrying species such as mosquitoes. However, there is a sense of urgency as the changing climate threatens to disrupt these delicate interactions before they can be fully understood and harnessed for pest control purposes.