New virus increases male-to-female ratio of insect-killing wasps

New virus increases male-to-female ratio of insect-killing wasps

Scientists have discovered a new virus that alters the sex ratio of lab-raised wasps — a strategy that may help it spread to more wasp offspring.

Gongyin Ye and his team at Zhejiang University, China, found the new virus while studying the wasp species Pteromalus puparum. P. puparum is a small parasitoid wasp, a type of wasp that lays its eggs inside the body of a living host insect. After the eggs hatch, the young wasps feed on the doomed insect’s body until it dies.

P. puparum typically attacks butterfly pupae and can help control populations of butterflies that damage vegetable crops (such as cabbage). While studying the relationship between P. puparum and its butterfly hosts, Ye’s team examined its transcriptome, the collection of all messenger RNA molecules produced in its cells.

Nestled among the wasp’s own RNA, the scientists noticed telltale signs of a viral genome. When they sequenced the viral genome, they realized they had found a new virus species, which they named “PpNSRV-1.”

PpNSRV-1 is just one of many viruses that are known to infect parasitoid wasps; many of these viruses provide symbiotic benefits. However, PpNSRV-1 represents a completely new genus, and its effects were not immediately clear.

To investigate the impact of PpNSRV-1, the researchers compared two groups of P. puparum, one infected with the virus and one uninfected. They found that the infected wasps tended to live longer, which could be a strategy used by PpNSRV-1 to give wasps more time to transmit the virus to more offspring.

The scientists also found that PpNSRV-1 reduced the number of female offspring produced by P. puparum. Both males and females can transmit the virus to their progeny; however, since male wasps can mate with multiple females, a higher male-to-female ratio could help spread PpNSRV-1 to many more offspring.

Further research will be needed to clarify the mechanism by which PpNSRV-1 influences the P. puparum sex ratio and to confirm whether these findings hold true outside of the lab.

Citation: Wang F, Fang Q, Wang B, Yan Z, Hong J, Bao Y, et al. (2017) A novel negative-stranded RNA virus mediates sex ratio in its parasitoid hostPLoS Pathog 13(3): e1006201. doi:10.1371/journal.ppat.1006201

Image Creditgailhampshire, Flickr Creative Commons

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Sarah is a San Francisco-based science writer and editor. She covers a wide variety of topics, including Earth science, space science, and cancer.

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